The theme's chrome is worked out once, not per grapheme; still post passes let the GUI rest; a perf gate

somtrmsz's contrast floors made ChromeTheme.fromTheme run its focus-tint
and separator searches (pow calls each), and Output's RowDecoration.styleAt
called it for every grapheme of every highlighted row: the 50k-line file's
render went from 0.11 ms to 13 ms. Pardes.bodyChrome now keeps the theme's
chrome, worked out again only when the theme differs; recolorSyntax asks
for it once a decorated row, and a plain row (nearly every row of a file)
never asks. ReleaseFast, medium fixture, median us, before -> after (main):
render 13150 -> 76 (111), key-down 14658 -> 79 (110), wheel 13589 -> 76
(109), open 14891 -> 2095 (2055), edit-char 16703 -> 3006 (1251; the rest of
that gap is editing and tree-sitter, not this).

Post.animating asked for frames whenever the window had focus and any pass
was ready, so a still pass kept the GUI drawing at the display's rate
(Bloom: 49% of a core idle, in a hidden test window). A pass now says
whether it moves on its own: the CRT (its hum and dither) and a Shadertoy
file whose source reads iTime, iFrame or iDate (shader_build.readsTime; the
flag rides the wire's post message); Bloom, Vignette and Grain are still.
Bloom idle: 49% -> 1.2%, as with no pass.

zig build perf-gate: the 50k-line file's gestures, each's fastest sample
within 3x of the recorded baseline's (test/perf-baseline-<platform>-
<optimize>.json, recorded from this build), run with every unit-test. On
the regressed code it fails at 180x for render.

1 files changed, 30 insertions, 4 deletions

diff --git a/src/shader_build.zig b/src/shader_build.zig
index 8aa7eb5e..c2610fd7 100644
--- a/src/shader_build.zig
+++ b/src/shader_build.zig
@@ -32,8 +32,24 @@ pub const Pass = struct {
     path: []const u8 = &.{},
     spirv: []const u8 = &.{},
     revision: u32 = 0,
+    /// It moves on its own (reads the clock or the frame count), so the
+    /// chain redraws while idle; a still pass draws only with a new frame.
+    animated: bool = false,
 };
 
+/// The bundled passes that move on their own: the CRT's hum and dither.
+pub fn sceneAnimated(scene: Scene) bool {
+    return scene == .crt;
+}
+
+/// Whether a Shadertoy source moves on its own: it reads the time
+/// (iTime, iTimeDelta and the times of a cursor move or a focus change),
+/// the frame count or the date. A mention in a comment counts too.
+pub fn readsTime(source: []const u8) bool {
+    for ([_][]const u8{ "iTime", "iFrame", "iDate" }) |name| if (std.mem.indexOf(u8, source, name) != null) return true;
+    return false;
+}
+
 /// Who to wake when a compile is done: the host's loop.
 pub const Wake = struct {
     ctx: ?*anyopaque = null,
@@ -47,6 +63,7 @@ const File = struct {
     source: ?u64 = null,
     spirv: []u8 = &.{},
     revision: u32 = 0,
+    animated: bool = false,
     /// Wants a compile: new to the chain, or its directory changed.
     stale: bool = true,
 };
@@ -56,7 +73,7 @@ const Result = union(enum) {
     unchanged,
     missing,
     failed: struct { text: []u8, source: u64 },
-    spirv: struct { bytes: []u8, source: u64 },
+    spirv: struct { bytes: []u8, source: u64, animated: bool },
 };
 
 /// One compile of the stale files, on its own thread.
@@ -148,8 +165,8 @@ pub fn recheck(b: *Build) void {
 /// The chain as passes, in its order.
 pub fn view(b: *const Build, chain: *const Chain, out: *[max]Pass) []const Pass {
     for (chain.list(), 0..) |entry, i| {
-        out[i] = if (entry.scene) |scene| .{ .scene = scene, .level = entry.level } else for (b.files[0..b.len]) |file| {
-            if (std.mem.eql(u8, file.path, entry.path.get())) break .{ .path = file.path, .spirv = file.spirv, .revision = file.revision };
+        out[i] = if (entry.scene) |scene| .{ .scene = scene, .level = entry.level, .animated = sceneAnimated(scene) } else for (b.files[0..b.len]) |file| {
+            if (std.mem.eql(u8, file.path, entry.path.get())) break .{ .path = file.path, .spirv = file.spirv, .revision = file.revision, .animated = file.animated };
         } else .{ .path = entry.path.get() };
     }
     return out[0..chain.len];
@@ -211,6 +228,7 @@ fn collect(b: *Build, gpa: std.mem.Allocator, core: *pardes.Pardes, job: *Job) v
                 gpa.free(f.spirv);
                 f.spirv = r.bytes;
                 f.source = r.source;
+                f.animated = r.animated;
                 f.revision +%= 1;
                 b.revision +%= 1;
             },
@@ -291,7 +309,7 @@ fn compileOne(gpa: std.mem.Allocator, io: std.Io, path: []const u8, known: ?u64)
         .exited => |code| code == 0,
         else => false,
     };
-    if (clean) return .{ .spirv = .{ .bytes = reader.toOwnedSlice(0) catch return .none, .source = source } };
+    if (clean) return .{ .spirv = .{ .bytes = reader.toOwnedSlice(0) catch return .none, .source = source, .animated = readsTime(body) } };
     const said = reader.toOwnedSlice(1) catch return .none;
     // glslc calls its input <stdin>; the file is what a person knows.
     defer gpa.free(said);
@@ -400,3 +418,11 @@ test "a save that changes a file compiles it again, a failed one keeps the last
     const second = b.view(&core.settings.post, &out)[0];
     try std.testing.expect(second.revision != first.revision and b.revision != at);
 }
+
+test "a pass animates when it reads the clock or the frame count, and only the CRT of the bundled ones" {
+    try std.testing.expect(readsTime("o = vec4(sin(iTime));"));
+    try std.testing.expect(readsTime("float f = float(iFrame % 64);"));
+    try std.testing.expect(readsTime("x = iTimeCursorChange;"));
+    try std.testing.expect(!readsTime("o = texture(iChannel0, p / iResolution.xy);"));
+    for (std.enums.values(Scene)) |scene| try std.testing.expectEqual(scene == .crt, sceneAnimated(scene));
+}