sdl ui backend

15 files changed, 7607 insertions, 16 deletions

diff --git a/assets/DejaVuSansMono.ttf b/assets/DejaVuSansMono.ttf
new file mode 100644
index 00000000..bcf640e2
--- /dev/null
+++ b/assets/DejaVuSansMono.ttf
diff --git a/build.zig b/build.zig
index 34450fa9..ca8560fd 100644
--- a/build.zig
+++ b/build.zig
@@ -16,6 +16,12 @@ pub fn build(b: *std.Build) void {
     const static_link = b.option(bool, "static", "link all build executables and test binaries statically") orelse false;
     const exe_linkage: ?std.builtin.LinkMode = if (static_link) .static else null;
     const strip = b.option(bool, "strip", "strip debug info from the compiled pardes binary") orelse false;
+    // -Dsdl: build the SDL3 GPU UI frontend (a windowed cell-grid renderer)
+    //   instead of the default libvaxis terminal backend. The sdl/stb deps are
+    //   lazy, so a plain `zig build` never fetches or compiles them; they're only
+    //   pulled in when this flag is set. Use `zig build test-sdl -Dsdl` for the
+    //   rendered-image SDL e2e suite.
+    const sdl = b.option(bool, "sdl", "build the SDL3 GPU UI frontend instead of the terminal backend") orelse false;
 
     const exe = b.addExecutable(.{
         .name = "pardes",
@@ -93,6 +99,50 @@ pub fn build(b: *std.Build) void {
     vaxis_mod.addImport("uucode", uucode_mod);
     exe.root_module.addImport("vaxis", vaxis_mod);
 
+    // The UI backend module (`-Dui`). main.zig + image.zig import `"ui"` instead of
+    // `"vaxis"` directly; the chosen backend file re-exports the shared UI types
+    // (Key/Mouse/Window/Cell/…) and provides the renderer/loop (`Vaxis`/`Tty`/
+    // `Loop`/`init`). vaxis = transparent passthrough; sdl = SDL3 GPU frontend.
+    const ui_root = if (sdl) b.path("ui_sdl.zig") else b.path("ui_vaxis.zig");
+    const ui_mod = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .root_source_file = ui_root,
+    });
+    ui_mod.addImport("vaxis", vaxis_mod);
+    exe.root_module.addImport("ui", ui_mod);
+
+    // SDL3 GPU backend wiring (`-Dsdl`). The sdl package builds SDL3 from source
+    // as a static lib + emits the SDL3/ headers; we @cImport those headers in
+    // ui_sdl.zig, link the lib, and pull in stb_truetype (for the glyph atlas) and
+    // the embedded DejaVuSansMono font. All gated on the flag so a plain `zig build`
+    // (vaxis) never fetches or compiles SDL.
+    if (sdl) {
+        const sdl_dep = b.lazyDependency("sdl", .{
+            .target = target,
+            .optimize = optimize,
+        }) orelse return; // not fetched (offline?) — skip SDL wiring
+        const sdl_lib = sdl_dep.artifact("SDL3");
+        ui_mod.linkLibrary(sdl_lib);
+        ui_mod.addIncludePath(sdl_dep.path("include"));
+        ui_mod.link_libc = true;
+
+        // stb_truetype: the header (declarations, via include path) + the impl TU
+        // + a small C shim (font.c) so ui_sdl.zig doesn't feed the whole
+        // single-header lib to translate-c.
+        ui_mod.addIncludePath(b.path("vendor/stb"));
+        ui_mod.addCSourceFile(.{ .file = b.path("vendor/stb/stb_truetype_impl.c") });
+        ui_mod.addCSourceFile(.{ .file = b.path("vendor/stb/font.c") });
+
+        // GLSL -> SPIR-V at build time, embedded into ui_sdl.zig via @embedFile.
+        ui_mod.addAnonymousImport("ui.vert.spv", .{
+            .root_source_file = compileGlsl(b, "shaders/ui.vert.glsl", "vertex", "ui.vert.spv"),
+        });
+        ui_mod.addAnonymousImport("ui.frag.spv", .{
+            .root_source_file = compileGlsl(b, "shaders/ui.frag.glsl", "fragment", "ui.frag.spv"),
+        });
+    }
+
     // zstbi: C (stb_image)-backed image decoder for the image-viewer panes. We use
     // it instead of zigimg because zigimg's pure-Zig decoder crashes the Zig 0.16
     // compiler here; stb_image is plain C (extern fns), so it compiles fine, decodes
@@ -201,6 +251,28 @@ pub fn build(b: *std.Build) void {
     const test_step = b.step("test", "run deterministic tests");
     test_step.dependOn(&run_tests.step);
 
+    // `test-sdl`: e2e tests for the SDL3 GPU backend. The SDL pardes exe runs in
+    // test mode (PARDES_TEST=1): stdin drives app events through a pty, while the
+    // real GPU renderer writes the latest framebuffer capture to a temp PPM file.
+    // Requires `-Dsdl` so the SDL exe is the one under test.
+    const sdl_tests = b.addExecutable(.{
+        .name = "pardes-e2e-sdl",
+        .linkage = exe_linkage,
+        .root_module = b.createModule(.{
+            .target = target,
+            .optimize = optimize,
+            .root_source_file = b.path("tests_sdl.zig"),
+            .link_libc = true,
+        }),
+    });
+    const run_sdl_tests = b.addRunArtifact(sdl_tests);
+    run_sdl_tests.addArtifactArg(exe);
+    const sdl_test_opts = b.addOptions();
+    sdl_test_opts.addOption(bool, "trace", trace);
+    sdl_tests.root_module.addOptions("config", sdl_test_opts);
+    const test_sdl_step = b.step("test-sdl", "run SDL3 GPU e2e tests (requires -Dsdl)");
+    test_sdl_step.dependOn(&run_sdl_tests.step);
+
     // Unit tests for the pure modal-editing math (modal.zig has no vaxis/ghostty
     // deps, so `zig test` on it is fast and needs no wired-in modules).
     const unit_tests = b.addTest(.{
@@ -254,3 +326,12 @@ pub fn build(b: *std.Build) void {
     tutor_step.dependOn(&run_tutor.step);
     test_step.dependOn(&run_tutor.step);
 }
+
+// glslc <src> -fshader-stage=<stage> -o <out> -> .spv, returned as a LazyPath to
+// @embedFile. Only used by the SDL3 GPU UI backend (`-Dui=sdl`).
+fn compileGlsl(b: *std.Build, src: []const u8, stage: []const u8, out: []const u8) std.Build.LazyPath {
+    const cmd = b.addSystemCommand(&.{ "glslc", b.fmt("-fshader-stage={s}", .{stage}) });
+    cmd.addFileArg(b.path(src));
+    cmd.addArg("-o");
+    return cmd.addOutputFileArg(out);
+}
diff --git a/build.zig.zon b/build.zig.zon
index 2d5a2b3a..3a29c77d 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -24,6 +24,14 @@
             .url = "git+https://github.com/zig-gamedev/zstbi#3813f5f113b26f644cfa01a30155cc76b3526e91",
             .hash = "zstbi-0.11.0-dev-L0Ea_3GWBwAh7m54XX055vwLKPTPij5hyqyeq92MXPE2",
         },
+        // SDL3 (castholm/SDL zig bindings) — only fetched/compiled when `-Dsdl`
+        // is set. Lazy so the default vaxis build never touches it. The sdl
+        // package resolves its own linux deps from its own build.zig.zon.
+        .sdl = .{
+            .url = "git+https://github.com/david-vanderson/SDL#5bbcf665494fe14acadf50601edf6d5f74ebf96a",
+            .hash = "sdl-0.4.2+3.4.4-SDL--tB1pQFLgwvCakiiOSoZIuVaz6a6-_gOZC66AGRD",
+            .lazy = true,
+        },
         // tree-sitter: Zig bindings + the C runtime, plus grammars (parser.c
         // we link, highlights.scm we read at build time into the ts_queries module).
         .tree_sitter = .{
diff --git a/e2e_harness_sdl.zig b/e2e_harness_sdl.zig
new file mode 100644
index 00000000..cac25473
--- /dev/null
+++ b/e2e_harness_sdl.zig
@@ -0,0 +1,332 @@
+// E2E harness for the SDL3 GPU backend's rendered-image test mode.
+//
+// The child app runs the real SDL/GPU renderer. Input is still delivered through
+// a pty so the same terminal escape sequences exercise the same app input path,
+// but rendered frames are captured by the app as PPM image files in a temp
+// directory. Assertions inspect pixels, not the retained cell grid.
+const std = @import("std");
+const posix = std.posix;
+const linux = std.os.linux;
+
+extern "c" fn forkpty(
+    amaster: *c_int,
+    name: ?[*:0]u8,
+    termp: ?*const anyopaque,
+    winp: ?*const posix.winsize,
+) c_int;
+extern "c" fn execvp(file: [*:0]const u8, argv: [*:null]const ?[*:0]const u8) c_int;
+extern "c" fn _exit(status: c_int) noreturn;
+extern "c" fn setenv(name: [*:0]const u8, value: [*:0]const u8, overwrite: c_int) c_int;
+
+fn nowMs() i64 {
+    var ts: linux.timespec = undefined;
+    _ = linux.clock_gettime(linux.CLOCK.MONOTONIC, &ts);
+    return ts.sec * 1000 + @divFloor(@as(i64, ts.nsec), 1_000_000);
+}
+
+pub const Image = struct {
+    width: u32,
+    height: u32,
+    pixels: []u8, // RGB, row-major
+
+    pub fn deinit(self: *Image, gpa: std.mem.Allocator) void {
+        gpa.free(self.pixels);
+        self.* = .{ .width = 0, .height = 0, .pixels = &.{} };
+    }
+
+    pub fn hash(self: Image) u64 {
+        return std.hash.Wyhash.hash(0, self.pixels);
+    }
+
+    pub fn brightPixels(self: Image, y0_in: u32, y1_in: u32, threshold: u8) usize {
+        const y0 = @min(y0_in, self.height);
+        const y1 = @min(y1_in, self.height);
+        var n: usize = 0;
+        var y = y0;
+        while (y < y1) : (y += 1) {
+            var x: u32 = 0;
+            while (x < self.width) : (x += 1) {
+                const i = (@as(usize, y) * @as(usize, self.width) + @as(usize, x)) * 3;
+                const lum = (@as(u16, self.pixels[i]) + @as(u16, self.pixels[i + 1]) + @as(u16, self.pixels[i + 2])) / 3;
+                if (lum >= threshold) n += 1;
+            }
+        }
+        return n;
+    }
+
+    pub fn changedPixels(self: Image, other: Image, threshold: u8) usize {
+        if (self.width != other.width or self.height != other.height) return std.math.maxInt(usize);
+        var n: usize = 0;
+        var i: usize = 0;
+        while (i < self.pixels.len) : (i += 3) {
+            const dr = absDiff(self.pixels[i], other.pixels[i]);
+            const dg = absDiff(self.pixels[i + 1], other.pixels[i + 1]);
+            const db = absDiff(self.pixels[i + 2], other.pixels[i + 2]);
+            if (dr + dg + db >= threshold) n += 1;
+        }
+        return n;
+    }
+};
+
+pub const SdlHarness = struct {
+    gpa: std.mem.Allocator,
+    io: std.Io,
+    master: c_int,
+    pid: posix.pid_t,
+    rows: u16,
+    cols: u16,
+    trace: bool = false,
+    capture_dir: [:0]u8,
+    latest_path: []u8,
+    image: ?Image = null,
+    rbuf: std.ArrayList(u8) = .empty,
+
+    pub fn init(gpa: std.mem.Allocator, io: std.Io, exe: [*:0]const u8, rows: u16, cols: u16) !SdlHarness {
+        return initArgs(gpa, io, exe, rows, cols, null);
+    }
+
+    pub fn initArgs(gpa: std.mem.Allocator, io: std.Io, exe: [*:0]const u8, rows: u16, cols: u16, arg: ?[*:0]const u8) !SdlHarness {
+        const base = ".zig-cache/pardes-sdl-e2e";
+        try std.Io.Dir.cwd().createDirPath(io, base);
+        const capture_dir_plain = try std.fmt.allocPrint(gpa, "{s}/{d}-{d}", .{ base, linux.getpid(), nowMs() });
+        defer gpa.free(capture_dir_plain);
+        const capture_dir = try gpa.dupeZ(u8, capture_dir_plain);
+        errdefer gpa.free(capture_dir);
+        try std.Io.Dir.cwd().createDirPath(io, capture_dir);
+        const latest_path = try std.fmt.allocPrint(gpa, "{s}/latest.ppm", .{capture_dir});
+        errdefer gpa.free(latest_path);
+
+        var master: c_int = undefined;
+        const ws = posix.winsize{ .row = rows, .col = cols, .xpixel = 0, .ypixel = 0 };
+        const pid = forkpty(&master, null, null, &ws);
+        if (pid == 0) {
+            _ = setenv("PARDES_TEST", "1", 1);
+            _ = setenv("PARDES_TEST_CAPTURE_DIR", capture_dir.ptr, 1);
+            var rows_buf: [16]u8 = undefined;
+            var cols_buf: [16]u8 = undefined;
+            const rows_z = std.fmt.bufPrintZ(&rows_buf, "{d}", .{rows}) catch unreachable;
+            const cols_z = std.fmt.bufPrintZ(&cols_buf, "{d}", .{cols}) catch unreachable;
+            _ = setenv("PARDES_TEST_ROWS", rows_z.ptr, 1);
+            _ = setenv("PARDES_TEST_COLS", cols_z.ptr, 1);
+            const argv: [3:null]?[*:0]const u8 = .{ exe, arg, null };
+            _ = execvp(exe, &argv);
+            _ = _exit(127);
+        }
+        return .{
+            .gpa = gpa,
+            .io = io,
+            .master = master,
+            .pid = pid,
+            .rows = rows,
+            .cols = cols,
+            .capture_dir = capture_dir,
+            .latest_path = latest_path,
+        };
+    }
+
+    pub fn deinit(self: *SdlHarness) void {
+        posix.kill(self.pid, posix.SIG.KILL) catch {};
+        _ = linux.close(self.master);
+        if (self.image) |*img| img.deinit(self.gpa);
+        self.rbuf.deinit(self.gpa);
+        self.gpa.free(self.latest_path);
+        self.gpa.free(self.capture_dir);
+    }
+
+    pub fn send(self: *SdlHarness, bytes: []const u8) !void {
+        var off: usize = 0;
+        while (off < bytes.len) {
+            const rc = linux.write(self.master, bytes[off..].ptr, bytes.len - off);
+            const n: isize = @bitCast(rc);
+            if (n < 0) {
+                if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+                return error.WriteFailed;
+            }
+            off += @intCast(n);
+        }
+    }
+
+    pub fn pump(self: *SdlHarness, ms: i64) !void {
+        const deadline = nowMs() + ms;
+        var buf: [4096]u8 = undefined;
+        while (nowMs() < deadline) {
+            var fds = [_]posix.pollfd{.{ .fd = self.master, .events = posix.POLL.IN, .revents = 0 }};
+            _ = posix.poll(&fds, 50) catch {};
+            if ((fds[0].revents & posix.POLL.IN) != 0) {
+                const n = posix.read(self.master, &buf) catch break;
+                if (n == 0) break;
+                self.rbuf.appendSlice(self.gpa, buf[0..n]) catch {};
+            }
+            self.loadLatest() catch {};
+        }
+        self.loadLatest() catch {};
+        if (self.trace) self.traceImage("pump");
+    }
+
+    pub fn resize(self: *SdlHarness, rows: u16, cols: u16) !void {
+        self.rows = rows;
+        self.cols = cols;
+        const ws = posix.winsize{ .row = rows, .col = cols, .xpixel = 0, .ypixel = 0 };
+        _ = posix.system.ioctl(self.master, posix.T.IOCSWINSZ, @intFromPtr(&ws));
+    }
+
+    pub fn waitForImage(self: *SdlHarness, ms: i64) !bool {
+        if (self.image != null) return true;
+        const deadline = nowMs() + ms;
+        while (nowMs() < deadline) {
+            try self.pump(100);
+            if (self.image != null) return true;
+        }
+        return false;
+    }
+
+    pub fn waitForChange(self: *SdlHarness, old_hash: u64, ms: i64) !bool {
+        const deadline = nowMs() + ms;
+        while (nowMs() < deadline) {
+            try self.pump(100);
+            if (self.image) |img| if (img.hash() != old_hash) return true;
+        }
+        return false;
+    }
+
+    pub fn imageHash(self: *SdlHarness) u64 {
+        return if (self.image) |img| img.hash() else 0;
+    }
+
+    pub fn imageCopy(self: *SdlHarness) !Image {
+        const img = self.image orelse return error.NoImage;
+        return .{
+            .width = img.width,
+            .height = img.height,
+            .pixels = try self.gpa.dupe(u8, img.pixels),
+        };
+    }
+
+    pub fn cellWidth(self: *SdlHarness) u32 {
+        const img = self.image orelse return 0;
+        return img.width / @as(u32, self.cols);
+    }
+
+    pub fn cellHeight(self: *SdlHarness) u32 {
+        const img = self.image orelse return 0;
+        return img.height / @as(u32, self.rows);
+    }
+
+    pub fn expectImage(self: *SdlHarness, msg: []const u8) !void {
+        if (self.image == null) {
+            self.dump(msg);
+            return error.ExpectFailed;
+        }
+    }
+
+    pub fn expectWaitForImage(self: *SdlHarness, ms: i64, msg: []const u8) !void {
+        if (!try self.waitForImage(ms)) {
+            self.dump(msg);
+            return error.ExpectFailed;
+        }
+    }
+
+    pub fn expectWaitForChange(self: *SdlHarness, old_hash: u64, ms: i64, msg: []const u8) !void {
+        if (!try self.waitForChange(old_hash, ms)) {
+            self.dump(msg);
+            return error.ExpectFailed;
+        }
+    }
+
+    pub fn expectGridPixels(self: *SdlHarness, msg: []const u8) !void {
+        const img = self.image orelse {
+            self.dump(msg);
+            return error.ExpectFailed;
+        };
+        if (self.cols == 0 or self.rows == 0 or img.width % self.cols != 0 or img.height % self.rows != 0) {
+            self.dump(msg);
+            return error.ExpectFailed;
+        }
+        if (img.width / self.cols < 6 or img.height / self.rows < 10) {
+            self.dump(msg);
+            return error.ExpectFailed;
+        }
+    }
+
+    pub fn expectBrightRows(self: *SdlHarness, row0: u16, row1: u16, min_bright: usize, msg: []const u8) !void {
+        const img = self.image orelse {
+            self.dump(msg);
+            return error.ExpectFailed;
+        };
+        const ch = self.cellHeight();
+        const y0 = @as(u32, row0) * ch;
+        const y1 = @as(u32, row1) * ch;
+        if (img.brightPixels(y0, y1, 60) < min_bright) {
+            self.dump(msg);
+            return error.ExpectFailed;
+        }
+    }
+
+    fn loadLatest(self: *SdlHarness) !void {
+        const data = std.Io.Dir.cwd().readFileAlloc(self.io, self.latest_path, self.gpa, .limited(128 * 1024 * 1024)) catch |err| switch (err) {
+            error.FileNotFound => return,
+            else => return err,
+        };
+        defer self.gpa.free(data);
+        const img = try parsePpm(self.gpa, data);
+        if (self.image) |*old| old.deinit(self.gpa);
+        self.image = img;
+    }
+
+    pub fn dump(self: *SdlHarness, msg: []const u8) void {
+        if (self.image) |img| {
+            std.debug.print("E2E FAIL: {s}\nimage {d}x{d} hash={x} path={s}\nraw tail:\n{s}\n", .{
+                msg, img.width, img.height, img.hash(), self.latest_path, rawTail(self.rbuf.items),
+            });
+        } else {
+            std.debug.print("E2E FAIL: {s}\n(no captured image yet) path={s}\nraw tail:\n{s}\n", .{
+                msg, self.latest_path, rawTail(self.rbuf.items),
+            });
+        }
+    }
+
+    pub fn traceImage(self: *SdlHarness, tag: []const u8) void {
+        if (self.image) |img| {
+            std.debug.print("[trace {s}] image {d}x{d} hash={x} path={s}\n", .{
+                tag, img.width, img.height, img.hash(), self.latest_path,
+            });
+        } else {
+            std.debug.print("[trace {s}] no image yet path={s}\n", .{ tag, self.latest_path });
+        }
+    }
+};
+
+fn parsePpm(gpa: std.mem.Allocator, data: []const u8) !Image {
+    if (!std.mem.startsWith(u8, data, "P6")) return error.BadPpm;
+    var idx: usize = 2;
+    const w = try parsePpmInt(data, &idx);
+    const h = try parsePpmInt(data, &idx);
+    const max = try parsePpmInt(data, &idx);
+    if (max != 255) return error.BadPpm;
+    if (idx >= data.len or !isWs(data[idx])) return error.BadPpm;
+    idx += 1;
+    const len = @as(usize, w) * @as(usize, h) * 3;
+    if (data.len < idx + len) return error.BadPpm;
+    return .{ .width = w, .height = h, .pixels = try gpa.dupe(u8, data[idx .. idx + len]) };
+}
+
+fn parsePpmInt(data: []const u8, idx: *usize) !u32 {
+    while (idx.* < data.len and isWs(data[idx.*])) idx.* += 1;
+    const start = idx.*;
+    while (idx.* < data.len and data[idx.*] >= '0' and data[idx.*] <= '9') idx.* += 1;
+    if (idx.* == start) return error.BadPpm;
+    return std.fmt.parseInt(u32, data[start..idx.*], 10);
+}
+
+fn isWs(b: u8) bool {
+    return b == ' ' or b == '\n' or b == '\r' or b == '\t';
+}
+
+fn absDiff(a: u8, b: u8) u16 {
+    return if (a >= b) @as(u16, a - b) else @as(u16, b - a);
+}
+
+fn rawTail(raw: []const u8) []const u8 {
+    const max = 4096;
+    return if (raw.len > max) raw[raw.len - max ..] else raw;
+}
diff --git a/image.zig b/image.zig
index b6ebcf71..4c83f8ad 100644
--- a/image.zig
+++ b/image.zig
@@ -9,7 +9,7 @@
 // or the user toggles "Petscii" on the pane — we instead render the kept RGBA as
 // PETSCII art (see petscii.zig). Call `start` once before any pane loads.
 const std = @import("std");
-const vaxis = @import("vaxis");
+const vaxis = @import("ui");
 const zstbi = @import("zstbi");
 const ghostty_vt = @import("ghostty-vt");
 const petscii = @import("petscii.zig");
diff --git a/main.zig b/main.zig
index 582fc133..d5cfa6c0 100644
--- a/main.zig
+++ b/main.zig
@@ -1,5 +1,5 @@
 const std = @import("std");
-const vaxis = @import("vaxis");
+const vaxis = @import("ui");
 const ghostty_vt = @import("ghostty-vt");
 const Term = @import("term.zig");
 const modal = @import("modal.zig");
@@ -191,6 +191,7 @@ const MINW: u16 = 10; // min pane width  (cells)
 const MINH: u16 = 3; // min pane height (cells)
 const MAX_TERMS: usize = 16;
 const MAX_COLS: usize = 6;
+const MAX_PTY_DRAIN_EVENTS: usize = 128;
 const PREFIX_W: u16 = 5; // file-pane line-number prefix width: "%4d "
 
 const Rect = struct { x: u16, y: u16, w: u16, h: u16 };
@@ -767,10 +768,10 @@ fn pty_set_size(pty: std.Io.File, rows: u16, cols: u16) void {
 // One reader task per terminal. Tags each chunk with the terminal's slot id so
 // the main loop knows which emulator to feed; posts pty_eof when the shell exits.
 fn readPty(io: std.Io, gpa: std.mem.Allocator, pty: std.Io.File, id: usize, loop: *Loop) anyerror!void {
-    var read_buf: [0x1000]u8 = undefined;
+    var read_buf: [0x10000]u8 = undefined;
     var reader = pty.readerStreaming(io, &read_buf);
     while (true) {
-        var buf: [0x1000]u8 = undefined;
+        var buf: [0x10000]u8 = undefined;
         var vec = [_][]u8{&buf};
         const n = reader.interface.readVec(&vec) catch break;
         if (n == 0) break;
@@ -783,6 +784,19 @@ fn readPty(io: std.Io, gpa: std.mem.Allocator, pty: std.Io.File, id: usize, loop
     loop.postEvent(.{ .pty_eof = id }) catch {};
 }
 
+fn feedPtyRead(gpa: std.mem.Allocator, terms: *[MAX_TERMS]?*Term, active: usize, pr: PtyRead) void {
+    defer gpa.free(pr.bytes);
+    if (pr.id >= MAX_TERMS) return;
+    if (terms[pr.id]) |t| {
+        t.stream.nextSlice(pr.bytes);
+        // follow new output to the bottom, so a command's result shows even in a
+        // pane you didn't focus. Exception: the pane you're actively navigating
+        // in a text mode — don't yank the cursor out from under you.
+        if (!(pr.id == active and t.mode != .tty))
+            t.term.screens.active.scroll(.active);
+    }
+}
+
 // fork the pty + boot the emulator. Forking is the dangerous part in a
 // multithreaded process, so this does NOT start the reader task (no new
 // threads) — call startReader once the term is wired in.
@@ -3054,9 +3068,14 @@ pub fn main(init: std.process.Init) !void {
     // middle release, freed on overwrite / app exit.
     var chord_arg: ?[]u8 = null;
     defer if (chord_arg) |a| gpa.free(a);
+    var pending_event: ?@TypeOf(Command.value) = null;
 
     while (true) {
-        const event = try loop.nextEvent();
+        const event = if (pending_event) |ev| blk: {
+            pending_event = null;
+            break :blk ev;
+        } else try loop.nextEvent();
+        var drain_pty_after = false;
         switch (event) {
             .mouse => |mouse| {
                 const mcol: u16 = if (mouse.col < 0) 0 else @min(@as(u16, @intCast(mouse.col)), screen_w -| 1);
@@ -3341,7 +3360,6 @@ pub fn main(init: std.process.Init) !void {
                 }
             },
             .key_press => |key| kpress: {
-
                 if (terms[active]) |at| {
                     // Ctrl-w prefix: helix-style pane focus (Ctrl-w h/j/k/l).
                     if (ctrl_w_pending) {
@@ -3461,16 +3479,8 @@ pub fn main(init: std.process.Init) !void {
                 }
             },
             .pty_read => |pr| {
-                defer gpa.free(pr.bytes);
-                if (terms[pr.id]) |t| {
-                    t.stream.nextSlice(pr.bytes);
-                    // follow new output to the bottom, so a command's result shows
-                    // even in a pane you didn't focus. Exception: the pane you're
-                    // actively navigating in a text mode — don't yank the cursor out
-                    // from under you (it still tracks the bottom on its own there).
-                    if (!(pr.id == active and t.mode != .tty))
-                        t.term.screens.active.scroll(.active);
-                }
+                feedPtyRead(gpa, &terms, active, pr);
+                drain_pty_after = true;
             },
             .pty_eof => |id| {
                 if (terms[id]) |t| {
@@ -3507,6 +3517,20 @@ pub fn main(init: std.process.Init) !void {
             else => {},
         }
 
+        if (drain_pty_after) {
+            var drained: usize = 0;
+            while (drained < MAX_PTY_DRAIN_EVENTS) : (drained += 1) {
+                const next = try loop.tryEvent() orelse break;
+                switch (next) {
+                    .pty_read => |pr| feedPtyRead(gpa, &terms, active, pr),
+                    else => {
+                        pending_event = next;
+                        break;
+                    },
+                }
+            }
+        }
+
         // a fresh yank (y/d/c) mirrors out to the system clipboard via OSC 52. Emit
         // here where the tty writer + vx are in scope; the vx.render() below flushes.
         // ponytail: OSC 52 has a per-terminal size cap, so a huge yank may be
diff --git a/shaders/ui.frag.glsl b/shaders/ui.frag.glsl
new file mode 100644
index 00000000..2284fa0b
--- /dev/null
+++ b/shaders/ui.frag.glsl
@@ -0,0 +1,18 @@
+#version 450
+
+// Sample the glyph atlas (R = coverage 0..1) and mix the cell's bg up to its fg
+// by that coverage. Fully opaque: the swapchain is SDR, no blending needed.
+
+layout(set = 2, binding = 0) uniform sampler2D u_atlas;
+
+layout(location = 0) in vec2 v_uv;
+layout(location = 1) in vec3 v_fg;
+layout(location = 2) in vec3 v_bg;
+
+layout(location = 0) out vec4 o_col;
+
+void main() {
+    float a = texture(u_atlas, v_uv).r;
+    vec3 col = mix(v_bg, v_fg, a);
+    o_col = vec4(col, 1.0);
+}
diff --git a/shaders/ui.vert.glsl b/shaders/ui.vert.glsl
new file mode 100644
index 00000000..c7567a8f
--- /dev/null
+++ b/shaders/ui.vert.glsl
@@ -0,0 +1,44 @@
+#version 450
+
+// Terminal cell renderer. The CPU uploads one instance per visible cell; this
+// shader expands each instance into a two-triangle quad with gl_VertexIndex.
+// The fragment shader mixes fg/bg by the atlas's alpha (a glyph mask in the R
+// channel), so background fills and glyph foregrounds draw in a single pass.
+
+layout(location = 0) in vec4 a_rect; // x0, y0, x1, y1
+layout(location = 1) in vec4 a_uv_rect; // u0, v0, u1, v1
+layout(location = 2) in vec3 a_fg;
+layout(location = 3) in vec3 a_bg;
+
+layout(location = 0) out vec2 v_uv;
+layout(location = 1) out vec3 v_fg;
+layout(location = 2) out vec3 v_bg;
+
+void main() {
+    vec2 pos;
+    vec2 uv;
+    int corner = gl_VertexIndex % 6;
+    if (corner == 0) {
+        pos = vec2(a_rect.x, a_rect.y);
+        uv = vec2(a_uv_rect.x, a_uv_rect.y);
+    } else if (corner == 1) {
+        pos = vec2(a_rect.z, a_rect.y);
+        uv = vec2(a_uv_rect.z, a_uv_rect.y);
+    } else if (corner == 2) {
+        pos = vec2(a_rect.z, a_rect.w);
+        uv = vec2(a_uv_rect.z, a_uv_rect.w);
+    } else if (corner == 3) {
+        pos = vec2(a_rect.x, a_rect.y);
+        uv = vec2(a_uv_rect.x, a_uv_rect.y);
+    } else if (corner == 4) {
+        pos = vec2(a_rect.z, a_rect.w);
+        uv = vec2(a_uv_rect.z, a_uv_rect.w);
+    } else {
+        pos = vec2(a_rect.x, a_rect.w);
+        uv = vec2(a_uv_rect.x, a_uv_rect.w);
+    }
+    v_uv = uv;
+    v_fg = a_fg;
+    v_bg = a_bg;
+    gl_Position = vec4(pos, 0.0, 1.0);
+}
diff --git a/tests_sdl.zig b/tests_sdl.zig
new file mode 100644
index 00000000..857fc0a2
--- /dev/null
+++ b/tests_sdl.zig
@@ -0,0 +1,165 @@
+// E2E tests for the SDL3 GPU backend.
+//
+// Unlike the terminal e2e suite, this harness validates the rendered framebuffer:
+// the SDL app runs its real GPU/font/shader path and writes the latest frame as
+// a PPM image in a temp capture directory. These assertions are intentionally
+// visual/pixel-level, not retained-grid text assertions.
+const std = @import("std");
+const h = @import("e2e_harness_sdl.zig");
+const config = @import("config");
+const Harness = h.SdlHarness;
+const Image = h.Image;
+
+fn expectPixelSize(hs: *Harness, width: u32, height: u32, msg: []const u8) !void {
+    const img = hs.image orelse {
+        hs.dump(msg);
+        return error.ExpectFailed;
+    };
+    if (img.width != width or img.height != height) {
+        hs.dump(msg);
+        return error.ExpectFailed;
+    }
+}
+
+fn expectChangedPixels(hs: *Harness, before: Image, min_changed: usize, msg: []const u8) !void {
+    const img = hs.image orelse {
+        hs.dump(msg);
+        return error.ExpectFailed;
+    };
+    if (img.changedPixels(before, 30) < min_changed) {
+        hs.dump(msg);
+        return error.ExpectFailed;
+    }
+}
+
+pub fn main(init: std.process.Init) !void {
+    const gpa = init.gpa;
+    const io = init.io;
+    const args = try init.minimal.args.toSlice(init.arena.allocator());
+    if (args.len != 2) {
+        std.debug.print("usage: {s} <pardes-sdl-exe>\n", .{args[0]});
+        return error.BadArgs;
+    }
+    const exe = args[1];
+
+    var hs = try Harness.init(gpa, io, exe.ptr, 24, 80);
+    defer hs.deinit();
+    hs.trace = config.trace;
+
+    try hs.expectWaitForImage(8000, "SDL: app never produced a rendered frame");
+    try hs.pump(2000);
+    try hs.expectGridPixels("SDL: initial rendered frame is not aligned to the pty grid");
+    const cw = hs.cellWidth();
+    const ch = hs.cellHeight();
+    try hs.expectBrightRows(0, 1, 80, "SDL: top bar text did not render as bright glyph pixels");
+    try hs.expectBrightRows(2, 20, 3000, "SDL: terminal body did not render directory-list glyph pixels");
+
+    // Resize must change the actual framebuffer dimensions, not just retained
+    // state. This catches the real SDL window/swapchain path.
+    try hs.resize(30, 100);
+    const before_resize = hs.imageHash();
+    try hs.expectWaitForChange(before_resize, 8000, "SDL: resize did not produce a new rendered frame");
+    try expectPixelSize(&hs, cw * 100, ch * 30, "SDL: resized framebuffer does not match 100x30 cells");
+    try hs.expectBrightRows(0, 1, 80, "SDL: top bar disappeared after resize");
+
+    // TTY toggle should visibly change the active pane tag/body because prompts
+    // become visible and the mode tag flips.
+    var before = try hs.imageCopy();
+    defer before.deinit(gpa);
+    try hs.send("\x02");
+    try hs.expectWaitForChange(before.hash(), 6000, "SDL: Ctrl-b did not visibly enter tty mode");
+    try expectChangedPixels(&hs, before, 100, "SDL: tty mode visual delta was too small");
+
+    // Shell output should show up in the real rendered framebuffer.
+    before.deinit(gpa);
+    before = try hs.imageCopy();
+    try hs.send("echo SDL_E2E_MARKER_42\r");
+    try hs.expectWaitForChange(before.hash(), 8000, "SDL: shell command did not visibly update rendered output");
+    try expectChangedPixels(&hs, before, 100, "SDL: shell output visual delta was too small");
+
+    // Leaving tty should hide prompt/command rows again, producing another real
+    // rendered change.
+    before.deinit(gpa);
+    before = try hs.imageCopy();
+    try hs.send("\x02");
+    try hs.expectWaitForChange(before.hash(), 6000, "SDL: Ctrl-b did not visibly return to normal mode");
+    try expectChangedPixels(&hs, before, 100, "SDL: normal-mode visual delta was too small");
+
+    // Global tagbar mouse execution: middle-click Tutor should visibly add a
+    // file-like tutor pane.
+    before.deinit(gpa);
+    before = try hs.imageCopy();
+    try hs.send("\x1b[<1;14;1M\x1b[<1;14;1m");
+    try hs.expectWaitForChange(before.hash(), 10000, "SDL: Tutor tagbar action did not visibly change the render");
+    try expectChangedPixels(&hs, before, 1000, "SDL: Tutor visual delta was too small");
+    try hs.expectBrightRows(1, 8, 300, "SDL: Tutor pane did not render bright text in the top rows");
+
+    // Fresh app: terminal char-mode overlay is visible, can be edited, hides in
+    // raw tty, and returns after leaving tty. Every step is asserted through
+    // rendered pixels.
+    {
+        var hs2 = try Harness.init(gpa, io, exe.ptr, 24, 80);
+        defer hs2.deinit();
+        hs2.trace = config.trace;
+        try hs2.expectWaitForImage(8000, "SDL overlay: no initial frame");
+        try hs2.send("\x1b[<0;5;8M\x1b[<0;5;8m");
+        try hs2.pump(400);
+        try hs2.send("i");
+        try hs2.pump(300);
+
+        var base = try hs2.imageCopy();
+        defer base.deinit(gpa);
+        try hs2.send("ZZSDLINSXYZ");
+        try hs2.expectWaitForChange(base.hash(), 5000, "SDL: typed overlay did not render");
+        try expectChangedPixels(&hs2, base, 80, "SDL: typed overlay visual delta was too small");
+
+        base.deinit(gpa);
+        base = try hs2.imageCopy();
+        try hs2.send("\x7f\x7f\x7f");
+        try hs2.expectWaitForChange(base.hash(), 5000, "SDL: overlay backspace did not render");
+
+        try hs2.send("\x1b");
+        try hs2.pump(300);
+        base.deinit(gpa);
+        base = try hs2.imageCopy();
+        try hs2.send("\x02");
+        try hs2.expectWaitForChange(base.hash(), 6000, "SDL: tty mode did not hide overlay visually");
+        try expectChangedPixels(&hs2, base, 40, "SDL: tty-hide overlay delta was too small");
+
+        base.deinit(gpa);
+        base = try hs2.imageCopy();
+        try hs2.send("\x02");
+        try hs2.expectWaitForChange(base.hash(), 6000, "SDL: leaving tty did not restore overlay visually");
+    }
+
+    // CLI mode parity: --tty starts as a raw shell; typed shell input must
+    // visibly alter the framebuffer.
+    {
+        var hs3 = try Harness.initArgs(gpa, io, exe.ptr, 24, 80, "--tty");
+        defer hs3.deinit();
+        hs3.trace = config.trace;
+        try hs3.expectWaitForImage(8000, "SDL --tty: no initial frame");
+        before.deinit(gpa);
+        before = try hs3.imageCopy();
+        try hs3.send("i=0; while [ $i -lt 30 ]; do echo ZZSDLTTYFLAG_$i; i=$((i+1)); done\r");
+        try hs3.pump(2500);
+        try expectChangedPixels(&hs3, before, 80, "SDL --tty: shell visual delta was too small");
+        try hs3.expectBrightRows(18, 23, 350, "SDL --tty: lower terminal rows were not rendered");
+    }
+
+    // Configurable tty toggle: Ctrl-g should visibly enter tty mode when the
+    // toggle is moved off Ctrl-b.
+    {
+        var hs4 = try Harness.initArgs(gpa, io, exe.ptr, 24, 80, "--tty-toggle=g");
+        defer hs4.deinit();
+        hs4.trace = config.trace;
+        try hs4.expectWaitForImage(8000, "SDL --tty-toggle=g: no initial frame");
+        before.deinit(gpa);
+        before = try hs4.imageCopy();
+        try hs4.send("\x07");
+        try hs4.expectWaitForChange(before.hash(), 6000, "SDL --tty-toggle=g: Ctrl-g did not visibly enter tty mode");
+        try expectChangedPixels(&hs4, before, 80, "SDL --tty-toggle=g: visual delta was too small");
+    }
+
+    std.debug.print("SDL rendered-image e2e: all tests passed\n", .{});
+}
diff --git a/ui_sdl.zig b/ui_sdl.zig
new file mode 100644
index 00000000..4e0a5bb2
--- /dev/null
+++ b/ui_sdl.zig
@@ -0,0 +1,1682 @@
+// The SDL3 GPU UI backend (`-Dui=sdl`). Same surface as `ui_vaxis.zig` — the
+// app (main.zig / image.zig) imports `"ui"` and talks to `Vaxis`/`Tty`/`Loop`/
+// `init` plus the shared cell types — but here those are backed by an SDL
+// window + SDL3 GPU renderer instead of a real terminal.
+//
+// The retained model is identical to libvaxis: `main` builds a 2D grid of
+// `Cell`s each frame (via `vaxis.Window` over a `vaxis.Screen` — both pure,
+// I/O-free libvaxis types we reuse verbatim) and hands it to `render()`. Instead
+// of diffing it into escape sequences, `render()` rasterizes the grid with SDL3
+// GPU: one textured-quad draw per cell, glyphs pulled from an stb_truetype
+// monospace atlas. Input flows the other way through `SdlLoop`, which polls SDL
+// events and converts them to the same `Key`/`Mouse`/`Winsize` the app already
+// handles, posting them on a thread-safe queue (so the per-terminal pty readers
+// work unchanged). Kitty image panes are unsupported (caps.kitty_graphics is
+// false), so image.zig falls back to its PETSCII cell-art path — which renders
+// fine here, since it just writes cells.
+//
+// This is the quick-and-dirty first cut: ASCII + box-drawing + block glyphs via
+// a fixed 1024² R8 atlas (dynamic, grows as new codepoints appear), reverse /
+// invisible / dim honored, bold/italic/underline/strikethrough ignored. Terminal
+// appearance is preserved: a monospace grid of styled cells on a dark page.
+const std = @import("std");
+const builtin = @import("builtin");
+const vaxis = @import("vaxis");
+const posix = std.posix;
+const linux = std.os.linux;
+
+pub const c = @cImport({
+    @cDefine("SDL_DISABLE_OLD_NAMES", "1");
+    @cInclude("SDL3/SDL.h");
+    @cInclude("font.h");
+});
+
+// ---- shared (backend-agnostic) types: re-exported straight from libvaxis ----
+pub const Key = vaxis.Key;
+pub const Mouse = vaxis.Mouse;
+pub const Winsize = vaxis.Winsize;
+pub const Color = vaxis.Color;
+pub const Style = vaxis.Style;
+pub const Cell = vaxis.Cell;
+pub const Segment = vaxis.Segment;
+pub const Window = vaxis.Window;
+pub const Screen = vaxis.Screen;
+pub const Image = vaxis.Image;
+pub const Event = vaxis.Event;
+pub const Capabilities = vaxis.Vaxis.Capabilities;
+pub const CursorShape = vaxis.Cell.CursorShape;
+
+// `Options` mirrors the subset of vaxis.Vaxis.Options the app constructs. Only
+// system_clipboard_allocator is used (for OSC 52 paste in the terminal backend);
+// here it's accepted and unused — SDL reads the clipboard synchronously.
+pub const Options = struct {
+    system_clipboard_allocator: ?std.mem.Allocator = null,
+};
+
+// The backend struct is named `Vaxis` so `image.zig`'s `*vaxis.Vaxis` resolves.
+pub const Vaxis = SdlBackend;
+pub const Tty = SdlTty;
+pub fn Loop(comptime EventType: type) type {
+    return SdlLoop(EventType);
+}
+
+const font_ttf = @embedFile("assets/DejaVuSansMono.ttf");
+const vert_spv_bytes = @embedFile("ui.vert.spv");
+const frag_spv_bytes = @embedFile("ui.frag.spv");
+
+const log = std.log.scoped(.ui_sdl);
+
+// A standard 16-color ANSI palette (xterm), used to resolve vaxis.Color.index
+// cells — the dark theme passes palette indices through (palColor), and there's
+// no real terminal here to resolve them.
+const ansi = [16][3]u8{
+    .{ 0, 0, 0 },       .{ 205, 0, 0 },   .{ 0, 205, 0 },   .{ 205, 205, 0 },
+    .{ 0, 0, 238 },     .{ 205, 0, 205 }, .{ 0, 205, 205 }, .{ 229, 229, 229 },
+    .{ 127, 127, 127 }, .{ 255, 0, 0 },   .{ 0, 255, 0 },   .{ 255, 255, 0 },
+    .{ 92, 92, 255 },   .{ 255, 0, 255 }, .{ 0, 255, 255 }, .{ 255, 255, 255 },
+};
+
+// =====================================================================
+// Backend
+// =====================================================================
+
+const SdlBackend = @This();
+
+io: std.Io,
+alloc: std.mem.Allocator,
+
+sdl_window: *c.SDL_Window,
+device: *c.SDL_GPUDevice,
+swapchain_format: c.SDL_GPUTextureFormat,
+present_mode: c.SDL_GPUPresentMode,
+
+pipeline: *c.SDL_GPUGraphicsPipeline,
+atlas_tex: *c.SDL_GPUTexture,
+atlas_sampler: *c.SDL_GPUSampler,
+atlas_xfer: *c.SDL_GPUTransferBuffer,
+
+vbuf: *c.SDL_GPUBuffer,
+vxfer: *c.SDL_GPUTransferBuffer,
+vbuf_cells: u32 = 0, // capacity (cols*rows) the vbuf/vxfer were sized for
+cell_keys: []CellKey = &.{},
+dirty_ranges: []DirtyRange = &.{},
+cell_cache_valid: bool = false,
+last_render_w: u32 = 0,
+last_render_h: u32 = 0,
+
+// font + cell metrics
+font: ?*c.UIFont,
+scale: f32,
+cell_w: u32,
+cell_h: u32,
+ascent: i32,
+
+// retained cell grid (the same type vaxis uses; main writes here via window())
+screen: vaxis.Screen,
+caps: vaxis.Vaxis.Capabilities = .{}, // kitty_graphics stays false → PETSCII images
+test_mode: bool = false, // PARDES_TEST=1: stdin→events for e2e
+grid_test_mode: bool = false, // PARDES_TEST_GRID=1: old no-SDL text-grid dump path
+capture_images: bool = false, // PARDES_TEST=1: capture real rendered framebuffer images
+capture_dir: ?[]const u8 = null,
+capture_tex: ?*c.SDL_GPUTexture = null,
+capture_tex_w: u32 = 0,
+capture_tex_h: u32 = 0,
+capture_xfer: ?*c.SDL_GPUTransferBuffer = null,
+capture_xfer_size: u32 = 0,
+capture_frame: u64 = 0,
+
+trace_enabled: bool = false,
+trace_fd: c_int = -1,
+trace_every: u32 = 1,
+trace_frame: u64 = 0,
+
+// glyph atlas: a 1024² R8 staging bitmap + a map codepoint → texel slot.
+atlas_stage: []u8,
+glyphs: std.AutoHashMap(u32, Slot),
+pen_x: u32 = 0,
+pen_y: u32 = 0,
+atlas_dirty: bool = true,
+space_slot: Slot = .{ .u = 0, .v = 0 },
+
+// default page colors (the dark-theme "terminal native" the app expects when a
+// cell's color is .default).
+bg_default: [3]u8 = .{ 18, 18, 18 },
+fg_default: [3]u8 = .{ 204, 204, 204 },
+
+// last grid size we reported to the app (so SDL only posts winsize on change)
+reported_cols: u16 = 0,
+reported_rows: u16 = 0,
+
+// ---- constants + helper types (must come after all fields in Zig 0.16) ----
+pub const atlas_w: u32 = 1024;
+pub const atlas_h: u32 = 1024;
+pub const Slot = struct { u: u32, v: u32 };
+pub const CellKey = packed struct { cp: u32, fg: u32, bg: u32 };
+pub const DirtyRange = struct { start: u32, count: u32 };
+
+// One instance per cell. The vertex shader expands each instance into a 2-triangle
+// quad using gl_VertexIndex, so dirty uploads move 56 B/cell instead of 240 B/cell.
+const CellInstance = extern struct {
+    x0: f32,
+    y0: f32,
+    x1: f32,
+    y1: f32,
+    u0: f32,
+    v0: f32,
+    u1: f32,
+    v1: f32,
+    fr: f32,
+    fg: f32,
+    fb: f32,
+    br: f32,
+    bg: f32,
+    bb: f32,
+};
+
+fn envU16(env_map: *std.process.Environ.Map, name: []const u8) ?u16 {
+    const raw = env_map.get(name) orelse return null;
+    return std.fmt.parseInt(u16, raw, 10) catch null;
+}
+
+fn envU32(env_map: *std.process.Environ.Map, name: []const u8) ?u32 {
+    const raw = env_map.get(name) orelse return null;
+    return std.fmt.parseInt(u32, raw, 10) catch null;
+}
+
+fn envFlag(env_map: *std.process.Environ.Map, name: []const u8) bool {
+    const raw = env_map.get(name) orelse return false;
+    return !(raw.len == 0 or std.mem.eql(u8, raw, "0") or std.ascii.eqlIgnoreCase(raw, "false"));
+}
+
+fn nowNs() i128 {
+    var ts: linux.timespec = undefined;
+    _ = linux.clock_gettime(linux.CLOCK.MONOTONIC, &ts);
+    return @as(i128, ts.sec) * 1_000_000_000 + @as(i128, ts.nsec);
+}
+
+fn nsToUs(delta: i128) u64 {
+    if (delta <= 0) return 0;
+    return @intCast(@divTrunc(delta, 1000));
+}
+
+fn parsePresentMode(raw: []const u8) ?c.SDL_GPUPresentMode {
+    if (std.ascii.eqlIgnoreCase(raw, "immediate")) return c.SDL_GPU_PRESENTMODE_IMMEDIATE;
+    if (std.ascii.eqlIgnoreCase(raw, "mailbox")) return c.SDL_GPU_PRESENTMODE_MAILBOX;
+    if (std.ascii.eqlIgnoreCase(raw, "vsync")) return c.SDL_GPU_PRESENTMODE_VSYNC;
+    return null;
+}
+
+fn presentModeName(mode: c.SDL_GPUPresentMode) []const u8 {
+    return switch (mode) {
+        c.SDL_GPU_PRESENTMODE_IMMEDIATE => "immediate",
+        c.SDL_GPU_PRESENTMODE_MAILBOX => "mailbox",
+        c.SDL_GPU_PRESENTMODE_VSYNC => "vsync",
+        else => "unknown",
+    };
+}
+
+fn choosePresentMode(env_map: *std.process.Environ.Map, device: *c.SDL_GPUDevice, sdl_win: *c.SDL_Window) c.SDL_GPUPresentMode {
+    if (env_map.get("PARDES_SDL_PRESENT")) |raw| {
+        if (parsePresentMode(raw)) |mode| {
+            if (c.SDL_WindowSupportsGPUPresentMode(device, sdl_win, mode)) return mode;
+        }
+    }
+    const preferred = [_]c.SDL_GPUPresentMode{
+        c.SDL_GPU_PRESENTMODE_IMMEDIATE,
+        c.SDL_GPU_PRESENTMODE_MAILBOX,
+        c.SDL_GPU_PRESENTMODE_VSYNC,
+    };
+    for (preferred) |mode| {
+        if (c.SDL_WindowSupportsGPUPresentMode(device, sdl_win, mode)) return mode;
+    }
+    return c.SDL_GPU_PRESENTMODE_VSYNC;
+}
+
+pub fn init(
+    io: std.Io,
+    alloc: std.mem.Allocator,
+    env_map: *std.process.Environ.Map,
+    opts: Options,
+) !SdlBackend {
+    _ = opts;
+
+    // ---- test modes -------------------------------------------------------
+    // PARDES_TEST=1 keeps the real SDL/GPU/window renderer active, but drives
+    // input from stdin (raw terminal escape sequences parsed by vaxis.Parser)
+    // and writes rendered-frame captures into PARDES_TEST_CAPTURE_DIR.
+    //
+    // PARDES_TEST_GRID=1 is retained as a debug escape hatch: no SDL/GPU/window,
+    // stdin→events, retained cell grid→stdout. The real SDL e2e suite does not
+    // use it because it bypasses the renderer.
+    const test_mode = env_map.get("PARDES_TEST") != null;
+    const grid_test_mode = env_map.get("PARDES_TEST_GRID") != null;
+    if (grid_test_mode) return initTest(io, alloc);
+    const capture_dir = env_map.get("PARDES_TEST_CAPTURE_DIR");
+    if (test_mode and capture_dir == null) {
+        log.err("PARDES_TEST requires PARDES_TEST_CAPTURE_DIR", .{});
+        return error.SdlInit;
+    }
+    const trace_enabled = envFlag(env_map, "PARDES_SDL_TRACE");
+    const trace_every = envU32(env_map, "PARDES_SDL_TRACE_EVERY") orelse 1;
+    var trace_fd: c_int = -1;
+    if (trace_enabled) {
+        if (env_map.get("PARDES_SDL_TRACE_FILE")) |path| {
+            trace_fd = openTraceFile(path);
+        } else if (capture_dir) |dir| {
+            var path_buf: [4096]u8 = undefined;
+            const path = std.fmt.bufPrintZ(&path_buf, "{s}/perf.log", .{dir}) catch null;
+            trace_fd = if (path) |p| openTraceFile(p) else 2;
+        } else {
+            trace_fd = 2;
+        }
+    }
+
+    if (!c.SDL_Init(c.SDL_INIT_VIDEO)) {
+        log.err("SDL_Init: {s}", .{c.SDL_GetError()});
+        return error.SdlInit;
+    }
+
+    const win_w: c_int = 1120;
+    const win_h: c_int = 720;
+    const win_flags: c.SDL_WindowFlags = if (test_mode)
+        c.SDL_WINDOW_RESIZABLE
+    else
+        c.SDL_WINDOW_HIGH_PIXEL_DENSITY | c.SDL_WINDOW_RESIZABLE;
+    const sdl_win = c.SDL_CreateWindow(
+        "pardes",
+        win_w,
+        win_h,
+        win_flags,
+    ) orelse {
+        log.err("SDL_CreateWindow: {s}", .{c.SDL_GetError()});
+        return error.SdlInit;
+    };
+
+    const device = c.SDL_CreateGPUDevice(
+        c.SDL_GPU_SHADERFORMAT_SPIRV,
+        true,
+        null,
+    ) orelse {
+        log.err("SDL_CreateGPUDevice: {s}", .{c.SDL_GetError()});
+        return error.SdlInit;
+    };
+    if (!c.SDL_ClaimWindowForGPUDevice(device, sdl_win)) {
+        log.err("ClaimWindowForGPUDevice: {s}", .{c.SDL_GetError()});
+        return error.SdlInit;
+    }
+    const present_mode = choosePresentMode(env_map, device, sdl_win);
+    if (!test_mode) _ = c.SDL_SetGPUAllowedFramesInFlight(device, 1);
+    _ = c.SDL_SetGPUSwapchainParameters(
+        device,
+        sdl_win,
+        c.SDL_GPU_SWAPCHAINCOMPOSITION_SDR,
+        present_mode,
+    );
+    const swapchain_format = c.SDL_GetGPUSwapchainTextureFormat(device, sdl_win);
+
+    // ---- font + cell metrics ----
+    const font = c.ui_font_new(font_ttf.ptr, @intCast(font_ttf.len)) orelse {
+        log.err("ui_font_new failed", .{});
+        return error.FontInit;
+    };
+    const px: f32 = 18.0;
+    const scale = c.ui_font_scale_for_height(font, px);
+    var cw: c_int = 10;
+    var chh: c_int = 20;
+    var asc: c_int = 16;
+    c.ui_font_cell_metrics(font, scale, &cw, &chh, &asc);
+    if (test_mode) {
+        const cols = envU16(env_map, "PARDES_TEST_COLS") orelse 80;
+        const rows = envU16(env_map, "PARDES_TEST_ROWS") orelse 24;
+        _ = c.SDL_SetWindowSize(
+            sdl_win,
+            @intCast(@as(u32, cols) * @as(u32, @intCast(@max(cw, 1)))),
+            @intCast(@as(u32, rows) * @as(u32, @intCast(@max(chh, 1)))),
+        );
+        _ = c.SDL_SyncWindow(sdl_win);
+    }
+
+    // ---- glyph atlas (R8) ----
+    var tex_info = std.mem.zeroes(c.SDL_GPUTextureCreateInfo);
+    tex_info.type = c.SDL_GPU_TEXTURETYPE_2D;
+    tex_info.format = c.SDL_GPU_TEXTUREFORMAT_R8_UNORM;
+    tex_info.usage = c.SDL_GPU_TEXTUREUSAGE_SAMPLER;
+    tex_info.width = atlas_w;
+    tex_info.height = atlas_h;
+    tex_info.layer_count_or_depth = 1;
+    tex_info.num_levels = 1;
+    tex_info.sample_count = c.SDL_GPU_SAMPLECOUNT_1;
+    const atlas_tex = c.SDL_CreateGPUTexture(device, &tex_info) orelse return error.GpuCreate;
+
+    var samp_info = std.mem.zeroes(c.SDL_GPUSamplerCreateInfo);
+    samp_info.min_filter = c.SDL_GPU_FILTER_LINEAR;
+    samp_info.mag_filter = c.SDL_GPU_FILTER_LINEAR;
+    samp_info.mipmap_mode = c.SDL_GPU_FILTER_LINEAR;
+    samp_info.address_mode_u = c.SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE;
+    samp_info.address_mode_v = c.SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE;
+    samp_info.address_mode_w = c.SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE;
+    const atlas_sampler = c.SDL_CreateGPUSampler(device, &samp_info) orelse return error.GpuCreate;
+
+    var ax_info = c.SDL_GPUTransferBufferCreateInfo{
+        .usage = c.SDL_GPU_TRANSFERBUFFERUSAGE_UPLOAD,
+        .size = atlas_w * atlas_h,
+        .props = 0,
+    };
+    const atlas_xfer = c.SDL_CreateGPUTransferBuffer(device, &ax_info) orelse return error.GpuCreate;
+
+    // ---- pipeline ----
+    const pipeline = try makePipeline(device, swapchain_format);
+
+    const atlas_stage = try alloc.alloc(u8, atlas_w * atlas_h);
+    @memset(atlas_stage, 0);
+
+    var self: SdlBackend = .{
+        .io = io,
+        .alloc = alloc,
+        .sdl_window = sdl_win,
+        .device = device,
+        .swapchain_format = swapchain_format,
+        .present_mode = present_mode,
+        .pipeline = pipeline,
+        .atlas_tex = atlas_tex,
+        .atlas_sampler = atlas_sampler,
+        .atlas_xfer = atlas_xfer,
+        .vbuf = undefined,
+        .vxfer = undefined,
+        .font = font,
+        .scale = scale,
+        .cell_w = @intCast(@max(cw, 1)),
+        .cell_h = @intCast(@max(chh, 1)),
+        .ascent = asc,
+        .screen = .{},
+        .atlas_stage = atlas_stage,
+        .glyphs = std.AutoHashMap(u32, Slot).init(alloc),
+        .test_mode = test_mode,
+        .capture_images = test_mode,
+        .capture_dir = capture_dir,
+        .trace_enabled = trace_enabled,
+        .trace_fd = trace_fd,
+        .trace_every = @max(trace_every, 1),
+    };
+    // reserve slot (0,0) for the space glyph (an empty cell), start the pen after it.
+    _ = c.ui_font_raster(font, scale, ' ', atlas_stage.ptr, @intCast(atlas_w), @intCast(self.cell_w), @intCast(self.cell_h), asc);
+    self.space_slot = .{ .u = 0, .v = 0 };
+    self.pen_x = self.cell_w;
+    self.tracef("sdl.init present={s} frames_in_flight={d} trace_every={d}", .{
+        presentModeName(self.present_mode),
+        if (test_mode) @as(u32, 2) else @as(u32, 1),
+        self.trace_every,
+    });
+    return self;
+}
+
+// Headless debug init for PARDES_TEST_GRID=1: no SDL/GPU/window, just the cell
+// grid. Input comes from stdin (the pty), output goes to stdout (grid text
+// snapshots). Cell metrics are dummies: the pty gives us rows/cols directly.
+fn initTest(io: std.Io, alloc: std.mem.Allocator) !SdlBackend {
+    return .{
+        .io = io,
+        .alloc = alloc,
+        .sdl_window = undefined,
+        .device = undefined,
+        .swapchain_format = undefined,
+        .present_mode = c.SDL_GPU_PRESENTMODE_VSYNC,
+        .pipeline = undefined,
+        .atlas_tex = undefined,
+        .atlas_sampler = undefined,
+        .atlas_xfer = undefined,
+        .vbuf = undefined,
+        .vxfer = undefined,
+        .font = null,
+        .scale = 1,
+        .cell_w = 10,
+        .cell_h = 20,
+        .ascent = 16,
+        .screen = .{},
+        .atlas_stage = &.{},
+        .glyphs = std.AutoHashMap(u32, Slot).init(alloc),
+        .test_mode = true,
+        .grid_test_mode = true,
+    };
+}
+
+pub fn deinit(self: *SdlBackend, alloc: ?std.mem.Allocator, writer: *std.Io.Writer) void {
+    _ = writer;
+    if (self.grid_test_mode) {
+        self.screen.deinit(self.alloc);
+        self.glyphs.deinit();
+        return;
+    }
+    if (self.capture_tex) |t| c.SDL_ReleaseGPUTexture(self.device, t);
+    if (self.capture_xfer) |x| c.SDL_ReleaseGPUTransferBuffer(self.device, x);
+    if (self.trace_fd >= 0 and self.trace_fd != 2) _ = linux.close(self.trace_fd);
+    c.SDL_ReleaseGPUBuffer(self.device, self.vbuf);
+    c.SDL_ReleaseGPUTransferBuffer(self.device, self.vxfer);
+    self.alloc.free(self.cell_keys);
+    self.alloc.free(self.dirty_ranges);
+    c.SDL_ReleaseGPUTransferBuffer(self.device, self.atlas_xfer);
+    c.SDL_ReleaseGPUSampler(self.device, self.atlas_sampler);
+    c.SDL_ReleaseGPUTexture(self.device, self.atlas_tex);
+    c.SDL_ReleaseGPUGraphicsPipeline(self.device, self.pipeline);
+    if (self.font) |f| c.ui_font_free(f);
+    self.screen.deinit(self.alloc);
+    self.glyphs.deinit();
+    if (alloc) |a| a.free(self.atlas_stage);
+    c.SDL_ReleaseWindowFromGPUDevice(self.device, self.sdl_window);
+    c.SDL_DestroyWindow(self.sdl_window);
+    c.SDL_DestroyGPUDevice(self.device);
+    c.SDL_Quit();
+}
+
+// ---- vaxis-compatible surface ----
+
+pub fn resize(self: *SdlBackend, alloc: std.mem.Allocator, writer: *std.Io.Writer, ws: Winsize) !void {
+    _ = writer;
+    if (ws.cols == 0 or ws.rows == 0) return; // ignore zero-size (no pty yet)
+    self.screen.deinit(alloc);
+    self.screen = try vaxis.Screen.init(alloc, ws);
+    self.screen.width_method = .wcwidth;
+    if (self.capture_images) {
+        _ = c.SDL_SetWindowSize(
+            self.sdl_window,
+            @intCast(@as(u32, ws.cols) * self.cell_w),
+            @intCast(@as(u32, ws.rows) * self.cell_h),
+        );
+        _ = c.SDL_SyncWindow(self.sdl_window);
+    }
+    if (!self.grid_test_mode) try self.ensureVbuf(ws.cols * ws.rows);
+}
+
+pub fn window(self: *SdlBackend) vaxis.Window {
+    return .{
+        .x_off = 0,
+        .y_off = 0,
+        .parent_x_off = 0,
+        .parent_y_off = 0,
+        .width = self.screen.width,
+        .height = self.screen.height,
+        .screen = &self.screen,
+    };
+}
+
+pub fn render(self: *SdlBackend, writer: *std.Io.Writer) !void {
+    _ = writer;
+    if (self.grid_test_mode) return self.dumpGrid();
+
+    const trace_this = self.trace_enabled and (self.trace_frame % self.trace_every == 0);
+    const t0 = nowNs();
+    const cmd = c.SDL_AcquireGPUCommandBuffer(self.device) orelse return;
+    const t_cmd = nowNs();
+    var sw: u32 = 0;
+    var sh: u32 = 0;
+    var target: *c.SDL_GPUTexture = undefined;
+    if (self.capture_images) {
+        sw = @as(u32, self.screen.width) * self.cell_w;
+        sh = @as(u32, self.screen.height) * self.cell_h;
+        if (sw == 0 or sh == 0) {
+            _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+            return;
+        }
+        try self.ensureCaptureTexture(sw, sh);
+        target = self.capture_tex orelse {
+            _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+            return;
+        };
+    } else {
+        var swap_tex: ?*c.SDL_GPUTexture = null;
+        const t_acquire0 = nowNs();
+        if (!c.SDL_AcquireGPUSwapchainTexture(cmd, self.sdl_window, &swap_tex, &sw, &sh)) {
+            _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+            return;
+        }
+        const t_acquire1 = nowNs();
+        if (trace_this) self.tracef("sdl.event swapchain_acquire_us={d}", .{nsToUs(t_acquire1 - t_acquire0)});
+        target = swap_tex orelse {
+            if (trace_this) {
+                self.tracef("sdl.frame n={d} skipped=swapchain_busy acquire_us={d}", .{ self.trace_frame, nsToUs(t_acquire1 - t_acquire0) });
+            }
+            self.trace_frame += 1;
+            _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+            return;
+        };
+    }
+    const t_acquired = nowNs();
+    const win_w: f32 = @floatFromInt(sw);
+    const win_h: f32 = @floatFromInt(sh);
+
+    const cols = self.screen.width;
+    const rows = self.screen.height;
+    const cells: u32 = @as(u32, cols) * @as(u32, rows);
+    var t_mapped = t_acquired;
+    var t_built = t_acquired;
+    var t_atlas = t_acquired;
+    var t_uploaded = t_acquired;
+    var t_drawn = t_acquired;
+    var dirty_cells: u32 = 0;
+    var dirty_ranges: u32 = 0;
+    var atlas_uploaded = false;
+
+    // 1. build + upload the vertex buffer (one quad per cell).
+    if (cells != 0 and self.vbuf_cells >= cells) {
+        try self.ensureVbuf(cells); // no-op if already sized; safe guard
+        const force_full_upload = !self.cell_cache_valid or self.last_render_w != sw or self.last_render_h != sh;
+        const vptr: [*]u8 = @ptrCast(c.SDL_MapGPUTransferBuffer(self.device, self.vxfer, false) orelse {
+            _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+            return;
+        });
+        const instances: [*]CellInstance = @ptrCast(@alignCast(vptr));
+        t_mapped = nowNs();
+        const cw_f: f32 = @floatFromInt(self.cell_w);
+        const ch_f: f32 = @floatFromInt(self.cell_h);
+        var r: u16 = 0;
+        while (r < rows) : (r += 1) {
+            var col: u16 = 0;
+            while (col < cols) : (col += 1) {
+                const cell_index: u32 = @as(u32, r) * @as(u32, cols) + @as(u32, col);
+                const key = self.cellKey(self.screen.buf[cell_index]);
+                if (!force_full_upload and sameCellKey(self.cell_keys[cell_index], key)) continue;
+                self.cell_keys[cell_index] = key;
+                self.addDirtyRange(&dirty_ranges, cell_index);
+                dirty_cells += 1;
+                self.emitInstance(instances, cell_index, col, r, cw_f, ch_f, win_w, win_h, key);
+            }
+        }
+        c.SDL_UnmapGPUTransferBuffer(self.device, self.vxfer);
+        t_built = nowNs();
+        self.cell_cache_valid = true;
+        self.last_render_w = sw;
+        self.last_render_h = sh;
+
+        // `emitQuad` calls ensureGlyph, which may rasterize new glyphs into the
+        // atlas staging buffer. Upload after vertex generation so the first
+        // rendered frame has the glyphs it references.
+        if (self.atlas_dirty) {
+            self.uploadAtlas(cmd);
+            atlas_uploaded = true;
+        }
+        t_atlas = nowNs();
+
+        if (dirty_cells != 0) {
+            const copy = c.SDL_BeginGPUCopyPass(cmd);
+            var i: u32 = 0;
+            while (i < dirty_ranges) : (i += 1) {
+                const range = self.dirty_ranges[i];
+                const byte_offset: u32 = range.start * @sizeOf(CellInstance);
+                const byte_size: u32 = range.count * @sizeOf(CellInstance);
+                const src = c.SDL_GPUTransferBufferLocation{ .transfer_buffer = self.vxfer, .offset = byte_offset };
+                const dst = c.SDL_GPUBufferRegion{ .buffer = self.vbuf, .offset = byte_offset, .size = byte_size };
+                c.SDL_UploadToGPUBuffer(copy, &src, &dst, false);
+            }
+            c.SDL_EndGPUCopyPass(copy);
+        }
+        t_uploaded = nowNs();
+
+        // 3. render pass: clear to the page bg, draw every cell's quad.
+        var color_target = std.mem.zeroes(c.SDL_GPUColorTargetInfo);
+        color_target.texture = target;
+        color_target.clear_color = .{
+            .r = @as(f32, @floatFromInt(self.bg_default[0])) / 255.0,
+            .g = @as(f32, @floatFromInt(self.bg_default[1])) / 255.0,
+            .b = @as(f32, @floatFromInt(self.bg_default[2])) / 255.0,
+            .a = 1.0,
+        };
+        color_target.load_op = c.SDL_GPU_LOADOP_CLEAR;
+        color_target.store_op = c.SDL_GPU_STOREOP_STORE;
+
+        const rp = c.SDL_BeginGPURenderPass(cmd, &color_target, 1, null);
+        c.SDL_BindGPUGraphicsPipeline(rp, self.pipeline);
+        const samp_binding = c.SDL_GPUTextureSamplerBinding{ .texture = self.atlas_tex, .sampler = self.atlas_sampler };
+        c.SDL_BindGPUFragmentSamplers(rp, 0, &samp_binding, 1);
+        const vbinding = c.SDL_GPUBufferBinding{ .buffer = self.vbuf, .offset = 0 };
+        c.SDL_BindGPUVertexBuffers(rp, 0, &vbinding, 1);
+        c.SDL_DrawGPUPrimitives(rp, 6, cells, 0, 0);
+        c.SDL_EndGPURenderPass(rp);
+        t_drawn = nowNs();
+    } else {
+        // no grid yet (or vbuf not sized): just clear the swapchain to the page bg.
+        var color_target = std.mem.zeroes(c.SDL_GPUColorTargetInfo);
+        color_target.texture = target;
+        color_target.clear_color = .{
+            .r = @as(f32, @floatFromInt(self.bg_default[0])) / 255.0,
+            .g = @as(f32, @floatFromInt(self.bg_default[1])) / 255.0,
+            .b = @as(f32, @floatFromInt(self.bg_default[2])) / 255.0,
+            .a = 1.0,
+        };
+        color_target.load_op = c.SDL_GPU_LOADOP_CLEAR;
+        color_target.store_op = c.SDL_GPU_STOREOP_STORE;
+        const rp = c.SDL_BeginGPURenderPass(cmd, &color_target, 1, null);
+        c.SDL_EndGPURenderPass(rp);
+        t_drawn = nowNs();
+    }
+
+    if (self.capture_images) {
+        const t_capture0 = nowNs();
+        try self.captureSwapchain(cmd, target, sw, sh);
+        const t_done = nowNs();
+        if (trace_this) self.traceFrame(cells, dirty_cells, dirty_ranges, sw, sh, atlas_uploaded, t0, t_cmd, t_acquired, t_mapped, t_built, t_atlas, t_uploaded, t_drawn, t_capture0, t_done);
+        self.trace_frame += 1;
+        return;
+    }
+
+    const t_submit0 = nowNs();
+    _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+    const t_done = nowNs();
+    if (trace_this) self.traceFrame(cells, dirty_cells, dirty_ranges, sw, sh, atlas_uploaded, t0, t_cmd, t_acquired, t_mapped, t_built, t_atlas, t_uploaded, t_drawn, t_submit0, t_done);
+    self.trace_frame += 1;
+}
+
+// PARDES_TEST_GRID debug mode: dump the retained cell grid as text to stdout
+// (fd 1). One frame per render, delimited by ---FRAME---/---ENDFRAME--- markers.
+fn dumpGrid(self: *SdlBackend) !void {
+    const w = self.screen.width;
+    const h = self.screen.height;
+    if (w == 0 or h == 0) return;
+
+    // Build the whole frame into one buffer, then write it in one syscall so
+    // the harness sees an atomic snapshot (no torn frames).
+    var buf: std.ArrayList(u8) = .empty;
+    defer buf.deinit(self.alloc);
+    // header: rows cols cursor_x cursor_y cursor_vis
+    var hdr: [128]u8 = undefined;
+    const hdr_str = std.fmt.bufPrint(&hdr, "\n---FRAME:{d}:{d}:{d}:{d}:{}---\n", .{
+        h, w, self.screen.cursor.col, self.screen.cursor.row, self.screen.cursor_vis,
+    }) catch return;
+    buf.appendSlice(self.alloc, hdr_str) catch return;
+    for (0..h) |row| {
+        for (0..w) |col| {
+            const cell = self.screen.buf[row * w + col];
+            const g = cell.char.grapheme;
+            if (g.len > 0) buf.appendSlice(self.alloc, g) catch return else buf.append(self.alloc, ' ') catch return;
+        }
+        buf.append(self.alloc, '\n') catch return;
+    }
+    buf.appendSlice(self.alloc, "---ENDFRAME---\n") catch return;
+
+    // write to stdout (fd 1)
+    var off: usize = 0;
+    while (off < buf.items.len) {
+        const rc = linux.write(1, buf.items[off..].ptr, buf.items.len - off);
+        const n: isize = @bitCast(rc);
+        if (n < 0) {
+            if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+            return;
+        }
+        off += @intCast(n);
+    }
+}
+
+fn captureSwapchain(self: *SdlBackend, cmd: *c.SDL_GPUCommandBuffer, target: *c.SDL_GPUTexture, sw: u32, sh: u32) !void {
+    if (sw == 0 or sh == 0) {
+        _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+        return;
+    }
+    const size = c.SDL_CalculateGPUTextureFormatSize(self.swapchain_format, sw, sh, 1);
+    if (size == 0) {
+        _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+        return error.UnsupportedCaptureFormat;
+    }
+    try self.ensureCaptureXfer(size);
+
+    const xfer = self.capture_xfer orelse {
+        _ = c.SDL_SubmitGPUCommandBuffer(cmd);
+        return error.GpuCreate;
+    };
+    const copy = c.SDL_BeginGPUCopyPass(cmd);
+    const src = c.SDL_GPUTextureRegion{
+        .texture = target,
+        .mip_level = 0,
+        .layer = 0,
+        .x = 0,
+        .y = 0,
+        .z = 0,
+        .w = sw,
+        .h = sh,
+        .d = 1,
+    };
+    const dst = c.SDL_GPUTextureTransferInfo{
+        .transfer_buffer = xfer,
+        .offset = 0,
+        .pixels_per_row = sw,
+        .rows_per_layer = sh,
+    };
+    c.SDL_DownloadFromGPUTexture(copy, &src, &dst);
+    c.SDL_EndGPUCopyPass(copy);
+
+    const fence = c.SDL_SubmitGPUCommandBufferAndAcquireFence(cmd) orelse return error.GpuSubmit;
+    defer c.SDL_ReleaseGPUFence(self.device, fence);
+    var fences = [_]*c.SDL_GPUFence{fence};
+    if (!c.SDL_WaitForGPUFences(self.device, true, &fences, 1)) return error.GpuSubmit;
+
+    const mapped = c.SDL_MapGPUTransferBuffer(self.device, xfer, false) orelse return error.GpuMap;
+    defer c.SDL_UnmapGPUTransferBuffer(self.device, xfer);
+    const pixels: [*]const u8 = @ptrCast(mapped);
+    try self.writeCapturePpm(pixels[0..size], sw, sh);
+}
+
+fn ensureCaptureTexture(self: *SdlBackend, width: u32, height: u32) !void {
+    if (self.capture_tex != null and self.capture_tex_w == width and self.capture_tex_h == height) return;
+    if (self.capture_tex) |t| c.SDL_ReleaseGPUTexture(self.device, t);
+    var info = std.mem.zeroes(c.SDL_GPUTextureCreateInfo);
+    info.type = c.SDL_GPU_TEXTURETYPE_2D;
+    info.format = self.swapchain_format;
+    info.usage = c.SDL_GPU_TEXTUREUSAGE_COLOR_TARGET;
+    info.width = width;
+    info.height = height;
+    info.layer_count_or_depth = 1;
+    info.num_levels = 1;
+    info.sample_count = c.SDL_GPU_SAMPLECOUNT_1;
+    self.capture_tex = c.SDL_CreateGPUTexture(self.device, &info) orelse return error.GpuCreate;
+    self.capture_tex_w = width;
+    self.capture_tex_h = height;
+}
+
+fn ensureCaptureXfer(self: *SdlBackend, size: u32) !void {
+    if (self.capture_xfer != null and self.capture_xfer_size >= size) return;
+    if (self.capture_xfer) |x| c.SDL_ReleaseGPUTransferBuffer(self.device, x);
+    var info = c.SDL_GPUTransferBufferCreateInfo{
+        .usage = c.SDL_GPU_TRANSFERBUFFERUSAGE_DOWNLOAD,
+        .size = size,
+        .props = 0,
+    };
+    self.capture_xfer = c.SDL_CreateGPUTransferBuffer(self.device, &info) orelse return error.GpuCreate;
+    self.capture_xfer_size = size;
+}
+
+fn writeCapturePpm(self: *SdlBackend, pixels: []const u8, width: u32, height: u32) !void {
+    const dir = self.capture_dir orelse return;
+    const bpp = c.SDL_GPUTextureFormatTexelBlockSize(self.swapchain_format);
+    if (bpp != 4) return error.UnsupportedCaptureFormat;
+
+    var tmp_buf: [4096]u8 = undefined;
+    var final_buf: [4096]u8 = undefined;
+    const tmp_path = std.fmt.bufPrintZ(&tmp_buf, "{s}/latest.ppm.tmp", .{dir}) catch return error.CapturePathTooLong;
+    const final_path = std.fmt.bufPrintZ(&final_buf, "{s}/latest.ppm", .{dir}) catch return error.CapturePathTooLong;
+
+    const fd_rc = linux.open(tmp_path.ptr, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, 0o644);
+    const fd_s: isize = @bitCast(fd_rc);
+    if (fd_s < 0) return error.CaptureWriteFailed;
+    const fd: c_int = @intCast(fd_s);
+    defer _ = linux.close(fd);
+
+    var header: [64]u8 = undefined;
+    const hdr = std.fmt.bufPrint(&header, "P6\n{d} {d}\n255\n", .{ width, height }) catch return error.CaptureWriteFailed;
+    try writeAllFd(fd, hdr);
+
+    const row_rgb = try self.alloc.alloc(u8, @as(usize, width) * 3);
+    defer self.alloc.free(row_rgb);
+    for (0..height) |row| {
+        const row_start = @as(usize, row) * @as(usize, width) * 4;
+        const src = pixels[row_start .. row_start + @as(usize, width) * 4];
+        var x: usize = 0;
+        while (x < @as(usize, width)) : (x += 1) {
+            const si = x * 4;
+            const di = x * 3;
+            switch (self.swapchain_format) {
+                c.SDL_GPU_TEXTUREFORMAT_R8G8B8A8_UNORM,
+                c.SDL_GPU_TEXTUREFORMAT_R8G8B8A8_UNORM_SRGB,
+                => {
+                    row_rgb[di + 0] = src[si + 0];
+                    row_rgb[di + 1] = src[si + 1];
+                    row_rgb[di + 2] = src[si + 2];
+                },
+                c.SDL_GPU_TEXTUREFORMAT_B8G8R8A8_UNORM,
+                c.SDL_GPU_TEXTUREFORMAT_B8G8R8A8_UNORM_SRGB,
+                => {
+                    row_rgb[di + 0] = src[si + 2];
+                    row_rgb[di + 1] = src[si + 1];
+                    row_rgb[di + 2] = src[si + 0];
+                },
+                else => return error.UnsupportedCaptureFormat,
+            }
+        }
+        try writeAllFd(fd, row_rgb);
+    }
+
+    const rr = linux.rename(tmp_path.ptr, final_path.ptr);
+    const rs: isize = @bitCast(rr);
+    if (rs < 0) return error.CaptureWriteFailed;
+    self.capture_frame += 1;
+}
+
+fn writeAllFd(fd: c_int, bytes: []const u8) !void {
+    var off: usize = 0;
+    while (off < bytes.len) {
+        const rc = linux.write(fd, bytes[off..].ptr, bytes.len - off);
+        const n: isize = @bitCast(rc);
+        if (n < 0) {
+            if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+            return error.CaptureWriteFailed;
+        }
+        if (n == 0) return error.CaptureWriteFailed;
+        off += @intCast(n);
+    }
+}
+
+fn openTraceFile(path: []const u8) c_int {
+    var buf: [4096]u8 = undefined;
+    const z = std.fmt.bufPrintZ(&buf, "{s}", .{path}) catch return 2;
+    const fd_rc = linux.open(z.ptr, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, 0o644);
+    const fd_s: isize = @bitCast(fd_rc);
+    if (fd_s < 0) return 2;
+    return @intCast(fd_s);
+}
+
+fn writeAllFdIgnore(fd: c_int, bytes: []const u8) void {
+    var off: usize = 0;
+    while (off < bytes.len) {
+        const rc = linux.write(fd, bytes[off..].ptr, bytes.len - off);
+        const n: isize = @bitCast(rc);
+        if (n < 0) {
+            if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+            return;
+        }
+        if (n == 0) return;
+        off += @intCast(n);
+    }
+}
+
+fn tracef(self: *SdlBackend, comptime fmt: []const u8, args: anytype) void {
+    if (!self.trace_enabled or self.trace_fd < 0) return;
+    var buf: [1024]u8 = undefined;
+    const line = std.fmt.bufPrint(&buf, fmt ++ "\n", args) catch return;
+    writeAllFdIgnore(self.trace_fd, line);
+}
+
+fn traceFrame(
+    self: *SdlBackend,
+    cells: u32,
+    dirty_cells: u32,
+    dirty_ranges: u32,
+    sw: u32,
+    sh: u32,
+    atlas_uploaded: bool,
+    t0: i128,
+    t_cmd: i128,
+    t_acquired: i128,
+    t_mapped: i128,
+    t_built: i128,
+    t_atlas: i128,
+    t_uploaded: i128,
+    t_drawn: i128,
+    t_submit0: i128,
+    t_done: i128,
+) void {
+    self.tracef(
+        "sdl.frame n={d} size={d}x{d} cells={d} dirty={d} ranges={d} atlas={} cmd_us={d} acquire_us={d} map_us={d} build_us={d} atlas_us={d} upload_us={d} draw_us={d} submit_or_capture_us={d} total_us={d}",
+        .{
+            self.trace_frame,
+            sw,
+            sh,
+            cells,
+            dirty_cells,
+            dirty_ranges,
+            atlas_uploaded,
+            nsToUs(t_cmd - t0),
+            nsToUs(t_acquired - t_cmd),
+            nsToUs(t_mapped - t_acquired),
+            nsToUs(t_built - t_mapped),
+            nsToUs(t_atlas - t_built),
+            nsToUs(t_uploaded - t_atlas),
+            nsToUs(t_drawn - t_uploaded),
+            nsToUs(t_done - t_submit0),
+            nsToUs(t_done - t0),
+        },
+    );
+}
+
+// no-ops for the terminal-protocol surface; SDL needs none of them.
+pub fn setMouseMode(self: *SdlBackend, writer: *std.Io.Writer, enable: bool) !void {
+    _ = self;
+    _ = writer;
+    _ = enable;
+}
+pub fn enterAltScreen(self: *SdlBackend, writer: *std.Io.Writer) !void {
+    _ = self;
+    _ = writer;
+}
+pub fn exitAltScreen(self: *SdlBackend, writer: *std.Io.Writer) !void {
+    _ = self;
+    _ = writer;
+}
+pub fn queryTerminal(self: *SdlBackend, writer: *std.Io.Writer, timeout: std.Io.Duration) !void {
+    _ = self;
+    _ = writer;
+    _ = timeout;
+}
+pub fn requestSystemClipboard(self: *SdlBackend, writer: *std.Io.Writer) !void {
+    _ = self;
+    _ = writer;
+    // ponytail: the terminal backend gets the clipboard asynchronously via an
+    // OSC 52 reply (.paste event). SDL could read it synchronously here, but the
+    // result can't be posted without a loop pointer — left as a TODO for now.
+}
+pub fn copyToSystemClipboard(self: *SdlBackend, writer: *std.Io.Writer, text: []const u8, encode_allocator: std.mem.Allocator) !void {
+    _ = self;
+    _ = writer;
+    _ = encode_allocator;
+    var buf: [4096]u8 = undefined;
+    const z = std.fmt.bufPrintZ(&buf, "{s}", .{text}) catch return;
+    _ = c.SDL_SetClipboardText(z.ptr);
+}
+pub fn transmitPreEncodedImage(
+    self: *SdlBackend,
+    writer: *std.Io.Writer,
+    bytes: []const u8,
+    width: u16,
+    height: u16,
+    format: vaxis.Image.TransmitFormat,
+) !vaxis.Image {
+    _ = self;
+    _ = writer;
+    _ = bytes;
+    _ = width;
+    _ = height;
+    _ = format;
+    return error.NoGraphicsCapability;
+}
+
+// ---- internals ----
+
+fn ensureVbuf(self: *SdlBackend, cells: u32) !void {
+    if (self.vbuf_cells == cells and cells != 0) return;
+    if (self.vbuf_cells != 0) {
+        c.SDL_ReleaseGPUBuffer(self.device, self.vbuf);
+        c.SDL_ReleaseGPUTransferBuffer(self.device, self.vxfer);
+    }
+    self.alloc.free(self.cell_keys);
+    self.alloc.free(self.dirty_ranges);
+    self.cell_keys = &.{};
+    self.dirty_ranges = &.{};
+    self.cell_cache_valid = false;
+    self.last_render_w = 0;
+    self.last_render_h = 0;
+    const size = cells * @sizeOf(CellInstance);
+    var vb_info = c.SDL_GPUBufferCreateInfo{ .usage = c.SDL_GPU_BUFFERUSAGE_VERTEX, .size = size, .props = 0 };
+    self.vbuf = c.SDL_CreateGPUBuffer(self.device, &vb_info) orelse return error.GpuCreate;
+    var xf_info = c.SDL_GPUTransferBufferCreateInfo{ .usage = c.SDL_GPU_TRANSFERBUFFERUSAGE_UPLOAD, .size = size, .props = 0 };
+    self.vxfer = c.SDL_CreateGPUTransferBuffer(self.device, &xf_info) orelse return error.GpuCreate;
+    self.cell_keys = try self.alloc.alloc(CellKey, cells);
+    self.dirty_ranges = try self.alloc.alloc(DirtyRange, cells);
+    self.vbuf_cells = cells;
+}
+
+fn resolveColor(self: *const SdlBackend, col: vaxis.Color, is_bg: bool) [3]u8 {
+    return switch (col) {
+        .default => if (is_bg) self.bg_default else self.fg_default,
+        .index => |i| ansi[i & 15],
+        .rgb => |r| r,
+    };
+}
+
+fn packRgb(rgb: [3]u8) u32 {
+    return (@as(u32, rgb[0]) << 16) | (@as(u32, rgb[1]) << 8) | @as(u32, rgb[2]);
+}
+
+fn unpackRgb(rgb: u32) [3]u8 {
+    return .{
+        @intCast((rgb >> 16) & 0xff),
+        @intCast((rgb >> 8) & 0xff),
+        @intCast(rgb & 0xff),
+    };
+}
+
+fn isDefaultColor(color: vaxis.Color) bool {
+    return switch (color) {
+        .default => true,
+        else => false,
+    };
+}
+
+// Decode the first codepoint of a UTF-8 grapheme; 0x20 (" ") on failure/empty.
+fn firstCp(s: []const u8) u32 {
+    if (s.len == 0) return ' ';
+    const cp = std.unicode.utf8Decode(s[0 .. std.unicode.utf8ByteSequenceLength(s[0]) catch return ' ']) catch return ' ';
+    return @intCast(cp);
+}
+
+fn cellKey(self: *const SdlBackend, cell: vaxis.Cell) CellKey {
+    if (cell.char.grapheme.len == 0 and
+        isDefaultColor(cell.style.fg) and
+        isDefaultColor(cell.style.bg) and
+        !cell.style.reverse and
+        !cell.style.invisible and
+        !cell.style.dim)
+    {
+        return .{
+            .cp = ' ',
+            .fg = packRgb(self.fg_default),
+            .bg = packRgb(self.bg_default),
+        };
+    }
+
+    var fg = self.resolveColor(cell.style.fg, false);
+    var bg = self.resolveColor(cell.style.bg, true);
+    if (cell.style.reverse) {
+        const t = fg;
+        fg = bg;
+        bg = t;
+    }
+    if (cell.style.invisible) fg = bg;
+    if (cell.style.dim) {
+        fg[0] = fg[0] * 6 / 10;
+        fg[1] = fg[1] * 6 / 10;
+        fg[2] = fg[2] * 6 / 10;
+    }
+    const cp = if (cell.char.grapheme.len == 0) ' ' else firstCp(cell.char.grapheme);
+    return .{ .cp = cp, .fg = packRgb(fg), .bg = packRgb(bg) };
+}
+
+fn sameCellKey(a: CellKey, b: CellKey) bool {
+    return a.cp == b.cp and a.fg == b.fg and a.bg == b.bg;
+}
+
+fn addDirtyRange(self: *SdlBackend, range_count: *u32, cell_index: u32) void {
+    if (range_count.* > 0) {
+        const last = &self.dirty_ranges[range_count.* - 1];
+        if (last.start + last.count == cell_index) {
+            last.count += 1;
+            return;
+        }
+    }
+    self.dirty_ranges[range_count.*] = .{ .start = cell_index, .count = 1 };
+    range_count.* += 1;
+}
+
+fn ensureGlyph(self: *SdlBackend, cp: u32) Slot {
+    if (self.glyphs.get(cp)) |s| return s;
+    if (self.pen_x + self.cell_w > atlas_w) {
+        self.pen_x = 0;
+        self.pen_y += self.cell_h;
+    }
+    if (self.pen_y + self.cell_h > atlas_h) return self.space_slot; // atlas full: fall back
+    const su = self.pen_x;
+    const sv = self.pen_y;
+    const out = self.atlas_stage.ptr + @as(usize, sv) * atlas_w + su;
+    _ = c.ui_font_raster(
+        self.font.?,
+        self.scale,
+        @intCast(cp),
+        out,
+        @intCast(atlas_w),
+        @intCast(self.cell_w),
+        @intCast(self.cell_h),
+        self.ascent,
+    );
+    const s = Slot{ .u = su, .v = sv };
+    self.glyphs.put(cp, s) catch return self.space_slot;
+    self.pen_x += self.cell_w;
+    self.atlas_dirty = true;
+    return s;
+}
+
+fn emitInstance(
+    self: *SdlBackend,
+    instances: [*]CellInstance,
+    cell_index: u32,
+    col: u16,
+    row: u16,
+    cw_f: f32,
+    ch_f: f32,
+    win_w: f32,
+    win_h: f32,
+    key: CellKey,
+) void {
+    // cell pixel rect (top-left origin)
+    const px0 = @as(f32, @floatFromInt(col)) * cw_f;
+    const py0 = @as(f32, @floatFromInt(row)) * ch_f;
+    const px1 = px0 + cw_f;
+    const py1 = py0 + ch_f;
+    // -> NDC (SDL GPU clip space: x right, y up; framebuffer row 0 = top)
+    const x0 = (px0 / win_w) * 2.0 - 1.0;
+    const x1 = (px1 / win_w) * 2.0 - 1.0;
+    const y0 = 1.0 - (py0 / win_h) * 2.0;
+    const y1 = 1.0 - (py1 / win_h) * 2.0;
+
+    const fg = unpackRgb(key.fg);
+    const bg = unpackRgb(key.bg);
+    const fgn: [3]f32 = .{
+        @as(f32, @floatFromInt(fg[0])) / 255.0,
+        @as(f32, @floatFromInt(fg[1])) / 255.0,
+        @as(f32, @floatFromInt(fg[2])) / 255.0,
+    };
+    const bgn: [3]f32 = .{
+        @as(f32, @floatFromInt(bg[0])) / 255.0,
+        @as(f32, @floatFromInt(bg[1])) / 255.0,
+        @as(f32, @floatFromInt(bg[2])) / 255.0,
+    };
+
+    // glyph slot (the space slot covers blanks, which sample alpha=0 → bg only)
+    const slot = if (key.cp == ' ') self.space_slot else self.ensureGlyph(key.cp);
+    const aw_f: f32 = @floatFromInt(atlas_w);
+    const ah_f: f32 = @floatFromInt(atlas_h);
+    const u_start = @as(f32, @floatFromInt(slot.u)) / aw_f;
+    const v_start = @as(f32, @floatFromInt(slot.v)) / ah_f;
+    const u_end = @as(f32, @floatFromInt(slot.u + self.cell_w)) / aw_f;
+    const v_end = @as(f32, @floatFromInt(slot.v + self.cell_h)) / ah_f;
+
+    instances[cell_index] = .{
+        .x0 = x0,
+        .y0 = y0,
+        .x1 = x1,
+        .y1 = y1,
+        .u0 = u_start,
+        .v0 = v_start,
+        .u1 = u_end,
+        .v1 = v_end,
+        .fr = fgn[0],
+        .fg = fgn[1],
+        .fb = fgn[2],
+        .br = bgn[0],
+        .bg = bgn[1],
+        .bb = bgn[2],
+    };
+}
+
+fn uploadAtlas(self: *SdlBackend, cmd: *c.SDL_GPUCommandBuffer) void {
+    const ptr = c.SDL_MapGPUTransferBuffer(self.device, self.atlas_xfer, false) orelse return;
+    const dst: [*]u8 = @ptrCast(ptr);
+    @memcpy(dst[0 .. atlas_w * atlas_h], self.atlas_stage);
+    c.SDL_UnmapGPUTransferBuffer(self.device, self.atlas_xfer);
+
+    const copy = c.SDL_BeginGPUCopyPass(cmd);
+    const src = c.SDL_GPUTextureTransferInfo{
+        .transfer_buffer = self.atlas_xfer,
+        .offset = 0,
+        .pixels_per_row = atlas_w,
+        .rows_per_layer = atlas_h,
+    };
+    const dstregion = c.SDL_GPUTextureRegion{
+        .texture = self.atlas_tex,
+        .mip_level = 0,
+        .layer = 0,
+        .x = 0,
+        .y = 0,
+        .z = 0,
+        .w = atlas_w,
+        .h = atlas_h,
+        .d = 1,
+    };
+    c.SDL_UploadToGPUTexture(copy, &src, &dstregion, false);
+    c.SDL_EndGPUCopyPass(copy);
+    self.atlas_dirty = false;
+}
+
+fn makePipeline(device: *c.SDL_GPUDevice, color_format: c.SDL_GPUTextureFormat) !*c.SDL_GPUGraphicsPipeline {
+    const vs = try makeShader(device, vert_spv_bytes, c.SDL_GPU_SHADERSTAGE_VERTEX, 0);
+    defer c.SDL_ReleaseGPUShader(device, vs);
+    const fs = try makeShader(device, frag_spv_bytes, c.SDL_GPU_SHADERSTAGE_FRAGMENT, 1);
+    defer c.SDL_ReleaseGPUShader(device, fs);
+
+    var vbuf_desc = c.SDL_GPUVertexBufferDescription{
+        .slot = 0,
+        .pitch = @sizeOf(CellInstance),
+        .input_rate = c.SDL_GPU_VERTEXINPUTRATE_INSTANCE,
+        .instance_step_rate = 0,
+    };
+    var attrs = [_]c.SDL_GPUVertexAttribute{
+        .{ .location = 0, .buffer_slot = 0, .format = c.SDL_GPU_VERTEXELEMENTFORMAT_FLOAT4, .offset = @offsetOf(CellInstance, "x0") },
+        .{ .location = 1, .buffer_slot = 0, .format = c.SDL_GPU_VERTEXELEMENTFORMAT_FLOAT4, .offset = @offsetOf(CellInstance, "u0") },
+        .{ .location = 2, .buffer_slot = 0, .format = c.SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3, .offset = @offsetOf(CellInstance, "fr") },
+        .{ .location = 3, .buffer_slot = 0, .format = c.SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3, .offset = @offsetOf(CellInstance, "br") },
+    };
+    var col_desc = c.SDL_GPUColorTargetDescription{ .format = color_format, .blend_state = std.mem.zeroes(c.SDL_GPUColorTargetBlendState) };
+
+    var info = std.mem.zeroes(c.SDL_GPUGraphicsPipelineCreateInfo);
+    info.vertex_shader = vs;
+    info.fragment_shader = fs;
+    info.primitive_type = c.SDL_GPU_PRIMITIVETYPE_TRIANGLELIST;
+    info.vertex_input_state = .{
+        .vertex_buffer_descriptions = &vbuf_desc,
+        .num_vertex_buffers = 1,
+        .vertex_attributes = &attrs,
+        .num_vertex_attributes = attrs.len,
+    };
+    info.rasterizer_state.fill_mode = c.SDL_GPU_FILLMODE_FILL;
+    info.rasterizer_state.cull_mode = c.SDL_GPU_CULLMODE_NONE;
+    info.multisample_state.sample_count = c.SDL_GPU_SAMPLECOUNT_1;
+    info.target_info = .{
+        .color_target_descriptions = &col_desc,
+        .num_color_targets = 1,
+    };
+    return c.SDL_CreateGPUGraphicsPipeline(device, &info) orelse error.GpuCreate;
+}
+
+fn makeShader(
+    device: *c.SDL_GPUDevice,
+    code: []const u8,
+    stage: c.SDL_GPUShaderStage,
+    n_samplers: u32,
+) !*c.SDL_GPUShader {
+    var info = std.mem.zeroes(c.SDL_GPUShaderCreateInfo);
+    info.code = code.ptr;
+    info.code_size = code.len;
+    info.entrypoint = "main";
+    info.format = c.SDL_GPU_SHADERFORMAT_SPIRV;
+    info.stage = stage;
+    info.num_samplers = n_samplers;
+    return c.SDL_CreateGPUShader(device, &info) orelse error.GpuCreate;
+}
+
+// =====================================================================
+// Tty stub — the app threads a `*std.Io.Writer` through every backend call; SDL
+// needs none of it, so we back it with /dev/null. The pointer just has to stay
+// valid for the app's lifetime.
+// =====================================================================
+
+const SdlTty = struct {
+    file: std.Io.File,
+    tty_writer: std.Io.File.Writer,
+
+    pub fn init(io: std.Io, buffer: []u8) !SdlTty {
+        const f = try std.Io.Dir.openFileAbsolute(io, "/dev/null", .{ .mode = .read_write });
+        return .{ .file = f, .tty_writer = f.writerStreaming(io, buffer) };
+    }
+    pub fn deinit(self: SdlTty, io: std.Io) void {
+        self.file.close(io);
+    }
+    pub fn writer(self: *SdlTty) *std.Io.Writer {
+        return &self.tty_writer.interface;
+    }
+};
+
+// =====================================================================
+// Event loop — polls SDL on the main thread and feeds the same `Event` union
+// the app expects onto a thread-safe queue (so per-terminal pty readers, which
+// call postEvent from their own threads, keep working unchanged).
+// =====================================================================
+
+fn SdlLoop(comptime EventType: type) type {
+    return struct {
+        const Self = @This();
+
+        io: std.Io,
+        vx: *SdlBackend,
+        queue: vaxis.Queue(EventType, 512),
+        // live keyboard modifier state (updated on every key down/up), so
+        // SDL_TEXT_INPUT — which carries no modifiers — can attach them.
+        live_mods: vaxis.Key.Modifiers = .{},
+        last_cols: u16 = 0,
+        last_rows: u16 = 0,
+        // test-mode stdin reader task + quit flag
+        reader: ?std.Io.Future(void) = null,
+        should_quit: bool = false,
+
+        pub fn init(io: std.Io, tty: *SdlTty, vx: *SdlBackend) Self {
+            _ = tty;
+            return .{ .io = io, .vx = vx, .queue = .init(io) };
+        }
+
+        pub fn start(self: *Self) !void {
+            if (self.vx.test_mode) {
+                setStdinRaw() catch {};
+                // e2e: spawn a stdin reader that parses terminal escape sequences
+                // (vaxis.Parser) into Key/Mouse/Winsize events and posts them.
+                self.reader = try self.io.concurrent(Self.stdinRun, .{self});
+                return;
+            }
+            // start delivering text input events (for printable keys)
+            _ = c.SDL_StartTextInput(self.vx.sdl_window);
+            // report the initial window size so the app sizes its grid
+            self.postWinsize();
+        }
+        pub fn stop(self: *Self) void {
+            if (self.vx.test_mode) {
+                self.should_quit = true;
+                if (self.reader) |*r| r.await(self.io);
+                self.reader = null;
+                return;
+            }
+        }
+        pub fn installResizeHandler(self: *Self) !void {
+            if (self.vx.test_mode) {
+                var act = posix.Sigaction{
+                    .handler = .{ .handler = winchHandler },
+                    .mask = switch (builtin.os.tag) {
+                        .macos => 0,
+                        else => posix.sigemptyset(),
+                    },
+                    .flags = 0,
+                };
+                posix.sigaction(posix.SIG.WINCH, &act, null);
+                return;
+            }
+        }
+
+        pub fn postEvent(self: *Self, event: EventType) !void {
+            try self.queue.push(event);
+            if (!self.vx.test_mode) {
+                // wake a blocking SDL_WaitEventTimeout in nextEvent (pty reads come
+                // from other threads; without this the app wouldn't notice them
+                // until the timeout elapses).
+                var sev = std.mem.zeroes(c.SDL_Event);
+                sev.type = c.SDL_EVENT_USER;
+                _ = c.SDL_PushEvent(&sev);
+            }
+        }
+
+        pub fn nextEvent(self: *Self) !EventType {
+            if (self.vx.test_mode) return try self.queue.pop();
+            while (true) {
+                // pty/queued events first (they're already decoded)
+                if (try self.queue.tryPop()) |ev| {
+                    if (self.vx.trace_enabled) self.vx.tracef("sdl.event source=queue wait_us=0", .{});
+                    return ev;
+                }
+                var sev = std.mem.zeroes(c.SDL_Event);
+                const t0 = nowNs();
+                if (c.SDL_WaitEventTimeout(&sev, 16)) {
+                    const t1 = nowNs();
+                    if (try self.dispatch(&sev)) |ev| {
+                        if (self.vx.trace_enabled) self.vx.tracef("sdl.event source=sdl type={d} wait_us={d}", .{ sev.type, nsToUs(t1 - t0) });
+                        return ev;
+                    }
+                    // else: an SDL event we ignore — loop and re-check the queue
+                } else {
+                    if (self.vx.trace_enabled) self.vx.tracef("sdl.event source=tick wait_us={d}", .{nsToUs(nowNs() - t0)});
+                    return .tick; // timeout: a no-op that drives a render
+                }
+            }
+        }
+
+        pub fn tryEvent(self: *Self) !?EventType {
+            return try self.queue.tryPop();
+        }
+
+        fn postWinsize(self: *Self) void {
+            if (self.vx.test_mode) {
+                // read winsize from stdin (fd 0 = the pty slave)
+                var ws: posix.winsize = std.mem.zeroes(posix.winsize);
+                const iorc = posix.system.ioctl(0, posix.T.IOCGWINSZ, @intFromPtr(&ws));
+                if (iorc < 0) return; // fd 0 is not a pty
+                const cols: u16 = ws.col;
+                const rows: u16 = ws.row;
+                if (cols == 0 or rows == 0 or cols > 1000 or rows > 1000) return;
+                if (cols == self.last_cols and rows == self.last_rows) return;
+                self.last_cols = cols;
+                self.last_rows = rows;
+                self.postEvent(.{ .winsize = .{
+                    .cols = cols,
+                    .rows = rows,
+                    .x_pixel = ws.xpixel,
+                    .y_pixel = ws.ypixel,
+                } }) catch {};
+                return;
+            }
+            var pw: c_int = 0;
+            var ph: c_int = 0;
+            _ = c.SDL_GetWindowSizeInPixels(self.vx.sdl_window, &pw, &ph);
+            const cw: u32 = self.vx.cell_w;
+            const ch: u32 = self.vx.cell_h;
+            const cols: u16 = @intCast(@max(1, @divTrunc(@as(u32, @intCast(pw)), cw)));
+            const rows: u16 = @intCast(@max(1, @divTrunc(@as(u32, @intCast(ph)), ch)));
+            if (cols == self.last_cols and rows == self.last_rows) return;
+            self.last_cols = cols;
+            self.last_rows = rows;
+            self.postEvent(.{ .winsize = .{
+                .cols = cols,
+                .rows = rows,
+                .x_pixel = @intCast(pw),
+                .y_pixel = @intCast(ph),
+            } }) catch {};
+        }
+
+        fn dispatch(self: *Self, sev: *const c.SDL_Event) !?EventType {
+            switch (sev.type) {
+                c.SDL_EVENT_QUIT, c.SDL_EVENT_WINDOW_CLOSE_REQUESTED => return .quit,
+                c.SDL_EVENT_WINDOW_RESIZED, c.SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED => {
+                    self.postWinsize();
+                    return null;
+                },
+                c.SDL_EVENT_WINDOW_EXPOSED => return .tick,
+                c.SDL_EVENT_KEY_DOWN => {
+                    const k = sev.key;
+                    self.live_mods = sdlMods(k.mod);
+                    return self.keyDown(k.key, k.mod);
+                },
+                c.SDL_EVENT_KEY_UP => {
+                    self.live_mods = sdlMods(sev.key.mod);
+                    return null;
+                },
+                c.SDL_EVENT_TEXT_INPUT => {
+                    const tptr: [*c]const u8 = sev.text.text;
+                    if (tptr == null) return null;
+                    var tlen: usize = 0;
+                    while (tptr[tlen] != 0) : (tlen += 1) {}
+                    const text: []const u8 = tptr[0..tlen];
+                    if (text.len == 0) return null;
+                    const len = std.unicode.utf8ByteSequenceLength(text[0]) catch return null;
+                    if (len > text.len) return null;
+                    const cp = std.unicode.utf8Decode(text[0..len]) catch return null;
+                    return EventType{ .key_press = .{
+                        .codepoint = @intCast(cp),
+                        .text = text[0..len],
+                        .mods = self.live_mods,
+                    } };
+                },
+                c.SDL_EVENT_MOUSE_BUTTON_DOWN, c.SDL_EVENT_MOUSE_BUTTON_UP => {
+                    const b = sev.button;
+                    const t: vaxis.Mouse.Type = if (b.down) .press else .release;
+                    const button = mouseButton(b.button) orelse return null;
+                    const col = @as(i16, @intCast(@divTrunc(@as(i32, @intFromFloat(b.x)), @as(i32, @intCast(self.vx.cell_w)))));
+                    const row = @as(i16, @intCast(@divTrunc(@as(i32, @intFromFloat(b.y)), @as(i32, @intCast(self.vx.cell_h)))));
+                    return EventType{ .mouse = .{
+                        .col = col,
+                        .row = row,
+                        .button = button,
+                        .mods = sdlMouseMods(self.live_mods),
+                        .type = t,
+                    } };
+                },
+                c.SDL_EVENT_MOUSE_MOTION => {
+                    const m = sev.motion;
+                    // drag = motion with a button held; the app keys selection
+                    // extension off .drag (it never reads .motion).
+                    const held = heldButton(m.state);
+                    const t: vaxis.Mouse.Type = if (held != null) .drag else .motion;
+                    const button = held orelse .none;
+                    const col = @as(i16, @intCast(@divTrunc(@as(i32, @intFromFloat(m.x)), @as(i32, @intCast(self.vx.cell_w)))));
+                    const row = @as(i16, @intCast(@divTrunc(@as(i32, @intFromFloat(m.y)), @as(i32, @intCast(self.vx.cell_h)))));
+                    return EventType{ .mouse = .{
+                        .col = col,
+                        .row = row,
+                        .button = button,
+                        .mods = sdlMouseMods(self.live_mods),
+                        .type = t,
+                    } };
+                },
+                c.SDL_EVENT_MOUSE_WHEEL => {
+                    const w = sev.wheel;
+                    const dy = w.y;
+                    const button: vaxis.Mouse.Button = if (dy > 0) .wheel_up else if (dy < 0) .wheel_down else return null;
+                    const col = @as(i16, @intCast(@divTrunc(@as(i32, @intFromFloat(w.mouse_x)), @as(i32, @intCast(self.vx.cell_w)))));
+                    const row = @as(i16, @intCast(@divTrunc(@as(i32, @intFromFloat(w.mouse_y)), @as(i32, @intCast(self.vx.cell_h)))));
+                    return EventType{ .mouse = .{
+                        .col = col,
+                        .row = row,
+                        .button = button,
+                        .mods = sdlMouseMods(self.live_mods),
+                        .type = .press,
+                    } };
+                },
+                else => return null,
+            }
+        }
+
+        // KEY_DOWN: special keys + ctrl/alt shortcuts. Plain printable keys
+        // arrive as SDL_TEXT_INPUT instead (so shift/layout map correctly).
+        fn keyDown(self: *Self, sym: c.SDL_Keycode, mod: c.SDL_Keymod) ?EventType {
+            const mods = sdlMods(mod);
+            const cp: u21 = switch (sym) {
+                c.SDLK_RETURN => vaxis.Key.enter,
+                c.SDLK_KP_ENTER => vaxis.Key.enter,
+                c.SDLK_BACKSPACE => vaxis.Key.backspace,
+                c.SDLK_TAB => vaxis.Key.tab,
+                c.SDLK_ESCAPE => vaxis.Key.escape,
+                c.SDLK_SPACE => ' ',
+                c.SDLK_LEFT => vaxis.Key.left,
+                c.SDLK_RIGHT => vaxis.Key.right,
+                c.SDLK_UP => vaxis.Key.up,
+                c.SDLK_DOWN => vaxis.Key.down,
+                c.SDLK_HOME => vaxis.Key.home,
+                c.SDLK_END => vaxis.Key.end,
+                c.SDLK_PAGEUP => vaxis.Key.page_up,
+                c.SDLK_PAGEDOWN => vaxis.Key.page_down,
+                c.SDLK_INSERT => vaxis.Key.insert,
+                c.SDLK_DELETE => vaxis.Key.delete,
+                c.SDLK_F1 => vaxis.Key.f1,
+                c.SDLK_F2 => vaxis.Key.f2,
+                c.SDLK_F3 => vaxis.Key.f3,
+                c.SDLK_F4 => vaxis.Key.f4,
+                c.SDLK_F5 => vaxis.Key.f5,
+                c.SDLK_F6 => vaxis.Key.f6,
+                c.SDLK_F7 => vaxis.Key.f7,
+                c.SDLK_F8 => vaxis.Key.f8,
+                c.SDLK_F9 => vaxis.Key.f9,
+                c.SDLK_F10 => vaxis.Key.f10,
+                c.SDLK_F11 => vaxis.Key.f11,
+                c.SDLK_F12 => vaxis.Key.f12,
+                else => blk: {
+                    // letters / digits / punctuation: only emit on a modifier
+                    // shortcut (ctrl/alt/gui); plain printable goes via TEXT_INPUT.
+                    const has_mod = (mod & (c.SDL_KMOD_CTRL | c.SDL_KMOD_ALT | c.SDL_KMOD_GUI)) != 0;
+                    if (!has_mod) break :blk 0;
+                    if (sym >= 'a' and sym <= 'z') break :blk @intCast(sym);
+                    if (sym >= '0' and sym <= '9') break :blk @intCast(sym);
+                    if (sym < 128) break :blk @intCast(sym);
+                    break :blk 0;
+                },
+            };
+            if (cp == 0) return null;
+            _ = self;
+            return EventType{ .key_press = .{ .codepoint = cp, .mods = mods } };
+        }
+
+        // ---- test-mode stdin reader ----
+        // Parses terminal escape sequences from fd 0 (the pty slave) into the
+        // app's Event union and posts them to the queue. Identical to vaxis's
+        // ttyRun but reading from stdin instead of /dev/tty, and checking a
+        // SIGWINCH flag for resizes.
+        fn stdinRun(self: *Self) void {
+            self.stdinRunTyped() catch {};
+        }
+
+        fn stdinRunTyped(self: *Self) !void {
+            // post the initial winsize (read from stdin)
+            self.postWinsize();
+
+            var parser: vaxis.Parser = .{};
+            var cache: vaxis.GraphemeCache = .{};
+            var buf: [1024]u8 = undefined;
+            var read_start: usize = 0;
+
+            while (!self.should_quit) {
+                // check for a pending SIGWINCH (flag set by the signal handler)
+                if (g_winsize_dirty) {
+                    g_winsize_dirty = false;
+                    self.postWinsize();
+                }
+
+                var fds = [_]posix.pollfd{.{ .fd = 0, .events = posix.POLL.IN, .revents = 0 }};
+                _ = posix.poll(&fds, 50) catch continue;
+                if ((fds[0].revents & posix.POLL.IN) == 0) continue;
+
+                const rc = linux.read(0, buf[read_start..].ptr, buf.len - read_start);
+                const n: isize = @bitCast(rc);
+                if (n < 0) {
+                    if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+                    break;
+                }
+                if (n == 0) break;
+                const len: usize = read_start + @as(usize, @intCast(n));
+                var seq_start: usize = 0;
+                while (seq_start < len) {
+                    const result = parser.parse(buf[seq_start..len], null) catch break;
+                    if (result.n == 0) {
+                        // partial sequence — shift to front of buffer
+                        const initial = seq_start;
+                        while (seq_start < len) : (seq_start += 1) {
+                            buf[seq_start - initial] = buf[seq_start];
+                        }
+                        read_start = len - initial;
+                        break;
+                    }
+                    read_start = 0;
+                    seq_start += result.n;
+                    const event = result.event orelse continue;
+                    // convert vaxis.Event → app EventType and post
+                    switch (event) {
+                        .key_press => |key| {
+                            var mut_key = key;
+                            if (key.text) |text| mut_key.text = cache.put(text);
+                            try self.postEvent(.{ .key_press = mut_key });
+                        },
+                        .mouse => |mouse| try self.postEvent(.{ .mouse = mouse }),
+                        .winsize => |ws| try self.postEvent(.{ .winsize = ws }),
+                        .paste => |text| {
+                            try self.postEvent(.{ .paste = text });
+                        },
+                        else => {},
+                    }
+                }
+            }
+        }
+    };
+}
+
+fn setStdinRaw() !void {
+    var term = try posix.tcgetattr(0);
+    term.iflag.BRKINT = false;
+    term.iflag.ICRNL = false;
+    term.iflag.INPCK = false;
+    term.iflag.ISTRIP = false;
+    term.iflag.IXON = false;
+    term.oflag.OPOST = false;
+    term.lflag.ECHO = false;
+    term.lflag.ICANON = false;
+    term.lflag.IEXTEN = false;
+    term.lflag.ISIG = false;
+    term.cc[@intFromEnum(linux.V.MIN)] = 1;
+    term.cc[@intFromEnum(linux.V.TIME)] = 0;
+    try posix.tcsetattr(0, .NOW, term);
+}
+
+// ---- test-mode SIGWINCH handler ----
+// Signal handlers can't take closures, so we just set a flag; the stdin reader
+// (SdlLoop.stdinRunTyped) checks it and reads + posts the new winsize.
+var g_winsize_dirty: bool = false;
+
+fn winchHandler(_: posix.SIG) callconv(.c) void {
+    g_winsize_dirty = true;
+}
+
+fn sdlMouseMods(km: vaxis.Key.Modifiers) vaxis.Mouse.Modifiers {
+    return .{ .shift = km.shift, .alt = km.alt, .ctrl = km.ctrl };
+}
+
+fn sdlMods(mod: c.SDL_Keymod) vaxis.Key.Modifiers {
+    return .{
+        .shift = (mod & c.SDL_KMOD_SHIFT) != 0,
+        .ctrl = (mod & c.SDL_KMOD_CTRL) != 0,
+        .alt = (mod & c.SDL_KMOD_ALT) != 0,
+        .super = (mod & c.SDL_KMOD_GUI) != 0,
+    };
+}
+
+fn mouseButton(b: u8) ?vaxis.Mouse.Button {
+    return switch (b) {
+        1 => .left,
+        2 => .middle,
+        3 => .right,
+        else => null,
+    };
+}
+
+// the SDL mouse button bitmask (`state` in a motion event) → the single button
+// being dragged with, if any. Left wins on a chord, matching the app's
+// "later buttons win" only loosely — good enough for selection drags.
+fn heldButton(state: u32) ?vaxis.Mouse.Button {
+    if ((state & c.SDL_BUTTON_LMASK) != 0) return .left;
+    if ((state & c.SDL_BUTTON_MMASK) != 0) return .middle;
+    if ((state & c.SDL_BUTTON_RMASK) != 0) return .right;
+    return null;
+}
diff --git a/ui_vaxis.zig b/ui_vaxis.zig
new file mode 100644
index 00000000..61bf51ca
--- /dev/null
+++ b/ui_vaxis.zig
@@ -0,0 +1,33 @@
+// The UI abstraction surface. `main.zig` and `image.zig` program against THIS
+// module (importing `"ui"`) instead of libvaxis directly, so the rendering +
+// input backend can be swapped at build time (`-Dui=vaxis|sdl`).
+//
+// This is the *vaxis* (real terminal) backend: a transparent passthrough. It
+// re-exports the libvaxis declarations the app uses, so every type (`Key`,
+// `Mouse`, `Window`, `Cell`, …), the `Vaxis` renderer/loop, `Tty`, and `init`
+// are exactly libvaxis's. All the UI logic therefore behaves identically to the
+// pre-refactor app — this file exists purely as the seam a different backend
+// (`ui_sdl.zig`) can replace.
+//
+// (Zig 0.16 dropped `pub usingnamespace`, so the re-export is explicit.)
+const vaxis = @import("vaxis");
+
+pub const Vaxis = vaxis.Vaxis;
+pub const Tty = vaxis.Tty;
+pub const Loop = vaxis.Loop;
+pub const init = vaxis.init;
+
+pub const Key = vaxis.Key;
+pub const Mouse = vaxis.Mouse;
+pub const Winsize = vaxis.Winsize;
+pub const Color = vaxis.Color;
+pub const Style = vaxis.Style;
+pub const Cell = vaxis.Cell;
+pub const Segment = vaxis.Segment;
+pub const Window = vaxis.Window;
+pub const Screen = vaxis.Screen;
+pub const Image = vaxis.Image;
+pub const Event = vaxis.Event;
+pub const Capabilities = vaxis.Capabilities;
+pub const Options = vaxis.Options;
+pub const CursorShape = vaxis.Cell.CursorShape;
diff --git a/vendor/stb/font.c b/vendor/stb/font.c
new file mode 100644
index 00000000..6c5106f6
--- /dev/null
+++ b/vendor/stb/font.c
@@ -0,0 +1,81 @@
+// stb_truetype wrapper for ui_sdl.zig. See font.h. Compiled into the SDL UI
+// backend module alongside stb_truetype_impl.c (which defines the impl).
+#include "font.h"
+#include "stb_truetype.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+struct UIFont {
+    stbtt_fontinfo info;
+    const uint8_t *data;
+};
+
+UIFont *ui_font_new(const uint8_t *data, int32_t len) {
+    if (!data || len <= 0) return NULL;
+    UIFont *f = (UIFont *)calloc(1, sizeof(UIFont));
+    if (!f) return NULL;
+    f->data = data;
+    int offset = stbtt_GetFontOffsetForIndex(data, 0);
+    if (offset < 0 || !stbtt_InitFont(&f->info, (const unsigned char *)data, offset)) {
+        free(f);
+        return NULL;
+    }
+    return f;
+}
+
+void ui_font_free(UIFont *f) {
+    free(f);
+}
+
+float ui_font_scale_for_height(UIFont *f, float px) {
+    return stbtt_ScaleForPixelHeight(&f->info, px);
+}
+
+void ui_font_cell_metrics(UIFont *f, float scale, int32_t *cell_w, int32_t *cell_h, int32_t *ascent) {
+    int asc = 0, desc = 0, gap = 0;
+    stbtt_GetFontVMetrics(&f->info, &asc, &desc, &gap);
+    int a = (int)(asc * scale + 0.5f);
+    int d = (int)(-desc * scale + 0.5f);
+    int g = (int)(gap * scale + 0.5f);
+    *ascent = a;
+    *cell_h = a + d + g;
+    if (*cell_h < 1) *cell_h = 1;
+    // monospace advance of 'M'
+    int adv = 0, lsb = 0;
+    stbtt_GetCodepointHMetrics(&f->info, 'M', &adv, &lsb);
+    int w = (int)(adv * scale + 0.5f);
+    if (w < 1) w = 1;
+    *cell_w = w;
+}
+
+int ui_font_raster(UIFont *f, float scale, int32_t cp,
+                   uint8_t *out, int32_t stride, int32_t cell_w, int32_t cell_h,
+                   int32_t ascent) {
+    if (!out || cell_w <= 0 || cell_h <= 0) return 0;
+    // zero the cell
+    for (int y = 0; y < cell_h; y++)
+        memset(out + (size_t)y * stride, 0, (size_t)cell_w);
+
+    int w = 0, h = 0, xoff = 0, yoff = 0;
+    unsigned char *bm = stbtt_GetCodepointBitmap(&f->info, scale, scale, cp, &w, &h, &xoff, &yoff);
+    if (!bm || w <= 0 || h <= 0) {
+        if (bm) stbtt_FreeBitmap(bm, NULL);
+        return 0;
+    }
+    // origin = (0, baseline=ascent); glyph top-left = (xoff, ascent + yoff).
+    int gx = xoff;
+    int gy = ascent + yoff;
+    for (int y = 0; y < h; y++) {
+        int dy = gy + y;
+        if (dy < 0 || dy >= cell_h) continue;
+        for (int x = 0; x < w; x++) {
+            int dx = gx + x;
+            if (dx < 0 || dx >= cell_w) continue;
+            uint8_t v = bm[y * w + x];
+            if (v) out[(size_t)dy * stride + dx] = v;
+        }
+    }
+    stbtt_FreeBitmap(bm, NULL);
+    return 1;
+}
diff --git a/vendor/stb/font.h b/vendor/stb/font.h
new file mode 100644
index 00000000..93bbac8d
--- /dev/null
+++ b/vendor/stb/font.h
@@ -0,0 +1,41 @@
+// Tiny C shim over stb_truetype, so ui_sdl.zig can @cInclude a small header
+// instead of feeding the whole single-header lib to translate-c. The
+// implementation (font.c) pulls in stb_truetype.h (declarations only —
+// stb_truetype_impl.c defines STB_TRUETYPE_IMPLEMENTATION once elsewhere).
+//
+// A "font" is an opaque handle owning a stbtt_fontinfo; all rasterization goes
+// through these functions so the Zig side never touches stb internals.
+#ifndef UI_FONT_H
+#define UI_FONT_H
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct UIFont UIFont;
+
+// Parse the embedded TTF. `data` must stay alive for the lifetime of the font.
+// Returns NULL on failure.
+UIFont *ui_font_new(const uint8_t *data, int32_t len);
+
+// Font metrics at a given pixel height. cell_w is the monospace advance (rounded
+// up); ascent is the baseline offset from the top of a cell.
+float ui_font_scale_for_height(UIFont *f, float px);
+void ui_font_cell_metrics(UIFont *f, float scale, int32_t *cell_w, int32_t *cell_h, int32_t *ascent);
+
+// Rasterize `cp` into `out` (a cell_w*cell_h single-channel mask, row-major,
+// `stride` bytes per row). The glyph is positioned for a monospace cell: origin
+// at the baseline `ascent` pixels from the top. Pixels outside the glyph are 0.
+// Returns 1 if the glyph produced any coverage (0 for an empty/missing glyph,
+// but `out` is still zeroed).
+int ui_font_raster(UIFont *f, float scale, int32_t cp,
+                   uint8_t *out, int32_t stride, int32_t cell_w, int32_t cell_h,
+                   int32_t ascent);
+
+void ui_font_free(UIFont *f);
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/vendor/stb/stb_truetype.h b/vendor/stb/stb_truetype.h
new file mode 100644
index 00000000..bbf2284b
--- /dev/null
+++ b/vendor/stb/stb_truetype.h
@@ -0,0 +1,5077 @@
+// stb_truetype.h - v1.26 - public domain
+// authored from 2009-2021 by Sean Barrett / RAD Game Tools
+//
+// =======================================================================
+//
+//    NO SECURITY GUARANTEE -- DO NOT USE THIS ON UNTRUSTED FONT FILES
+//
+// This library does no range checking of the offsets found in the file,
+// meaning an attacker can use it to read arbitrary memory.
+//
+// =======================================================================
+//
+//   This library processes TrueType files:
+//        parse files
+//        extract glyph metrics
+//        extract glyph shapes
+//        render glyphs to one-channel bitmaps with antialiasing (box filter)
+//        render glyphs to one-channel SDF bitmaps (signed-distance field/function)
+//
+//   Todo:
+//        non-MS cmaps
+//        crashproof on bad data
+//        hinting? (no longer patented)
+//        cleartype-style AA?
+//        optimize: use simple memory allocator for intermediates
+//        optimize: build edge-list directly from curves
+//        optimize: rasterize directly from curves?
+//
+// ADDITIONAL CONTRIBUTORS
+//
+//   Mikko Mononen: compound shape support, more cmap formats
+//   Tor Andersson: kerning, subpixel rendering
+//   Dougall Johnson: OpenType / Type 2 font handling
+//   Daniel Ribeiro Maciel: basic GPOS-based kerning
+//
+//   Misc other:
+//       Ryan Gordon
+//       Simon Glass
+//       github:IntellectualKitty
+//       Imanol Celaya
+//       Daniel Ribeiro Maciel
+//
+//   Bug/warning reports/fixes:
+//       "Zer" on mollyrocket       Fabian "ryg" Giesen   github:NiLuJe
+//       Cass Everitt               Martins Mozeiko       github:aloucks
+//       stoiko (Haemimont Games)   Cap Petschulat        github:oyvindjam
+//       Brian Hook                 Omar Cornut           github:vassvik
+//       Walter van Niftrik         Ryan Griege
+//       David Gow                  Peter LaValle
+//       David Given                Sergey Popov
+//       Ivan-Assen Ivanov          Giumo X. Clanjor
+//       Anthony Pesch              Higor Euripedes
+//       Johan Duparc               Thomas Fields
+//       Hou Qiming                 Derek Vinyard
+//       Rob Loach                  Cort Stratton
+//       Kenney Phillis Jr.         Brian Costabile
+//       Ken Voskuil (kaesve)
+//
+// VERSION HISTORY
+//
+//   1.26 (2021-08-28) fix broken rasterizer
+//   1.25 (2021-07-11) many fixes
+//   1.24 (2020-02-05) fix warning
+//   1.23 (2020-02-02) query SVG data for glyphs; query whole kerning table (but only kern not GPOS)
+//   1.22 (2019-08-11) minimize missing-glyph duplication; fix kerning if both 'GPOS' and 'kern' are defined
+//   1.21 (2019-02-25) fix warning
+//   1.20 (2019-02-07) PackFontRange skips missing codepoints; GetScaleFontVMetrics()
+//   1.19 (2018-02-11) GPOS kerning, STBTT_fmod
+//   1.18 (2018-01-29) add missing function
+//   1.17 (2017-07-23) make more arguments const; doc fix
+//   1.16 (2017-07-12) SDF support
+//   1.15 (2017-03-03) make more arguments const
+//   1.14 (2017-01-16) num-fonts-in-TTC function
+//   1.13 (2017-01-02) support OpenType fonts, certain Apple fonts
+//   1.12 (2016-10-25) suppress warnings about casting away const with -Wcast-qual
+//   1.11 (2016-04-02) fix unused-variable warning
+//   1.10 (2016-04-02) user-defined fabs(); rare memory leak; remove duplicate typedef
+//   1.09 (2016-01-16) warning fix; avoid crash on outofmem; use allocation userdata properly
+//   1.08 (2015-09-13) document stbtt_Rasterize(); fixes for vertical & horizontal edges
+//   1.07 (2015-08-01) allow PackFontRanges to accept arrays of sparse codepoints;
+//                     variant PackFontRanges to pack and render in separate phases;
+//                     fix stbtt_GetFontOFfsetForIndex (never worked for non-0 input?);
+//                     fixed an assert() bug in the new rasterizer
+//                     replace assert() with STBTT_assert() in new rasterizer
+//
+//   Full history can be found at the end of this file.
+//
+// LICENSE
+//
+//   See end of file for license information.
+//
+// USAGE
+//
+//   Include this file in whatever places need to refer to it. In ONE C/C++
+//   file, write:
+//      #define STB_TRUETYPE_IMPLEMENTATION
+//   before the #include of this file. This expands out the actual
+//   implementation into that C/C++ file.
+//
+//   To make the implementation private to the file that generates the implementation,
+//      #define STBTT_STATIC
+//
+//   Simple 3D API (don't ship this, but it's fine for tools and quick start)
+//           stbtt_BakeFontBitmap()               -- bake a font to a bitmap for use as texture
+//           stbtt_GetBakedQuad()                 -- compute quad to draw for a given char
+//
+//   Improved 3D API (more shippable):
+//           #include "stb_rect_pack.h"           -- optional, but you really want it
+//           stbtt_PackBegin()
+//           stbtt_PackSetOversampling()          -- for improved quality on small fonts
+//           stbtt_PackFontRanges()               -- pack and renders
+//           stbtt_PackEnd()
+//           stbtt_GetPackedQuad()
+//
+//   "Load" a font file from a memory buffer (you have to keep the buffer loaded)
+//           stbtt_InitFont()
+//           stbtt_GetFontOffsetForIndex()        -- indexing for TTC font collections
+//           stbtt_GetNumberOfFonts()             -- number of fonts for TTC font collections
+//
+//   Render a unicode codepoint to a bitmap
+//           stbtt_GetCodepointBitmap()           -- allocates and returns a bitmap
+//           stbtt_MakeCodepointBitmap()          -- renders into bitmap you provide
+//           stbtt_GetCodepointBitmapBox()        -- how big the bitmap must be
+//
+//   Character advance/positioning
+//           stbtt_GetCodepointHMetrics()
+//           stbtt_GetFontVMetrics()
+//           stbtt_GetFontVMetricsOS2()
+//           stbtt_GetCodepointKernAdvance()
+//
+//   Starting with version 1.06, the rasterizer was replaced with a new,
+//   faster and generally-more-precise rasterizer. The new rasterizer more
+//   accurately measures pixel coverage for anti-aliasing, except in the case
+//   where multiple shapes overlap, in which case it overestimates the AA pixel
+//   coverage. Thus, anti-aliasing of intersecting shapes may look wrong. If
+//   this turns out to be a problem, you can re-enable the old rasterizer with
+//        #define STBTT_RASTERIZER_VERSION 1
+//   which will incur about a 15% speed hit.
+//
+// ADDITIONAL DOCUMENTATION
+//
+//   Immediately after this block comment are a series of sample programs.
+//
+//   After the sample programs is the "header file" section. This section
+//   includes documentation for each API function.
+//
+//   Some important concepts to understand to use this library:
+//
+//      Codepoint
+//         Characters are defined by unicode codepoints, e.g. 65 is
+//         uppercase A, 231 is lowercase c with a cedilla, 0x7e30 is
+//         the hiragana for "ma".
+//
+//      Glyph
+//         A visual character shape (every codepoint is rendered as
+//         some glyph)
+//
+//      Glyph index
+//         A font-specific integer ID representing a glyph
+//
+//      Baseline
+//         Glyph shapes are defined relative to a baseline, which is the
+//         bottom of uppercase characters. Characters extend both above
+//         and below the baseline.
+//
+//      Current Point
+//         As you draw text to the screen, you keep track of a "current point"
+//         which is the origin of each character. The current point's vertical
+//         position is the baseline. Even "baked fonts" use this model.
+//
+//      Vertical Font Metrics
+//         The vertical qualities of the font, used to vertically position
+//         and space the characters. See docs for stbtt_GetFontVMetrics.
+//
+//      Font Size in Pixels or Points
+//         The preferred interface for specifying font sizes in stb_truetype
+//         is to specify how tall the font's vertical extent should be in pixels.
+//         If that sounds good enough, skip the next paragraph.
+//
+//         Most font APIs instead use "points", which are a common typographic
+//         measurement for describing font size, defined as 72 points per inch.
+//         stb_truetype provides a point API for compatibility. However, true
+//         "per inch" conventions don't make much sense on computer displays
+//         since different monitors have different number of pixels per
+//         inch. For example, Windows traditionally uses a convention that
+//         there are 96 pixels per inch, thus making 'inch' measurements have
+//         nothing to do with inches, and thus effectively defining a point to
+//         be 1.333 pixels. Additionally, the TrueType font data provides
+//         an explicit scale factor to scale a given font's glyphs to points,
+//         but the author has observed that this scale factor is often wrong
+//         for non-commercial fonts, thus making fonts scaled in points
+//         according to the TrueType spec incoherently sized in practice.
+//
+// DETAILED USAGE:
+//
+//  Scale:
+//    Select how high you want the font to be, in points or pixels.
+//    Call ScaleForPixelHeight or ScaleForMappingEmToPixels to compute
+//    a scale factor SF that will be used by all other functions.
+//
+//  Baseline:
+//    You need to select a y-coordinate that is the baseline of where
+//    your text will appear. Call GetFontBoundingBox to get the baseline-relative
+//    bounding box for all characters. SF*-y0 will be the distance in pixels
+//    that the worst-case character could extend above the baseline, so if
+//    you want the top edge of characters to appear at the top of the
+//    screen where y=0, then you would set the baseline to SF*-y0.
+//
+//  Current point:
+//    Set the current point where the first character will appear. The
+//    first character could extend left of the current point; this is font
+//    dependent. You can either choose a current point that is the leftmost
+//    point and hope, or add some padding, or check the bounding box or
+//    left-side-bearing of the first character to be displayed and set
+//    the current point based on that.
+//
+//  Displaying a character:
+//    Compute the bounding box of the character. It will contain signed values
+//    relative to <current_point, baseline>. I.e. if it returns x0,y0,x1,y1,
+//    then the character should be displayed in the rectangle from
+//    <current_point+SF*x0, baseline+SF*y0> to <current_point+SF*x1,baseline+SF*y1).
+//
+//  Advancing for the next character:
+//    Call GlyphHMetrics, and compute 'current_point += SF * advance'.
+//
+//
+// ADVANCED USAGE
+//
+//   Quality:
+//
+//    - Use the functions with Subpixel at the end to allow your characters
+//      to have subpixel positioning. Since the font is anti-aliased, not
+//      hinted, this is very import for quality. (This is not possible with
+//      baked fonts.)
+//
+//    - Kerning is now supported, and if you're supporting subpixel rendering
+//      then kerning is worth using to give your text a polished look.
+//
+//   Performance:
+//
+//    - Convert Unicode codepoints to glyph indexes and operate on the glyphs;
+//      if you don't do this, stb_truetype is forced to do the conversion on
+//      every call.
+//
+//    - There are a lot of memory allocations. We should modify it to take
+//      a temp buffer and allocate from the temp buffer (without freeing),
+//      should help performance a lot.
+//
+// NOTES
+//
+//   The system uses the raw data found in the .ttf file without changing it
+//   and without building auxiliary data structures. This is a bit inefficient
+//   on little-endian systems (the data is big-endian), but assuming you're
+//   caching the bitmaps or glyph shapes this shouldn't be a big deal.
+//
+//   It appears to be very hard to programmatically determine what font a
+//   given file is in a general way. I provide an API for this, but I don't
+//   recommend it.
+//
+//
+// PERFORMANCE MEASUREMENTS FOR 1.06:
+//
+//                      32-bit     64-bit
+//   Previous release:  8.83 s     7.68 s
+//   Pool allocations:  7.72 s     6.34 s
+//   Inline sort     :  6.54 s     5.65 s
+//   New rasterizer  :  5.63 s     5.00 s
+
+//////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////
+////
+////  SAMPLE PROGRAMS
+////
+//
+//  Incomplete text-in-3d-api example, which draws quads properly aligned to be lossless.
+//  See "tests/truetype_demo_win32.c" for a complete version.
+#if 0
+#define STB_TRUETYPE_IMPLEMENTATION  // force following include to generate implementation
+#include "stb_truetype.h"
+
+unsigned char ttf_buffer[1<<20];
+unsigned char temp_bitmap[512*512];
+
+stbtt_bakedchar cdata[96]; // ASCII 32..126 is 95 glyphs
+GLuint ftex;
+
+void my_stbtt_initfont(void)
+{
+   fread(ttf_buffer, 1, 1<<20, fopen("c:/windows/fonts/times.ttf", "rb"));
+   stbtt_BakeFontBitmap(ttf_buffer,0, 32.0, temp_bitmap,512,512, 32,96, cdata); // no guarantee this fits!
+   // can free ttf_buffer at this point
+   glGenTextures(1, &ftex);
+   glBindTexture(GL_TEXTURE_2D, ftex);
+   glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, 512,512, 0, GL_ALPHA, GL_UNSIGNED_BYTE, temp_bitmap);
+   // can free temp_bitmap at this point
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+}
+
+void my_stbtt_print(float x, float y, char *text)
+{
+   // assume orthographic projection with units = screen pixels, origin at top left
+   glEnable(GL_BLEND);
+   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+   glEnable(GL_TEXTURE_2D);
+   glBindTexture(GL_TEXTURE_2D, ftex);
+   glBegin(GL_QUADS);
+   while (*text) {
+      if (*text >= 32 && *text < 128) {
+         stbtt_aligned_quad q;
+         stbtt_GetBakedQuad(cdata, 512,512, *text-32, &x,&y,&q,1);//1=opengl & d3d10+,0=d3d9
+         glTexCoord2f(q.s0,q.t0); glVertex2f(q.x0,q.y0);
+         glTexCoord2f(q.s1,q.t0); glVertex2f(q.x1,q.y0);
+         glTexCoord2f(q.s1,q.t1); glVertex2f(q.x1,q.y1);
+         glTexCoord2f(q.s0,q.t1); glVertex2f(q.x0,q.y1);
+      }
+      ++text;
+   }
+   glEnd();
+}
+#endif
+//
+//
+//////////////////////////////////////////////////////////////////////////////
+//
+// Complete program (this compiles): get a single bitmap, print as ASCII art
+//
+#if 0
+#include <stdio.h>
+#define STB_TRUETYPE_IMPLEMENTATION  // force following include to generate implementation
+#include "stb_truetype.h"
+
+char ttf_buffer[1<<25];
+
+int main(int argc, char **argv)
+{
+   stbtt_fontinfo font;
+   unsigned char *bitmap;
+   int w,h,i,j,c = (argc > 1 ? atoi(argv[1]) : 'a'), s = (argc > 2 ? atoi(argv[2]) : 20);
+
+   fread(ttf_buffer, 1, 1<<25, fopen(argc > 3 ? argv[3] : "c:/windows/fonts/arialbd.ttf", "rb"));
+
+   stbtt_InitFont(&font, ttf_buffer, stbtt_GetFontOffsetForIndex(ttf_buffer,0));
+   bitmap = stbtt_GetCodepointBitmap(&font, 0,stbtt_ScaleForPixelHeight(&font, s), c, &w, &h, 0,0);
+
+   for (j=0; j < h; ++j) {
+      for (i=0; i < w; ++i)
+         putchar(" .:ioVM@"[bitmap[j*w+i]>>5]);
+      putchar('\n');
+   }
+   return 0;
+}
+#endif
+//
+// Output:
+//
+//     .ii.
+//    @@@@@@.
+//   V@Mio@@o
+//   :i.  V@V
+//     :oM@@M
+//   :@@@MM@M
+//   @@o  o@M
+//  :@@.  M@M
+//   @@@o@@@@
+//   :M@@V:@@.
+//
+//////////////////////////////////////////////////////////////////////////////
+//
+// Complete program: print "Hello World!" banner, with bugs
+//
+#if 0
+char buffer[24<<20];
+unsigned char screen[20][79];
+
+int main(int arg, char **argv)
+{
+   stbtt_fontinfo font;
+   int i,j,ascent,baseline,ch=0;
+   float scale, xpos=2; // leave a little padding in case the character extends left
+   char *text = "Heljo World!"; // intentionally misspelled to show 'lj' brokenness
+
+   fread(buffer, 1, 1000000, fopen("c:/windows/fonts/arialbd.ttf", "rb"));
+   stbtt_InitFont(&font, buffer, 0);
+
+   scale = stbtt_ScaleForPixelHeight(&font, 15);
+   stbtt_GetFontVMetrics(&font, &ascent,0,0);
+   baseline = (int) (ascent*scale);
+
+   while (text[ch]) {
+      int advance,lsb,x0,y0,x1,y1;
+      float x_shift = xpos - (float) floor(xpos);
+      stbtt_GetCodepointHMetrics(&font, text[ch], &advance, &lsb);
+      stbtt_GetCodepointBitmapBoxSubpixel(&font, text[ch], scale,scale,x_shift,0, &x0,&y0,&x1,&y1);
+      stbtt_MakeCodepointBitmapSubpixel(&font, &screen[baseline + y0][(int) xpos + x0], x1-x0,y1-y0, 79, scale,scale,x_shift,0, text[ch]);
+      // note that this stomps the old data, so where character boxes overlap (e.g. 'lj') it's wrong
+      // because this API is really for baking character bitmaps into textures. if you want to render
+      // a sequence of characters, you really need to render each bitmap to a temp buffer, then
+      // "alpha blend" that into the working buffer
+      xpos += (advance * scale);
+      if (text[ch+1])
+         xpos += scale*stbtt_GetCodepointKernAdvance(&font, text[ch],text[ch+1]);
+      ++ch;
+   }
+
+   for (j=0; j < 20; ++j) {
+      for (i=0; i < 78; ++i)
+         putchar(" .:ioVM@"[screen[j][i]>>5]);
+      putchar('\n');
+   }
+
+   return 0;
+}
+#endif
+
+
+//////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////
+////
+////   INTEGRATION WITH YOUR CODEBASE
+////
+////   The following sections allow you to supply alternate definitions
+////   of C library functions used by stb_truetype, e.g. if you don't
+////   link with the C runtime library.
+
+#ifdef STB_TRUETYPE_IMPLEMENTATION
+   // #define your own (u)stbtt_int8/16/32 before including to override this
+   #ifndef stbtt_uint8
+   typedef unsigned char   stbtt_uint8;
+   typedef signed   char   stbtt_int8;
+   typedef unsigned short  stbtt_uint16;
+   typedef signed   short  stbtt_int16;
+   typedef unsigned int    stbtt_uint32;
+   typedef signed   int    stbtt_int32;
+   #endif
+
+   typedef char stbtt__check_size32[sizeof(stbtt_int32)==4 ? 1 : -1];
+   typedef char stbtt__check_size16[sizeof(stbtt_int16)==2 ? 1 : -1];
+
+   // e.g. #define your own STBTT_ifloor/STBTT_iceil() to avoid math.h
+   #ifndef STBTT_ifloor
+   #include <math.h>
+   #define STBTT_ifloor(x)   ((int) floor(x))
+   #define STBTT_iceil(x)    ((int) ceil(x))
+   #endif
+
+   #ifndef STBTT_sqrt
+   #include <math.h>
+   #define STBTT_sqrt(x)      sqrt(x)
+   #define STBTT_pow(x,y)     pow(x,y)
+   #endif
+
+   #ifndef STBTT_fmod
+   #include <math.h>
+   #define STBTT_fmod(x,y)    fmod(x,y)
+   #endif
+
+   #ifndef STBTT_cos
+   #include <math.h>
+   #define STBTT_cos(x)       cos(x)
+   #define STBTT_acos(x)      acos(x)
+   #endif
+
+   #ifndef STBTT_fabs
+   #include <math.h>
+   #define STBTT_fabs(x)      fabs(x)
+   #endif
+
+   // #define your own functions "STBTT_malloc" / "STBTT_free" to avoid malloc.h
+   #ifndef STBTT_malloc
+   #include <stdlib.h>
+   #define STBTT_malloc(x,u)  ((void)(u),malloc(x))
+   #define STBTT_free(x,u)    ((void)(u),free(x))
+   #endif
+
+   #ifndef STBTT_assert
+   #include <assert.h>
+   #define STBTT_assert(x)    assert(x)
+   #endif
+
+   #ifndef STBTT_strlen
+   #include <string.h>
+   #define STBTT_strlen(x)    strlen(x)
+   #endif
+
+   #ifndef STBTT_memcpy
+   #include <string.h>
+   #define STBTT_memcpy       memcpy
+   #define STBTT_memset       memset
+   #endif
+#endif
+
+///////////////////////////////////////////////////////////////////////////////
+///////////////////////////////////////////////////////////////////////////////
+////
+////   INTERFACE
+////
+////
+
+#ifndef __STB_INCLUDE_STB_TRUETYPE_H__
+#define __STB_INCLUDE_STB_TRUETYPE_H__
+
+#ifdef STBTT_STATIC
+#define STBTT_DEF static
+#else
+#define STBTT_DEF extern
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// private structure
+typedef struct
+{
+   unsigned char *data;
+   int cursor;
+   int size;
+} stbtt__buf;
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// TEXTURE BAKING API
+//
+// If you use this API, you only have to call two functions ever.
+//
+
+typedef struct
+{
+   unsigned short x0,y0,x1,y1; // coordinates of bbox in bitmap
+   float xoff,yoff,xadvance;
+} stbtt_bakedchar;
+
+STBTT_DEF int stbtt_BakeFontBitmap(const unsigned char *data, int offset,  // font location (use offset=0 for plain .ttf)
+                                float pixel_height,                     // height of font in pixels
+                                unsigned char *pixels, int pw, int ph,  // bitmap to be filled in
+                                int first_char, int num_chars,          // characters to bake
+                                stbtt_bakedchar *chardata);             // you allocate this, it's num_chars long
+// if return is positive, the first unused row of the bitmap
+// if return is negative, returns the negative of the number of characters that fit
+// if return is 0, no characters fit and no rows were used
+// This uses a very crappy packing.
+
+typedef struct
+{
+   float x0,y0,s0,t0; // top-left
+   float x1,y1,s1,t1; // bottom-right
+} stbtt_aligned_quad;
+
+STBTT_DEF void stbtt_GetBakedQuad(const stbtt_bakedchar *chardata, int pw, int ph,  // same data as above
+                               int char_index,             // character to display
+                               float *xpos, float *ypos,   // pointers to current position in screen pixel space
+                               stbtt_aligned_quad *q,      // output: quad to draw
+                               int opengl_fillrule);       // true if opengl fill rule; false if DX9 or earlier
+// Call GetBakedQuad with char_index = 'character - first_char', and it
+// creates the quad you need to draw and advances the current position.
+//
+// The coordinate system used assumes y increases downwards.
+//
+// Characters will extend both above and below the current position;
+// see discussion of "BASELINE" above.
+//
+// It's inefficient; you might want to c&p it and optimize it.
+
+STBTT_DEF void stbtt_GetScaledFontVMetrics(const unsigned char *fontdata, int index, float size, float *ascent, float *descent, float *lineGap);
+// Query the font vertical metrics without having to create a font first.
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// NEW TEXTURE BAKING API
+//
+// This provides options for packing multiple fonts into one atlas, not
+// perfectly but better than nothing.
+
+typedef struct
+{
+   unsigned short x0,y0,x1,y1; // coordinates of bbox in bitmap
+   float xoff,yoff,xadvance;
+   float xoff2,yoff2;
+} stbtt_packedchar;
+
+typedef struct stbtt_pack_context stbtt_pack_context;
+typedef struct stbtt_fontinfo stbtt_fontinfo;
+#ifndef STB_RECT_PACK_VERSION
+typedef struct stbrp_rect stbrp_rect;
+#endif
+
+STBTT_DEF int  stbtt_PackBegin(stbtt_pack_context *spc, unsigned char *pixels, int width, int height, int stride_in_bytes, int padding, void *alloc_context);
+// Initializes a packing context stored in the passed-in stbtt_pack_context.
+// Future calls using this context will pack characters into the bitmap passed
+// in here: a 1-channel bitmap that is width * height. stride_in_bytes is
+// the distance from one row to the next (or 0 to mean they are packed tightly
+// together). "padding" is the amount of padding to leave between each
+// character (normally you want '1' for bitmaps you'll use as textures with
+// bilinear filtering).
+//
+// Returns 0 on failure, 1 on success.
+
+STBTT_DEF void stbtt_PackEnd  (stbtt_pack_context *spc);
+// Cleans up the packing context and frees all memory.
+
+#define STBTT_POINT_SIZE(x)   (-(x))
+
+STBTT_DEF int  stbtt_PackFontRange(stbtt_pack_context *spc, const unsigned char *fontdata, int font_index, float font_size,
+                                int first_unicode_char_in_range, int num_chars_in_range, stbtt_packedchar *chardata_for_range);
+// Creates character bitmaps from the font_index'th font found in fontdata (use
+// font_index=0 if you don't know what that is). It creates num_chars_in_range
+// bitmaps for characters with unicode values starting at first_unicode_char_in_range
+// and increasing. Data for how to render them is stored in chardata_for_range;
+// pass these to stbtt_GetPackedQuad to get back renderable quads.
+//
+// font_size is the full height of the character from ascender to descender,
+// as computed by stbtt_ScaleForPixelHeight. To use a point size as computed
+// by stbtt_ScaleForMappingEmToPixels, wrap the point size in STBTT_POINT_SIZE()
+// and pass that result as 'font_size':
+//       ...,                  20 , ... // font max minus min y is 20 pixels tall
+//       ..., STBTT_POINT_SIZE(20), ... // 'M' is 20 pixels tall
+
+typedef struct
+{
+   float font_size;
+   int first_unicode_codepoint_in_range;  // if non-zero, then the chars are continuous, and this is the first codepoint
+   int *array_of_unicode_codepoints;       // if non-zero, then this is an array of unicode codepoints
+   int num_chars;
+   stbtt_packedchar *chardata_for_range; // output
+   unsigned char h_oversample, v_oversample; // don't set these, they're used internally
+} stbtt_pack_range;
+
+STBTT_DEF int  stbtt_PackFontRanges(stbtt_pack_context *spc, const unsigned char *fontdata, int font_index, stbtt_pack_range *ranges, int num_ranges);
+// Creates character bitmaps from multiple ranges of characters stored in
+// ranges. This will usually create a better-packed bitmap than multiple
+// calls to stbtt_PackFontRange. Note that you can call this multiple
+// times within a single PackBegin/PackEnd.
+
+STBTT_DEF void stbtt_PackSetOversampling(stbtt_pack_context *spc, unsigned int h_oversample, unsigned int v_oversample);
+// Oversampling a font increases the quality by allowing higher-quality subpixel
+// positioning, and is especially valuable at smaller text sizes.
+//
+// This function sets the amount of oversampling for all following calls to
+// stbtt_PackFontRange(s) or stbtt_PackFontRangesGatherRects for a given
+// pack context. The default (no oversampling) is achieved by h_oversample=1
+// and v_oversample=1. The total number of pixels required is
+// h_oversample*v_oversample larger than the default; for example, 2x2
+// oversampling requires 4x the storage of 1x1. For best results, render
+// oversampled textures with bilinear filtering. Look at the readme in
+// stb/tests/oversample for information about oversampled fonts
+//
+// To use with PackFontRangesGather etc., you must set it before calls
+// call to PackFontRangesGatherRects.
+
+STBTT_DEF void stbtt_PackSetSkipMissingCodepoints(stbtt_pack_context *spc, int skip);
+// If skip != 0, this tells stb_truetype to skip any codepoints for which
+// there is no corresponding glyph. If skip=0, which is the default, then
+// codepoints without a glyph recived the font's "missing character" glyph,
+// typically an empty box by convention.
+
+STBTT_DEF void stbtt_GetPackedQuad(const stbtt_packedchar *chardata, int pw, int ph,  // same data as above
+                               int char_index,             // character to display
+                               float *xpos, float *ypos,   // pointers to current position in screen pixel space
+                               stbtt_aligned_quad *q,      // output: quad to draw
+                               int align_to_integer);
+
+STBTT_DEF int  stbtt_PackFontRangesGatherRects(stbtt_pack_context *spc, const stbtt_fontinfo *info, stbtt_pack_range *ranges, int num_ranges, stbrp_rect *rects);
+STBTT_DEF void stbtt_PackFontRangesPackRects(stbtt_pack_context *spc, stbrp_rect *rects, int num_rects);
+STBTT_DEF int  stbtt_PackFontRangesRenderIntoRects(stbtt_pack_context *spc, const stbtt_fontinfo *info, stbtt_pack_range *ranges, int num_ranges, stbrp_rect *rects);
+// Calling these functions in sequence is roughly equivalent to calling
+// stbtt_PackFontRanges(). If you more control over the packing of multiple
+// fonts, or if you want to pack custom data into a font texture, take a look
+// at the source to of stbtt_PackFontRanges() and create a custom version
+// using these functions, e.g. call GatherRects multiple times,
+// building up a single array of rects, then call PackRects once,
+// then call RenderIntoRects repeatedly. This may result in a
+// better packing than calling PackFontRanges multiple times
+// (or it may not).
+
+// this is an opaque structure that you shouldn't mess with which holds
+// all the context needed from PackBegin to PackEnd.
+struct stbtt_pack_context {
+   void *user_allocator_context;
+   void *pack_info;
+   int   width;
+   int   height;
+   int   stride_in_bytes;
+   int   padding;
+   int   skip_missing;
+   unsigned int   h_oversample, v_oversample;
+   unsigned char *pixels;
+   void  *nodes;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// FONT LOADING
+//
+//
+
+STBTT_DEF int stbtt_GetNumberOfFonts(const unsigned char *data);
+// This function will determine the number of fonts in a font file.  TrueType
+// collection (.ttc) files may contain multiple fonts, while TrueType font
+// (.ttf) files only contain one font. The number of fonts can be used for
+// indexing with the previous function where the index is between zero and one
+// less than the total fonts. If an error occurs, -1 is returned.
+
+STBTT_DEF int stbtt_GetFontOffsetForIndex(const unsigned char *data, int index);
+// Each .ttf/.ttc file may have more than one font. Each font has a sequential
+// index number starting from 0. Call this function to get the font offset for
+// a given index; it returns -1 if the index is out of range. A regular .ttf
+// file will only define one font and it always be at offset 0, so it will
+// return '0' for index 0, and -1 for all other indices.
+
+// The following structure is defined publicly so you can declare one on
+// the stack or as a global or etc, but you should treat it as opaque.
+struct stbtt_fontinfo
+{
+   void           * userdata;
+   unsigned char  * data;              // pointer to .ttf file
+   int              fontstart;         // offset of start of font
+
+   int numGlyphs;                     // number of glyphs, needed for range checking
+
+   int loca,head,glyf,hhea,hmtx,kern,gpos,svg; // table locations as offset from start of .ttf
+   int index_map;                     // a cmap mapping for our chosen character encoding
+   int indexToLocFormat;              // format needed to map from glyph index to glyph
+
+   stbtt__buf cff;                    // cff font data
+   stbtt__buf charstrings;            // the charstring index
+   stbtt__buf gsubrs;                 // global charstring subroutines index
+   stbtt__buf subrs;                  // private charstring subroutines index
+   stbtt__buf fontdicts;              // array of font dicts
+   stbtt__buf fdselect;               // map from glyph to fontdict
+};
+
+STBTT_DEF int stbtt_InitFont(stbtt_fontinfo *info, const unsigned char *data, int offset);
+// Given an offset into the file that defines a font, this function builds
+// the necessary cached info for the rest of the system. You must allocate
+// the stbtt_fontinfo yourself, and stbtt_InitFont will fill it out. You don't
+// need to do anything special to free it, because the contents are pure
+// value data with no additional data structures. Returns 0 on failure.
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// CHARACTER TO GLYPH-INDEX CONVERSIOn
+
+STBTT_DEF int stbtt_FindGlyphIndex(const stbtt_fontinfo *info, int unicode_codepoint);
+// If you're going to perform multiple operations on the same character
+// and you want a speed-up, call this function with the character you're
+// going to process, then use glyph-based functions instead of the
+// codepoint-based functions.
+// Returns 0 if the character codepoint is not defined in the font.
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// CHARACTER PROPERTIES
+//
+
+STBTT_DEF float stbtt_ScaleForPixelHeight(const stbtt_fontinfo *info, float pixels);
+// computes a scale factor to produce a font whose "height" is 'pixels' tall.
+// Height is measured as the distance from the highest ascender to the lowest
+// descender; in other words, it's equivalent to calling stbtt_GetFontVMetrics
+// and computing:
+//       scale = pixels / (ascent - descent)
+// so if you prefer to measure height by the ascent only, use a similar calculation.
+
+STBTT_DEF float stbtt_ScaleForMappingEmToPixels(const stbtt_fontinfo *info, float pixels);
+// computes a scale factor to produce a font whose EM size is mapped to
+// 'pixels' tall. This is probably what traditional APIs compute, but
+// I'm not positive.
+
+STBTT_DEF void stbtt_GetFontVMetrics(const stbtt_fontinfo *info, int *ascent, int *descent, int *lineGap);
+// ascent is the coordinate above the baseline the font extends; descent
+// is the coordinate below the baseline the font extends (i.e. it is typically negative)
+// lineGap is the spacing between one row's descent and the next row's ascent...
+// so you should advance the vertical position by "*ascent - *descent + *lineGap"
+//   these are expressed in unscaled coordinates, so you must multiply by
+//   the scale factor for a given size
+
+STBTT_DEF int  stbtt_GetFontVMetricsOS2(const stbtt_fontinfo *info, int *typoAscent, int *typoDescent, int *typoLineGap);
+// analogous to GetFontVMetrics, but returns the "typographic" values from the OS/2
+// table (specific to MS/Windows TTF files).
+//
+// Returns 1 on success (table present), 0 on failure.
+
+STBTT_DEF void stbtt_GetFontBoundingBox(const stbtt_fontinfo *info, int *x0, int *y0, int *x1, int *y1);
+// the bounding box around all possible characters
+
+STBTT_DEF void stbtt_GetCodepointHMetrics(const stbtt_fontinfo *info, int codepoint, int *advanceWidth, int *leftSideBearing);
+// leftSideBearing is the offset from the current horizontal position to the left edge of the character
+// advanceWidth is the offset from the current horizontal position to the next horizontal position
+//   these are expressed in unscaled coordinates
+
+STBTT_DEF int  stbtt_GetCodepointKernAdvance(const stbtt_fontinfo *info, int ch1, int ch2);
+// an additional amount to add to the 'advance' value between ch1 and ch2
+
+STBTT_DEF int stbtt_GetCodepointBox(const stbtt_fontinfo *info, int codepoint, int *x0, int *y0, int *x1, int *y1);
+// Gets the bounding box of the visible part of the glyph, in unscaled coordinates
+
+STBTT_DEF void stbtt_GetGlyphHMetrics(const stbtt_fontinfo *info, int glyph_index, int *advanceWidth, int *leftSideBearing);
+STBTT_DEF int  stbtt_GetGlyphKernAdvance(const stbtt_fontinfo *info, int glyph1, int glyph2);
+STBTT_DEF int  stbtt_GetGlyphBox(const stbtt_fontinfo *info, int glyph_index, int *x0, int *y0, int *x1, int *y1);
+// as above, but takes one or more glyph indices for greater efficiency
+
+typedef struct stbtt_kerningentry
+{
+   int glyph1; // use stbtt_FindGlyphIndex
+   int glyph2;
+   int advance;
+} stbtt_kerningentry;
+
+STBTT_DEF int  stbtt_GetKerningTableLength(const stbtt_fontinfo *info);
+STBTT_DEF int  stbtt_GetKerningTable(const stbtt_fontinfo *info, stbtt_kerningentry* table, int table_length);
+// Retrieves a complete list of all of the kerning pairs provided by the font
+// stbtt_GetKerningTable never writes more than table_length entries and returns how many entries it did write.
+// The table will be sorted by (a.glyph1 == b.glyph1)?(a.glyph2 < b.glyph2):(a.glyph1 < b.glyph1)
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// GLYPH SHAPES (you probably don't need these, but they have to go before
+// the bitmaps for C declaration-order reasons)
+//
+
+#ifndef STBTT_vmove // you can predefine these to use different values (but why?)
+   enum {
+      STBTT_vmove=1,
+      STBTT_vline,
+      STBTT_vcurve,
+      STBTT_vcubic
+   };
+#endif
+
+#ifndef stbtt_vertex // you can predefine this to use different values
+                   // (we share this with other code at RAD)
+   #define stbtt_vertex_type short // can't use stbtt_int16 because that's not visible in the header file
+   typedef struct
+   {
+      stbtt_vertex_type x,y,cx,cy,cx1,cy1;
+      unsigned char type,padding;
+   } stbtt_vertex;
+#endif
+
+STBTT_DEF int stbtt_IsGlyphEmpty(const stbtt_fontinfo *info, int glyph_index);
+// returns non-zero if nothing is drawn for this glyph
+
+STBTT_DEF int stbtt_GetCodepointShape(const stbtt_fontinfo *info, int unicode_codepoint, stbtt_vertex **vertices);
+STBTT_DEF int stbtt_GetGlyphShape(const stbtt_fontinfo *info, int glyph_index, stbtt_vertex **vertices);
+// returns # of vertices and fills *vertices with the pointer to them
+//   these are expressed in "unscaled" coordinates
+//
+// The shape is a series of contours. Each one starts with
+// a STBTT_moveto, then consists of a series of mixed
+// STBTT_lineto and STBTT_curveto segments. A lineto
+// draws a line from previous endpoint to its x,y; a curveto
+// draws a quadratic bezier from previous endpoint to
+// its x,y, using cx,cy as the bezier control point.
+
+STBTT_DEF void stbtt_FreeShape(const stbtt_fontinfo *info, stbtt_vertex *vertices);
+// frees the data allocated above
+
+STBTT_DEF unsigned char *stbtt_FindSVGDoc(const stbtt_fontinfo *info, int gl);
+STBTT_DEF int stbtt_GetCodepointSVG(const stbtt_fontinfo *info, int unicode_codepoint, const char **svg);
+STBTT_DEF int stbtt_GetGlyphSVG(const stbtt_fontinfo *info, int gl, const char **svg);
+// fills svg with the character's SVG data.
+// returns data size or 0 if SVG not found.
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// BITMAP RENDERING
+//
+
+STBTT_DEF void stbtt_FreeBitmap(unsigned char *bitmap, void *userdata);
+// frees the bitmap allocated below
+
+STBTT_DEF unsigned char *stbtt_GetCodepointBitmap(const stbtt_fontinfo *info, float scale_x, float scale_y, int codepoint, int *width, int *height, int *xoff, int *yoff);
+// allocates a large-enough single-channel 8bpp bitmap and renders the
+// specified character/glyph at the specified scale into it, with
+// antialiasing. 0 is no coverage (transparent), 255 is fully covered (opaque).
+// *width & *height are filled out with the width & height of the bitmap,
+// which is stored left-to-right, top-to-bottom.
+//
+// xoff/yoff are the offset it pixel space from the glyph origin to the top-left of the bitmap
+
+STBTT_DEF unsigned char *stbtt_GetCodepointBitmapSubpixel(const stbtt_fontinfo *info, float scale_x, float scale_y, float shift_x, float shift_y, int codepoint, int *width, int *height, int *xoff, int *yoff);
+// the same as stbtt_GetCodepoitnBitmap, but you can specify a subpixel
+// shift for the character
+
+STBTT_DEF void stbtt_MakeCodepointBitmap(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, int codepoint);
+// the same as stbtt_GetCodepointBitmap, but you pass in storage for the bitmap
+// in the form of 'output', with row spacing of 'out_stride' bytes. the bitmap
+// is clipped to out_w/out_h bytes. Call stbtt_GetCodepointBitmapBox to get the
+// width and height and positioning info for it first.
+
+STBTT_DEF void stbtt_MakeCodepointBitmapSubpixel(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int codepoint);
+// same as stbtt_MakeCodepointBitmap, but you can specify a subpixel
+// shift for the character
+
+STBTT_DEF void stbtt_MakeCodepointBitmapSubpixelPrefilter(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int oversample_x, int oversample_y, float *sub_x, float *sub_y, int codepoint);
+// same as stbtt_MakeCodepointBitmapSubpixel, but prefiltering
+// is performed (see stbtt_PackSetOversampling)
+
+STBTT_DEF void stbtt_GetCodepointBitmapBox(const stbtt_fontinfo *font, int codepoint, float scale_x, float scale_y, int *ix0, int *iy0, int *ix1, int *iy1);
+// get the bbox of the bitmap centered around the glyph origin; so the
+// bitmap width is ix1-ix0, height is iy1-iy0, and location to place
+// the bitmap top left is (leftSideBearing*scale,iy0).
+// (Note that the bitmap uses y-increases-down, but the shape uses
+// y-increases-up, so CodepointBitmapBox and CodepointBox are inverted.)
+
+STBTT_DEF void stbtt_GetCodepointBitmapBoxSubpixel(const stbtt_fontinfo *font, int codepoint, float scale_x, float scale_y, float shift_x, float shift_y, int *ix0, int *iy0, int *ix1, int *iy1);
+// same as stbtt_GetCodepointBitmapBox, but you can specify a subpixel
+// shift for the character
+
+// the following functions are equivalent to the above functions, but operate
+// on glyph indices instead of Unicode codepoints (for efficiency)
+STBTT_DEF unsigned char *stbtt_GetGlyphBitmap(const stbtt_fontinfo *info, float scale_x, float scale_y, int glyph, int *width, int *height, int *xoff, int *yoff);
+STBTT_DEF unsigned char *stbtt_GetGlyphBitmapSubpixel(const stbtt_fontinfo *info, float scale_x, float scale_y, float shift_x, float shift_y, int glyph, int *width, int *height, int *xoff, int *yoff);
+STBTT_DEF void stbtt_MakeGlyphBitmap(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, int glyph);
+STBTT_DEF void stbtt_MakeGlyphBitmapSubpixel(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int glyph);
+STBTT_DEF void stbtt_MakeGlyphBitmapSubpixelPrefilter(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int oversample_x, int oversample_y, float *sub_x, float *sub_y, int glyph);
+STBTT_DEF void stbtt_GetGlyphBitmapBox(const stbtt_fontinfo *font, int glyph, float scale_x, float scale_y, int *ix0, int *iy0, int *ix1, int *iy1);
+STBTT_DEF void stbtt_GetGlyphBitmapBoxSubpixel(const stbtt_fontinfo *font, int glyph, float scale_x, float scale_y,float shift_x, float shift_y, int *ix0, int *iy0, int *ix1, int *iy1);
+
+
+// @TODO: don't expose this structure
+typedef struct
+{
+   int w,h,stride;
+   unsigned char *pixels;
+} stbtt__bitmap;
+
+// rasterize a shape with quadratic beziers into a bitmap
+STBTT_DEF void stbtt_Rasterize(stbtt__bitmap *result,        // 1-channel bitmap to draw into
+                               float flatness_in_pixels,     // allowable error of curve in pixels
+                               stbtt_vertex *vertices,       // array of vertices defining shape
+                               int num_verts,                // number of vertices in above array
+                               float scale_x, float scale_y, // scale applied to input vertices
+                               float shift_x, float shift_y, // translation applied to input vertices
+                               int x_off, int y_off,         // another translation applied to input
+                               int invert,                   // if non-zero, vertically flip shape
+                               void *userdata);              // context for to STBTT_MALLOC
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Signed Distance Function (or Field) rendering
+
+STBTT_DEF void stbtt_FreeSDF(unsigned char *bitmap, void *userdata);
+// frees the SDF bitmap allocated below
+
+STBTT_DEF unsigned char * stbtt_GetGlyphSDF(const stbtt_fontinfo *info, float scale, int glyph, int padding, unsigned char onedge_value, float pixel_dist_scale, int *width, int *height, int *xoff, int *yoff);
+STBTT_DEF unsigned char * stbtt_GetCodepointSDF(const stbtt_fontinfo *info, float scale, int codepoint, int padding, unsigned char onedge_value, float pixel_dist_scale, int *width, int *height, int *xoff, int *yoff);
+// These functions compute a discretized SDF field for a single character, suitable for storing
+// in a single-channel texture, sampling with bilinear filtering, and testing against
+// larger than some threshold to produce scalable fonts.
+//        info              --  the font
+//        scale             --  controls the size of the resulting SDF bitmap, same as it would be creating a regular bitmap
+//        glyph/codepoint   --  the character to generate the SDF for
+//        padding           --  extra "pixels" around the character which are filled with the distance to the character (not 0),
+//                                 which allows effects like bit outlines
+//        onedge_value      --  value 0-255 to test the SDF against to reconstruct the character (i.e. the isocontour of the character)
+//        pixel_dist_scale  --  what value the SDF should increase by when moving one SDF "pixel" away from the edge (on the 0..255 scale)
+//                                 if positive, > onedge_value is inside; if negative, < onedge_value is inside
+//        width,height      --  output height & width of the SDF bitmap (including padding)
+//        xoff,yoff         --  output origin of the character
+//        return value      --  a 2D array of bytes 0..255, width*height in size
+//
+// pixel_dist_scale & onedge_value are a scale & bias that allows you to make
+// optimal use of the limited 0..255 for your application, trading off precision
+// and special effects. SDF values outside the range 0..255 are clamped to 0..255.
+//
+// Example:
+//      scale = stbtt_ScaleForPixelHeight(22)
+//      padding = 5
+//      onedge_value = 180
+//      pixel_dist_scale = 180/5.0 = 36.0
+//
+//      This will create an SDF bitmap in which the character is about 22 pixels
+//      high but the whole bitmap is about 22+5+5=32 pixels high. To produce a filled
+//      shape, sample the SDF at each pixel and fill the pixel if the SDF value
+//      is greater than or equal to 180/255. (You'll actually want to antialias,
+//      which is beyond the scope of this example.) Additionally, you can compute
+//      offset outlines (e.g. to stroke the character border inside & outside,
+//      or only outside). For example, to fill outside the character up to 3 SDF
+//      pixels, you would compare against (180-36.0*3)/255 = 72/255. The above
+//      choice of variables maps a range from 5 pixels outside the shape to
+//      2 pixels inside the shape to 0..255; this is intended primarily for apply
+//      outside effects only (the interior range is needed to allow proper
+//      antialiasing of the font at *smaller* sizes)
+//
+// The function computes the SDF analytically at each SDF pixel, not by e.g.
+// building a higher-res bitmap and approximating it. In theory the quality
+// should be as high as possible for an SDF of this size & representation, but
+// unclear if this is true in practice (perhaps building a higher-res bitmap
+// and computing from that can allow drop-out prevention).
+//
+// The algorithm has not been optimized at all, so expect it to be slow
+// if computing lots of characters or very large sizes.
+
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Finding the right font...
+//
+// You should really just solve this offline, keep your own tables
+// of what font is what, and don't try to get it out of the .ttf file.
+// That's because getting it out of the .ttf file is really hard, because
+// the names in the file can appear in many possible encodings, in many
+// possible languages, and e.g. if you need a case-insensitive comparison,
+// the details of that depend on the encoding & language in a complex way
+// (actually underspecified in truetype, but also gigantic).
+//
+// But you can use the provided functions in two possible ways:
+//     stbtt_FindMatchingFont() will use *case-sensitive* comparisons on
+//             unicode-encoded names to try to find the font you want;
+//             you can run this before calling stbtt_InitFont()
+//
+//     stbtt_GetFontNameString() lets you get any of the various strings
+//             from the file yourself and do your own comparisons on them.
+//             You have to have called stbtt_InitFont() first.
+
+
+STBTT_DEF int stbtt_FindMatchingFont(const unsigned char *fontdata, const char *name, int flags);
+// returns the offset (not index) of the font that matches, or -1 if none
+//   if you use STBTT_MACSTYLE_DONTCARE, use a font name like "Arial Bold".
+//   if you use any other flag, use a font name like "Arial"; this checks
+//     the 'macStyle' header field; i don't know if fonts set this consistently
+#define STBTT_MACSTYLE_DONTCARE     0
+#define STBTT_MACSTYLE_BOLD         1
+#define STBTT_MACSTYLE_ITALIC       2
+#define STBTT_MACSTYLE_UNDERSCORE   4
+#define STBTT_MACSTYLE_NONE         8   // <= not same as 0, this makes us check the bitfield is 0
+
+STBTT_DEF int stbtt_CompareUTF8toUTF16_bigendian(const char *s1, int len1, const char *s2, int len2);
+// returns 1/0 whether the first string interpreted as utf8 is identical to
+// the second string interpreted as big-endian utf16... useful for strings from next func
+
+STBTT_DEF const char *stbtt_GetFontNameString(const stbtt_fontinfo *font, int *length, int platformID, int encodingID, int languageID, int nameID);
+// returns the string (which may be big-endian double byte, e.g. for unicode)
+// and puts the length in bytes in *length.
+//
+// some of the values for the IDs are below; for more see the truetype spec:
+//     http://developer.apple.com/textfonts/TTRefMan/RM06/Chap6name.html
+//     http://www.microsoft.com/typography/otspec/name.htm
+
+enum { // platformID
+   STBTT_PLATFORM_ID_UNICODE   =0,
+   STBTT_PLATFORM_ID_MAC       =1,
+   STBTT_PLATFORM_ID_ISO       =2,
+   STBTT_PLATFORM_ID_MICROSOFT =3
+};
+
+enum { // encodingID for STBTT_PLATFORM_ID_UNICODE
+   STBTT_UNICODE_EID_UNICODE_1_0    =0,
+   STBTT_UNICODE_EID_UNICODE_1_1    =1,
+   STBTT_UNICODE_EID_ISO_10646      =2,
+   STBTT_UNICODE_EID_UNICODE_2_0_BMP=3,
+   STBTT_UNICODE_EID_UNICODE_2_0_FULL=4
+};
+
+enum { // encodingID for STBTT_PLATFORM_ID_MICROSOFT
+   STBTT_MS_EID_SYMBOL        =0,
+   STBTT_MS_EID_UNICODE_BMP   =1,
+   STBTT_MS_EID_SHIFTJIS      =2,
+   STBTT_MS_EID_UNICODE_FULL  =10
+};
+
+enum { // encodingID for STBTT_PLATFORM_ID_MAC; same as Script Manager codes
+   STBTT_MAC_EID_ROMAN        =0,   STBTT_MAC_EID_ARABIC       =4,
+   STBTT_MAC_EID_JAPANESE     =1,   STBTT_MAC_EID_HEBREW       =5,
+   STBTT_MAC_EID_CHINESE_TRAD =2,   STBTT_MAC_EID_GREEK        =6,
+   STBTT_MAC_EID_KOREAN       =3,   STBTT_MAC_EID_RUSSIAN      =7
+};
+
+enum { // languageID for STBTT_PLATFORM_ID_MICROSOFT; same as LCID...
+       // problematic because there are e.g. 16 english LCIDs and 16 arabic LCIDs
+   STBTT_MS_LANG_ENGLISH     =0x0409,   STBTT_MS_LANG_ITALIAN     =0x0410,
+   STBTT_MS_LANG_CHINESE     =0x0804,   STBTT_MS_LANG_JAPANESE    =0x0411,
+   STBTT_MS_LANG_DUTCH       =0x0413,   STBTT_MS_LANG_KOREAN      =0x0412,
+   STBTT_MS_LANG_FRENCH      =0x040c,   STBTT_MS_LANG_RUSSIAN     =0x0419,
+   STBTT_MS_LANG_GERMAN      =0x0407,   STBTT_MS_LANG_SPANISH     =0x0409,
+   STBTT_MS_LANG_HEBREW      =0x040d,   STBTT_MS_LANG_SWEDISH     =0x041D
+};
+
+enum { // languageID for STBTT_PLATFORM_ID_MAC
+   STBTT_MAC_LANG_ENGLISH      =0 ,   STBTT_MAC_LANG_JAPANESE     =11,
+   STBTT_MAC_LANG_ARABIC       =12,   STBTT_MAC_LANG_KOREAN       =23,
+   STBTT_MAC_LANG_DUTCH        =4 ,   STBTT_MAC_LANG_RUSSIAN      =32,
+   STBTT_MAC_LANG_FRENCH       =1 ,   STBTT_MAC_LANG_SPANISH      =6 ,
+   STBTT_MAC_LANG_GERMAN       =2 ,   STBTT_MAC_LANG_SWEDISH      =5 ,
+   STBTT_MAC_LANG_HEBREW       =10,   STBTT_MAC_LANG_CHINESE_SIMPLIFIED =33,
+   STBTT_MAC_LANG_ITALIAN      =3 ,   STBTT_MAC_LANG_CHINESE_TRAD =19
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // __STB_INCLUDE_STB_TRUETYPE_H__
+
+///////////////////////////////////////////////////////////////////////////////
+///////////////////////////////////////////////////////////////////////////////
+////
+////   IMPLEMENTATION
+////
+////
+
+#ifdef STB_TRUETYPE_IMPLEMENTATION
+
+#ifndef STBTT_MAX_OVERSAMPLE
+#define STBTT_MAX_OVERSAMPLE   8
+#endif
+
+#if STBTT_MAX_OVERSAMPLE > 255
+#error "STBTT_MAX_OVERSAMPLE cannot be > 255"
+#endif
+
+typedef int stbtt__test_oversample_pow2[(STBTT_MAX_OVERSAMPLE & (STBTT_MAX_OVERSAMPLE-1)) == 0 ? 1 : -1];
+
+#ifndef STBTT_RASTERIZER_VERSION
+#define STBTT_RASTERIZER_VERSION 2
+#endif
+
+#ifdef _MSC_VER
+#define STBTT__NOTUSED(v)  (void)(v)
+#else
+#define STBTT__NOTUSED(v)  (void)sizeof(v)
+#endif
+
+//////////////////////////////////////////////////////////////////////////
+//
+// stbtt__buf helpers to parse data from file
+//
+
+static stbtt_uint8 stbtt__buf_get8(stbtt__buf *b)
+{
+   if (b->cursor >= b->size)
+      return 0;
+   return b->data[b->cursor++];
+}
+
+static stbtt_uint8 stbtt__buf_peek8(stbtt__buf *b)
+{
+   if (b->cursor >= b->size)
+      return 0;
+   return b->data[b->cursor];
+}
+
+static void stbtt__buf_seek(stbtt__buf *b, int o)
+{
+   STBTT_assert(!(o > b->size || o < 0));
+   b->cursor = (o > b->size || o < 0) ? b->size : o;
+}
+
+static void stbtt__buf_skip(stbtt__buf *b, int o)
+{
+   stbtt__buf_seek(b, b->cursor + o);
+}
+
+static stbtt_uint32 stbtt__buf_get(stbtt__buf *b, int n)
+{
+   stbtt_uint32 v = 0;
+   int i;
+   STBTT_assert(n >= 1 && n <= 4);
+   for (i = 0; i < n; i++)
+      v = (v << 8) | stbtt__buf_get8(b);
+   return v;
+}
+
+static stbtt__buf stbtt__new_buf(const void *p, size_t size)
+{
+   stbtt__buf r;
+   STBTT_assert(size < 0x40000000);
+   r.data = (stbtt_uint8*) p;
+   r.size = (int) size;
+   r.cursor = 0;
+   return r;
+}
+
+#define stbtt__buf_get16(b)  stbtt__buf_get((b), 2)
+#define stbtt__buf_get32(b)  stbtt__buf_get((b), 4)
+
+static stbtt__buf stbtt__buf_range(const stbtt__buf *b, int o, int s)
+{
+   stbtt__buf r = stbtt__new_buf(NULL, 0);
+   if (o < 0 || s < 0 || o > b->size || s > b->size - o) return r;
+   r.data = b->data + o;
+   r.size = s;
+   return r;
+}
+
+static stbtt__buf stbtt__cff_get_index(stbtt__buf *b)
+{
+   int count, start, offsize;
+   start = b->cursor;
+   count = stbtt__buf_get16(b);
+   if (count) {
+      offsize = stbtt__buf_get8(b);
+      STBTT_assert(offsize >= 1 && offsize <= 4);
+      stbtt__buf_skip(b, offsize * count);
+      stbtt__buf_skip(b, stbtt__buf_get(b, offsize) - 1);
+   }
+   return stbtt__buf_range(b, start, b->cursor - start);
+}
+
+static stbtt_uint32 stbtt__cff_int(stbtt__buf *b)
+{
+   int b0 = stbtt__buf_get8(b);
+   if (b0 >= 32 && b0 <= 246)       return b0 - 139;
+   else if (b0 >= 247 && b0 <= 250) return (b0 - 247)*256 + stbtt__buf_get8(b) + 108;
+   else if (b0 >= 251 && b0 <= 254) return -(b0 - 251)*256 - stbtt__buf_get8(b) - 108;
+   else if (b0 == 28)               return stbtt__buf_get16(b);
+   else if (b0 == 29)               return stbtt__buf_get32(b);
+   STBTT_assert(0);
+   return 0;
+}
+
+static void stbtt__cff_skip_operand(stbtt__buf *b) {
+   int v, b0 = stbtt__buf_peek8(b);
+   STBTT_assert(b0 >= 28);
+   if (b0 == 30) {
+      stbtt__buf_skip(b, 1);
+      while (b->cursor < b->size) {
+         v = stbtt__buf_get8(b);
+         if ((v & 0xF) == 0xF || (v >> 4) == 0xF)
+            break;
+      }
+   } else {
+      stbtt__cff_int(b);
+   }
+}
+
+static stbtt__buf stbtt__dict_get(stbtt__buf *b, int key)
+{
+   stbtt__buf_seek(b, 0);
+   while (b->cursor < b->size) {
+      int start = b->cursor, end, op;
+      while (stbtt__buf_peek8(b) >= 28)
+         stbtt__cff_skip_operand(b);
+      end = b->cursor;
+      op = stbtt__buf_get8(b);
+      if (op == 12)  op = stbtt__buf_get8(b) | 0x100;
+      if (op == key) return stbtt__buf_range(b, start, end-start);
+   }
+   return stbtt__buf_range(b, 0, 0);
+}
+
+static void stbtt__dict_get_ints(stbtt__buf *b, int key, int outcount, stbtt_uint32 *out)
+{
+   int i;
+   stbtt__buf operands = stbtt__dict_get(b, key);
+   for (i = 0; i < outcount && operands.cursor < operands.size; i++)
+      out[i] = stbtt__cff_int(&operands);
+}
+
+static int stbtt__cff_index_count(stbtt__buf *b)
+{
+   stbtt__buf_seek(b, 0);
+   return stbtt__buf_get16(b);
+}
+
+static stbtt__buf stbtt__cff_index_get(stbtt__buf b, int i)
+{
+   int count, offsize, start, end;
+   stbtt__buf_seek(&b, 0);
+   count = stbtt__buf_get16(&b);
+   offsize = stbtt__buf_get8(&b);
+   STBTT_assert(i >= 0 && i < count);
+   STBTT_assert(offsize >= 1 && offsize <= 4);
+   stbtt__buf_skip(&b, i*offsize);
+   start = stbtt__buf_get(&b, offsize);
+   end = stbtt__buf_get(&b, offsize);
+   return stbtt__buf_range(&b, 2+(count+1)*offsize+start, end - start);
+}
+
+//////////////////////////////////////////////////////////////////////////
+//
+// accessors to parse data from file
+//
+
+// on platforms that don't allow misaligned reads, if we want to allow
+// truetype fonts that aren't padded to alignment, define ALLOW_UNALIGNED_TRUETYPE
+
+#define ttBYTE(p)     (* (stbtt_uint8 *) (p))
+#define ttCHAR(p)     (* (stbtt_int8 *) (p))
+#define ttFixed(p)    ttLONG(p)
+
+static stbtt_uint16 ttUSHORT(stbtt_uint8 *p) { return p[0]*256 + p[1]; }
+static stbtt_int16 ttSHORT(stbtt_uint8 *p)   { return p[0]*256 + p[1]; }
+static stbtt_uint32 ttULONG(stbtt_uint8 *p)  { return (p[0]<<24) + (p[1]<<16) + (p[2]<<8) + p[3]; }
+static stbtt_int32 ttLONG(stbtt_uint8 *p)    { return (p[0]<<24) + (p[1]<<16) + (p[2]<<8) + p[3]; }
+
+#define stbtt_tag4(p,c0,c1,c2,c3) ((p)[0] == (c0) && (p)[1] == (c1) && (p)[2] == (c2) && (p)[3] == (c3))
+#define stbtt_tag(p,str)           stbtt_tag4(p,str[0],str[1],str[2],str[3])
+
+static int stbtt__isfont(stbtt_uint8 *font)
+{
+   // check the version number
+   if (stbtt_tag4(font, '1',0,0,0))  return 1; // TrueType 1
+   if (stbtt_tag(font, "typ1"))   return 1; // TrueType with type 1 font -- we don't support this!
+   if (stbtt_tag(font, "OTTO"))   return 1; // OpenType with CFF
+   if (stbtt_tag4(font, 0,1,0,0)) return 1; // OpenType 1.0
+   if (stbtt_tag(font, "true"))   return 1; // Apple specification for TrueType fonts
+   return 0;
+}
+
+// @OPTIMIZE: binary search
+static stbtt_uint32 stbtt__find_table(stbtt_uint8 *data, stbtt_uint32 fontstart, const char *tag)
+{
+   stbtt_int32 num_tables = ttUSHORT(data+fontstart+4);
+   stbtt_uint32 tabledir = fontstart + 12;
+   stbtt_int32 i;
+   for (i=0; i < num_tables; ++i) {
+      stbtt_uint32 loc = tabledir + 16*i;
+      if (stbtt_tag(data+loc+0, tag))
+         return ttULONG(data+loc+8);
+   }
+   return 0;
+}
+
+static int stbtt_GetFontOffsetForIndex_internal(unsigned char *font_collection, int index)
+{
+   // if it's just a font, there's only one valid index
+   if (stbtt__isfont(font_collection))
+      return index == 0 ? 0 : -1;
+
+   // check if it's a TTC
+   if (stbtt_tag(font_collection, "ttcf")) {
+      // version 1?
+      if (ttULONG(font_collection+4) == 0x00010000 || ttULONG(font_collection+4) == 0x00020000) {
+         stbtt_int32 n = ttLONG(font_collection+8);
+         if (index >= n)
+            return -1;
+         return ttULONG(font_collection+12+index*4);
+      }
+   }
+   return -1;
+}
+
+static int stbtt_GetNumberOfFonts_internal(unsigned char *font_collection)
+{
+   // if it's just a font, there's only one valid font
+   if (stbtt__isfont(font_collection))
+      return 1;
+
+   // check if it's a TTC
+   if (stbtt_tag(font_collection, "ttcf")) {
+      // version 1?
+      if (ttULONG(font_collection+4) == 0x00010000 || ttULONG(font_collection+4) == 0x00020000) {
+         return ttLONG(font_collection+8);
+      }
+   }
+   return 0;
+}
+
+static stbtt__buf stbtt__get_subrs(stbtt__buf cff, stbtt__buf fontdict)
+{
+   stbtt_uint32 subrsoff = 0, private_loc[2] = { 0, 0 };
+   stbtt__buf pdict;
+   stbtt__dict_get_ints(&fontdict, 18, 2, private_loc);
+   if (!private_loc[1] || !private_loc[0]) return stbtt__new_buf(NULL, 0);
+   pdict = stbtt__buf_range(&cff, private_loc[1], private_loc[0]);
+   stbtt__dict_get_ints(&pdict, 19, 1, &subrsoff);
+   if (!subrsoff) return stbtt__new_buf(NULL, 0);
+   stbtt__buf_seek(&cff, private_loc[1]+subrsoff);
+   return stbtt__cff_get_index(&cff);
+}
+
+// since most people won't use this, find this table the first time it's needed
+static int stbtt__get_svg(stbtt_fontinfo *info)
+{
+   stbtt_uint32 t;
+   if (info->svg < 0) {
+      t = stbtt__find_table(info->data, info->fontstart, "SVG ");
+      if (t) {
+         stbtt_uint32 offset = ttULONG(info->data + t + 2);
+         info->svg = t + offset;
+      } else {
+         info->svg = 0;
+      }
+   }
+   return info->svg;
+}
+
+static int stbtt_InitFont_internal(stbtt_fontinfo *info, unsigned char *data, int fontstart)
+{
+   stbtt_uint32 cmap, t;
+   stbtt_int32 i,numTables;
+
+   info->data = data;
+   info->fontstart = fontstart;
+   info->cff = stbtt__new_buf(NULL, 0);
+
+   cmap = stbtt__find_table(data, fontstart, "cmap");       // required
+   info->loca = stbtt__find_table(data, fontstart, "loca"); // required
+   info->head = stbtt__find_table(data, fontstart, "head"); // required
+   info->glyf = stbtt__find_table(data, fontstart, "glyf"); // required
+   info->hhea = stbtt__find_table(data, fontstart, "hhea"); // required
+   info->hmtx = stbtt__find_table(data, fontstart, "hmtx"); // required
+   info->kern = stbtt__find_table(data, fontstart, "kern"); // not required
+   info->gpos = stbtt__find_table(data, fontstart, "GPOS"); // not required
+
+   if (!cmap || !info->head || !info->hhea || !info->hmtx)
+      return 0;
+   if (info->glyf) {
+      // required for truetype
+      if (!info->loca) return 0;
+   } else {
+      // initialization for CFF / Type2 fonts (OTF)
+      stbtt__buf b, topdict, topdictidx;
+      stbtt_uint32 cstype = 2, charstrings = 0, fdarrayoff = 0, fdselectoff = 0;
+      stbtt_uint32 cff;
+
+      cff = stbtt__find_table(data, fontstart, "CFF ");
+      if (!cff) return 0;
+
+      info->fontdicts = stbtt__new_buf(NULL, 0);
+      info->fdselect = stbtt__new_buf(NULL, 0);
+
+      // @TODO this should use size from table (not 512MB)
+      info->cff = stbtt__new_buf(data+cff, 512*1024*1024);
+      b = info->cff;
+
+      // read the header
+      stbtt__buf_skip(&b, 2);
+      stbtt__buf_seek(&b, stbtt__buf_get8(&b)); // hdrsize
+
+      // @TODO the name INDEX could list multiple fonts,
+      // but we just use the first one.
+      stbtt__cff_get_index(&b);  // name INDEX
+      topdictidx = stbtt__cff_get_index(&b);
+      topdict = stbtt__cff_index_get(topdictidx, 0);
+      stbtt__cff_get_index(&b);  // string INDEX
+      info->gsubrs = stbtt__cff_get_index(&b);
+
+      stbtt__dict_get_ints(&topdict, 17, 1, &charstrings);
+      stbtt__dict_get_ints(&topdict, 0x100 | 6, 1, &cstype);
+      stbtt__dict_get_ints(&topdict, 0x100 | 36, 1, &fdarrayoff);
+      stbtt__dict_get_ints(&topdict, 0x100 | 37, 1, &fdselectoff);
+      info->subrs = stbtt__get_subrs(b, topdict);
+
+      // we only support Type 2 charstrings
+      if (cstype != 2) return 0;
+      if (charstrings == 0) return 0;
+
+      if (fdarrayoff) {
+         // looks like a CID font
+         if (!fdselectoff) return 0;
+         stbtt__buf_seek(&b, fdarrayoff);
+         info->fontdicts = stbtt__cff_get_index(&b);
+         info->fdselect = stbtt__buf_range(&b, fdselectoff, b.size-fdselectoff);
+      }
+
+      stbtt__buf_seek(&b, charstrings);
+      info->charstrings = stbtt__cff_get_index(&b);
+   }
+
+   t = stbtt__find_table(data, fontstart, "maxp");
+   if (t)
+      info->numGlyphs = ttUSHORT(data+t+4);
+   else
+      info->numGlyphs = 0xffff;
+
+   info->svg = -1;
+
+   // find a cmap encoding table we understand *now* to avoid searching
+   // later. (todo: could make this installable)
+   // the same regardless of glyph.
+   numTables = ttUSHORT(data + cmap + 2);
+   info->index_map = 0;
+   for (i=0; i < numTables; ++i) {
+      stbtt_uint32 encoding_record = cmap + 4 + 8 * i;
+      // find an encoding we understand:
+      switch(ttUSHORT(data+encoding_record)) {
+         case STBTT_PLATFORM_ID_MICROSOFT:
+            switch (ttUSHORT(data+encoding_record+2)) {
+               case STBTT_MS_EID_UNICODE_BMP:
+               case STBTT_MS_EID_UNICODE_FULL:
+                  // MS/Unicode
+                  info->index_map = cmap + ttULONG(data+encoding_record+4);
+                  break;
+            }
+            break;
+        case STBTT_PLATFORM_ID_UNICODE:
+            // Mac/iOS has these
+            // all the encodingIDs are unicode, so we don't bother to check it
+            info->index_map = cmap + ttULONG(data+encoding_record+4);
+            break;
+      }
+   }
+   if (info->index_map == 0)
+      return 0;
+
+   info->indexToLocFormat = ttUSHORT(data+info->head + 50);
+   return 1;
+}
+
+STBTT_DEF int stbtt_FindGlyphIndex(const stbtt_fontinfo *info, int unicode_codepoint)
+{
+   stbtt_uint8 *data = info->data;
+   stbtt_uint32 index_map = info->index_map;
+
+   stbtt_uint16 format = ttUSHORT(data + index_map + 0);
+   if (format == 0) { // apple byte encoding
+      stbtt_int32 bytes = ttUSHORT(data + index_map + 2);
+      if (unicode_codepoint < bytes-6)
+         return ttBYTE(data + index_map + 6 + unicode_codepoint);
+      return 0;
+   } else if (format == 6) {
+      stbtt_uint32 first = ttUSHORT(data + index_map + 6);
+      stbtt_uint32 count = ttUSHORT(data + index_map + 8);
+      if ((stbtt_uint32) unicode_codepoint >= first && (stbtt_uint32) unicode_codepoint < first+count)
+         return ttUSHORT(data + index_map + 10 + (unicode_codepoint - first)*2);
+      return 0;
+   } else if (format == 2) {
+      STBTT_assert(0); // @TODO: high-byte mapping for japanese/chinese/korean
+      return 0;
+   } else if (format == 4) { // standard mapping for windows fonts: binary search collection of ranges
+      stbtt_uint16 segcount = ttUSHORT(data+index_map+6) >> 1;
+      stbtt_uint16 searchRange = ttUSHORT(data+index_map+8) >> 1;
+      stbtt_uint16 entrySelector = ttUSHORT(data+index_map+10);
+      stbtt_uint16 rangeShift = ttUSHORT(data+index_map+12) >> 1;
+
+      // do a binary search of the segments
+      stbtt_uint32 endCount = index_map + 14;
+      stbtt_uint32 search = endCount;
+
+      if (unicode_codepoint > 0xffff)
+         return 0;
+
+      // they lie from endCount .. endCount + segCount
+      // but searchRange is the nearest power of two, so...
+      if (unicode_codepoint >= ttUSHORT(data + search + rangeShift*2))
+         search += rangeShift*2;
+
+      // now decrement to bias correctly to find smallest
+      search -= 2;
+      while (entrySelector) {
+         stbtt_uint16 end;
+         searchRange >>= 1;
+         end = ttUSHORT(data + search + searchRange*2);
+         if (unicode_codepoint > end)
+            search += searchRange*2;
+         --entrySelector;
+      }
+      search += 2;
+
+      {
+         stbtt_uint16 offset, start, last;
+         stbtt_uint16 item = (stbtt_uint16) ((search - endCount) >> 1);
+
+         start = ttUSHORT(data + index_map + 14 + segcount*2 + 2 + 2*item);
+         last = ttUSHORT(data + endCount + 2*item);
+         if (unicode_codepoint < start || unicode_codepoint > last)
+            return 0;
+
+         offset = ttUSHORT(data + index_map + 14 + segcount*6 + 2 + 2*item);
+         if (offset == 0)
+            return (stbtt_uint16) (unicode_codepoint + ttSHORT(data + index_map + 14 + segcount*4 + 2 + 2*item));
+
+         return ttUSHORT(data + offset + (unicode_codepoint-start)*2 + index_map + 14 + segcount*6 + 2 + 2*item);
+      }
+   } else if (format == 12 || format == 13) {
+      stbtt_uint32 ngroups = ttULONG(data+index_map+12);
+      stbtt_int32 low,high;
+      low = 0; high = (stbtt_int32)ngroups;
+      // Binary search the right group.
+      while (low < high) {
+         stbtt_int32 mid = low + ((high-low) >> 1); // rounds down, so low <= mid < high
+         stbtt_uint32 start_char = ttULONG(data+index_map+16+mid*12);
+         stbtt_uint32 end_char = ttULONG(data+index_map+16+mid*12+4);
+         if ((stbtt_uint32) unicode_codepoint < start_char)
+            high = mid;
+         else if ((stbtt_uint32) unicode_codepoint > end_char)
+            low = mid+1;
+         else {
+            stbtt_uint32 start_glyph = ttULONG(data+index_map+16+mid*12+8);
+            if (format == 12)
+               return start_glyph + unicode_codepoint-start_char;
+            else // format == 13
+               return start_glyph;
+         }
+      }
+      return 0; // not found
+   }
+   // @TODO
+   STBTT_assert(0);
+   return 0;
+}
+
+STBTT_DEF int stbtt_GetCodepointShape(const stbtt_fontinfo *info, int unicode_codepoint, stbtt_vertex **vertices)
+{
+   return stbtt_GetGlyphShape(info, stbtt_FindGlyphIndex(info, unicode_codepoint), vertices);
+}
+
+static void stbtt_setvertex(stbtt_vertex *v, stbtt_uint8 type, stbtt_int32 x, stbtt_int32 y, stbtt_int32 cx, stbtt_int32 cy)
+{
+   v->type = type;
+   v->x = (stbtt_int16) x;
+   v->y = (stbtt_int16) y;
+   v->cx = (stbtt_int16) cx;
+   v->cy = (stbtt_int16) cy;
+}
+
+static int stbtt__GetGlyfOffset(const stbtt_fontinfo *info, int glyph_index)
+{
+   int g1,g2;
+
+   STBTT_assert(!info->cff.size);
+
+   if (glyph_index >= info->numGlyphs) return -1; // glyph index out of range
+   if (info->indexToLocFormat >= 2)    return -1; // unknown index->glyph map format
+
+   if (info->indexToLocFormat == 0) {
+      g1 = info->glyf + ttUSHORT(info->data + info->loca + glyph_index * 2) * 2;
+      g2 = info->glyf + ttUSHORT(info->data + info->loca + glyph_index * 2 + 2) * 2;
+   } else {
+      g1 = info->glyf + ttULONG (info->data + info->loca + glyph_index * 4);
+      g2 = info->glyf + ttULONG (info->data + info->loca + glyph_index * 4 + 4);
+   }
+
+   return g1==g2 ? -1 : g1; // if length is 0, return -1
+}
+
+static int stbtt__GetGlyphInfoT2(const stbtt_fontinfo *info, int glyph_index, int *x0, int *y0, int *x1, int *y1);
+
+STBTT_DEF int stbtt_GetGlyphBox(const stbtt_fontinfo *info, int glyph_index, int *x0, int *y0, int *x1, int *y1)
+{
+   if (info->cff.size) {
+      stbtt__GetGlyphInfoT2(info, glyph_index, x0, y0, x1, y1);
+   } else {
+      int g = stbtt__GetGlyfOffset(info, glyph_index);
+      if (g < 0) return 0;
+
+      if (x0) *x0 = ttSHORT(info->data + g + 2);
+      if (y0) *y0 = ttSHORT(info->data + g + 4);
+      if (x1) *x1 = ttSHORT(info->data + g + 6);
+      if (y1) *y1 = ttSHORT(info->data + g + 8);
+   }
+   return 1;
+}
+
+STBTT_DEF int stbtt_GetCodepointBox(const stbtt_fontinfo *info, int codepoint, int *x0, int *y0, int *x1, int *y1)
+{
+   return stbtt_GetGlyphBox(info, stbtt_FindGlyphIndex(info,codepoint), x0,y0,x1,y1);
+}
+
+STBTT_DEF int stbtt_IsGlyphEmpty(const stbtt_fontinfo *info, int glyph_index)
+{
+   stbtt_int16 numberOfContours;
+   int g;
+   if (info->cff.size)
+      return stbtt__GetGlyphInfoT2(info, glyph_index, NULL, NULL, NULL, NULL) == 0;
+   g = stbtt__GetGlyfOffset(info, glyph_index);
+   if (g < 0) return 1;
+   numberOfContours = ttSHORT(info->data + g);
+   return numberOfContours == 0;
+}
+
+static int stbtt__close_shape(stbtt_vertex *vertices, int num_vertices, int was_off, int start_off,
+    stbtt_int32 sx, stbtt_int32 sy, stbtt_int32 scx, stbtt_int32 scy, stbtt_int32 cx, stbtt_int32 cy)
+{
+   if (start_off) {
+      if (was_off)
+         stbtt_setvertex(&vertices[num_vertices++], STBTT_vcurve, (cx+scx)>>1, (cy+scy)>>1, cx,cy);
+      stbtt_setvertex(&vertices[num_vertices++], STBTT_vcurve, sx,sy,scx,scy);
+   } else {
+      if (was_off)
+         stbtt_setvertex(&vertices[num_vertices++], STBTT_vcurve,sx,sy,cx,cy);
+      else
+         stbtt_setvertex(&vertices[num_vertices++], STBTT_vline,sx,sy,0,0);
+   }
+   return num_vertices;
+}
+
+static int stbtt__GetGlyphShapeTT(const stbtt_fontinfo *info, int glyph_index, stbtt_vertex **pvertices)
+{
+   stbtt_int16 numberOfContours;
+   stbtt_uint8 *endPtsOfContours;
+   stbtt_uint8 *data = info->data;
+   stbtt_vertex *vertices=0;
+   int num_vertices=0;
+   int g = stbtt__GetGlyfOffset(info, glyph_index);
+
+   *pvertices = NULL;
+
+   if (g < 0) return 0;
+
+   numberOfContours = ttSHORT(data + g);
+
+   if (numberOfContours > 0) {
+      stbtt_uint8 flags=0,flagcount;
+      stbtt_int32 ins, i,j=0,m,n, next_move, was_off=0, off, start_off=0;
+      stbtt_int32 x,y,cx,cy,sx,sy, scx,scy;
+      stbtt_uint8 *points;
+      endPtsOfContours = (data + g + 10);
+      ins = ttUSHORT(data + g + 10 + numberOfContours * 2);
+      points = data + g + 10 + numberOfContours * 2 + 2 + ins;
+
+      n = 1+ttUSHORT(endPtsOfContours + numberOfContours*2-2);
+
+      m = n + 2*numberOfContours;  // a loose bound on how many vertices we might need
+      vertices = (stbtt_vertex *) STBTT_malloc(m * sizeof(vertices[0]), info->userdata);
+      if (vertices == 0)
+         return 0;
+
+      next_move = 0;
+      flagcount=0;
+
+      // in first pass, we load uninterpreted data into the allocated array
+      // above, shifted to the end of the array so we won't overwrite it when
+      // we create our final data starting from the front
+
+      off = m - n; // starting offset for uninterpreted data, regardless of how m ends up being calculated
+
+      // first load flags
+
+      for (i=0; i < n; ++i) {
+         if (flagcount == 0) {
+            flags = *points++;
+            if (flags & 8)
+               flagcount = *points++;
+         } else
+            --flagcount;
+         vertices[off+i].type = flags;
+      }
+
+      // now load x coordinates
+      x=0;
+      for (i=0; i < n; ++i) {
+         flags = vertices[off+i].type;
+         if (flags & 2) {
+            stbtt_int16 dx = *points++;
+            x += (flags & 16) ? dx : -dx; // ???
+         } else {
+            if (!(flags & 16)) {
+               x = x + (stbtt_int16) (points[0]*256 + points[1]);
+               points += 2;
+            }
+         }
+         vertices[off+i].x = (stbtt_int16) x;
+      }
+
+      // now load y coordinates
+      y=0;
+      for (i=0; i < n; ++i) {
+         flags = vertices[off+i].type;
+         if (flags & 4) {
+            stbtt_int16 dy = *points++;
+            y += (flags & 32) ? dy : -dy; // ???
+         } else {
+            if (!(flags & 32)) {
+               y = y + (stbtt_int16) (points[0]*256 + points[1]);
+               points += 2;
+            }
+         }
+         vertices[off+i].y = (stbtt_int16) y;
+      }
+
+      // now convert them to our format
+      num_vertices=0;
+      sx = sy = cx = cy = scx = scy = 0;
+      for (i=0; i < n; ++i) {
+         flags = vertices[off+i].type;
+         x     = (stbtt_int16) vertices[off+i].x;
+         y     = (stbtt_int16) vertices[off+i].y;
+
+         if (next_move == i) {
+            if (i != 0)
+               num_vertices = stbtt__close_shape(vertices, num_vertices, was_off, start_off, sx,sy,scx,scy,cx,cy);
+
+            // now start the new one
+            start_off = !(flags & 1);
+            if (start_off) {
+               // if we start off with an off-curve point, then when we need to find a point on the curve
+               // where we can start, and we need to save some state for when we wraparound.
+               scx = x;
+               scy = y;
+               if (!(vertices[off+i+1].type & 1)) {
+                  // next point is also a curve point, so interpolate an on-point curve
+                  sx = (x + (stbtt_int32) vertices[off+i+1].x) >> 1;
+                  sy = (y + (stbtt_int32) vertices[off+i+1].y) >> 1;
+               } else {
+                  // otherwise just use the next point as our start point
+                  sx = (stbtt_int32) vertices[off+i+1].x;
+                  sy = (stbtt_int32) vertices[off+i+1].y;
+                  ++i; // we're using point i+1 as the starting point, so skip it
+               }
+            } else {
+               sx = x;
+               sy = y;
+            }
+            stbtt_setvertex(&vertices[num_vertices++], STBTT_vmove,sx,sy,0,0);
+            was_off = 0;
+            next_move = 1 + ttUSHORT(endPtsOfContours+j*2);
+            ++j;
+         } else {
+            if (!(flags & 1)) { // if it's a curve
+               if (was_off) // two off-curve control points in a row means interpolate an on-curve midpoint
+                  stbtt_setvertex(&vertices[num_vertices++], STBTT_vcurve, (cx+x)>>1, (cy+y)>>1, cx, cy);
+               cx = x;
+               cy = y;
+               was_off = 1;
+            } else {
+               if (was_off)
+                  stbtt_setvertex(&vertices[num_vertices++], STBTT_vcurve, x,y, cx, cy);
+               else
+                  stbtt_setvertex(&vertices[num_vertices++], STBTT_vline, x,y,0,0);
+               was_off = 0;
+            }
+         }
+      }
+      num_vertices = stbtt__close_shape(vertices, num_vertices, was_off, start_off, sx,sy,scx,scy,cx,cy);
+   } else if (numberOfContours < 0) {
+      // Compound shapes.
+      int more = 1;
+      stbtt_uint8 *comp = data + g + 10;
+      num_vertices = 0;
+      vertices = 0;
+      while (more) {
+         stbtt_uint16 flags, gidx;
+         int comp_num_verts = 0, i;
+         stbtt_vertex *comp_verts = 0, *tmp = 0;
+         float mtx[6] = {1,0,0,1,0,0}, m, n;
+
+         flags = ttSHORT(comp); comp+=2;
+         gidx = ttSHORT(comp); comp+=2;
+
+         if (flags & 2) { // XY values
+            if (flags & 1) { // shorts
+               mtx[4] = ttSHORT(comp); comp+=2;
+               mtx[5] = ttSHORT(comp); comp+=2;
+            } else {
+               mtx[4] = ttCHAR(comp); comp+=1;
+               mtx[5] = ttCHAR(comp); comp+=1;
+            }
+         }
+         else {
+            // @TODO handle matching point
+            STBTT_assert(0);
+         }
+         if (flags & (1<<3)) { // WE_HAVE_A_SCALE
+            mtx[0] = mtx[3] = ttSHORT(comp)/16384.0f; comp+=2;
+            mtx[1] = mtx[2] = 0;
+         } else if (flags & (1<<6)) { // WE_HAVE_AN_X_AND_YSCALE
+            mtx[0] = ttSHORT(comp)/16384.0f; comp+=2;
+            mtx[1] = mtx[2] = 0;
+            mtx[3] = ttSHORT(comp)/16384.0f; comp+=2;
+         } else if (flags & (1<<7)) { // WE_HAVE_A_TWO_BY_TWO
+            mtx[0] = ttSHORT(comp)/16384.0f; comp+=2;
+            mtx[1] = ttSHORT(comp)/16384.0f; comp+=2;
+            mtx[2] = ttSHORT(comp)/16384.0f; comp+=2;
+            mtx[3] = ttSHORT(comp)/16384.0f; comp+=2;
+         }
+
+         // Find transformation scales.
+         m = (float) STBTT_sqrt(mtx[0]*mtx[0] + mtx[1]*mtx[1]);
+         n = (float) STBTT_sqrt(mtx[2]*mtx[2] + mtx[3]*mtx[3]);
+
+         // Get indexed glyph.
+         comp_num_verts = stbtt_GetGlyphShape(info, gidx, &comp_verts);
+         if (comp_num_verts > 0) {
+            // Transform vertices.
+            for (i = 0; i < comp_num_verts; ++i) {
+               stbtt_vertex* v = &comp_verts[i];
+               stbtt_vertex_type x,y;
+               x=v->x; y=v->y;
+               v->x = (stbtt_vertex_type)(m * (mtx[0]*x + mtx[2]*y + mtx[4]));
+               v->y = (stbtt_vertex_type)(n * (mtx[1]*x + mtx[3]*y + mtx[5]));
+               x=v->cx; y=v->cy;
+               v->cx = (stbtt_vertex_type)(m * (mtx[0]*x + mtx[2]*y + mtx[4]));
+               v->cy = (stbtt_vertex_type)(n * (mtx[1]*x + mtx[3]*y + mtx[5]));
+            }
+            // Append vertices.
+            tmp = (stbtt_vertex*)STBTT_malloc((num_vertices+comp_num_verts)*sizeof(stbtt_vertex), info->userdata);
+            if (!tmp) {
+               if (vertices) STBTT_free(vertices, info->userdata);
+               if (comp_verts) STBTT_free(comp_verts, info->userdata);
+               return 0;
+            }
+            if (num_vertices > 0 && vertices) STBTT_memcpy(tmp, vertices, num_vertices*sizeof(stbtt_vertex));
+            STBTT_memcpy(tmp+num_vertices, comp_verts, comp_num_verts*sizeof(stbtt_vertex));
+            if (vertices) STBTT_free(vertices, info->userdata);
+            vertices = tmp;
+            STBTT_free(comp_verts, info->userdata);
+            num_vertices += comp_num_verts;
+         }
+         // More components ?
+         more = flags & (1<<5);
+      }
+   } else {
+      // numberOfCounters == 0, do nothing
+   }
+
+   *pvertices = vertices;
+   return num_vertices;
+}
+
+typedef struct
+{
+   int bounds;
+   int started;
+   float first_x, first_y;
+   float x, y;
+   stbtt_int32 min_x, max_x, min_y, max_y;
+
+   stbtt_vertex *pvertices;
+   int num_vertices;
+} stbtt__csctx;
+
+#define STBTT__CSCTX_INIT(bounds) {bounds,0, 0,0, 0,0, 0,0,0,0, NULL, 0}
+
+static void stbtt__track_vertex(stbtt__csctx *c, stbtt_int32 x, stbtt_int32 y)
+{
+   if (x > c->max_x || !c->started) c->max_x = x;
+   if (y > c->max_y || !c->started) c->max_y = y;
+   if (x < c->min_x || !c->started) c->min_x = x;
+   if (y < c->min_y || !c->started) c->min_y = y;
+   c->started = 1;
+}
+
+static void stbtt__csctx_v(stbtt__csctx *c, stbtt_uint8 type, stbtt_int32 x, stbtt_int32 y, stbtt_int32 cx, stbtt_int32 cy, stbtt_int32 cx1, stbtt_int32 cy1)
+{
+   if (c->bounds) {
+      stbtt__track_vertex(c, x, y);
+      if (type == STBTT_vcubic) {
+         stbtt__track_vertex(c, cx, cy);
+         stbtt__track_vertex(c, cx1, cy1);
+      }
+   } else {
+      stbtt_setvertex(&c->pvertices[c->num_vertices], type, x, y, cx, cy);
+      c->pvertices[c->num_vertices].cx1 = (stbtt_int16) cx1;
+      c->pvertices[c->num_vertices].cy1 = (stbtt_int16) cy1;
+   }
+   c->num_vertices++;
+}
+
+static void stbtt__csctx_close_shape(stbtt__csctx *ctx)
+{
+   if (ctx->first_x != ctx->x || ctx->first_y != ctx->y)
+      stbtt__csctx_v(ctx, STBTT_vline, (int)ctx->first_x, (int)ctx->first_y, 0, 0, 0, 0);
+}
+
+static void stbtt__csctx_rmove_to(stbtt__csctx *ctx, float dx, float dy)
+{
+   stbtt__csctx_close_shape(ctx);
+   ctx->first_x = ctx->x = ctx->x + dx;
+   ctx->first_y = ctx->y = ctx->y + dy;
+   stbtt__csctx_v(ctx, STBTT_vmove, (int)ctx->x, (int)ctx->y, 0, 0, 0, 0);
+}
+
+static void stbtt__csctx_rline_to(stbtt__csctx *ctx, float dx, float dy)
+{
+   ctx->x += dx;
+   ctx->y += dy;
+   stbtt__csctx_v(ctx, STBTT_vline, (int)ctx->x, (int)ctx->y, 0, 0, 0, 0);
+}
+
+static void stbtt__csctx_rccurve_to(stbtt__csctx *ctx, float dx1, float dy1, float dx2, float dy2, float dx3, float dy3)
+{
+   float cx1 = ctx->x + dx1;
+   float cy1 = ctx->y + dy1;
+   float cx2 = cx1 + dx2;
+   float cy2 = cy1 + dy2;
+   ctx->x = cx2 + dx3;
+   ctx->y = cy2 + dy3;
+   stbtt__csctx_v(ctx, STBTT_vcubic, (int)ctx->x, (int)ctx->y, (int)cx1, (int)cy1, (int)cx2, (int)cy2);
+}
+
+static stbtt__buf stbtt__get_subr(stbtt__buf idx, int n)
+{
+   int count = stbtt__cff_index_count(&idx);
+   int bias = 107;
+   if (count >= 33900)
+      bias = 32768;
+   else if (count >= 1240)
+      bias = 1131;
+   n += bias;
+   if (n < 0 || n >= count)
+      return stbtt__new_buf(NULL, 0);
+   return stbtt__cff_index_get(idx, n);
+}
+
+static stbtt__buf stbtt__cid_get_glyph_subrs(const stbtt_fontinfo *info, int glyph_index)
+{
+   stbtt__buf fdselect = info->fdselect;
+   int nranges, start, end, v, fmt, fdselector = -1, i;
+
+   stbtt__buf_seek(&fdselect, 0);
+   fmt = stbtt__buf_get8(&fdselect);
+   if (fmt == 0) {
+      // untested
+      stbtt__buf_skip(&fdselect, glyph_index);
+      fdselector = stbtt__buf_get8(&fdselect);
+   } else if (fmt == 3) {
+      nranges = stbtt__buf_get16(&fdselect);
+      start = stbtt__buf_get16(&fdselect);
+      for (i = 0; i < nranges; i++) {
+         v = stbtt__buf_get8(&fdselect);
+         end = stbtt__buf_get16(&fdselect);
+         if (glyph_index >= start && glyph_index < end) {
+            fdselector = v;
+            break;
+         }
+         start = end;
+      }
+   }
+   if (fdselector == -1) stbtt__new_buf(NULL, 0);
+   return stbtt__get_subrs(info->cff, stbtt__cff_index_get(info->fontdicts, fdselector));
+}
+
+static int stbtt__run_charstring(const stbtt_fontinfo *info, int glyph_index, stbtt__csctx *c)
+{
+   int in_header = 1, maskbits = 0, subr_stack_height = 0, sp = 0, v, i, b0;
+   int has_subrs = 0, clear_stack;
+   float s[48];
+   stbtt__buf subr_stack[10], subrs = info->subrs, b;
+   float f;
+
+#define STBTT__CSERR(s) (0)
+
+   // this currently ignores the initial width value, which isn't needed if we have hmtx
+   b = stbtt__cff_index_get(info->charstrings, glyph_index);
+   while (b.cursor < b.size) {
+      i = 0;
+      clear_stack = 1;
+      b0 = stbtt__buf_get8(&b);
+      switch (b0) {
+      // @TODO implement hinting
+      case 0x13: // hintmask
+      case 0x14: // cntrmask
+         if (in_header)
+            maskbits += (sp / 2); // implicit "vstem"
+         in_header = 0;
+         stbtt__buf_skip(&b, (maskbits + 7) / 8);
+         break;
+
+      case 0x01: // hstem
+      case 0x03: // vstem
+      case 0x12: // hstemhm
+      case 0x17: // vstemhm
+         maskbits += (sp / 2);
+         break;
+
+      case 0x15: // rmoveto
+         in_header = 0;
+         if (sp < 2) return STBTT__CSERR("rmoveto stack");
+         stbtt__csctx_rmove_to(c, s[sp-2], s[sp-1]);
+         break;
+      case 0x04: // vmoveto
+         in_header = 0;
+         if (sp < 1) return STBTT__CSERR("vmoveto stack");
+         stbtt__csctx_rmove_to(c, 0, s[sp-1]);
+         break;
+      case 0x16: // hmoveto
+         in_header = 0;
+         if (sp < 1) return STBTT__CSERR("hmoveto stack");
+         stbtt__csctx_rmove_to(c, s[sp-1], 0);
+         break;
+
+      case 0x05: // rlineto
+         if (sp < 2) return STBTT__CSERR("rlineto stack");
+         for (; i + 1 < sp; i += 2)
+            stbtt__csctx_rline_to(c, s[i], s[i+1]);
+         break;
+
+      // hlineto/vlineto and vhcurveto/hvcurveto alternate horizontal and vertical
+      // starting from a different place.
+
+      case 0x07: // vlineto
+         if (sp < 1) return STBTT__CSERR("vlineto stack");
+         goto vlineto;
+      case 0x06: // hlineto
+         if (sp < 1) return STBTT__CSERR("hlineto stack");
+         for (;;) {
+            if (i >= sp) break;
+            stbtt__csctx_rline_to(c, s[i], 0);
+            i++;
+      vlineto:
+            if (i >= sp) break;
+            stbtt__csctx_rline_to(c, 0, s[i]);
+            i++;
+         }
+         break;
+
+      case 0x1F: // hvcurveto
+         if (sp < 4) return STBTT__CSERR("hvcurveto stack");
+         goto hvcurveto;
+      case 0x1E: // vhcurveto
+         if (sp < 4) return STBTT__CSERR("vhcurveto stack");
+         for (;;) {
+            if (i + 3 >= sp) break;
+            stbtt__csctx_rccurve_to(c, 0, s[i], s[i+1], s[i+2], s[i+3], (sp - i == 5) ? s[i + 4] : 0.0f);
+            i += 4;
+      hvcurveto:
+            if (i + 3 >= sp) break;
+            stbtt__csctx_rccurve_to(c, s[i], 0, s[i+1], s[i+2], (sp - i == 5) ? s[i+4] : 0.0f, s[i+3]);
+            i += 4;
+         }
+         break;
+
+      case 0x08: // rrcurveto
+         if (sp < 6) return STBTT__CSERR("rcurveline stack");
+         for (; i + 5 < sp; i += 6)
+            stbtt__csctx_rccurve_to(c, s[i], s[i+1], s[i+2], s[i+3], s[i+4], s[i+5]);
+         break;
+
+      case 0x18: // rcurveline
+         if (sp < 8) return STBTT__CSERR("rcurveline stack");
+         for (; i + 5 < sp - 2; i += 6)
+            stbtt__csctx_rccurve_to(c, s[i], s[i+1], s[i+2], s[i+3], s[i+4], s[i+5]);
+         if (i + 1 >= sp) return STBTT__CSERR("rcurveline stack");
+         stbtt__csctx_rline_to(c, s[i], s[i+1]);
+         break;
+
+      case 0x19: // rlinecurve
+         if (sp < 8) return STBTT__CSERR("rlinecurve stack");
+         for (; i + 1 < sp - 6; i += 2)
+            stbtt__csctx_rline_to(c, s[i], s[i+1]);
+         if (i + 5 >= sp) return STBTT__CSERR("rlinecurve stack");
+         stbtt__csctx_rccurve_to(c, s[i], s[i+1], s[i+2], s[i+3], s[i+4], s[i+5]);
+         break;
+
+      case 0x1A: // vvcurveto
+      case 0x1B: // hhcurveto
+         if (sp < 4) return STBTT__CSERR("(vv|hh)curveto stack");
+         f = 0.0;
+         if (sp & 1) { f = s[i]; i++; }
+         for (; i + 3 < sp; i += 4) {
+            if (b0 == 0x1B)
+               stbtt__csctx_rccurve_to(c, s[i], f, s[i+1], s[i+2], s[i+3], 0.0);
+            else
+               stbtt__csctx_rccurve_to(c, f, s[i], s[i+1], s[i+2], 0.0, s[i+3]);
+            f = 0.0;
+         }
+         break;
+
+      case 0x0A: // callsubr
+         if (!has_subrs) {
+            if (info->fdselect.size)
+               subrs = stbtt__cid_get_glyph_subrs(info, glyph_index);
+            has_subrs = 1;
+         }
+         // FALLTHROUGH
+      case 0x1D: // callgsubr
+         if (sp < 1) return STBTT__CSERR("call(g|)subr stack");
+         v = (int) s[--sp];
+         if (subr_stack_height >= 10) return STBTT__CSERR("recursion limit");
+         subr_stack[subr_stack_height++] = b;
+         b = stbtt__get_subr(b0 == 0x0A ? subrs : info->gsubrs, v);
+         if (b.size == 0) return STBTT__CSERR("subr not found");
+         b.cursor = 0;
+         clear_stack = 0;
+         break;
+
+      case 0x0B: // return
+         if (subr_stack_height <= 0) return STBTT__CSERR("return outside subr");
+         b = subr_stack[--subr_stack_height];
+         clear_stack = 0;
+         break;
+
+      case 0x0E: // endchar
+         stbtt__csctx_close_shape(c);
+         return 1;
+
+      case 0x0C: { // two-byte escape
+         float dx1, dx2, dx3, dx4, dx5, dx6, dy1, dy2, dy3, dy4, dy5, dy6;
+         float dx, dy;
+         int b1 = stbtt__buf_get8(&b);
+         switch (b1) {
+         // @TODO These "flex" implementations ignore the flex-depth and resolution,
+         // and always draw beziers.
+         case 0x22: // hflex
+            if (sp < 7) return STBTT__CSERR("hflex stack");
+            dx1 = s[0];
+            dx2 = s[1];
+            dy2 = s[2];
+            dx3 = s[3];
+            dx4 = s[4];
+            dx5 = s[5];
+            dx6 = s[6];
+            stbtt__csctx_rccurve_to(c, dx1, 0, dx2, dy2, dx3, 0);
+            stbtt__csctx_rccurve_to(c, dx4, 0, dx5, -dy2, dx6, 0);
+            break;
+
+         case 0x23: // flex
+            if (sp < 13) return STBTT__CSERR("flex stack");
+            dx1 = s[0];
+            dy1 = s[1];
+            dx2 = s[2];
+            dy2 = s[3];
+            dx3 = s[4];
+            dy3 = s[5];
+            dx4 = s[6];
+            dy4 = s[7];
+            dx5 = s[8];
+            dy5 = s[9];
+            dx6 = s[10];
+            dy6 = s[11];
+            //fd is s[12]
+            stbtt__csctx_rccurve_to(c, dx1, dy1, dx2, dy2, dx3, dy3);
+            stbtt__csctx_rccurve_to(c, dx4, dy4, dx5, dy5, dx6, dy6);
+            break;
+
+         case 0x24: // hflex1
+            if (sp < 9) return STBTT__CSERR("hflex1 stack");
+            dx1 = s[0];
+            dy1 = s[1];
+            dx2 = s[2];
+            dy2 = s[3];
+            dx3 = s[4];
+            dx4 = s[5];
+            dx5 = s[6];
+            dy5 = s[7];
+            dx6 = s[8];
+            stbtt__csctx_rccurve_to(c, dx1, dy1, dx2, dy2, dx3, 0);
+            stbtt__csctx_rccurve_to(c, dx4, 0, dx5, dy5, dx6, -(dy1+dy2+dy5));
+            break;
+
+         case 0x25: // flex1
+            if (sp < 11) return STBTT__CSERR("flex1 stack");
+            dx1 = s[0];
+            dy1 = s[1];
+            dx2 = s[2];
+            dy2 = s[3];
+            dx3 = s[4];
+            dy3 = s[5];
+            dx4 = s[6];
+            dy4 = s[7];
+            dx5 = s[8];
+            dy5 = s[9];
+            dx6 = dy6 = s[10];
+            dx = dx1+dx2+dx3+dx4+dx5;
+            dy = dy1+dy2+dy3+dy4+dy5;
+            if (STBTT_fabs(dx) > STBTT_fabs(dy))
+               dy6 = -dy;
+            else
+               dx6 = -dx;
+            stbtt__csctx_rccurve_to(c, dx1, dy1, dx2, dy2, dx3, dy3);
+            stbtt__csctx_rccurve_to(c, dx4, dy4, dx5, dy5, dx6, dy6);
+            break;
+
+         default:
+            return STBTT__CSERR("unimplemented");
+         }
+      } break;
+
+      default:
+         if (b0 != 255 && b0 != 28 && b0 < 32)
+            return STBTT__CSERR("reserved operator");
+
+         // push immediate
+         if (b0 == 255) {
+            f = (float)(stbtt_int32)stbtt__buf_get32(&b) / 0x10000;
+         } else {
+            stbtt__buf_skip(&b, -1);
+            f = (float)(stbtt_int16)stbtt__cff_int(&b);
+         }
+         if (sp >= 48) return STBTT__CSERR("push stack overflow");
+         s[sp++] = f;
+         clear_stack = 0;
+         break;
+      }
+      if (clear_stack) sp = 0;
+   }
+   return STBTT__CSERR("no endchar");
+
+#undef STBTT__CSERR
+}
+
+static int stbtt__GetGlyphShapeT2(const stbtt_fontinfo *info, int glyph_index, stbtt_vertex **pvertices)
+{
+   // runs the charstring twice, once to count and once to output (to avoid realloc)
+   stbtt__csctx count_ctx = STBTT__CSCTX_INIT(1);
+   stbtt__csctx output_ctx = STBTT__CSCTX_INIT(0);
+   if (stbtt__run_charstring(info, glyph_index, &count_ctx)) {
+      *pvertices = (stbtt_vertex*)STBTT_malloc(count_ctx.num_vertices*sizeof(stbtt_vertex), info->userdata);
+      output_ctx.pvertices = *pvertices;
+      if (stbtt__run_charstring(info, glyph_index, &output_ctx)) {
+         STBTT_assert(output_ctx.num_vertices == count_ctx.num_vertices);
+         return output_ctx.num_vertices;
+      }
+   }
+   *pvertices = NULL;
+   return 0;
+}
+
+static int stbtt__GetGlyphInfoT2(const stbtt_fontinfo *info, int glyph_index, int *x0, int *y0, int *x1, int *y1)
+{
+   stbtt__csctx c = STBTT__CSCTX_INIT(1);
+   int r = stbtt__run_charstring(info, glyph_index, &c);
+   if (x0)  *x0 = r ? c.min_x : 0;
+   if (y0)  *y0 = r ? c.min_y : 0;
+   if (x1)  *x1 = r ? c.max_x : 0;
+   if (y1)  *y1 = r ? c.max_y : 0;
+   return r ? c.num_vertices : 0;
+}
+
+STBTT_DEF int stbtt_GetGlyphShape(const stbtt_fontinfo *info, int glyph_index, stbtt_vertex **pvertices)
+{
+   if (!info->cff.size)
+      return stbtt__GetGlyphShapeTT(info, glyph_index, pvertices);
+   else
+      return stbtt__GetGlyphShapeT2(info, glyph_index, pvertices);
+}
+
+STBTT_DEF void stbtt_GetGlyphHMetrics(const stbtt_fontinfo *info, int glyph_index, int *advanceWidth, int *leftSideBearing)
+{
+   stbtt_uint16 numOfLongHorMetrics = ttUSHORT(info->data+info->hhea + 34);
+   if (glyph_index < numOfLongHorMetrics) {
+      if (advanceWidth)     *advanceWidth    = ttSHORT(info->data + info->hmtx + 4*glyph_index);
+      if (leftSideBearing)  *leftSideBearing = ttSHORT(info->data + info->hmtx + 4*glyph_index + 2);
+   } else {
+      if (advanceWidth)     *advanceWidth    = ttSHORT(info->data + info->hmtx + 4*(numOfLongHorMetrics-1));
+      if (leftSideBearing)  *leftSideBearing = ttSHORT(info->data + info->hmtx + 4*numOfLongHorMetrics + 2*(glyph_index - numOfLongHorMetrics));
+   }
+}
+
+STBTT_DEF int  stbtt_GetKerningTableLength(const stbtt_fontinfo *info)
+{
+   stbtt_uint8 *data = info->data + info->kern;
+
+   // we only look at the first table. it must be 'horizontal' and format 0.
+   if (!info->kern)
+      return 0;
+   if (ttUSHORT(data+2) < 1) // number of tables, need at least 1
+      return 0;
+   if (ttUSHORT(data+8) != 1) // horizontal flag must be set in format
+      return 0;
+
+   return ttUSHORT(data+10);
+}
+
+STBTT_DEF int stbtt_GetKerningTable(const stbtt_fontinfo *info, stbtt_kerningentry* table, int table_length)
+{
+   stbtt_uint8 *data = info->data + info->kern;
+   int k, length;
+
+   // we only look at the first table. it must be 'horizontal' and format 0.
+   if (!info->kern)
+      return 0;
+   if (ttUSHORT(data+2) < 1) // number of tables, need at least 1
+      return 0;
+   if (ttUSHORT(data+8) != 1) // horizontal flag must be set in format
+      return 0;
+
+   length = ttUSHORT(data+10);
+   if (table_length < length)
+      length = table_length;
+
+   for (k = 0; k < length; k++)
+   {
+      table[k].glyph1 = ttUSHORT(data+18+(k*6));
+      table[k].glyph2 = ttUSHORT(data+20+(k*6));
+      table[k].advance = ttSHORT(data+22+(k*6));
+   }
+
+   return length;
+}
+
+static int stbtt__GetGlyphKernInfoAdvance(const stbtt_fontinfo *info, int glyph1, int glyph2)
+{
+   stbtt_uint8 *data = info->data + info->kern;
+   stbtt_uint32 needle, straw;
+   int l, r, m;
+
+   // we only look at the first table. it must be 'horizontal' and format 0.
+   if (!info->kern)
+      return 0;
+   if (ttUSHORT(data+2) < 1) // number of tables, need at least 1
+      return 0;
+   if (ttUSHORT(data+8) != 1) // horizontal flag must be set in format
+      return 0;
+
+   l = 0;
+   r = ttUSHORT(data+10) - 1;
+   needle = glyph1 << 16 | glyph2;
+   while (l <= r) {
+      m = (l + r) >> 1;
+      straw = ttULONG(data+18+(m*6)); // note: unaligned read
+      if (needle < straw)
+         r = m - 1;
+      else if (needle > straw)
+         l = m + 1;
+      else
+         return ttSHORT(data+22+(m*6));
+   }
+   return 0;
+}
+
+static stbtt_int32 stbtt__GetCoverageIndex(stbtt_uint8 *coverageTable, int glyph)
+{
+   stbtt_uint16 coverageFormat = ttUSHORT(coverageTable);
+   switch (coverageFormat) {
+      case 1: {
+         stbtt_uint16 glyphCount = ttUSHORT(coverageTable + 2);
+
+         // Binary search.
+         stbtt_int32 l=0, r=glyphCount-1, m;
+         int straw, needle=glyph;
+         while (l <= r) {
+            stbtt_uint8 *glyphArray = coverageTable + 4;
+            stbtt_uint16 glyphID;
+            m = (l + r) >> 1;
+            glyphID = ttUSHORT(glyphArray + 2 * m);
+            straw = glyphID;
+            if (needle < straw)
+               r = m - 1;
+            else if (needle > straw)
+               l = m + 1;
+            else {
+               return m;
+            }
+         }
+         break;
+      }
+
+      case 2: {
+         stbtt_uint16 rangeCount = ttUSHORT(coverageTable + 2);
+         stbtt_uint8 *rangeArray = coverageTable + 4;
+
+         // Binary search.
+         stbtt_int32 l=0, r=rangeCount-1, m;
+         int strawStart, strawEnd, needle=glyph;
+         while (l <= r) {
+            stbtt_uint8 *rangeRecord;
+            m = (l + r) >> 1;
+            rangeRecord = rangeArray + 6 * m;
+            strawStart = ttUSHORT(rangeRecord);
+            strawEnd = ttUSHORT(rangeRecord + 2);
+            if (needle < strawStart)
+               r = m - 1;
+            else if (needle > strawEnd)
+               l = m + 1;
+            else {
+               stbtt_uint16 startCoverageIndex = ttUSHORT(rangeRecord + 4);
+               return startCoverageIndex + glyph - strawStart;
+            }
+         }
+         break;
+      }
+
+      default: return -1; // unsupported
+   }
+
+   return -1;
+}
+
+static stbtt_int32  stbtt__GetGlyphClass(stbtt_uint8 *classDefTable, int glyph)
+{
+   stbtt_uint16 classDefFormat = ttUSHORT(classDefTable);
+   switch (classDefFormat)
+   {
+      case 1: {
+         stbtt_uint16 startGlyphID = ttUSHORT(classDefTable + 2);
+         stbtt_uint16 glyphCount = ttUSHORT(classDefTable + 4);
+         stbtt_uint8 *classDef1ValueArray = classDefTable + 6;
+
+         if (glyph >= startGlyphID && glyph < startGlyphID + glyphCount)
+            return (stbtt_int32)ttUSHORT(classDef1ValueArray + 2 * (glyph - startGlyphID));
+         break;
+      }
+
+      case 2: {
+         stbtt_uint16 classRangeCount = ttUSHORT(classDefTable + 2);
+         stbtt_uint8 *classRangeRecords = classDefTable + 4;
+
+         // Binary search.
+         stbtt_int32 l=0, r=classRangeCount-1, m;
+         int strawStart, strawEnd, needle=glyph;
+         while (l <= r) {
+            stbtt_uint8 *classRangeRecord;
+            m = (l + r) >> 1;
+            classRangeRecord = classRangeRecords + 6 * m;
+            strawStart = ttUSHORT(classRangeRecord);
+            strawEnd = ttUSHORT(classRangeRecord + 2);
+            if (needle < strawStart)
+               r = m - 1;
+            else if (needle > strawEnd)
+               l = m + 1;
+            else
+               return (stbtt_int32)ttUSHORT(classRangeRecord + 4);
+         }
+         break;
+      }
+
+      default:
+         return -1; // Unsupported definition type, return an error.
+   }
+
+   // "All glyphs not assigned to a class fall into class 0". (OpenType spec)
+   return 0;
+}
+
+// Define to STBTT_assert(x) if you want to break on unimplemented formats.
+#define STBTT_GPOS_TODO_assert(x)
+
+static stbtt_int32 stbtt__GetGlyphGPOSInfoAdvance(const stbtt_fontinfo *info, int glyph1, int glyph2)
+{
+   stbtt_uint16 lookupListOffset;
+   stbtt_uint8 *lookupList;
+   stbtt_uint16 lookupCount;
+   stbtt_uint8 *data;
+   stbtt_int32 i, sti;
+
+   if (!info->gpos) return 0;
+
+   data = info->data + info->gpos;
+
+   if (ttUSHORT(data+0) != 1) return 0; // Major version 1
+   if (ttUSHORT(data+2) != 0) return 0; // Minor version 0
+
+   lookupListOffset = ttUSHORT(data+8);
+   lookupList = data + lookupListOffset;
+   lookupCount = ttUSHORT(lookupList);
+
+   for (i=0; i<lookupCount; ++i) {
+      stbtt_uint16 lookupOffset = ttUSHORT(lookupList + 2 + 2 * i);
+      stbtt_uint8 *lookupTable = lookupList + lookupOffset;
+
+      stbtt_uint16 lookupType = ttUSHORT(lookupTable);
+      stbtt_uint16 subTableCount = ttUSHORT(lookupTable + 4);
+      stbtt_uint8 *subTableOffsets = lookupTable + 6;
+      if (lookupType != 2) // Pair Adjustment Positioning Subtable
+         continue;
+
+      for (sti=0; sti<subTableCount; sti++) {
+         stbtt_uint16 subtableOffset = ttUSHORT(subTableOffsets + 2 * sti);
+         stbtt_uint8 *table = lookupTable + subtableOffset;
+         stbtt_uint16 posFormat = ttUSHORT(table);
+         stbtt_uint16 coverageOffset = ttUSHORT(table + 2);
+         stbtt_int32 coverageIndex = stbtt__GetCoverageIndex(table + coverageOffset, glyph1);
+         if (coverageIndex == -1) continue;
+
+         switch (posFormat) {
+            case 1: {
+               stbtt_int32 l, r, m;
+               int straw, needle;
+               stbtt_uint16 valueFormat1 = ttUSHORT(table + 4);
+               stbtt_uint16 valueFormat2 = ttUSHORT(table + 6);
+               if (valueFormat1 == 4 && valueFormat2 == 0) { // Support more formats?
+                  stbtt_int32 valueRecordPairSizeInBytes = 2;
+                  stbtt_uint16 pairSetCount = ttUSHORT(table + 8);
+                  stbtt_uint16 pairPosOffset = ttUSHORT(table + 10 + 2 * coverageIndex);
+                  stbtt_uint8 *pairValueTable = table + pairPosOffset;
+                  stbtt_uint16 pairValueCount = ttUSHORT(pairValueTable);
+                  stbtt_uint8 *pairValueArray = pairValueTable + 2;
+
+                  if (coverageIndex >= pairSetCount) return 0;
+
+                  needle=glyph2;
+                  r=pairValueCount-1;
+                  l=0;
+
+                  // Binary search.
+                  while (l <= r) {
+                     stbtt_uint16 secondGlyph;
+                     stbtt_uint8 *pairValue;
+                     m = (l + r) >> 1;
+                     pairValue = pairValueArray + (2 + valueRecordPairSizeInBytes) * m;
+                     secondGlyph = ttUSHORT(pairValue);
+                     straw = secondGlyph;
+                     if (needle < straw)
+                        r = m - 1;
+                     else if (needle > straw)
+                        l = m + 1;
+                     else {
+                        stbtt_int16 xAdvance = ttSHORT(pairValue + 2);
+                        return xAdvance;
+                     }
+                  }
+               } else
+                  return 0;
+               break;
+            }
+
+            case 2: {
+               stbtt_uint16 valueFormat1 = ttUSHORT(table + 4);
+               stbtt_uint16 valueFormat2 = ttUSHORT(table + 6);
+               if (valueFormat1 == 4 && valueFormat2 == 0) { // Support more formats?
+                  stbtt_uint16 classDef1Offset = ttUSHORT(table + 8);
+                  stbtt_uint16 classDef2Offset = ttUSHORT(table + 10);
+                  int glyph1class = stbtt__GetGlyphClass(table + classDef1Offset, glyph1);
+                  int glyph2class = stbtt__GetGlyphClass(table + classDef2Offset, glyph2);
+
+                  stbtt_uint16 class1Count = ttUSHORT(table + 12);
+                  stbtt_uint16 class2Count = ttUSHORT(table + 14);
+                  stbtt_uint8 *class1Records, *class2Records;
+                  stbtt_int16 xAdvance;
+
+                  if (glyph1class < 0 || glyph1class >= class1Count) return 0; // malformed
+                  if (glyph2class < 0 || glyph2class >= class2Count) return 0; // malformed
+
+                  class1Records = table + 16;
+                  class2Records = class1Records + 2 * (glyph1class * class2Count);
+                  xAdvance = ttSHORT(class2Records + 2 * glyph2class);
+                  return xAdvance;
+               } else
+                  return 0;
+               break;
+            }
+
+            default:
+               return 0; // Unsupported position format
+         }
+      }
+   }
+
+   return 0;
+}
+
+STBTT_DEF int  stbtt_GetGlyphKernAdvance(const stbtt_fontinfo *info, int g1, int g2)
+{
+   int xAdvance = 0;
+
+   if (info->gpos)
+      xAdvance += stbtt__GetGlyphGPOSInfoAdvance(info, g1, g2);
+   else if (info->kern)
+      xAdvance += stbtt__GetGlyphKernInfoAdvance(info, g1, g2);
+
+   return xAdvance;
+}
+
+STBTT_DEF int  stbtt_GetCodepointKernAdvance(const stbtt_fontinfo *info, int ch1, int ch2)
+{
+   if (!info->kern && !info->gpos) // if no kerning table, don't waste time looking up both codepoint->glyphs
+      return 0;
+   return stbtt_GetGlyphKernAdvance(info, stbtt_FindGlyphIndex(info,ch1), stbtt_FindGlyphIndex(info,ch2));
+}
+
+STBTT_DEF void stbtt_GetCodepointHMetrics(const stbtt_fontinfo *info, int codepoint, int *advanceWidth, int *leftSideBearing)
+{
+   stbtt_GetGlyphHMetrics(info, stbtt_FindGlyphIndex(info,codepoint), advanceWidth, leftSideBearing);
+}
+
+STBTT_DEF void stbtt_GetFontVMetrics(const stbtt_fontinfo *info, int *ascent, int *descent, int *lineGap)
+{
+   if (ascent ) *ascent  = ttSHORT(info->data+info->hhea + 4);
+   if (descent) *descent = ttSHORT(info->data+info->hhea + 6);
+   if (lineGap) *lineGap = ttSHORT(info->data+info->hhea + 8);
+}
+
+STBTT_DEF int  stbtt_GetFontVMetricsOS2(const stbtt_fontinfo *info, int *typoAscent, int *typoDescent, int *typoLineGap)
+{
+   int tab = stbtt__find_table(info->data, info->fontstart, "OS/2");
+   if (!tab)
+      return 0;
+   if (typoAscent ) *typoAscent  = ttSHORT(info->data+tab + 68);
+   if (typoDescent) *typoDescent = ttSHORT(info->data+tab + 70);
+   if (typoLineGap) *typoLineGap = ttSHORT(info->data+tab + 72);
+   return 1;
+}
+
+STBTT_DEF void stbtt_GetFontBoundingBox(const stbtt_fontinfo *info, int *x0, int *y0, int *x1, int *y1)
+{
+   *x0 = ttSHORT(info->data + info->head + 36);
+   *y0 = ttSHORT(info->data + info->head + 38);
+   *x1 = ttSHORT(info->data + info->head + 40);
+   *y1 = ttSHORT(info->data + info->head + 42);
+}
+
+STBTT_DEF float stbtt_ScaleForPixelHeight(const stbtt_fontinfo *info, float height)
+{
+   int fheight = ttSHORT(info->data + info->hhea + 4) - ttSHORT(info->data + info->hhea + 6);
+   return (float) height / fheight;
+}
+
+STBTT_DEF float stbtt_ScaleForMappingEmToPixels(const stbtt_fontinfo *info, float pixels)
+{
+   int unitsPerEm = ttUSHORT(info->data + info->head + 18);
+   return pixels / unitsPerEm;
+}
+
+STBTT_DEF void stbtt_FreeShape(const stbtt_fontinfo *info, stbtt_vertex *v)
+{
+   STBTT_free(v, info->userdata);
+}
+
+STBTT_DEF stbtt_uint8 *stbtt_FindSVGDoc(const stbtt_fontinfo *info, int gl)
+{
+   int i;
+   stbtt_uint8 *data = info->data;
+   stbtt_uint8 *svg_doc_list = data + stbtt__get_svg((stbtt_fontinfo *) info);
+
+   int numEntries = ttUSHORT(svg_doc_list);
+   stbtt_uint8 *svg_docs = svg_doc_list + 2;
+
+   for(i=0; i<numEntries; i++) {
+      stbtt_uint8 *svg_doc = svg_docs + (12 * i);
+      if ((gl >= ttUSHORT(svg_doc)) && (gl <= ttUSHORT(svg_doc + 2)))
+         return svg_doc;
+   }
+   return 0;
+}
+
+STBTT_DEF int stbtt_GetGlyphSVG(const stbtt_fontinfo *info, int gl, const char **svg)
+{
+   stbtt_uint8 *data = info->data;
+   stbtt_uint8 *svg_doc;
+
+   if (info->svg == 0)
+      return 0;
+
+   svg_doc = stbtt_FindSVGDoc(info, gl);
+   if (svg_doc != NULL) {
+      *svg = (char *) data + info->svg + ttULONG(svg_doc + 4);
+      return ttULONG(svg_doc + 8);
+   } else {
+      return 0;
+   }
+}
+
+STBTT_DEF int stbtt_GetCodepointSVG(const stbtt_fontinfo *info, int unicode_codepoint, const char **svg)
+{
+   return stbtt_GetGlyphSVG(info, stbtt_FindGlyphIndex(info, unicode_codepoint), svg);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// antialiasing software rasterizer
+//
+
+STBTT_DEF void stbtt_GetGlyphBitmapBoxSubpixel(const stbtt_fontinfo *font, int glyph, float scale_x, float scale_y,float shift_x, float shift_y, int *ix0, int *iy0, int *ix1, int *iy1)
+{
+   int x0=0,y0=0,x1,y1; // =0 suppresses compiler warning
+   if (!stbtt_GetGlyphBox(font, glyph, &x0,&y0,&x1,&y1)) {
+      // e.g. space character
+      if (ix0) *ix0 = 0;
+      if (iy0) *iy0 = 0;
+      if (ix1) *ix1 = 0;
+      if (iy1) *iy1 = 0;
+   } else {
+      // move to integral bboxes (treating pixels as little squares, what pixels get touched)?
+      if (ix0) *ix0 = STBTT_ifloor( x0 * scale_x + shift_x);
+      if (iy0) *iy0 = STBTT_ifloor(-y1 * scale_y + shift_y);
+      if (ix1) *ix1 = STBTT_iceil ( x1 * scale_x + shift_x);
+      if (iy1) *iy1 = STBTT_iceil (-y0 * scale_y + shift_y);
+   }
+}
+
+STBTT_DEF void stbtt_GetGlyphBitmapBox(const stbtt_fontinfo *font, int glyph, float scale_x, float scale_y, int *ix0, int *iy0, int *ix1, int *iy1)
+{
+   stbtt_GetGlyphBitmapBoxSubpixel(font, glyph, scale_x, scale_y,0.0f,0.0f, ix0, iy0, ix1, iy1);
+}
+
+STBTT_DEF void stbtt_GetCodepointBitmapBoxSubpixel(const stbtt_fontinfo *font, int codepoint, float scale_x, float scale_y, float shift_x, float shift_y, int *ix0, int *iy0, int *ix1, int *iy1)
+{
+   stbtt_GetGlyphBitmapBoxSubpixel(font, stbtt_FindGlyphIndex(font,codepoint), scale_x, scale_y,shift_x,shift_y, ix0,iy0,ix1,iy1);
+}
+
+STBTT_DEF void stbtt_GetCodepointBitmapBox(const stbtt_fontinfo *font, int codepoint, float scale_x, float scale_y, int *ix0, int *iy0, int *ix1, int *iy1)
+{
+   stbtt_GetCodepointBitmapBoxSubpixel(font, codepoint, scale_x, scale_y,0.0f,0.0f, ix0,iy0,ix1,iy1);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+//  Rasterizer
+
+typedef struct stbtt__hheap_chunk
+{
+   struct stbtt__hheap_chunk *next;
+} stbtt__hheap_chunk;
+
+typedef struct stbtt__hheap
+{
+   struct stbtt__hheap_chunk *head;
+   void   *first_free;
+   int    num_remaining_in_head_chunk;
+} stbtt__hheap;
+
+static void *stbtt__hheap_alloc(stbtt__hheap *hh, size_t size, void *userdata)
+{
+   if (hh->first_free) {
+      void *p = hh->first_free;
+      hh->first_free = * (void **) p;
+      return p;
+   } else {
+      if (hh->num_remaining_in_head_chunk == 0) {
+         int count = (size < 32 ? 2000 : size < 128 ? 800 : 100);
+         stbtt__hheap_chunk *c = (stbtt__hheap_chunk *) STBTT_malloc(sizeof(stbtt__hheap_chunk) + size * count, userdata);
+         if (c == NULL)
+            return NULL;
+         c->next = hh->head;
+         hh->head = c;
+         hh->num_remaining_in_head_chunk = count;
+      }
+      --hh->num_remaining_in_head_chunk;
+      return (char *) (hh->head) + sizeof(stbtt__hheap_chunk) + size * hh->num_remaining_in_head_chunk;
+   }
+}
+
+static void stbtt__hheap_free(stbtt__hheap *hh, void *p)
+{
+   *(void **) p = hh->first_free;
+   hh->first_free = p;
+}
+
+static void stbtt__hheap_cleanup(stbtt__hheap *hh, void *userdata)
+{
+   stbtt__hheap_chunk *c = hh->head;
+   while (c) {
+      stbtt__hheap_chunk *n = c->next;
+      STBTT_free(c, userdata);
+      c = n;
+   }
+}
+
+typedef struct stbtt__edge {
+   float x0,y0, x1,y1;
+   int invert;
+} stbtt__edge;
+
+
+typedef struct stbtt__active_edge
+{
+   struct stbtt__active_edge *next;
+   #if STBTT_RASTERIZER_VERSION==1
+   int x,dx;
+   float ey;
+   int direction;
+   #elif STBTT_RASTERIZER_VERSION==2
+   float fx,fdx,fdy;
+   float direction;
+   float sy;
+   float ey;
+   #else
+   #error "Unrecognized value of STBTT_RASTERIZER_VERSION"
+   #endif
+} stbtt__active_edge;
+
+#if STBTT_RASTERIZER_VERSION == 1
+#define STBTT_FIXSHIFT   10
+#define STBTT_FIX        (1 << STBTT_FIXSHIFT)
+#define STBTT_FIXMASK    (STBTT_FIX-1)
+
+static stbtt__active_edge *stbtt__new_active(stbtt__hheap *hh, stbtt__edge *e, int off_x, float start_point, void *userdata)
+{
+   stbtt__active_edge *z = (stbtt__active_edge *) stbtt__hheap_alloc(hh, sizeof(*z), userdata);
+   float dxdy = (e->x1 - e->x0) / (e->y1 - e->y0);
+   STBTT_assert(z != NULL);
+   if (!z) return z;
+
+   // round dx down to avoid overshooting
+   if (dxdy < 0)
+      z->dx = -STBTT_ifloor(STBTT_FIX * -dxdy);
+   else
+      z->dx = STBTT_ifloor(STBTT_FIX * dxdy);
+
+   z->x = STBTT_ifloor(STBTT_FIX * e->x0 + z->dx * (start_point - e->y0)); // use z->dx so when we offset later it's by the same amount
+   z->x -= off_x * STBTT_FIX;
+
+   z->ey = e->y1;
+   z->next = 0;
+   z->direction = e->invert ? 1 : -1;
+   return z;
+}
+#elif STBTT_RASTERIZER_VERSION == 2
+static stbtt__active_edge *stbtt__new_active(stbtt__hheap *hh, stbtt__edge *e, int off_x, float start_point, void *userdata)
+{
+   stbtt__active_edge *z = (stbtt__active_edge *) stbtt__hheap_alloc(hh, sizeof(*z), userdata);
+   float dxdy = (e->x1 - e->x0) / (e->y1 - e->y0);
+   STBTT_assert(z != NULL);
+   //STBTT_assert(e->y0 <= start_point);
+   if (!z) return z;
+   z->fdx = dxdy;
+   z->fdy = dxdy != 0.0f ? (1.0f/dxdy) : 0.0f;
+   z->fx = e->x0 + dxdy * (start_point - e->y0);
+   z->fx -= off_x;
+   z->direction = e->invert ? 1.0f : -1.0f;
+   z->sy = e->y0;
+   z->ey = e->y1;
+   z->next = 0;
+   return z;
+}
+#else
+#error "Unrecognized value of STBTT_RASTERIZER_VERSION"
+#endif
+
+#if STBTT_RASTERIZER_VERSION == 1
+// note: this routine clips fills that extend off the edges... ideally this
+// wouldn't happen, but it could happen if the truetype glyph bounding boxes
+// are wrong, or if the user supplies a too-small bitmap
+static void stbtt__fill_active_edges(unsigned char *scanline, int len, stbtt__active_edge *e, int max_weight)
+{
+   // non-zero winding fill
+   int x0=0, w=0;
+
+   while (e) {
+      if (w == 0) {
+         // if we're currently at zero, we need to record the edge start point
+         x0 = e->x; w += e->direction;
+      } else {
+         int x1 = e->x; w += e->direction;
+         // if we went to zero, we need to draw
+         if (w == 0) {
+            int i = x0 >> STBTT_FIXSHIFT;
+            int j = x1 >> STBTT_FIXSHIFT;
+
+            if (i < len && j >= 0) {
+               if (i == j) {
+                  // x0,x1 are the same pixel, so compute combined coverage
+                  scanline[i] = scanline[i] + (stbtt_uint8) ((x1 - x0) * max_weight >> STBTT_FIXSHIFT);
+               } else {
+                  if (i >= 0) // add antialiasing for x0
+                     scanline[i] = scanline[i] + (stbtt_uint8) (((STBTT_FIX - (x0 & STBTT_FIXMASK)) * max_weight) >> STBTT_FIXSHIFT);
+                  else
+                     i = -1; // clip
+
+                  if (j < len) // add antialiasing for x1
+                     scanline[j] = scanline[j] + (stbtt_uint8) (((x1 & STBTT_FIXMASK) * max_weight) >> STBTT_FIXSHIFT);
+                  else
+                     j = len; // clip
+
+                  for (++i; i < j; ++i) // fill pixels between x0 and x1
+                     scanline[i] = scanline[i] + (stbtt_uint8) max_weight;
+               }
+            }
+         }
+      }
+
+      e = e->next;
+   }
+}
+
+static void stbtt__rasterize_sorted_edges(stbtt__bitmap *result, stbtt__edge *e, int n, int vsubsample, int off_x, int off_y, void *userdata)
+{
+   stbtt__hheap hh = { 0, 0, 0 };
+   stbtt__active_edge *active = NULL;
+   int y,j=0;
+   int max_weight = (255 / vsubsample);  // weight per vertical scanline
+   int s; // vertical subsample index
+   unsigned char scanline_data[512], *scanline;
+
+   if (result->w > 512)
+      scanline = (unsigned char *) STBTT_malloc(result->w, userdata);
+   else
+      scanline = scanline_data;
+
+   y = off_y * vsubsample;
+   e[n].y0 = (off_y + result->h) * (float) vsubsample + 1;
+
+   while (j < result->h) {
+      STBTT_memset(scanline, 0, result->w);
+      for (s=0; s < vsubsample; ++s) {
+         // find center of pixel for this scanline
+         float scan_y = y + 0.5f;
+         stbtt__active_edge **step = &active;
+
+         // update all active edges;
+         // remove all active edges that terminate before the center of this scanline
+         while (*step) {
+            stbtt__active_edge * z = *step;
+            if (z->ey <= scan_y) {
+               *step = z->next; // delete from list
+               STBTT_assert(z->direction);
+               z->direction = 0;
+               stbtt__hheap_free(&hh, z);
+            } else {
+               z->x += z->dx; // advance to position for current scanline
+               step = &((*step)->next); // advance through list
+            }
+         }
+
+         // resort the list if needed
+         for(;;) {
+            int changed=0;
+            step = &active;
+            while (*step && (*step)->next) {
+               if ((*step)->x > (*step)->next->x) {
+                  stbtt__active_edge *t = *step;
+                  stbtt__active_edge *q = t->next;
+
+                  t->next = q->next;
+                  q->next = t;
+                  *step = q;
+                  changed = 1;
+               }
+               step = &(*step)->next;
+            }
+            if (!changed) break;
+         }
+
+         // insert all edges that start before the center of this scanline -- omit ones that also end on this scanline
+         while (e->y0 <= scan_y) {
+            if (e->y1 > scan_y) {
+               stbtt__active_edge *z = stbtt__new_active(&hh, e, off_x, scan_y, userdata);
+               if (z != NULL) {
+                  // find insertion point
+                  if (active == NULL)
+                     active = z;
+                  else if (z->x < active->x) {
+                     // insert at front
+                     z->next = active;
+                     active = z;
+                  } else {
+                     // find thing to insert AFTER
+                     stbtt__active_edge *p = active;
+                     while (p->next && p->next->x < z->x)
+                        p = p->next;
+                     // at this point, p->next->x is NOT < z->x
+                     z->next = p->next;
+                     p->next = z;
+                  }
+               }
+            }
+            ++e;
+         }
+
+         // now process all active edges in XOR fashion
+         if (active)
+            stbtt__fill_active_edges(scanline, result->w, active, max_weight);
+
+         ++y;
+      }
+      STBTT_memcpy(result->pixels + j * result->stride, scanline, result->w);
+      ++j;
+   }
+
+   stbtt__hheap_cleanup(&hh, userdata);
+
+   if (scanline != scanline_data)
+      STBTT_free(scanline, userdata);
+}
+
+#elif STBTT_RASTERIZER_VERSION == 2
+
+// the edge passed in here does not cross the vertical line at x or the vertical line at x+1
+// (i.e. it has already been clipped to those)
+static void stbtt__handle_clipped_edge(float *scanline, int x, stbtt__active_edge *e, float x0, float y0, float x1, float y1)
+{
+   if (y0 == y1) return;
+   STBTT_assert(y0 < y1);
+   STBTT_assert(e->sy <= e->ey);
+   if (y0 > e->ey) return;
+   if (y1 < e->sy) return;
+   if (y0 < e->sy) {
+      x0 += (x1-x0) * (e->sy - y0) / (y1-y0);
+      y0 = e->sy;
+   }
+   if (y1 > e->ey) {
+      x1 += (x1-x0) * (e->ey - y1) / (y1-y0);
+      y1 = e->ey;
+   }
+
+   if (x0 == x)
+      STBTT_assert(x1 <= x+1);
+   else if (x0 == x+1)
+      STBTT_assert(x1 >= x);
+   else if (x0 <= x)
+      STBTT_assert(x1 <= x);
+   else if (x0 >= x+1)
+      STBTT_assert(x1 >= x+1);
+   else
+      STBTT_assert(x1 >= x && x1 <= x+1);
+
+   if (x0 <= x && x1 <= x)
+      scanline[x] += e->direction * (y1-y0);
+   else if (x0 >= x+1 && x1 >= x+1)
+      ;
+   else {
+      STBTT_assert(x0 >= x && x0 <= x+1 && x1 >= x && x1 <= x+1);
+      scanline[x] += e->direction * (y1-y0) * (1-((x0-x)+(x1-x))/2); // coverage = 1 - average x position
+   }
+}
+
+static float stbtt__sized_trapezoid_area(float height, float top_width, float bottom_width)
+{
+   STBTT_assert(top_width >= 0);
+   STBTT_assert(bottom_width >= 0);
+   return (top_width + bottom_width) / 2.0f * height;
+}
+
+static float stbtt__position_trapezoid_area(float height, float tx0, float tx1, float bx0, float bx1)
+{
+   return stbtt__sized_trapezoid_area(height, tx1 - tx0, bx1 - bx0);
+}
+
+static float stbtt__sized_triangle_area(float height, float width)
+{
+   return height * width / 2;
+}
+
+static void stbtt__fill_active_edges_new(float *scanline, float *scanline_fill, int len, stbtt__active_edge *e, float y_top)
+{
+   float y_bottom = y_top+1;
+
+   while (e) {
+      // brute force every pixel
+
+      // compute intersection points with top & bottom
+      STBTT_assert(e->ey >= y_top);
+
+      if (e->fdx == 0) {
+         float x0 = e->fx;
+         if (x0 < len) {
+            if (x0 >= 0) {
+               stbtt__handle_clipped_edge(scanline,(int) x0,e, x0,y_top, x0,y_bottom);
+               stbtt__handle_clipped_edge(scanline_fill-1,(int) x0+1,e, x0,y_top, x0,y_bottom);
+            } else {
+               stbtt__handle_clipped_edge(scanline_fill-1,0,e, x0,y_top, x0,y_bottom);
+            }
+         }
+      } else {
+         float x0 = e->fx;
+         float dx = e->fdx;
+         float xb = x0 + dx;
+         float x_top, x_bottom;
+         float sy0,sy1;
+         float dy = e->fdy;
+         STBTT_assert(e->sy <= y_bottom && e->ey >= y_top);
+
+         // compute endpoints of line segment clipped to this scanline (if the
+         // line segment starts on this scanline. x0 is the intersection of the
+         // line with y_top, but that may be off the line segment.
+         if (e->sy > y_top) {
+            x_top = x0 + dx * (e->sy - y_top);
+            sy0 = e->sy;
+         } else {
+            x_top = x0;
+            sy0 = y_top;
+         }
+         if (e->ey < y_bottom) {
+            x_bottom = x0 + dx * (e->ey - y_top);
+            sy1 = e->ey;
+         } else {
+            x_bottom = xb;
+            sy1 = y_bottom;
+         }
+
+         if (x_top >= 0 && x_bottom >= 0 && x_top < len && x_bottom < len) {
+            // from here on, we don't have to range check x values
+
+            if ((int) x_top == (int) x_bottom) {
+               float height;
+               // simple case, only spans one pixel
+               int x = (int) x_top;
+               height = (sy1 - sy0) * e->direction;
+               STBTT_assert(x >= 0 && x < len);
+               scanline[x]      += stbtt__position_trapezoid_area(height, x_top, x+1.0f, x_bottom, x+1.0f);
+               scanline_fill[x] += height; // everything right of this pixel is filled
+            } else {
+               int x,x1,x2;
+               float y_crossing, y_final, step, sign, area;
+               // covers 2+ pixels
+               if (x_top > x_bottom) {
+                  // flip scanline vertically; signed area is the same
+                  float t;
+                  sy0 = y_bottom - (sy0 - y_top);
+                  sy1 = y_bottom - (sy1 - y_top);
+                  t = sy0, sy0 = sy1, sy1 = t;
+                  t = x_bottom, x_bottom = x_top, x_top = t;
+                  dx = -dx;
+                  dy = -dy;
+                  t = x0, x0 = xb, xb = t;
+               }
+               STBTT_assert(dy >= 0);
+               STBTT_assert(dx >= 0);
+
+               x1 = (int) x_top;
+               x2 = (int) x_bottom;
+               // compute intersection with y axis at x1+1
+               y_crossing = y_top + dy * (x1+1 - x0);
+
+               // compute intersection with y axis at x2
+               y_final = y_top + dy * (x2 - x0);
+
+               //           x1    x_top                            x2    x_bottom
+               //     y_top  +------|-----+------------+------------+--------|---+------------+
+               //            |            |            |            |            |            |
+               //            |            |            |            |            |            |
+               //       sy0  |      Txxxxx|............|............|............|............|
+               // y_crossing |            *xxxxx.......|............|............|............|
+               //            |            |     xxxxx..|............|............|............|
+               //            |            |     /-   xx*xxxx........|............|............|
+               //            |            | dy <       |    xxxxxx..|............|............|
+               //   y_final  |            |     \-     |          xx*xxx.........|............|
+               //       sy1  |            |            |            |   xxxxxB...|............|
+               //            |            |            |            |            |            |
+               //            |            |            |            |            |            |
+               //  y_bottom  +------------+------------+------------+------------+------------+
+               //
+               // goal is to measure the area covered by '.' in each pixel
+
+               // if x2 is right at the right edge of x1, y_crossing can blow up, github #1057
+               // @TODO: maybe test against sy1 rather than y_bottom?
+               if (y_crossing > y_bottom)
+                  y_crossing = y_bottom;
+
+               sign = e->direction;
+
+               // area of the rectangle covered from sy0..y_crossing
+               area = sign * (y_crossing-sy0);
+
+               // area of the triangle (x_top,sy0), (x1+1,sy0), (x1+1,y_crossing)
+               scanline[x1] += stbtt__sized_triangle_area(area, x1+1 - x_top);
+
+               // check if final y_crossing is blown up; no test case for this
+               if (y_final > y_bottom) {
+                  y_final = y_bottom;
+                  dy = (y_final - y_crossing ) / (x2 - (x1+1)); // if denom=0, y_final = y_crossing, so y_final <= y_bottom
+               }
+
+               // in second pixel, area covered by line segment found in first pixel
+               // is always a rectangle 1 wide * the height of that line segment; this
+               // is exactly what the variable 'area' stores. it also gets a contribution
+               // from the line segment within it. the THIRD pixel will get the first
+               // pixel's rectangle contribution, the second pixel's rectangle contribution,
+               // and its own contribution. the 'own contribution' is the same in every pixel except
+               // the leftmost and rightmost, a trapezoid that slides down in each pixel.
+               // the second pixel's contribution to the third pixel will be the
+               // rectangle 1 wide times the height change in the second pixel, which is dy.
+
+               step = sign * dy * 1; // dy is dy/dx, change in y for every 1 change in x,
+               // which multiplied by 1-pixel-width is how much pixel area changes for each step in x
+               // so the area advances by 'step' every time
+
+               for (x = x1+1; x < x2; ++x) {
+                  scanline[x] += area + step/2; // area of trapezoid is 1*step/2
+                  area += step;
+               }
+               STBTT_assert(STBTT_fabs(area) <= 1.01f); // accumulated error from area += step unless we round step down
+               STBTT_assert(sy1 > y_final-0.01f);
+
+               // area covered in the last pixel is the rectangle from all the pixels to the left,
+               // plus the trapezoid filled by the line segment in this pixel all the way to the right edge
+               scanline[x2] += area + sign * stbtt__position_trapezoid_area(sy1-y_final, (float) x2, x2+1.0f, x_bottom, x2+1.0f);
+
+               // the rest of the line is filled based on the total height of the line segment in this pixel
+               scanline_fill[x2] += sign * (sy1-sy0);
+            }
+         } else {
+            // if edge goes outside of box we're drawing, we require
+            // clipping logic. since this does not match the intended use
+            // of this library, we use a different, very slow brute
+            // force implementation
+            // note though that this does happen some of the time because
+            // x_top and x_bottom can be extrapolated at the top & bottom of
+            // the shape and actually lie outside the bounding box
+            int x;
+            for (x=0; x < len; ++x) {
+               // cases:
+               //
+               // there can be up to two intersections with the pixel. any intersection
+               // with left or right edges can be handled by splitting into two (or three)
+               // regions. intersections with top & bottom do not necessitate case-wise logic.
+               //
+               // the old way of doing this found the intersections with the left & right edges,
+               // then used some simple logic to produce up to three segments in sorted order
+               // from top-to-bottom. however, this had a problem: if an x edge was epsilon
+               // across the x border, then the corresponding y position might not be distinct
+               // from the other y segment, and it might ignored as an empty segment. to avoid
+               // that, we need to explicitly produce segments based on x positions.
+
+               // rename variables to clearly-defined pairs
+               float y0 = y_top;
+               float x1 = (float) (x);
+               float x2 = (float) (x+1);
+               float x3 = xb;
+               float y3 = y_bottom;
+
+               // x = e->x + e->dx * (y-y_top)
+               // (y-y_top) = (x - e->x) / e->dx
+               // y = (x - e->x) / e->dx + y_top
+               float y1 = (x - x0) / dx + y_top;
+               float y2 = (x+1 - x0) / dx + y_top;
+
+               if (x0 < x1 && x3 > x2) {         // three segments descending down-right
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x1,y1);
+                  stbtt__handle_clipped_edge(scanline,x,e, x1,y1, x2,y2);
+                  stbtt__handle_clipped_edge(scanline,x,e, x2,y2, x3,y3);
+               } else if (x3 < x1 && x0 > x2) {  // three segments descending down-left
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x2,y2);
+                  stbtt__handle_clipped_edge(scanline,x,e, x2,y2, x1,y1);
+                  stbtt__handle_clipped_edge(scanline,x,e, x1,y1, x3,y3);
+               } else if (x0 < x1 && x3 > x1) {  // two segments across x, down-right
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x1,y1);
+                  stbtt__handle_clipped_edge(scanline,x,e, x1,y1, x3,y3);
+               } else if (x3 < x1 && x0 > x1) {  // two segments across x, down-left
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x1,y1);
+                  stbtt__handle_clipped_edge(scanline,x,e, x1,y1, x3,y3);
+               } else if (x0 < x2 && x3 > x2) {  // two segments across x+1, down-right
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x2,y2);
+                  stbtt__handle_clipped_edge(scanline,x,e, x2,y2, x3,y3);
+               } else if (x3 < x2 && x0 > x2) {  // two segments across x+1, down-left
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x2,y2);
+                  stbtt__handle_clipped_edge(scanline,x,e, x2,y2, x3,y3);
+               } else {  // one segment
+                  stbtt__handle_clipped_edge(scanline,x,e, x0,y0, x3,y3);
+               }
+            }
+         }
+      }
+      e = e->next;
+   }
+}
+
+// directly AA rasterize edges w/o supersampling
+static void stbtt__rasterize_sorted_edges(stbtt__bitmap *result, stbtt__edge *e, int n, int vsubsample, int off_x, int off_y, void *userdata)
+{
+   stbtt__hheap hh = { 0, 0, 0 };
+   stbtt__active_edge *active = NULL;
+   int y,j=0, i;
+   float scanline_data[129], *scanline, *scanline2;
+
+   STBTT__NOTUSED(vsubsample);
+
+   if (result->w > 64)
+      scanline = (float *) STBTT_malloc((result->w*2+1) * sizeof(float), userdata);
+   else
+      scanline = scanline_data;
+
+   scanline2 = scanline + result->w;
+
+   y = off_y;
+   e[n].y0 = (float) (off_y + result->h) + 1;
+
+   while (j < result->h) {
+      // find center of pixel for this scanline
+      float scan_y_top    = y + 0.0f;
+      float scan_y_bottom = y + 1.0f;
+      stbtt__active_edge **step = &active;
+
+      STBTT_memset(scanline , 0, result->w*sizeof(scanline[0]));
+      STBTT_memset(scanline2, 0, (result->w+1)*sizeof(scanline[0]));
+
+      // update all active edges;
+      // remove all active edges that terminate before the top of this scanline
+      while (*step) {
+         stbtt__active_edge * z = *step;
+         if (z->ey <= scan_y_top) {
+            *step = z->next; // delete from list
+            STBTT_assert(z->direction);
+            z->direction = 0;
+            stbtt__hheap_free(&hh, z);
+         } else {
+            step = &((*step)->next); // advance through list
+         }
+      }
+
+      // insert all edges that start before the bottom of this scanline
+      while (e->y0 <= scan_y_bottom) {
+         if (e->y0 != e->y1) {
+            stbtt__active_edge *z = stbtt__new_active(&hh, e, off_x, scan_y_top, userdata);
+            if (z != NULL) {
+               if (j == 0 && off_y != 0) {
+                  if (z->ey < scan_y_top) {
+                     // this can happen due to subpixel positioning and some kind of fp rounding error i think
+                     z->ey = scan_y_top;
+                  }
+               }
+               STBTT_assert(z->ey >= scan_y_top); // if we get really unlucky a tiny bit of an edge can be out of bounds
+               // insert at front
+               z->next = active;
+               active = z;
+            }
+         }
+         ++e;
+      }
+
+      // now process all active edges
+      if (active)
+         stbtt__fill_active_edges_new(scanline, scanline2+1, result->w, active, scan_y_top);
+
+      {
+         float sum = 0;
+         for (i=0; i < result->w; ++i) {
+            float k;
+            int m;
+            sum += scanline2[i];
+            k = scanline[i] + sum;
+            k = (float) STBTT_fabs(k)*255 + 0.5f;
+            m = (int) k;
+            if (m > 255) m = 255;
+            result->pixels[j*result->stride + i] = (unsigned char) m;
+         }
+      }
+      // advance all the edges
+      step = &active;
+      while (*step) {
+         stbtt__active_edge *z = *step;
+         z->fx += z->fdx; // advance to position for current scanline
+         step = &((*step)->next); // advance through list
+      }
+
+      ++y;
+      ++j;
+   }
+
+   stbtt__hheap_cleanup(&hh, userdata);
+
+   if (scanline != scanline_data)
+      STBTT_free(scanline, userdata);
+}
+#else
+#error "Unrecognized value of STBTT_RASTERIZER_VERSION"
+#endif
+
+#define STBTT__COMPARE(a,b)  ((a)->y0 < (b)->y0)
+
+static void stbtt__sort_edges_ins_sort(stbtt__edge *p, int n)
+{
+   int i,j;
+   for (i=1; i < n; ++i) {
+      stbtt__edge t = p[i], *a = &t;
+      j = i;
+      while (j > 0) {
+         stbtt__edge *b = &p[j-1];
+         int c = STBTT__COMPARE(a,b);
+         if (!c) break;
+         p[j] = p[j-1];
+         --j;
+      }
+      if (i != j)
+         p[j] = t;
+   }
+}
+
+static void stbtt__sort_edges_quicksort(stbtt__edge *p, int n)
+{
+   /* threshold for transitioning to insertion sort */
+   while (n > 12) {
+      stbtt__edge t;
+      int c01,c12,c,m,i,j;
+
+      /* compute median of three */
+      m = n >> 1;
+      c01 = STBTT__COMPARE(&p[0],&p[m]);
+      c12 = STBTT__COMPARE(&p[m],&p[n-1]);
+      /* if 0 >= mid >= end, or 0 < mid < end, then use mid */
+      if (c01 != c12) {
+         /* otherwise, we'll need to swap something else to middle */
+         int z;
+         c = STBTT__COMPARE(&p[0],&p[n-1]);
+         /* 0>mid && mid<n:  0>n => n; 0<n => 0 */
+         /* 0<mid && mid>n:  0>n => 0; 0<n => n */
+         z = (c == c12) ? 0 : n-1;
+         t = p[z];
+         p[z] = p[m];
+         p[m] = t;
+      }
+      /* now p[m] is the median-of-three */
+      /* swap it to the beginning so it won't move around */
+      t = p[0];
+      p[0] = p[m];
+      p[m] = t;
+
+      /* partition loop */
+      i=1;
+      j=n-1;
+      for(;;) {
+         /* handling of equality is crucial here */
+         /* for sentinels & efficiency with duplicates */
+         for (;;++i) {
+            if (!STBTT__COMPARE(&p[i], &p[0])) break;
+         }
+         for (;;--j) {
+            if (!STBTT__COMPARE(&p[0], &p[j])) break;
+         }
+         /* make sure we haven't crossed */
+         if (i >= j) break;
+         t = p[i];
+         p[i] = p[j];
+         p[j] = t;
+
+         ++i;
+         --j;
+      }
+      /* recurse on smaller side, iterate on larger */
+      if (j < (n-i)) {
+         stbtt__sort_edges_quicksort(p,j);
+         p = p+i;
+         n = n-i;
+      } else {
+         stbtt__sort_edges_quicksort(p+i, n-i);
+         n = j;
+      }
+   }
+}
+
+static void stbtt__sort_edges(stbtt__edge *p, int n)
+{
+   stbtt__sort_edges_quicksort(p, n);
+   stbtt__sort_edges_ins_sort(p, n);
+}
+
+typedef struct
+{
+   float x,y;
+} stbtt__point;
+
+static void stbtt__rasterize(stbtt__bitmap *result, stbtt__point *pts, int *wcount, int windings, float scale_x, float scale_y, float shift_x, float shift_y, int off_x, int off_y, int invert, void *userdata)
+{
+   float y_scale_inv = invert ? -scale_y : scale_y;
+   stbtt__edge *e;
+   int n,i,j,k,m;
+#if STBTT_RASTERIZER_VERSION == 1
+   int vsubsample = result->h < 8 ? 15 : 5;
+#elif STBTT_RASTERIZER_VERSION == 2
+   int vsubsample = 1;
+#else
+   #error "Unrecognized value of STBTT_RASTERIZER_VERSION"
+#endif
+   // vsubsample should divide 255 evenly; otherwise we won't reach full opacity
+
+   // now we have to blow out the windings into explicit edge lists
+   n = 0;
+   for (i=0; i < windings; ++i)
+      n += wcount[i];
+
+   e = (stbtt__edge *) STBTT_malloc(sizeof(*e) * (n+1), userdata); // add an extra one as a sentinel
+   if (e == 0) return;
+   n = 0;
+
+   m=0;
+   for (i=0; i < windings; ++i) {
+      stbtt__point *p = pts + m;
+      m += wcount[i];
+      j = wcount[i]-1;
+      for (k=0; k < wcount[i]; j=k++) {
+         int a=k,b=j;
+         // skip the edge if horizontal
+         if (p[j].y == p[k].y)
+            continue;
+         // add edge from j to k to the list
+         e[n].invert = 0;
+         if (invert ? p[j].y > p[k].y : p[j].y < p[k].y) {
+            e[n].invert = 1;
+            a=j,b=k;
+         }
+         e[n].x0 = p[a].x * scale_x + shift_x;
+         e[n].y0 = (p[a].y * y_scale_inv + shift_y) * vsubsample;
+         e[n].x1 = p[b].x * scale_x + shift_x;
+         e[n].y1 = (p[b].y * y_scale_inv + shift_y) * vsubsample;
+         ++n;
+      }
+   }
+
+   // now sort the edges by their highest point (should snap to integer, and then by x)
+   //STBTT_sort(e, n, sizeof(e[0]), stbtt__edge_compare);
+   stbtt__sort_edges(e, n);
+
+   // now, traverse the scanlines and find the intersections on each scanline, use xor winding rule
+   stbtt__rasterize_sorted_edges(result, e, n, vsubsample, off_x, off_y, userdata);
+
+   STBTT_free(e, userdata);
+}
+
+static void stbtt__add_point(stbtt__point *points, int n, float x, float y)
+{
+   if (!points) return; // during first pass, it's unallocated
+   points[n].x = x;
+   points[n].y = y;
+}
+
+// tessellate until threshold p is happy... @TODO warped to compensate for non-linear stretching
+static int stbtt__tesselate_curve(stbtt__point *points, int *num_points, float x0, float y0, float x1, float y1, float x2, float y2, float objspace_flatness_squared, int n)
+{
+   // midpoint
+   float mx = (x0 + 2*x1 + x2)/4;
+   float my = (y0 + 2*y1 + y2)/4;
+   // versus directly drawn line
+   float dx = (x0+x2)/2 - mx;
+   float dy = (y0+y2)/2 - my;
+   if (n > 16) // 65536 segments on one curve better be enough!
+      return 1;
+   if (dx*dx+dy*dy > objspace_flatness_squared) { // half-pixel error allowed... need to be smaller if AA
+      stbtt__tesselate_curve(points, num_points, x0,y0, (x0+x1)/2.0f,(y0+y1)/2.0f, mx,my, objspace_flatness_squared,n+1);
+      stbtt__tesselate_curve(points, num_points, mx,my, (x1+x2)/2.0f,(y1+y2)/2.0f, x2,y2, objspace_flatness_squared,n+1);
+   } else {
+      stbtt__add_point(points, *num_points,x2,y2);
+      *num_points = *num_points+1;
+   }
+   return 1;
+}
+
+static void stbtt__tesselate_cubic(stbtt__point *points, int *num_points, float x0, float y0, float x1, float y1, float x2, float y2, float x3, float y3, float objspace_flatness_squared, int n)
+{
+   // @TODO this "flatness" calculation is just made-up nonsense that seems to work well enough
+   float dx0 = x1-x0;
+   float dy0 = y1-y0;
+   float dx1 = x2-x1;
+   float dy1 = y2-y1;
+   float dx2 = x3-x2;
+   float dy2 = y3-y2;
+   float dx = x3-x0;
+   float dy = y3-y0;
+   float longlen = (float) (STBTT_sqrt(dx0*dx0+dy0*dy0)+STBTT_sqrt(dx1*dx1+dy1*dy1)+STBTT_sqrt(dx2*dx2+dy2*dy2));
+   float shortlen = (float) STBTT_sqrt(dx*dx+dy*dy);
+   float flatness_squared = longlen*longlen-shortlen*shortlen;
+
+   if (n > 16) // 65536 segments on one curve better be enough!
+      return;
+
+   if (flatness_squared > objspace_flatness_squared) {
+      float x01 = (x0+x1)/2;
+      float y01 = (y0+y1)/2;
+      float x12 = (x1+x2)/2;
+      float y12 = (y1+y2)/2;
+      float x23 = (x2+x3)/2;
+      float y23 = (y2+y3)/2;
+
+      float xa = (x01+x12)/2;
+      float ya = (y01+y12)/2;
+      float xb = (x12+x23)/2;
+      float yb = (y12+y23)/2;
+
+      float mx = (xa+xb)/2;
+      float my = (ya+yb)/2;
+
+      stbtt__tesselate_cubic(points, num_points, x0,y0, x01,y01, xa,ya, mx,my, objspace_flatness_squared,n+1);
+      stbtt__tesselate_cubic(points, num_points, mx,my, xb,yb, x23,y23, x3,y3, objspace_flatness_squared,n+1);
+   } else {
+      stbtt__add_point(points, *num_points,x3,y3);
+      *num_points = *num_points+1;
+   }
+}
+
+// returns number of contours
+static stbtt__point *stbtt_FlattenCurves(stbtt_vertex *vertices, int num_verts, float objspace_flatness, int **contour_lengths, int *num_contours, void *userdata)
+{
+   stbtt__point *points=0;
+   int num_points=0;
+
+   float objspace_flatness_squared = objspace_flatness * objspace_flatness;
+   int i,n=0,start=0, pass;
+
+   // count how many "moves" there are to get the contour count
+   for (i=0; i < num_verts; ++i)
+      if (vertices[i].type == STBTT_vmove)
+         ++n;
+
+   *num_contours = n;
+   if (n == 0) return 0;
+
+   *contour_lengths = (int *) STBTT_malloc(sizeof(**contour_lengths) * n, userdata);
+
+   if (*contour_lengths == 0) {
+      *num_contours = 0;
+      return 0;
+   }
+
+   // make two passes through the points so we don't need to realloc
+   for (pass=0; pass < 2; ++pass) {
+      float x=0,y=0;
+      if (pass == 1) {
+         points = (stbtt__point *) STBTT_malloc(num_points * sizeof(points[0]), userdata);
+         if (points == NULL) goto error;
+      }
+      num_points = 0;
+      n= -1;
+      for (i=0; i < num_verts; ++i) {
+         switch (vertices[i].type) {
+            case STBTT_vmove:
+               // start the next contour
+               if (n >= 0)
+                  (*contour_lengths)[n] = num_points - start;
+               ++n;
+               start = num_points;
+
+               x = vertices[i].x, y = vertices[i].y;
+               stbtt__add_point(points, num_points++, x,y);
+               break;
+            case STBTT_vline:
+               x = vertices[i].x, y = vertices[i].y;
+               stbtt__add_point(points, num_points++, x, y);
+               break;
+            case STBTT_vcurve:
+               stbtt__tesselate_curve(points, &num_points, x,y,
+                                        vertices[i].cx, vertices[i].cy,
+                                        vertices[i].x,  vertices[i].y,
+                                        objspace_flatness_squared, 0);
+               x = vertices[i].x, y = vertices[i].y;
+               break;
+            case STBTT_vcubic:
+               stbtt__tesselate_cubic(points, &num_points, x,y,
+                                        vertices[i].cx, vertices[i].cy,
+                                        vertices[i].cx1, vertices[i].cy1,
+                                        vertices[i].x,  vertices[i].y,
+                                        objspace_flatness_squared, 0);
+               x = vertices[i].x, y = vertices[i].y;
+               break;
+         }
+      }
+      (*contour_lengths)[n] = num_points - start;
+   }
+
+   return points;
+error:
+   STBTT_free(points, userdata);
+   STBTT_free(*contour_lengths, userdata);
+   *contour_lengths = 0;
+   *num_contours = 0;
+   return NULL;
+}
+
+STBTT_DEF void stbtt_Rasterize(stbtt__bitmap *result, float flatness_in_pixels, stbtt_vertex *vertices, int num_verts, float scale_x, float scale_y, float shift_x, float shift_y, int x_off, int y_off, int invert, void *userdata)
+{
+   float scale            = scale_x > scale_y ? scale_y : scale_x;
+   int winding_count      = 0;
+   int *winding_lengths   = NULL;
+   stbtt__point *windings = stbtt_FlattenCurves(vertices, num_verts, flatness_in_pixels / scale, &winding_lengths, &winding_count, userdata);
+   if (windings) {
+      stbtt__rasterize(result, windings, winding_lengths, winding_count, scale_x, scale_y, shift_x, shift_y, x_off, y_off, invert, userdata);
+      STBTT_free(winding_lengths, userdata);
+      STBTT_free(windings, userdata);
+   }
+}
+
+STBTT_DEF void stbtt_FreeBitmap(unsigned char *bitmap, void *userdata)
+{
+   STBTT_free(bitmap, userdata);
+}
+
+STBTT_DEF unsigned char *stbtt_GetGlyphBitmapSubpixel(const stbtt_fontinfo *info, float scale_x, float scale_y, float shift_x, float shift_y, int glyph, int *width, int *height, int *xoff, int *yoff)
+{
+   int ix0,iy0,ix1,iy1;
+   stbtt__bitmap gbm;
+   stbtt_vertex *vertices;
+   int num_verts = stbtt_GetGlyphShape(info, glyph, &vertices);
+
+   if (scale_x == 0) scale_x = scale_y;
+   if (scale_y == 0) {
+      if (scale_x == 0) {
+         STBTT_free(vertices, info->userdata);
+         return NULL;
+      }
+      scale_y = scale_x;
+   }
+
+   stbtt_GetGlyphBitmapBoxSubpixel(info, glyph, scale_x, scale_y, shift_x, shift_y, &ix0,&iy0,&ix1,&iy1);
+
+   // now we get the size
+   gbm.w = (ix1 - ix0);
+   gbm.h = (iy1 - iy0);
+   gbm.pixels = NULL; // in case we error
+
+   if (width ) *width  = gbm.w;
+   if (height) *height = gbm.h;
+   if (xoff  ) *xoff   = ix0;
+   if (yoff  ) *yoff   = iy0;
+
+   if (gbm.w && gbm.h) {
+      gbm.pixels = (unsigned char *) STBTT_malloc(gbm.w * gbm.h, info->userdata);
+      if (gbm.pixels) {
+         gbm.stride = gbm.w;
+
+         stbtt_Rasterize(&gbm, 0.35f, vertices, num_verts, scale_x, scale_y, shift_x, shift_y, ix0, iy0, 1, info->userdata);
+      }
+   }
+   STBTT_free(vertices, info->userdata);
+   return gbm.pixels;
+}
+
+STBTT_DEF unsigned char *stbtt_GetGlyphBitmap(const stbtt_fontinfo *info, float scale_x, float scale_y, int glyph, int *width, int *height, int *xoff, int *yoff)
+{
+   return stbtt_GetGlyphBitmapSubpixel(info, scale_x, scale_y, 0.0f, 0.0f, glyph, width, height, xoff, yoff);
+}
+
+STBTT_DEF void stbtt_MakeGlyphBitmapSubpixel(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int glyph)
+{
+   int ix0,iy0;
+   stbtt_vertex *vertices;
+   int num_verts = stbtt_GetGlyphShape(info, glyph, &vertices);
+   stbtt__bitmap gbm;
+
+   stbtt_GetGlyphBitmapBoxSubpixel(info, glyph, scale_x, scale_y, shift_x, shift_y, &ix0,&iy0,0,0);
+   gbm.pixels = output;
+   gbm.w = out_w;
+   gbm.h = out_h;
+   gbm.stride = out_stride;
+
+   if (gbm.w && gbm.h)
+      stbtt_Rasterize(&gbm, 0.35f, vertices, num_verts, scale_x, scale_y, shift_x, shift_y, ix0,iy0, 1, info->userdata);
+
+   STBTT_free(vertices, info->userdata);
+}
+
+STBTT_DEF void stbtt_MakeGlyphBitmap(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, int glyph)
+{
+   stbtt_MakeGlyphBitmapSubpixel(info, output, out_w, out_h, out_stride, scale_x, scale_y, 0.0f,0.0f, glyph);
+}
+
+STBTT_DEF unsigned char *stbtt_GetCodepointBitmapSubpixel(const stbtt_fontinfo *info, float scale_x, float scale_y, float shift_x, float shift_y, int codepoint, int *width, int *height, int *xoff, int *yoff)
+{
+   return stbtt_GetGlyphBitmapSubpixel(info, scale_x, scale_y,shift_x,shift_y, stbtt_FindGlyphIndex(info,codepoint), width,height,xoff,yoff);
+}
+
+STBTT_DEF void stbtt_MakeCodepointBitmapSubpixelPrefilter(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int oversample_x, int oversample_y, float *sub_x, float *sub_y, int codepoint)
+{
+   stbtt_MakeGlyphBitmapSubpixelPrefilter(info, output, out_w, out_h, out_stride, scale_x, scale_y, shift_x, shift_y, oversample_x, oversample_y, sub_x, sub_y, stbtt_FindGlyphIndex(info,codepoint));
+}
+
+STBTT_DEF void stbtt_MakeCodepointBitmapSubpixel(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int codepoint)
+{
+   stbtt_MakeGlyphBitmapSubpixel(info, output, out_w, out_h, out_stride, scale_x, scale_y, shift_x, shift_y, stbtt_FindGlyphIndex(info,codepoint));
+}
+
+STBTT_DEF unsigned char *stbtt_GetCodepointBitmap(const stbtt_fontinfo *info, float scale_x, float scale_y, int codepoint, int *width, int *height, int *xoff, int *yoff)
+{
+   return stbtt_GetCodepointBitmapSubpixel(info, scale_x, scale_y, 0.0f,0.0f, codepoint, width,height,xoff,yoff);
+}
+
+STBTT_DEF void stbtt_MakeCodepointBitmap(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, int codepoint)
+{
+   stbtt_MakeCodepointBitmapSubpixel(info, output, out_w, out_h, out_stride, scale_x, scale_y, 0.0f,0.0f, codepoint);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// bitmap baking
+//
+// This is SUPER-CRAPPY packing to keep source code small
+
+static int stbtt_BakeFontBitmap_internal(unsigned char *data, int offset,  // font location (use offset=0 for plain .ttf)
+                                float pixel_height,                     // height of font in pixels
+                                unsigned char *pixels, int pw, int ph,  // bitmap to be filled in
+                                int first_char, int num_chars,          // characters to bake
+                                stbtt_bakedchar *chardata)
+{
+   float scale;
+   int x,y,bottom_y, i;
+   stbtt_fontinfo f;
+   f.userdata = NULL;
+   if (!stbtt_InitFont(&f, data, offset))
+      return -1;
+   STBTT_memset(pixels, 0, pw*ph); // background of 0 around pixels
+   x=y=1;
+   bottom_y = 1;
+
+   scale = stbtt_ScaleForPixelHeight(&f, pixel_height);
+
+   for (i=0; i < num_chars; ++i) {
+      int advance, lsb, x0,y0,x1,y1,gw,gh;
+      int g = stbtt_FindGlyphIndex(&f, first_char + i);
+      stbtt_GetGlyphHMetrics(&f, g, &advance, &lsb);
+      stbtt_GetGlyphBitmapBox(&f, g, scale,scale, &x0,&y0,&x1,&y1);
+      gw = x1-x0;
+      gh = y1-y0;
+      if (x + gw + 1 >= pw)
+         y = bottom_y, x = 1; // advance to next row
+      if (y + gh + 1 >= ph) // check if it fits vertically AFTER potentially moving to next row
+         return -i;
+      STBTT_assert(x+gw < pw);
+      STBTT_assert(y+gh < ph);
+      stbtt_MakeGlyphBitmap(&f, pixels+x+y*pw, gw,gh,pw, scale,scale, g);
+      chardata[i].x0 = (stbtt_int16) x;
+      chardata[i].y0 = (stbtt_int16) y;
+      chardata[i].x1 = (stbtt_int16) (x + gw);
+      chardata[i].y1 = (stbtt_int16) (y + gh);
+      chardata[i].xadvance = scale * advance;
+      chardata[i].xoff     = (float) x0;
+      chardata[i].yoff     = (float) y0;
+      x = x + gw + 1;
+      if (y+gh+1 > bottom_y)
+         bottom_y = y+gh+1;
+   }
+   return bottom_y;
+}
+
+STBTT_DEF void stbtt_GetBakedQuad(const stbtt_bakedchar *chardata, int pw, int ph, int char_index, float *xpos, float *ypos, stbtt_aligned_quad *q, int opengl_fillrule)
+{
+   float d3d_bias = opengl_fillrule ? 0 : -0.5f;
+   float ipw = 1.0f / pw, iph = 1.0f / ph;
+   const stbtt_bakedchar *b = chardata + char_index;
+   int round_x = STBTT_ifloor((*xpos + b->xoff) + 0.5f);
+   int round_y = STBTT_ifloor((*ypos + b->yoff) + 0.5f);
+
+   q->x0 = round_x + d3d_bias;
+   q->y0 = round_y + d3d_bias;
+   q->x1 = round_x + b->x1 - b->x0 + d3d_bias;
+   q->y1 = round_y + b->y1 - b->y0 + d3d_bias;
+
+   q->s0 = b->x0 * ipw;
+   q->t0 = b->y0 * iph;
+   q->s1 = b->x1 * ipw;
+   q->t1 = b->y1 * iph;
+
+   *xpos += b->xadvance;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// rectangle packing replacement routines if you don't have stb_rect_pack.h
+//
+
+#ifndef STB_RECT_PACK_VERSION
+
+typedef int stbrp_coord;
+
+////////////////////////////////////////////////////////////////////////////////////
+//                                                                                //
+//                                                                                //
+// COMPILER WARNING ?!?!?                                                         //
+//                                                                                //
+//                                                                                //
+// if you get a compile warning due to these symbols being defined more than      //
+// once, move #include "stb_rect_pack.h" before #include "stb_truetype.h"         //
+//                                                                                //
+////////////////////////////////////////////////////////////////////////////////////
+
+typedef struct
+{
+   int width,height;
+   int x,y,bottom_y;
+} stbrp_context;
+
+typedef struct
+{
+   unsigned char x;
+} stbrp_node;
+
+struct stbrp_rect
+{
+   stbrp_coord x,y;
+   int id,w,h,was_packed;
+};
+
+static void stbrp_init_target(stbrp_context *con, int pw, int ph, stbrp_node *nodes, int num_nodes)
+{
+   con->width  = pw;
+   con->height = ph;
+   con->x = 0;
+   con->y = 0;
+   con->bottom_y = 0;
+   STBTT__NOTUSED(nodes);
+   STBTT__NOTUSED(num_nodes);
+}
+
+static void stbrp_pack_rects(stbrp_context *con, stbrp_rect *rects, int num_rects)
+{
+   int i;
+   for (i=0; i < num_rects; ++i) {
+      if (con->x + rects[i].w > con->width) {
+         con->x = 0;
+         con->y = con->bottom_y;
+      }
+      if (con->y + rects[i].h > con->height)
+         break;
+      rects[i].x = con->x;
+      rects[i].y = con->y;
+      rects[i].was_packed = 1;
+      con->x += rects[i].w;
+      if (con->y + rects[i].h > con->bottom_y)
+         con->bottom_y = con->y + rects[i].h;
+   }
+   for (   ; i < num_rects; ++i)
+      rects[i].was_packed = 0;
+}
+#endif
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// bitmap baking
+//
+// This is SUPER-AWESOME (tm Ryan Gordon) packing using stb_rect_pack.h. If
+// stb_rect_pack.h isn't available, it uses the BakeFontBitmap strategy.
+
+STBTT_DEF int stbtt_PackBegin(stbtt_pack_context *spc, unsigned char *pixels, int pw, int ph, int stride_in_bytes, int padding, void *alloc_context)
+{
+   stbrp_context *context = (stbrp_context *) STBTT_malloc(sizeof(*context)            ,alloc_context);
+   int            num_nodes = pw - padding;
+   stbrp_node    *nodes   = (stbrp_node    *) STBTT_malloc(sizeof(*nodes  ) * num_nodes,alloc_context);
+
+   if (context == NULL || nodes == NULL) {
+      if (context != NULL) STBTT_free(context, alloc_context);
+      if (nodes   != NULL) STBTT_free(nodes  , alloc_context);
+      return 0;
+   }
+
+   spc->user_allocator_context = alloc_context;
+   spc->width = pw;
+   spc->height = ph;
+   spc->pixels = pixels;
+   spc->pack_info = context;
+   spc->nodes = nodes;
+   spc->padding = padding;
+   spc->stride_in_bytes = stride_in_bytes != 0 ? stride_in_bytes : pw;
+   spc->h_oversample = 1;
+   spc->v_oversample = 1;
+   spc->skip_missing = 0;
+
+   stbrp_init_target(context, pw-padding, ph-padding, nodes, num_nodes);
+
+   if (pixels)
+      STBTT_memset(pixels, 0, pw*ph); // background of 0 around pixels
+
+   return 1;
+}
+
+STBTT_DEF void stbtt_PackEnd  (stbtt_pack_context *spc)
+{
+   STBTT_free(spc->nodes    , spc->user_allocator_context);
+   STBTT_free(spc->pack_info, spc->user_allocator_context);
+}
+
+STBTT_DEF void stbtt_PackSetOversampling(stbtt_pack_context *spc, unsigned int h_oversample, unsigned int v_oversample)
+{
+   STBTT_assert(h_oversample <= STBTT_MAX_OVERSAMPLE);
+   STBTT_assert(v_oversample <= STBTT_MAX_OVERSAMPLE);
+   if (h_oversample <= STBTT_MAX_OVERSAMPLE)
+      spc->h_oversample = h_oversample;
+   if (v_oversample <= STBTT_MAX_OVERSAMPLE)
+      spc->v_oversample = v_oversample;
+}
+
+STBTT_DEF void stbtt_PackSetSkipMissingCodepoints(stbtt_pack_context *spc, int skip)
+{
+   spc->skip_missing = skip;
+}
+
+#define STBTT__OVER_MASK  (STBTT_MAX_OVERSAMPLE-1)
+
+static void stbtt__h_prefilter(unsigned char *pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width)
+{
+   unsigned char buffer[STBTT_MAX_OVERSAMPLE];
+   int safe_w = w - kernel_width;
+   int j;
+   STBTT_memset(buffer, 0, STBTT_MAX_OVERSAMPLE); // suppress bogus warning from VS2013 -analyze
+   for (j=0; j < h; ++j) {
+      int i;
+      unsigned int total;
+      STBTT_memset(buffer, 0, kernel_width);
+
+      total = 0;
+
+      // make kernel_width a constant in common cases so compiler can optimize out the divide
+      switch (kernel_width) {
+         case 2:
+            for (i=0; i <= safe_w; ++i) {
+               total += pixels[i] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i];
+               pixels[i] = (unsigned char) (total / 2);
+            }
+            break;
+         case 3:
+            for (i=0; i <= safe_w; ++i) {
+               total += pixels[i] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i];
+               pixels[i] = (unsigned char) (total / 3);
+            }
+            break;
+         case 4:
+            for (i=0; i <= safe_w; ++i) {
+               total += pixels[i] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i];
+               pixels[i] = (unsigned char) (total / 4);
+            }
+            break;
+         case 5:
+            for (i=0; i <= safe_w; ++i) {
+               total += pixels[i] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i];
+               pixels[i] = (unsigned char) (total / 5);
+            }
+            break;
+         default:
+            for (i=0; i <= safe_w; ++i) {
+               total += pixels[i] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i];
+               pixels[i] = (unsigned char) (total / kernel_width);
+            }
+            break;
+      }
+
+      for (; i < w; ++i) {
+         STBTT_assert(pixels[i] == 0);
+         total -= buffer[i & STBTT__OVER_MASK];
+         pixels[i] = (unsigned char) (total / kernel_width);
+      }
+
+      pixels += stride_in_bytes;
+   }
+}
+
+static void stbtt__v_prefilter(unsigned char *pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width)
+{
+   unsigned char buffer[STBTT_MAX_OVERSAMPLE];
+   int safe_h = h - kernel_width;
+   int j;
+   STBTT_memset(buffer, 0, STBTT_MAX_OVERSAMPLE); // suppress bogus warning from VS2013 -analyze
+   for (j=0; j < w; ++j) {
+      int i;
+      unsigned int total;
+      STBTT_memset(buffer, 0, kernel_width);
+
+      total = 0;
+
+      // make kernel_width a constant in common cases so compiler can optimize out the divide
+      switch (kernel_width) {
+         case 2:
+            for (i=0; i <= safe_h; ++i) {
+               total += pixels[i*stride_in_bytes] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i*stride_in_bytes];
+               pixels[i*stride_in_bytes] = (unsigned char) (total / 2);
+            }
+            break;
+         case 3:
+            for (i=0; i <= safe_h; ++i) {
+               total += pixels[i*stride_in_bytes] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i*stride_in_bytes];
+               pixels[i*stride_in_bytes] = (unsigned char) (total / 3);
+            }
+            break;
+         case 4:
+            for (i=0; i <= safe_h; ++i) {
+               total += pixels[i*stride_in_bytes] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i*stride_in_bytes];
+               pixels[i*stride_in_bytes] = (unsigned char) (total / 4);
+            }
+            break;
+         case 5:
+            for (i=0; i <= safe_h; ++i) {
+               total += pixels[i*stride_in_bytes] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i*stride_in_bytes];
+               pixels[i*stride_in_bytes] = (unsigned char) (total / 5);
+            }
+            break;
+         default:
+            for (i=0; i <= safe_h; ++i) {
+               total += pixels[i*stride_in_bytes] - buffer[i & STBTT__OVER_MASK];
+               buffer[(i+kernel_width) & STBTT__OVER_MASK] = pixels[i*stride_in_bytes];
+               pixels[i*stride_in_bytes] = (unsigned char) (total / kernel_width);
+            }
+            break;
+      }
+
+      for (; i < h; ++i) {
+         STBTT_assert(pixels[i*stride_in_bytes] == 0);
+         total -= buffer[i & STBTT__OVER_MASK];
+         pixels[i*stride_in_bytes] = (unsigned char) (total / kernel_width);
+      }
+
+      pixels += 1;
+   }
+}
+
+static float stbtt__oversample_shift(int oversample)
+{
+   if (!oversample)
+      return 0.0f;
+
+   // The prefilter is a box filter of width "oversample",
+   // which shifts phase by (oversample - 1)/2 pixels in
+   // oversampled space. We want to shift in the opposite
+   // direction to counter this.
+   return (float)-(oversample - 1) / (2.0f * (float)oversample);
+}
+
+// rects array must be big enough to accommodate all characters in the given ranges
+STBTT_DEF int stbtt_PackFontRangesGatherRects(stbtt_pack_context *spc, const stbtt_fontinfo *info, stbtt_pack_range *ranges, int num_ranges, stbrp_rect *rects)
+{
+   int i,j,k;
+   int missing_glyph_added = 0;
+
+   k=0;
+   for (i=0; i < num_ranges; ++i) {
+      float fh = ranges[i].font_size;
+      float scale = fh > 0 ? stbtt_ScaleForPixelHeight(info, fh) : stbtt_ScaleForMappingEmToPixels(info, -fh);
+      ranges[i].h_oversample = (unsigned char) spc->h_oversample;
+      ranges[i].v_oversample = (unsigned char) spc->v_oversample;
+      for (j=0; j < ranges[i].num_chars; ++j) {
+         int x0,y0,x1,y1;
+         int codepoint = ranges[i].array_of_unicode_codepoints == NULL ? ranges[i].first_unicode_codepoint_in_range + j : ranges[i].array_of_unicode_codepoints[j];
+         int glyph = stbtt_FindGlyphIndex(info, codepoint);
+         if (glyph == 0 && (spc->skip_missing || missing_glyph_added)) {
+            rects[k].w = rects[k].h = 0;
+         } else {
+            stbtt_GetGlyphBitmapBoxSubpixel(info,glyph,
+                                            scale * spc->h_oversample,
+                                            scale * spc->v_oversample,
+                                            0,0,
+                                            &x0,&y0,&x1,&y1);
+            rects[k].w = (stbrp_coord) (x1-x0 + spc->padding + spc->h_oversample-1);
+            rects[k].h = (stbrp_coord) (y1-y0 + spc->padding + spc->v_oversample-1);
+            if (glyph == 0)
+               missing_glyph_added = 1;
+         }
+         ++k;
+      }
+   }
+
+   return k;
+}
+
+STBTT_DEF void stbtt_MakeGlyphBitmapSubpixelPrefilter(const stbtt_fontinfo *info, unsigned char *output, int out_w, int out_h, int out_stride, float scale_x, float scale_y, float shift_x, float shift_y, int prefilter_x, int prefilter_y, float *sub_x, float *sub_y, int glyph)
+{
+   stbtt_MakeGlyphBitmapSubpixel(info,
+                                 output,
+                                 out_w - (prefilter_x - 1),
+                                 out_h - (prefilter_y - 1),
+                                 out_stride,
+                                 scale_x,
+                                 scale_y,
+                                 shift_x,
+                                 shift_y,
+                                 glyph);
+
+   if (prefilter_x > 1)
+      stbtt__h_prefilter(output, out_w, out_h, out_stride, prefilter_x);
+
+   if (prefilter_y > 1)
+      stbtt__v_prefilter(output, out_w, out_h, out_stride, prefilter_y);
+
+   *sub_x = stbtt__oversample_shift(prefilter_x);
+   *sub_y = stbtt__oversample_shift(prefilter_y);
+}
+
+// rects array must be big enough to accommodate all characters in the given ranges
+STBTT_DEF int stbtt_PackFontRangesRenderIntoRects(stbtt_pack_context *spc, const stbtt_fontinfo *info, stbtt_pack_range *ranges, int num_ranges, stbrp_rect *rects)
+{
+   int i,j,k, missing_glyph = -1, return_value = 1;
+
+   // save current values
+   int old_h_over = spc->h_oversample;
+   int old_v_over = spc->v_oversample;
+
+   k = 0;
+   for (i=0; i < num_ranges; ++i) {
+      float fh = ranges[i].font_size;
+      float scale = fh > 0 ? stbtt_ScaleForPixelHeight(info, fh) : stbtt_ScaleForMappingEmToPixels(info, -fh);
+      float recip_h,recip_v,sub_x,sub_y;
+      spc->h_oversample = ranges[i].h_oversample;
+      spc->v_oversample = ranges[i].v_oversample;
+      recip_h = 1.0f / spc->h_oversample;
+      recip_v = 1.0f / spc->v_oversample;
+      sub_x = stbtt__oversample_shift(spc->h_oversample);
+      sub_y = stbtt__oversample_shift(spc->v_oversample);
+      for (j=0; j < ranges[i].num_chars; ++j) {
+         stbrp_rect *r = &rects[k];
+         if (r->was_packed && r->w != 0 && r->h != 0) {
+            stbtt_packedchar *bc = &ranges[i].chardata_for_range[j];
+            int advance, lsb, x0,y0,x1,y1;
+            int codepoint = ranges[i].array_of_unicode_codepoints == NULL ? ranges[i].first_unicode_codepoint_in_range + j : ranges[i].array_of_unicode_codepoints[j];
+            int glyph = stbtt_FindGlyphIndex(info, codepoint);
+            stbrp_coord pad = (stbrp_coord) spc->padding;
+
+            // pad on left and top
+            r->x += pad;
+            r->y += pad;
+            r->w -= pad;
+            r->h -= pad;
+            stbtt_GetGlyphHMetrics(info, glyph, &advance, &lsb);
+            stbtt_GetGlyphBitmapBox(info, glyph,
+                                    scale * spc->h_oversample,
+                                    scale * spc->v_oversample,
+                                    &x0,&y0,&x1,&y1);
+            stbtt_MakeGlyphBitmapSubpixel(info,
+                                          spc->pixels + r->x + r->y*spc->stride_in_bytes,
+                                          r->w - spc->h_oversample+1,
+                                          r->h - spc->v_oversample+1,
+                                          spc->stride_in_bytes,
+                                          scale * spc->h_oversample,
+                                          scale * spc->v_oversample,
+                                          0,0,
+                                          glyph);
+
+            if (spc->h_oversample > 1)
+               stbtt__h_prefilter(spc->pixels + r->x + r->y*spc->stride_in_bytes,
+                                  r->w, r->h, spc->stride_in_bytes,
+                                  spc->h_oversample);
+
+            if (spc->v_oversample > 1)
+               stbtt__v_prefilter(spc->pixels + r->x + r->y*spc->stride_in_bytes,
+                                  r->w, r->h, spc->stride_in_bytes,
+                                  spc->v_oversample);
+
+            bc->x0       = (stbtt_int16)  r->x;
+            bc->y0       = (stbtt_int16)  r->y;
+            bc->x1       = (stbtt_int16) (r->x + r->w);
+            bc->y1       = (stbtt_int16) (r->y + r->h);
+            bc->xadvance =                scale * advance;
+            bc->xoff     =       (float)  x0 * recip_h + sub_x;
+            bc->yoff     =       (float)  y0 * recip_v + sub_y;
+            bc->xoff2    =                (x0 + r->w) * recip_h + sub_x;
+            bc->yoff2    =                (y0 + r->h) * recip_v + sub_y;
+
+            if (glyph == 0)
+               missing_glyph = j;
+         } else if (spc->skip_missing) {
+            return_value = 0;
+         } else if (r->was_packed && r->w == 0 && r->h == 0 && missing_glyph >= 0) {
+            ranges[i].chardata_for_range[j] = ranges[i].chardata_for_range[missing_glyph];
+         } else {
+            return_value = 0; // if any fail, report failure
+         }
+
+         ++k;
+      }
+   }
+
+   // restore original values
+   spc->h_oversample = old_h_over;
+   spc->v_oversample = old_v_over;
+
+   return return_value;
+}
+
+STBTT_DEF void stbtt_PackFontRangesPackRects(stbtt_pack_context *spc, stbrp_rect *rects, int num_rects)
+{
+   stbrp_pack_rects((stbrp_context *) spc->pack_info, rects, num_rects);
+}
+
+STBTT_DEF int stbtt_PackFontRanges(stbtt_pack_context *spc, const unsigned char *fontdata, int font_index, stbtt_pack_range *ranges, int num_ranges)
+{
+   stbtt_fontinfo info;
+   int i,j,n, return_value = 1;
+   //stbrp_context *context = (stbrp_context *) spc->pack_info;
+   stbrp_rect    *rects;
+
+   // flag all characters as NOT packed
+   for (i=0; i < num_ranges; ++i)
+      for (j=0; j < ranges[i].num_chars; ++j)
+         ranges[i].chardata_for_range[j].x0 =
+         ranges[i].chardata_for_range[j].y0 =
+         ranges[i].chardata_for_range[j].x1 =
+         ranges[i].chardata_for_range[j].y1 = 0;
+
+   n = 0;
+   for (i=0; i < num_ranges; ++i)
+      n += ranges[i].num_chars;
+
+   rects = (stbrp_rect *) STBTT_malloc(sizeof(*rects) * n, spc->user_allocator_context);
+   if (rects == NULL)
+      return 0;
+
+   info.userdata = spc->user_allocator_context;
+   stbtt_InitFont(&info, fontdata, stbtt_GetFontOffsetForIndex(fontdata,font_index));
+
+   n = stbtt_PackFontRangesGatherRects(spc, &info, ranges, num_ranges, rects);
+
+   stbtt_PackFontRangesPackRects(spc, rects, n);
+
+   return_value = stbtt_PackFontRangesRenderIntoRects(spc, &info, ranges, num_ranges, rects);
+
+   STBTT_free(rects, spc->user_allocator_context);
+   return return_value;
+}
+
+STBTT_DEF int stbtt_PackFontRange(stbtt_pack_context *spc, const unsigned char *fontdata, int font_index, float font_size,
+            int first_unicode_codepoint_in_range, int num_chars_in_range, stbtt_packedchar *chardata_for_range)
+{
+   stbtt_pack_range range;
+   range.first_unicode_codepoint_in_range = first_unicode_codepoint_in_range;
+   range.array_of_unicode_codepoints = NULL;
+   range.num_chars                   = num_chars_in_range;
+   range.chardata_for_range          = chardata_for_range;
+   range.font_size                   = font_size;
+   return stbtt_PackFontRanges(spc, fontdata, font_index, &range, 1);
+}
+
+STBTT_DEF void stbtt_GetScaledFontVMetrics(const unsigned char *fontdata, int index, float size, float *ascent, float *descent, float *lineGap)
+{
+   int i_ascent, i_descent, i_lineGap;
+   float scale;
+   stbtt_fontinfo info;
+   stbtt_InitFont(&info, fontdata, stbtt_GetFontOffsetForIndex(fontdata, index));
+   scale = size > 0 ? stbtt_ScaleForPixelHeight(&info, size) : stbtt_ScaleForMappingEmToPixels(&info, -size);
+   stbtt_GetFontVMetrics(&info, &i_ascent, &i_descent, &i_lineGap);
+   *ascent  = (float) i_ascent  * scale;
+   *descent = (float) i_descent * scale;
+   *lineGap = (float) i_lineGap * scale;
+}
+
+STBTT_DEF void stbtt_GetPackedQuad(const stbtt_packedchar *chardata, int pw, int ph, int char_index, float *xpos, float *ypos, stbtt_aligned_quad *q, int align_to_integer)
+{
+   float ipw = 1.0f / pw, iph = 1.0f / ph;
+   const stbtt_packedchar *b = chardata + char_index;
+
+   if (align_to_integer) {
+      float x = (float) STBTT_ifloor((*xpos + b->xoff) + 0.5f);
+      float y = (float) STBTT_ifloor((*ypos + b->yoff) + 0.5f);
+      q->x0 = x;
+      q->y0 = y;
+      q->x1 = x + b->xoff2 - b->xoff;
+      q->y1 = y + b->yoff2 - b->yoff;
+   } else {
+      q->x0 = *xpos + b->xoff;
+      q->y0 = *ypos + b->yoff;
+      q->x1 = *xpos + b->xoff2;
+      q->y1 = *ypos + b->yoff2;
+   }
+
+   q->s0 = b->x0 * ipw;
+   q->t0 = b->y0 * iph;
+   q->s1 = b->x1 * ipw;
+   q->t1 = b->y1 * iph;
+
+   *xpos += b->xadvance;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// sdf computation
+//
+
+#define STBTT_min(a,b)  ((a) < (b) ? (a) : (b))
+#define STBTT_max(a,b)  ((a) < (b) ? (b) : (a))
+
+static int stbtt__ray_intersect_bezier(float orig[2], float ray[2], float q0[2], float q1[2], float q2[2], float hits[2][2])
+{
+   float q0perp = q0[1]*ray[0] - q0[0]*ray[1];
+   float q1perp = q1[1]*ray[0] - q1[0]*ray[1];
+   float q2perp = q2[1]*ray[0] - q2[0]*ray[1];
+   float roperp = orig[1]*ray[0] - orig[0]*ray[1];
+
+   float a = q0perp - 2*q1perp + q2perp;
+   float b = q1perp - q0perp;
+   float c = q0perp - roperp;
+
+   float s0 = 0., s1 = 0.;
+   int num_s = 0;
+
+   if (a != 0.0) {
+      float discr = b*b - a*c;
+      if (discr > 0.0) {
+         float rcpna = -1 / a;
+         float d = (float) STBTT_sqrt(discr);
+         s0 = (b+d) * rcpna;
+         s1 = (b-d) * rcpna;
+         if (s0 >= 0.0 && s0 <= 1.0)
+            num_s = 1;
+         if (d > 0.0 && s1 >= 0.0 && s1 <= 1.0) {
+            if (num_s == 0) s0 = s1;
+            ++num_s;
+         }
+      }
+   } else {
+      // 2*b*s + c = 0
+      // s = -c / (2*b)
+      s0 = c / (-2 * b);
+      if (s0 >= 0.0 && s0 <= 1.0)
+         num_s = 1;
+   }
+
+   if (num_s == 0)
+      return 0;
+   else {
+      float rcp_len2 = 1 / (ray[0]*ray[0] + ray[1]*ray[1]);
+      float rayn_x = ray[0] * rcp_len2, rayn_y = ray[1] * rcp_len2;
+
+      float q0d =   q0[0]*rayn_x +   q0[1]*rayn_y;
+      float q1d =   q1[0]*rayn_x +   q1[1]*rayn_y;
+      float q2d =   q2[0]*rayn_x +   q2[1]*rayn_y;
+      float rod = orig[0]*rayn_x + orig[1]*rayn_y;
+
+      float q10d = q1d - q0d;
+      float q20d = q2d - q0d;
+      float q0rd = q0d - rod;
+
+      hits[0][0] = q0rd + s0*(2.0f - 2.0f*s0)*q10d + s0*s0*q20d;
+      hits[0][1] = a*s0+b;
+
+      if (num_s > 1) {
+         hits[1][0] = q0rd + s1*(2.0f - 2.0f*s1)*q10d + s1*s1*q20d;
+         hits[1][1] = a*s1+b;
+         return 2;
+      } else {
+         return 1;
+      }
+   }
+}
+
+static int equal(float *a, float *b)
+{
+   return (a[0] == b[0] && a[1] == b[1]);
+}
+
+static int stbtt__compute_crossings_x(float x, float y, int nverts, stbtt_vertex *verts)
+{
+   int i;
+   float orig[2], ray[2] = { 1, 0 };
+   float y_frac;
+   int winding = 0;
+
+   // make sure y never passes through a vertex of the shape
+   y_frac = (float) STBTT_fmod(y, 1.0f);
+   if (y_frac < 0.01f)
+      y += 0.01f;
+   else if (y_frac > 0.99f)
+      y -= 0.01f;
+
+   orig[0] = x;
+   orig[1] = y;
+
+   // test a ray from (-infinity,y) to (x,y)
+   for (i=0; i < nverts; ++i) {
+      if (verts[i].type == STBTT_vline) {
+         int x0 = (int) verts[i-1].x, y0 = (int) verts[i-1].y;
+         int x1 = (int) verts[i  ].x, y1 = (int) verts[i  ].y;
+         if (y > STBTT_min(y0,y1) && y < STBTT_max(y0,y1) && x > STBTT_min(x0,x1)) {
+            float x_inter = (y - y0) / (y1 - y0) * (x1-x0) + x0;
+            if (x_inter < x)
+               winding += (y0 < y1) ? 1 : -1;
+         }
+      }
+      if (verts[i].type == STBTT_vcurve) {
+         int x0 = (int) verts[i-1].x , y0 = (int) verts[i-1].y ;
+         int x1 = (int) verts[i  ].cx, y1 = (int) verts[i  ].cy;
+         int x2 = (int) verts[i  ].x , y2 = (int) verts[i  ].y ;
+         int ax = STBTT_min(x0,STBTT_min(x1,x2)), ay = STBTT_min(y0,STBTT_min(y1,y2));
+         int by = STBTT_max(y0,STBTT_max(y1,y2));
+         if (y > ay && y < by && x > ax) {
+            float q0[2],q1[2],q2[2];
+            float hits[2][2];
+            q0[0] = (float)x0;
+            q0[1] = (float)y0;
+            q1[0] = (float)x1;
+            q1[1] = (float)y1;
+            q2[0] = (float)x2;
+            q2[1] = (float)y2;
+            if (equal(q0,q1) || equal(q1,q2)) {
+               x0 = (int)verts[i-1].x;
+               y0 = (int)verts[i-1].y;
+               x1 = (int)verts[i  ].x;
+               y1 = (int)verts[i  ].y;
+               if (y > STBTT_min(y0,y1) && y < STBTT_max(y0,y1) && x > STBTT_min(x0,x1)) {
+                  float x_inter = (y - y0) / (y1 - y0) * (x1-x0) + x0;
+                  if (x_inter < x)
+                     winding += (y0 < y1) ? 1 : -1;
+               }
+            } else {
+               int num_hits = stbtt__ray_intersect_bezier(orig, ray, q0, q1, q2, hits);
+               if (num_hits >= 1)
+                  if (hits[0][0] < 0)
+                     winding += (hits[0][1] < 0 ? -1 : 1);
+               if (num_hits >= 2)
+                  if (hits[1][0] < 0)
+                     winding += (hits[1][1] < 0 ? -1 : 1);
+            }
+         }
+      }
+   }
+   return winding;
+}
+
+static float stbtt__cuberoot( float x )
+{
+   if (x<0)
+      return -(float) STBTT_pow(-x,1.0f/3.0f);
+   else
+      return  (float) STBTT_pow( x,1.0f/3.0f);
+}
+
+// x^3 + a*x^2 + b*x + c = 0
+static int stbtt__solve_cubic(float a, float b, float c, float* r)
+{
+   float s = -a / 3;
+   float p = b - a*a / 3;
+   float q = a * (2*a*a - 9*b) / 27 + c;
+   float p3 = p*p*p;
+   float d = q*q + 4*p3 / 27;
+   if (d >= 0) {
+      float z = (float) STBTT_sqrt(d);
+      float u = (-q + z) / 2;
+      float v = (-q - z) / 2;
+      u = stbtt__cuberoot(u);
+      v = stbtt__cuberoot(v);
+      r[0] = s + u + v;
+      return 1;
+   } else {
+      float u = (float) STBTT_sqrt(-p/3);
+      float v = (float) STBTT_acos(-STBTT_sqrt(-27/p3) * q / 2) / 3; // p3 must be negative, since d is negative
+      float m = (float) STBTT_cos(v);
+      float n = (float) STBTT_cos(v-3.141592/2)*1.732050808f;
+      r[0] = s + u * 2 * m;
+      r[1] = s - u * (m + n);
+      r[2] = s - u * (m - n);
+
+      //STBTT_assert( STBTT_fabs(((r[0]+a)*r[0]+b)*r[0]+c) < 0.05f);  // these asserts may not be safe at all scales, though they're in bezier t parameter units so maybe?
+      //STBTT_assert( STBTT_fabs(((r[1]+a)*r[1]+b)*r[1]+c) < 0.05f);
+      //STBTT_assert( STBTT_fabs(((r[2]+a)*r[2]+b)*r[2]+c) < 0.05f);
+      return 3;
+   }
+}
+
+STBTT_DEF unsigned char * stbtt_GetGlyphSDF(const stbtt_fontinfo *info, float scale, int glyph, int padding, unsigned char onedge_value, float pixel_dist_scale, int *width, int *height, int *xoff, int *yoff)
+{
+   float scale_x = scale, scale_y = scale;
+   int ix0,iy0,ix1,iy1;
+   int w,h;
+   unsigned char *data;
+
+   if (scale == 0) return NULL;
+
+   stbtt_GetGlyphBitmapBoxSubpixel(info, glyph, scale, scale, 0.0f,0.0f, &ix0,&iy0,&ix1,&iy1);
+
+   // if empty, return NULL
+   if (ix0 == ix1 || iy0 == iy1)
+      return NULL;
+
+   ix0 -= padding;
+   iy0 -= padding;
+   ix1 += padding;
+   iy1 += padding;
+
+   w = (ix1 - ix0);
+   h = (iy1 - iy0);
+
+   if (width ) *width  = w;
+   if (height) *height = h;
+   if (xoff  ) *xoff   = ix0;
+   if (yoff  ) *yoff   = iy0;
+
+   // invert for y-downwards bitmaps
+   scale_y = -scale_y;
+
+   {
+      int x,y,i,j;
+      float *precompute;
+      stbtt_vertex *verts;
+      int num_verts = stbtt_GetGlyphShape(info, glyph, &verts);
+      data = (unsigned char *) STBTT_malloc(w * h, info->userdata);
+      precompute = (float *) STBTT_malloc(num_verts * sizeof(float), info->userdata);
+
+      for (i=0,j=num_verts-1; i < num_verts; j=i++) {
+         if (verts[i].type == STBTT_vline) {
+            float x0 = verts[i].x*scale_x, y0 = verts[i].y*scale_y;
+            float x1 = verts[j].x*scale_x, y1 = verts[j].y*scale_y;
+            float dist = (float) STBTT_sqrt((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0));
+            precompute[i] = (dist == 0) ? 0.0f : 1.0f / dist;
+         } else if (verts[i].type == STBTT_vcurve) {
+            float x2 = verts[j].x *scale_x, y2 = verts[j].y *scale_y;
+            float x1 = verts[i].cx*scale_x, y1 = verts[i].cy*scale_y;
+            float x0 = verts[i].x *scale_x, y0 = verts[i].y *scale_y;
+            float bx = x0 - 2*x1 + x2, by = y0 - 2*y1 + y2;
+            float len2 = bx*bx + by*by;
+            if (len2 != 0.0f)
+               precompute[i] = 1.0f / (bx*bx + by*by);
+            else
+               precompute[i] = 0.0f;
+         } else
+            precompute[i] = 0.0f;
+      }
+
+      for (y=iy0; y < iy1; ++y) {
+         for (x=ix0; x < ix1; ++x) {
+            float val;
+            float min_dist = 999999.0f;
+            float sx = (float) x + 0.5f;
+            float sy = (float) y + 0.5f;
+            float x_gspace = (sx / scale_x);
+            float y_gspace = (sy / scale_y);
+
+            int winding = stbtt__compute_crossings_x(x_gspace, y_gspace, num_verts, verts); // @OPTIMIZE: this could just be a rasterization, but needs to be line vs. non-tesselated curves so a new path
+
+            for (i=0; i < num_verts; ++i) {
+               float x0 = verts[i].x*scale_x, y0 = verts[i].y*scale_y;
+
+               if (verts[i].type == STBTT_vline && precompute[i] != 0.0f) {
+                  float x1 = verts[i-1].x*scale_x, y1 = verts[i-1].y*scale_y;
+
+                  float dist,dist2 = (x0-sx)*(x0-sx) + (y0-sy)*(y0-sy);
+                  if (dist2 < min_dist*min_dist)
+                     min_dist = (float) STBTT_sqrt(dist2);
+
+                  // coarse culling against bbox
+                  //if (sx > STBTT_min(x0,x1)-min_dist && sx < STBTT_max(x0,x1)+min_dist &&
+                  //    sy > STBTT_min(y0,y1)-min_dist && sy < STBTT_max(y0,y1)+min_dist)
+                  dist = (float) STBTT_fabs((x1-x0)*(y0-sy) - (y1-y0)*(x0-sx)) * precompute[i];
+                  STBTT_assert(i != 0);
+                  if (dist < min_dist) {
+                     // check position along line
+                     // x' = x0 + t*(x1-x0), y' = y0 + t*(y1-y0)
+                     // minimize (x'-sx)*(x'-sx)+(y'-sy)*(y'-sy)
+                     float dx = x1-x0, dy = y1-y0;
+                     float px = x0-sx, py = y0-sy;
+                     // minimize (px+t*dx)^2 + (py+t*dy)^2 = px*px + 2*px*dx*t + t^2*dx*dx + py*py + 2*py*dy*t + t^2*dy*dy
+                     // derivative: 2*px*dx + 2*py*dy + (2*dx*dx+2*dy*dy)*t, set to 0 and solve
+                     float t = -(px*dx + py*dy) / (dx*dx + dy*dy);
+                     if (t >= 0.0f && t <= 1.0f)
+                        min_dist = dist;
+                  }
+               } else if (verts[i].type == STBTT_vcurve) {
+                  float x2 = verts[i-1].x *scale_x, y2 = verts[i-1].y *scale_y;
+                  float x1 = verts[i  ].cx*scale_x, y1 = verts[i  ].cy*scale_y;
+                  float box_x0 = STBTT_min(STBTT_min(x0,x1),x2);
+                  float box_y0 = STBTT_min(STBTT_min(y0,y1),y2);
+                  float box_x1 = STBTT_max(STBTT_max(x0,x1),x2);
+                  float box_y1 = STBTT_max(STBTT_max(y0,y1),y2);
+                  // coarse culling against bbox to avoid computing cubic unnecessarily
+                  if (sx > box_x0-min_dist && sx < box_x1+min_dist && sy > box_y0-min_dist && sy < box_y1+min_dist) {
+                     int num=0;
+                     float ax = x1-x0, ay = y1-y0;
+                     float bx = x0 - 2*x1 + x2, by = y0 - 2*y1 + y2;
+                     float mx = x0 - sx, my = y0 - sy;
+                     float res[3] = {0.f,0.f,0.f};
+                     float px,py,t,it,dist2;
+                     float a_inv = precompute[i];
+                     if (a_inv == 0.0) { // if a_inv is 0, it's 2nd degree so use quadratic formula
+                        float a = 3*(ax*bx + ay*by);
+                        float b = 2*(ax*ax + ay*ay) + (mx*bx+my*by);
+                        float c = mx*ax+my*ay;
+                        if (a == 0.0) { // if a is 0, it's linear
+                           if (b != 0.0) {
+                              res[num++] = -c/b;
+                           }
+                        } else {
+                           float discriminant = b*b - 4*a*c;
+                           if (discriminant < 0)
+                              num = 0;
+                           else {
+                              float root = (float) STBTT_sqrt(discriminant);
+                              res[0] = (-b - root)/(2*a);
+                              res[1] = (-b + root)/(2*a);
+                              num = 2; // don't bother distinguishing 1-solution case, as code below will still work
+                           }
+                        }
+                     } else {
+                        float b = 3*(ax*bx + ay*by) * a_inv; // could precompute this as it doesn't depend on sample point
+                        float c = (2*(ax*ax + ay*ay) + (mx*bx+my*by)) * a_inv;
+                        float d = (mx*ax+my*ay) * a_inv;
+                        num = stbtt__solve_cubic(b, c, d, res);
+                     }
+                     dist2 = (x0-sx)*(x0-sx) + (y0-sy)*(y0-sy);
+                     if (dist2 < min_dist*min_dist)
+                        min_dist = (float) STBTT_sqrt(dist2);
+
+                     if (num >= 1 && res[0] >= 0.0f && res[0] <= 1.0f) {
+                        t = res[0], it = 1.0f - t;
+                        px = it*it*x0 + 2*t*it*x1 + t*t*x2;
+                        py = it*it*y0 + 2*t*it*y1 + t*t*y2;
+                        dist2 = (px-sx)*(px-sx) + (py-sy)*(py-sy);
+                        if (dist2 < min_dist * min_dist)
+                           min_dist = (float) STBTT_sqrt(dist2);
+                     }
+                     if (num >= 2 && res[1] >= 0.0f && res[1] <= 1.0f) {
+                        t = res[1], it = 1.0f - t;
+                        px = it*it*x0 + 2*t*it*x1 + t*t*x2;
+                        py = it*it*y0 + 2*t*it*y1 + t*t*y2;
+                        dist2 = (px-sx)*(px-sx) + (py-sy)*(py-sy);
+                        if (dist2 < min_dist * min_dist)
+                           min_dist = (float) STBTT_sqrt(dist2);
+                     }
+                     if (num >= 3 && res[2] >= 0.0f && res[2] <= 1.0f) {
+                        t = res[2], it = 1.0f - t;
+                        px = it*it*x0 + 2*t*it*x1 + t*t*x2;
+                        py = it*it*y0 + 2*t*it*y1 + t*t*y2;
+                        dist2 = (px-sx)*(px-sx) + (py-sy)*(py-sy);
+                        if (dist2 < min_dist * min_dist)
+                           min_dist = (float) STBTT_sqrt(dist2);
+                     }
+                  }
+               }
+            }
+            if (winding == 0)
+               min_dist = -min_dist;  // if outside the shape, value is negative
+            val = onedge_value + pixel_dist_scale * min_dist;
+            if (val < 0)
+               val = 0;
+            else if (val > 255)
+               val = 255;
+            data[(y-iy0)*w+(x-ix0)] = (unsigned char) val;
+         }
+      }
+      STBTT_free(precompute, info->userdata);
+      STBTT_free(verts, info->userdata);
+   }
+   return data;
+}
+
+STBTT_DEF unsigned char * stbtt_GetCodepointSDF(const stbtt_fontinfo *info, float scale, int codepoint, int padding, unsigned char onedge_value, float pixel_dist_scale, int *width, int *height, int *xoff, int *yoff)
+{
+   return stbtt_GetGlyphSDF(info, scale, stbtt_FindGlyphIndex(info, codepoint), padding, onedge_value, pixel_dist_scale, width, height, xoff, yoff);
+}
+
+STBTT_DEF void stbtt_FreeSDF(unsigned char *bitmap, void *userdata)
+{
+   STBTT_free(bitmap, userdata);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// font name matching -- recommended not to use this
+//
+
+// check if a utf8 string contains a prefix which is the utf16 string; if so return length of matching utf8 string
+static stbtt_int32 stbtt__CompareUTF8toUTF16_bigendian_prefix(stbtt_uint8 *s1, stbtt_int32 len1, stbtt_uint8 *s2, stbtt_int32 len2)
+{
+   stbtt_int32 i=0;
+
+   // convert utf16 to utf8 and compare the results while converting
+   while (len2) {
+      stbtt_uint16 ch = s2[0]*256 + s2[1];
+      if (ch < 0x80) {
+         if (i >= len1) return -1;
+         if (s1[i++] != ch) return -1;
+      } else if (ch < 0x800) {
+         if (i+1 >= len1) return -1;
+         if (s1[i++] != 0xc0 + (ch >> 6)) return -1;
+         if (s1[i++] != 0x80 + (ch & 0x3f)) return -1;
+      } else if (ch >= 0xd800 && ch < 0xdc00) {
+         stbtt_uint32 c;
+         stbtt_uint16 ch2 = s2[2]*256 + s2[3];
+         if (i+3 >= len1) return -1;
+         c = ((ch - 0xd800) << 10) + (ch2 - 0xdc00) + 0x10000;
+         if (s1[i++] != 0xf0 + (c >> 18)) return -1;
+         if (s1[i++] != 0x80 + ((c >> 12) & 0x3f)) return -1;
+         if (s1[i++] != 0x80 + ((c >>  6) & 0x3f)) return -1;
+         if (s1[i++] != 0x80 + ((c      ) & 0x3f)) return -1;
+         s2 += 2; // plus another 2 below
+         len2 -= 2;
+      } else if (ch >= 0xdc00 && ch < 0xe000) {
+         return -1;
+      } else {
+         if (i+2 >= len1) return -1;
+         if (s1[i++] != 0xe0 + (ch >> 12)) return -1;
+         if (s1[i++] != 0x80 + ((ch >> 6) & 0x3f)) return -1;
+         if (s1[i++] != 0x80 + ((ch     ) & 0x3f)) return -1;
+      }
+      s2 += 2;
+      len2 -= 2;
+   }
+   return i;
+}
+
+static int stbtt_CompareUTF8toUTF16_bigendian_internal(char *s1, int len1, char *s2, int len2)
+{
+   return len1 == stbtt__CompareUTF8toUTF16_bigendian_prefix((stbtt_uint8*) s1, len1, (stbtt_uint8*) s2, len2);
+}
+
+// returns results in whatever encoding you request... but note that 2-byte encodings
+// will be BIG-ENDIAN... use stbtt_CompareUTF8toUTF16_bigendian() to compare
+STBTT_DEF const char *stbtt_GetFontNameString(const stbtt_fontinfo *font, int *length, int platformID, int encodingID, int languageID, int nameID)
+{
+   stbtt_int32 i,count,stringOffset;
+   stbtt_uint8 *fc = font->data;
+   stbtt_uint32 offset = font->fontstart;
+   stbtt_uint32 nm = stbtt__find_table(fc, offset, "name");
+   if (!nm) return NULL;
+
+   count = ttUSHORT(fc+nm+2);
+   stringOffset = nm + ttUSHORT(fc+nm+4);
+   for (i=0; i < count; ++i) {
+      stbtt_uint32 loc = nm + 6 + 12 * i;
+      if (platformID == ttUSHORT(fc+loc+0) && encodingID == ttUSHORT(fc+loc+2)
+          && languageID == ttUSHORT(fc+loc+4) && nameID == ttUSHORT(fc+loc+6)) {
+         *length = ttUSHORT(fc+loc+8);
+         return (const char *) (fc+stringOffset+ttUSHORT(fc+loc+10));
+      }
+   }
+   return NULL;
+}
+
+static int stbtt__matchpair(stbtt_uint8 *fc, stbtt_uint32 nm, stbtt_uint8 *name, stbtt_int32 nlen, stbtt_int32 target_id, stbtt_int32 next_id)
+{
+   stbtt_int32 i;
+   stbtt_int32 count = ttUSHORT(fc+nm+2);
+   stbtt_int32 stringOffset = nm + ttUSHORT(fc+nm+4);
+
+   for (i=0; i < count; ++i) {
+      stbtt_uint32 loc = nm + 6 + 12 * i;
+      stbtt_int32 id = ttUSHORT(fc+loc+6);
+      if (id == target_id) {
+         // find the encoding
+         stbtt_int32 platform = ttUSHORT(fc+loc+0), encoding = ttUSHORT(fc+loc+2), language = ttUSHORT(fc+loc+4);
+
+         // is this a Unicode encoding?
+         if (platform == 0 || (platform == 3 && encoding == 1) || (platform == 3 && encoding == 10)) {
+            stbtt_int32 slen = ttUSHORT(fc+loc+8);
+            stbtt_int32 off = ttUSHORT(fc+loc+10);
+
+            // check if there's a prefix match
+            stbtt_int32 matchlen = stbtt__CompareUTF8toUTF16_bigendian_prefix(name, nlen, fc+stringOffset+off,slen);
+            if (matchlen >= 0) {
+               // check for target_id+1 immediately following, with same encoding & language
+               if (i+1 < count && ttUSHORT(fc+loc+12+6) == next_id && ttUSHORT(fc+loc+12) == platform && ttUSHORT(fc+loc+12+2) == encoding && ttUSHORT(fc+loc+12+4) == language) {
+                  slen = ttUSHORT(fc+loc+12+8);
+                  off = ttUSHORT(fc+loc+12+10);
+                  if (slen == 0) {
+                     if (matchlen == nlen)
+                        return 1;
+                  } else if (matchlen < nlen && name[matchlen] == ' ') {
+                     ++matchlen;
+                     if (stbtt_CompareUTF8toUTF16_bigendian_internal((char*) (name+matchlen), nlen-matchlen, (char*)(fc+stringOffset+off),slen))
+                        return 1;
+                  }
+               } else {
+                  // if nothing immediately following
+                  if (matchlen == nlen)
+                     return 1;
+               }
+            }
+         }
+
+         // @TODO handle other encodings
+      }
+   }
+   return 0;
+}
+
+static int stbtt__matches(stbtt_uint8 *fc, stbtt_uint32 offset, stbtt_uint8 *name, stbtt_int32 flags)
+{
+   stbtt_int32 nlen = (stbtt_int32) STBTT_strlen((char *) name);
+   stbtt_uint32 nm,hd;
+   if (!stbtt__isfont(fc+offset)) return 0;
+
+   // check italics/bold/underline flags in macStyle...
+   if (flags) {
+      hd = stbtt__find_table(fc, offset, "head");
+      if ((ttUSHORT(fc+hd+44) & 7) != (flags & 7)) return 0;
+   }
+
+   nm = stbtt__find_table(fc, offset, "name");
+   if (!nm) return 0;
+
+   if (flags) {
+      // if we checked the macStyle flags, then just check the family and ignore the subfamily
+      if (stbtt__matchpair(fc, nm, name, nlen, 16, -1))  return 1;
+      if (stbtt__matchpair(fc, nm, name, nlen,  1, -1))  return 1;
+      if (stbtt__matchpair(fc, nm, name, nlen,  3, -1))  return 1;
+   } else {
+      if (stbtt__matchpair(fc, nm, name, nlen, 16, 17))  return 1;
+      if (stbtt__matchpair(fc, nm, name, nlen,  1,  2))  return 1;
+      if (stbtt__matchpair(fc, nm, name, nlen,  3, -1))  return 1;
+   }
+
+   return 0;
+}
+
+static int stbtt_FindMatchingFont_internal(unsigned char *font_collection, char *name_utf8, stbtt_int32 flags)
+{
+   stbtt_int32 i;
+   for (i=0;;++i) {
+      stbtt_int32 off = stbtt_GetFontOffsetForIndex(font_collection, i);
+      if (off < 0) return off;
+      if (stbtt__matches((stbtt_uint8 *) font_collection, off, (stbtt_uint8*) name_utf8, flags))
+         return off;
+   }
+}
+
+#if defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-qual"
+#endif
+
+STBTT_DEF int stbtt_BakeFontBitmap(const unsigned char *data, int offset,
+                                float pixel_height, unsigned char *pixels, int pw, int ph,
+                                int first_char, int num_chars, stbtt_bakedchar *chardata)
+{
+   return stbtt_BakeFontBitmap_internal((unsigned char *) data, offset, pixel_height, pixels, pw, ph, first_char, num_chars, chardata);
+}
+
+STBTT_DEF int stbtt_GetFontOffsetForIndex(const unsigned char *data, int index)
+{
+   return stbtt_GetFontOffsetForIndex_internal((unsigned char *) data, index);
+}
+
+STBTT_DEF int stbtt_GetNumberOfFonts(const unsigned char *data)
+{
+   return stbtt_GetNumberOfFonts_internal((unsigned char *) data);
+}
+
+STBTT_DEF int stbtt_InitFont(stbtt_fontinfo *info, const unsigned char *data, int offset)
+{
+   return stbtt_InitFont_internal(info, (unsigned char *) data, offset);
+}
+
+STBTT_DEF int stbtt_FindMatchingFont(const unsigned char *fontdata, const char *name, int flags)
+{
+   return stbtt_FindMatchingFont_internal((unsigned char *) fontdata, (char *) name, flags);
+}
+
+STBTT_DEF int stbtt_CompareUTF8toUTF16_bigendian(const char *s1, int len1, const char *s2, int len2)
+{
+   return stbtt_CompareUTF8toUTF16_bigendian_internal((char *) s1, len1, (char *) s2, len2);
+}
+
+#if defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
+
+#endif // STB_TRUETYPE_IMPLEMENTATION
+
+
+// FULL VERSION HISTORY
+//
+//   1.25 (2021-07-11) many fixes
+//   1.24 (2020-02-05) fix warning
+//   1.23 (2020-02-02) query SVG data for glyphs; query whole kerning table (but only kern not GPOS)
+//   1.22 (2019-08-11) minimize missing-glyph duplication; fix kerning if both 'GPOS' and 'kern' are defined
+//   1.21 (2019-02-25) fix warning
+//   1.20 (2019-02-07) PackFontRange skips missing codepoints; GetScaleFontVMetrics()
+//   1.19 (2018-02-11) OpenType GPOS kerning (horizontal only), STBTT_fmod
+//   1.18 (2018-01-29) add missing function
+//   1.17 (2017-07-23) make more arguments const; doc fix
+//   1.16 (2017-07-12) SDF support
+//   1.15 (2017-03-03) make more arguments const
+//   1.14 (2017-01-16) num-fonts-in-TTC function
+//   1.13 (2017-01-02) support OpenType fonts, certain Apple fonts
+//   1.12 (2016-10-25) suppress warnings about casting away const with -Wcast-qual
+//   1.11 (2016-04-02) fix unused-variable warning
+//   1.10 (2016-04-02) allow user-defined fabs() replacement
+//                     fix memory leak if fontsize=0.0
+//                     fix warning from duplicate typedef
+//   1.09 (2016-01-16) warning fix; avoid crash on outofmem; use alloc userdata for PackFontRanges
+//   1.08 (2015-09-13) document stbtt_Rasterize(); fixes for vertical & horizontal edges
+//   1.07 (2015-08-01) allow PackFontRanges to accept arrays of sparse codepoints;
+//                     allow PackFontRanges to pack and render in separate phases;
+//                     fix stbtt_GetFontOFfsetForIndex (never worked for non-0 input?);
+//                     fixed an assert() bug in the new rasterizer
+//                     replace assert() with STBTT_assert() in new rasterizer
+//   1.06 (2015-07-14) performance improvements (~35% faster on x86 and x64 on test machine)
+//                     also more precise AA rasterizer, except if shapes overlap
+//                     remove need for STBTT_sort
+//   1.05 (2015-04-15) fix misplaced definitions for STBTT_STATIC
+//   1.04 (2015-04-15) typo in example
+//   1.03 (2015-04-12) STBTT_STATIC, fix memory leak in new packing, various fixes
+//   1.02 (2014-12-10) fix various warnings & compile issues w/ stb_rect_pack, C++
+//   1.01 (2014-12-08) fix subpixel position when oversampling to exactly match
+//                        non-oversampled; STBTT_POINT_SIZE for packed case only
+//   1.00 (2014-12-06) add new PackBegin etc. API, w/ support for oversampling
+//   0.99 (2014-09-18) fix multiple bugs with subpixel rendering (ryg)
+//   0.9  (2014-08-07) support certain mac/iOS fonts without an MS platformID
+//   0.8b (2014-07-07) fix a warning
+//   0.8  (2014-05-25) fix a few more warnings
+//   0.7  (2013-09-25) bugfix: subpixel glyph bug fixed in 0.5 had come back
+//   0.6c (2012-07-24) improve documentation
+//   0.6b (2012-07-20) fix a few more warnings
+//   0.6  (2012-07-17) fix warnings; added stbtt_ScaleForMappingEmToPixels,
+//                        stbtt_GetFontBoundingBox, stbtt_IsGlyphEmpty
+//   0.5  (2011-12-09) bugfixes:
+//                        subpixel glyph renderer computed wrong bounding box
+//                        first vertex of shape can be off-curve (FreeSans)
+//   0.4b (2011-12-03) fixed an error in the font baking example
+//   0.4  (2011-12-01) kerning, subpixel rendering (tor)
+//                    bugfixes for:
+//                        codepoint-to-glyph conversion using table fmt=12
+//                        codepoint-to-glyph conversion using table fmt=4
+//                        stbtt_GetBakedQuad with non-square texture (Zer)
+//                    updated Hello World! sample to use kerning and subpixel
+//                    fixed some warnings
+//   0.3  (2009-06-24) cmap fmt=12, compound shapes (MM)
+//                    userdata, malloc-from-userdata, non-zero fill (stb)
+//   0.2  (2009-03-11) Fix unsigned/signed char warnings
+//   0.1  (2009-03-09) First public release
+//
+
+/*
+------------------------------------------------------------------------------
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+------------------------------------------------------------------------------
+*/
diff --git a/vendor/stb/stb_truetype_impl.c b/vendor/stb/stb_truetype_impl.c
new file mode 100644
index 00000000..ca6cf7b8
--- /dev/null
+++ b/vendor/stb/stb_truetype_impl.c
@@ -0,0 +1,5 @@
+// stb_truetype implementation unit — pulls the single-header lib's
+// implementation into one TU. ui_sdl.zig only needs the declarations (via the
+// include path); this .c defines STB_TRUETYPE_IMPLEMENTATION once.
+#define STB_TRUETYPE_IMPLEMENTATION
+#include "stb_truetype.h"