look: richer path/range parsing, pdf rendering, corner-drag and stepgrain snapshots

10 files changed, 1341 insertions, 26 deletions

diff --git a/test/pdf_scroll_bench.zig b/test/pdf_scroll_bench.zig
new file mode 100644
index 00000000..7bd644e4
--- /dev/null
+++ b/test/pdf_scroll_bench.zig
@@ -0,0 +1,567 @@
+//! ReleaseFast scoreboard for FAST scrolling of the continuous PDF strip.
+//!
+//!   zig build pdf-scroll-bench -Doptimize=ReleaseFast
+//!   zig build pdf-scroll-bench -Doptimize=ReleaseFast -- --json
+//!   zig build pdf-scroll-bench -Doptimize=ReleaseFast -- --warmup 1 --reps 15
+//!   zig build pdf-scroll-bench -Doptimize=ReleaseFast -- --path other.pdf
+//!
+//! What a fling IS, and why one-tick-per-frame benchmarks miss it: a shell
+//! pump drains every input the OS queued since the last present and then calls
+//! render() once. A trackpad fling therefore arrives as a BATCH of wheel
+//! notches inside one frame, and the frame budget is spent on the batch plus
+//! the single render — not on one notch. Every timed region below is exactly
+//! that: `ticks_per_frame` real `Mouse.wheel_down`/`wheel_up` presses through
+//! `Pardes.update`, one `render()` into a reset frame arena, and the effect
+//! drain, which is the loop src/tty/tty.zig and src/gui/gui.zig both run.
+//!
+//! Rows are per-FRAME latency, not per-notch: a dropped frame is what a reader
+//! feels, and the batch is indivisible from the reader's point of view.
+//!
+//! Two checksums, because they answer two different questions:
+//!
+//!   `visual`    is the no-regression proof. Frame count, emitted image count,
+//!               every placement rectangle, the presented RGBA (strided every
+//!               frame, in full every `full_rgba_stride`-th frame), and the
+//!               final scroll offset and page. Any optimization that changes
+//!               ONE presented pixel or ONE placement changes this. It must be
+//!               bit-identical across builds.
+//!   `transport` is the texture-upload trace: the (page, raster generation)
+//!               pair per emitted image, with generations rebased on the
+//!               counter's value at run start. Caching work legitimately
+//!               changes this while `visual` stays fixed — reusing a retained
+//!               raster keeps its old generation, which is precisely the
+//!               retransmit the revision mechanism exists to suppress.
+//!
+//! Setup, teardown, checksumming, and reporting are outside every timer.
+const std = @import("std");
+const libc = std.c;
+const pardes = @import("pardes");
+const pdf = @import("mupdf");
+const bench_config = @import("pdf_scroll_bench_config");
+
+pub const std_options: std.Options = .{ .log_level = .err };
+
+const gpa = std.heap.smp_allocator;
+
+// A reading-sized window. Wide enough that fit-width pages are taller than the
+// viewport (so a fling genuinely crosses page boundaries) and small enough
+// that the Kitty raster policy's 1200px cap is the binding quality term, which
+// is what the tty shell actually ships.
+const bench_cols: u16 = 120;
+const bench_rows: u16 = 40;
+const bench_cell_pixels: pardes.CellPixels = .{ .w = 8, .h = 16 };
+
+/// config.wheel_rows is one cell per notch, so a notch is `cell_pixels.h`
+/// display pixels. 192 notches is ~3072px — between two and three fit-width
+/// pages of travel inside a single frame, i.e. a hard flick whose momentum the
+/// OS delivers as one burst. This is the number that makes the benchmark about
+/// flinging rather than about nudging.
+const fling_ticks_per_frame: usize = 192;
+const slow_ticks_per_frame: usize = 1;
+/// The control row is a fixed wall of frames rather than a whole-document
+/// traversal: one notch per frame over a real document is tens of thousands of
+/// frames, and 240 already crosses several page boundaries at reading speed.
+const slow_frames: usize = 240;
+/// Guard against a pathological document turning one row into a multi-minute
+/// run. Deterministic either way: the frame count is derived from layout.
+const max_frames: usize = 2048;
+/// Full-RGBA hashing is O(document) per frame, so it samples the run instead of
+/// every frame; the strided hash below runs on every frame and every image.
+const full_rgba_stride: usize = 8;
+const checksum_seed: u64 = 0x7061_7264_6573_5343;
+
+const Config = struct {
+    path: []const u8 = "docs/design.pdf",
+    json: bool = false,
+    warmup: usize = 2,
+    reps: usize = 25,
+};
+
+/// The bit-exact description of one scrolling run. `visual` is the invariant;
+/// see the file header for why `transport` is reported beside it rather than
+/// folded into it.
+const Identity = struct {
+    frames: u64,
+    images: u64,
+    visual: u64,
+    transport: u64,
+
+    fn eql(a: Identity, b: Identity) bool {
+        return a.frames == b.frames and a.images == b.images and
+            a.visual == b.visual and a.transport == b.transport;
+    }
+};
+
+const Result = struct {
+    name: []const u8,
+    ticks_per_frame: usize,
+    frames: usize,
+    min_ns: u64,
+    median_ns: u64,
+    p90_ns: u64,
+    p99_ns: u64,
+    max_ns: u64,
+    total_ns: u64,
+    rasterizations: u64,
+    rasters_retained: u64,
+    identity: Identity,
+};
+
+const Scenario = enum {
+    /// Sustained high-velocity travel from page zero to the last page.
+    fling_down,
+    /// Down to the end and straight back up. Worst case for any cache that
+    /// only retains what the current frame shows: the way back finds nothing.
+    fling_reverse,
+    /// One notch per frame. The control: it must not regress.
+    slow_scroll,
+
+    fn label(scenario: Scenario) []const u8 {
+        return switch (scenario) {
+            .fling_down => "fling_down",
+            .fling_reverse => "fling_reverse",
+            .slow_scroll => "slow_scroll",
+        };
+    }
+
+    fn ticks(scenario: Scenario) usize {
+        return switch (scenario) {
+            .fling_down, .fling_reverse => fling_ticks_per_frame,
+            .slow_scroll => slow_ticks_per_frame,
+        };
+    }
+};
+
+const Plan = struct {
+    scenario: Scenario,
+    frames: usize,
+    /// Frames of downward travel before `fling_reverse` turns around.
+    down_frames: usize,
+
+    fn button(plan: Plan, frame: usize) pardes.Mouse.Button {
+        return switch (plan.scenario) {
+            .fling_reverse => if (frame < plan.down_frames) .wheel_down else .wheel_up,
+            .fling_down, .slow_scroll => .wheel_down,
+        };
+    }
+};
+
+pub fn main(init: std.process.Init) !void {
+    if (!bench_config.release_fast_core)
+        fatal("the production core must be ReleaseFast; add -Doptimize=ReleaseFast", .{});
+    const args = try init.minimal.args.toSlice(init.arena.allocator());
+    const config = parseArgs(args);
+
+    // One untimed probe boot supplies the strip height every plan is sized
+    // from, so the frame counts below are a property of the document and the
+    // viewport rather than of the machine.
+    const travel = probeTravel(config.path);
+
+    const results = [_]Result{
+        try measure(config, planFor(.fling_down, travel)),
+        try measure(config, planFor(.fling_reverse, travel)),
+        try measure(config, planFor(.slow_scroll, travel)),
+    };
+
+    if (config.json)
+        reportJson(init.io, config, &results)
+    else
+        reportText(config, &results);
+}
+
+fn parseArgs(args: []const []const u8) Config {
+    var config: Config = .{};
+    var i: usize = 1;
+    while (i < args.len) : (i += 1) {
+        if (std.mem.eql(u8, args[i], "--json")) {
+            config.json = true;
+        } else if (std.mem.eql(u8, args[i], "--warmup") and i + 1 < args.len) {
+            i += 1;
+            config.warmup = parseCount("--warmup", args[i]);
+        } else if (std.mem.eql(u8, args[i], "--reps") and i + 1 < args.len) {
+            i += 1;
+            config.reps = parseCount("--reps", args[i]);
+        } else if (std.mem.eql(u8, args[i], "--path") and i + 1 < args.len) {
+            i += 1;
+            config.path = args[i];
+        } else fatal(
+            "usage: pardes-pdf-scroll-bench [--json] [--warmup N] [--reps N] [--path FILE]",
+            .{},
+        );
+    }
+    return config;
+}
+
+fn parseCount(flag: []const u8, text: []const u8) usize {
+    const value = std.fmt.parseUnsigned(usize, text, 10) catch
+        fatal("{s} expects a positive integer", .{flag});
+    if (value == 0 or value > 10_000)
+        fatal("{s} must be in 1..10000", .{flag});
+    return value;
+}
+
+const Travel = struct {
+    /// Scrollable display pixels: the whole strip minus one screenful.
+    max_scroll: f64,
+    /// Display pixels one fling frame's notch batch covers.
+    per_frame: f64,
+};
+
+fn probeTravel(path: []const u8) Travel {
+    const core = bootCore(path) catch |err|
+        fatal("cannot boot a PDF pane on {s}: {t}", .{ path, err });
+    defer core.deinit();
+    var frame_arena = std.heap.ArenaAllocator.init(gpa);
+    defer frame_arena.deinit();
+    _ = core.render(frame_arena.allocator()) catch |err|
+        fatal("first render failed: {t}", .{err});
+    drainEffects(core);
+    const pane = core.panes[0] orelse fatal("PDF pane disappeared", .{});
+    if (pane.pdf == null) fatal("{s} did not open as a PDF", .{path});
+    const pv = &pane.pdf.?;
+    if (pv.page_count < 4)
+        fatal("{s} has {d} pages; a fling benchmark needs at least 4", .{ path, pv.page_count });
+    if (!pv.layout_valid or pv.document_height == 0)
+        fatal("the pixel strip never laid out; is native_images/cell_pixels wired?", .{});
+    // Exactly the clamp scrollPdfDocument enforces, so the last fling frame
+    // lands on the document end instead of adding a no-op frame to the row.
+    const viewport_h: u64 = @as(u64, bench_rows -| pardes.BOX_H) * bench_cell_pixels.h;
+    const notch: f64 = @floatFromInt(bench_cell_pixels.h);
+    return .{
+        .max_scroll = @max(notch, @as(f64, @floatFromInt(pv.document_height -| viewport_h))),
+        .per_frame = notch * @as(f64, @floatFromInt(fling_ticks_per_frame)),
+    };
+}
+
+fn planFor(scenario: Scenario, travel: Travel) Plan {
+    const down = @min(
+        max_frames,
+        @as(usize, @intFromFloat(@ceil(travel.max_scroll / travel.per_frame))),
+    );
+    return switch (scenario) {
+        .fling_down => .{ .scenario = scenario, .frames = down, .down_frames = down },
+        .fling_reverse => .{ .scenario = scenario, .frames = down * 2, .down_frames = down },
+        .slow_scroll => .{ .scenario = scenario, .frames = slow_frames, .down_frames = slow_frames },
+    };
+}
+
+/// A pane on a real multi-page document with the native pixel-strip path live
+/// and a genuine pixel viewport delivered the way a shell delivers one.
+fn bootCore(path: []const u8) !*pardes.Pardes {
+    const core = try pardes.Pardes.init(gpa, .{
+        .file = path,
+        .cols = bench_cols,
+        .rows = bench_rows,
+    });
+    errdefer core.deinit();
+    core.native_images = true;
+    core.update(.{ .resize = .{
+        .cols = bench_cols,
+        .rows = bench_rows,
+        .cell_pixels = bench_cell_pixels,
+    } });
+    drainEffects(core);
+    return core;
+}
+
+fn measure(config: Config, plan: Plan) !Result {
+    const name = plan.scenario.label();
+    const ticks = plan.scenario.ticks();
+    const totals = try gpa.alloc(u64, config.reps);
+    defer gpa.free(totals);
+    const pool = try gpa.alloc(u64, config.reps * plan.frames);
+    defer gpa.free(pool);
+    var pool_len: usize = 0;
+    const recorder = try gpa.create(Recorder);
+    defer gpa.destroy(recorder);
+    var expected: ?Identity = null;
+    var rasterizations: u64 = 0;
+    var rasters_retained: u64 = 0;
+
+    for (0..config.warmup + config.reps) |round| {
+        const core = try bootCore(config.path);
+        defer core.deinit();
+        var frame_arena = std.heap.ArenaAllocator.init(gpa);
+        defer frame_arena.deinit();
+        // Untimed: the steady state a reader flings FROM already has page zero
+        // resident and the strip laid out.
+        _ = try core.render(frame_arena.allocator());
+        drainEffects(core);
+        const pane = core.panes[0] orelse fatal("PDF pane disappeared", .{});
+        const pv = &pane.pdf.?;
+        const rect = core.rects[0];
+        // Anywhere inside the pane body resolves to this pane's hover, which
+        // is what routes the notch; the exact cell is irrelevant to a wheel.
+        const wheel: pardes.Mouse = .{
+            .button = .wheel_down,
+            .kind = .press,
+            .col = rect.x + rect.w / 2,
+            .row = rect.y + rect.h / 2,
+        };
+        const base_revision = pv.next_raster_revision;
+        recorder.reset(base_revision);
+
+        var total: u64 = 0;
+        for (0..plan.frames) |frame| {
+            var event = wheel;
+            event.button = plan.button(frame);
+            const started = nowNs();
+            for (0..ticks) |_| core.update(.{ .mouse = event });
+            _ = frame_arena.reset(.retain_capacity);
+            const surface = core.render(frame_arena.allocator()) catch |err|
+                fatal("render failed in {s} frame {d}: {t}", .{ name, frame, err });
+            drainEffects(core);
+            const elapsed = nowNs() -| started;
+            total += elapsed;
+            recorder.observe(frame, surface);
+            if (round >= config.warmup) {
+                pool[pool_len] = @max(1, elapsed);
+                pool_len += 1;
+            }
+        }
+
+        const identity = recorder.finish(pv);
+        try verifyIdentity(name, &expected, identity, round);
+        if (round >= config.warmup) {
+            totals[round - config.warmup] = total;
+            rasterizations = pv.next_raster_revision -% base_revision;
+            rasters_retained = pv.rasters_len;
+        }
+    }
+
+    std.debug.assert(pool_len == pool.len);
+    std.mem.sort(u64, pool, {}, std.sort.asc(u64));
+    std.mem.sort(u64, totals, {}, std.sort.asc(u64));
+    return .{
+        .name = name,
+        .ticks_per_frame = ticks,
+        .frames = plan.frames,
+        .min_ns = pool[0],
+        .median_ns = pool[pool.len / 2],
+        .p90_ns = pool[(pool.len * 9) / 10 -| 1],
+        .p99_ns = pool[(pool.len * 99) / 100 -| 1],
+        .max_ns = pool[pool.len - 1],
+        .total_ns = totals[totals.len / 2],
+        .rasterizations = rasterizations,
+        .rasters_retained = rasters_retained,
+        .identity = expected.?,
+    };
+}
+
+/// Accumulates the two checksums across one run. Raster generations are
+/// rebased on the counter's value at run start so the trace describes the
+/// ORDER textures were produced in rather than absolute counter values, which
+/// depend on how much the untimed boot happened to rasterize.
+const Recorder = struct {
+    frames: u64,
+    images: u64,
+    visual: u64,
+    transport: u64,
+    base_revision: u32,
+
+    fn reset(self: *Recorder, base_revision: u32) void {
+        self.* = .{
+            .frames = 0,
+            .images = 0,
+            .visual = checksum_seed,
+            .transport = checksum_seed,
+            .base_revision = base_revision,
+        };
+    }
+
+    fn observe(self: *Recorder, frame: usize, surface: *const pardes.Surface) void {
+        self.frames += 1;
+        self.visual = mix(self.visual, surface.nimages);
+        self.transport = mix(self.transport, surface.nimages);
+        const full = frame % full_rgba_stride == 0;
+        for (surface.images[0..surface.nimages]) |maybe| {
+            const place = maybe orelse {
+                self.visual = mix(self.visual, std.math.maxInt(u64));
+                continue;
+            };
+            self.images += 1;
+            self.visual = mix(self.visual, place.pane);
+            self.visual = mix(self.visual, place.x);
+            self.visual = mix(self.visual, place.y);
+            self.visual = mix(self.visual, place.w);
+            self.visual = mix(self.visual, place.h);
+            self.visual = mix(self.visual, place.iw);
+            self.visual = mix(self.visual, place.ih);
+            self.visual = mix(self.visual, place.rgba.len);
+            self.visual = mix(self.visual, place.native.page);
+            self.visual = mix(self.visual, @intFromEnum(place.native.fit));
+            self.visual = mix(self.visual, place.native.pan_x);
+            self.visual = mix(self.visual, place.native.pan_y);
+            self.visual = mix(self.visual, @as(u32, @bitCast(place.native.pixel_offset_y)));
+            if (place.native.geometry) |geometry| {
+                inline for (.{ geometry.src, geometry.dst }) |rect| {
+                    self.visual = mix(self.visual, rect.x);
+                    self.visual = mix(self.visual, rect.y);
+                    self.visual = mix(self.visual, rect.w);
+                    self.visual = mix(self.visual, rect.h);
+                }
+            } else self.visual = mix(self.visual, std.math.maxInt(u64));
+            self.visual = if (full)
+                std.hash.Wyhash.hash(self.visual, place.rgba)
+            else
+                stridedHash(self.visual, place.rgba);
+            self.transport = mix(self.transport, place.native.page);
+            self.transport = mix(self.transport, place.native.revision -% self.base_revision);
+        }
+    }
+
+    fn finish(self: *Recorder, pv: anytype) Identity {
+        var visual = mix(self.visual, @as(u64, @bitCast(pv.document_scroll_y)));
+        visual = mix(visual, pv.page);
+        visual = mix(visual, pv.page_count);
+        visual = mix(visual, pv.document_height);
+        return .{
+            .frames = self.frames,
+            .images = self.images,
+            .visual = visual,
+            .transport = self.transport,
+        };
+    }
+};
+
+/// 256 fixed-stride RGBA words. Cheap enough for every image of every frame
+/// while still failing on any change that touches a band of the page, and the
+/// full hash above closes the gap on sampled frames.
+fn stridedHash(seed: u64, rgba: []const u8) u64 {
+    if (rgba.len < 4) return mix(seed, rgba.len);
+    const stride = @max(@as(usize, 4), (rgba.len / 256) & ~@as(usize, 3));
+    var hash = seed;
+    var at: usize = 0;
+    while (at + 4 <= rgba.len) : (at += stride)
+        hash = std.hash.Wyhash.hash(hash, rgba[at..][0..4]);
+    return hash;
+}
+
+fn mix(seed: u64, value: anytype) u64 {
+    const Value = @TypeOf(value);
+    const Stable = switch (@typeInfo(Value)) {
+        .comptime_int => u64,
+        else => Value,
+    };
+    var stable: Stable = value;
+    return std.hash.Wyhash.hash(seed, std.mem.asBytes(&stable));
+}
+
+fn drainEffects(core: *pardes.Pardes) void {
+    while (core.nextEffect()) |_| {}
+}
+
+fn verifyIdentity(
+    name: []const u8,
+    expected: *?Identity,
+    got: Identity,
+    round: usize,
+) !void {
+    if (expected.*) |want| {
+        if (!want.eql(got)) {
+            std.debug.print(
+                "pdf-scroll-bench: unstable identity in {s} round {d}:\n" ++
+                    "  expected frames={d} images={d} visual={x:0>16} transport={x:0>16}\n" ++
+                    "  got      frames={d} images={d} visual={x:0>16} transport={x:0>16}\n",
+                .{
+                    name,          round,        want.frames, want.images,
+                    want.visual,   want.transport, got.frames,  got.images,
+                    got.visual,    got.transport,
+                },
+            );
+            return error.UnstableIdentity;
+        }
+    } else expected.* = got;
+}
+
+fn nowNs() u64 {
+    var ts: std.c.timespec = undefined;
+    _ = std.c.clock_gettime(.MONOTONIC, &ts);
+    return @as(u64, @intCast(ts.sec)) *| 1_000_000_000 +|
+        @as(u64, @intCast(ts.nsec));
+}
+
+fn reportText(config: Config, results: []const Result) void {
+    std.debug.print("pardes PDF fast-scroll benchmark (ReleaseFast)\n", .{});
+    std.debug.print(
+        "warmup: {d}, sampled reps: {d}; every number is ONE FRAME (notch batch + render + drain)\n\n",
+        .{ config.warmup, config.reps },
+    );
+    std.debug.print("{s:<16} {s:>6} {s:>7} {s:>10} {s:>10} {s:>10} {s:>10} {s:>10} {s:>11} {s:>7} {s:>5}  {s:<16}  {s}\n", .{
+        "scenario",  "frames",    "notches",   "min",
+        "median",    "p90",       "p99",       "max",
+        "total_us",  "rasters",   "kept",      "visual",
+        "transport",
+    });
+    std.debug.print("{s}\n", .{"-" ** 160});
+    for (results) |result| std.debug.print(
+        "{s:<16} {d:>6} {d:>7} {d:>10} {d:>10} {d:>10} {d:>10} {d:>10} {d:>11} {d:>7} {d:>5}  {x:0>16}  {x:0>16}\n",
+        .{
+            result.name,
+            result.frames,
+            result.ticks_per_frame,
+            result.min_ns,
+            result.median_ns,
+            result.p90_ns,
+            result.p99_ns,
+            result.max_ns,
+            result.total_ns / 1000,
+            result.rasterizations,
+            result.rasters_retained,
+            result.identity.visual,
+            result.identity.transport,
+        },
+    );
+    std.debug.print(
+        "\n`rasters` counts MuPDF page rasterizations over one run; `kept` is the retained raster count at the end.\n" ++
+            "`visual` pins presented pixels and placement and must never change; `transport` traces texture uploads.\n",
+        .{},
+    );
+}
+
+const json_report_max_bytes = 16 * 1024;
+
+fn reportJson(io: std.Io, config: Config, results: []const Result) void {
+    var storage: [json_report_max_bytes]u8 = undefined;
+    var out: std.Io.Writer = .fixed(&storage);
+    out.print(
+        "{{\"benchmark\":\"pardes-pdf-scroll\",\"build\":\"ReleaseFast\",\"warmup\":{d},\"reps\":{d},\"results\":[",
+        .{ config.warmup, config.reps },
+    ) catch return;
+    for (results, 0..) |result, i| out.print(
+        "{s}{{\"scenario\":\"{s}\",\"frames\":{d},\"notches_per_frame\":{d}," ++
+            "\"min_ns\":{d},\"median_ns\":{d},\"p90_ns\":{d},\"p99_ns\":{d},\"max_ns\":{d},\"total_ns\":{d}," ++
+            "\"rasterizations\":{d},\"rasters_retained\":{d},\"images\":{d}," ++
+            "\"visual\":\"{x:0>16}\",\"transport\":\"{x:0>16}\"}}",
+        .{
+            if (i == 0) "" else ",",
+            result.name,
+            result.frames,
+            result.ticks_per_frame,
+            result.min_ns,
+            result.median_ns,
+            result.p90_ns,
+            result.p99_ns,
+            result.max_ns,
+            result.total_ns,
+            result.rasterizations,
+            result.rasters_retained,
+            result.identity.images,
+            result.identity.visual,
+            result.identity.transport,
+        },
+    ) catch return;
+    out.writeAll("]}\n") catch return;
+    std.Io.File.stdout().writeStreamingAll(io, out.buffered()) catch {};
+}
+
+fn fatal(comptime format: []const u8, args: anytype) noreturn {
+    std.debug.print("pdf-scroll-bench: " ++ format ++ "\n", args);
+    std.process.exit(1);
+}
+
+comptime {
+    // The bench links the real MuPDF wrapper the core uses; keep the import
+    // load-bearing so a build that silently dropped it fails here.
+    _ = pdf.Document;
+}
diff --git a/test/snapshots/cornerdrag-left.golden b/test/snapshots/cornerdrag-left.golden
new file mode 100644
index 00000000..b87651b1
--- /dev/null
+++ b/test/snapshots/cornerdrag-left.golden
@@ -0,0 +1,155 @@
+== snap right-split grid=100x30 cursor=54,8
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/cornerdrag-left/cwd New Del      /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|  ls                                                ls
+|  w.txt                                             w.txt
+|
+|                                                    /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|                                                    ls
+|                                                    w.txt
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|  ls
+|  w.txt
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+== snap hover-corner grid=100x30 cursor=54,8
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/cornerdrag-left/cwd New Del   ╎  /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|  ls                                             ╎  ls
+|  w.txt                                          ╎  w.txt
+|                                                 ╎╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
+|                                                 ╎  /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|                                                 ╎  ls
+|                                                 ╎  w.txt
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|  /tmp/pardes-snap/cornerdrag-left/cwd New Del   ╎
+|  ls                                             ╎
+|  w.txt                                          ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+== snap hover-left-corner grid=100x30 cursor=54,8
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/cornerdrag-left/cwd New Del   ╎  /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|  ls                                             ╎  ls
+|  w.txt                                          ╎  w.txt
+|                                                 ╎
+|                                                 ╎  /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|                                                 ╎  ls
+|                                                 ╎  w.txt
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
+|  /tmp/pardes-snap/cornerdrag-left/cwd New Del   ╎
+|  ls                                             ╎
+|  w.txt                                          ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+|                                                 ╎
+== snap corner-drag grid=100x30 cursor=54,8
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/cornerdrag╎left/cwd New Del      /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|  ls                         ╎                      ls
+|  w.txt                      ╎                      w.txt
+|                             ╎
+|                             ╎                      /tmp/pardes-snap/cornerdrag-left/cwd New Del
+|                             ╎                      ls
+|                             ╎                      w.txt
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|  /tmp/pardes-snap/cornerdrag╎left/cwd New Del
+|  ls                         ╎
+|  w.txt                      ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+|                             ╎
+== snap corner-done grid=100x30 cursor=34,15
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/cornerdrag-  /tmp/pardes-snap/cornerdrag-left/cwd     New Del
+|  ls                            ls
+|  w.txt                         w.txt
+|
+|
+|
+|
+|
+|
+|
+|
+|                                /tmp/pardes-snap/cornerdrag-left/cwd     New Del
+|                                ls
+|                                w.txt
+|
+|  /tmp/pardes-snap/cornerdrag-
+|  ls
+|  w.txt
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
diff --git a/test/snapshots/cornerdrag-left.snap b/test/snapshots/cornerdrag-left.snap
new file mode 100644
index 00000000..c90dbc76
--- /dev/null
+++ b/test/snapshots/cornerdrag-left.snap
@@ -0,0 +1,41 @@
+# corner grabs on the RIGHT column's side of the v border. The v handle is the
+# LEFT column's last cell, so that column's own h hint runs THROUGH it while the
+# right column's hints start one cell further right — the crossing there reads as
+# a T butting into the junction rather than a full cross, and it is grabbable all
+# the same: one drag moves the column edge and the RIGHT column's pane edge.
+# Layout: windowops' -n 3 (col 0 x 0 w 50, panes on rows 1-15 and 16-29; col 1
+# x 50 w 50), then focus right and Alt-n so col 1 holds two panes as well, split
+# at ITS own row. The two corners on col 49 are then row 16 (col 0's seam, the
+# one that already worked) and row 5 (col 1's, the one this script is about).
+file w.txt x
+start 30 100 -n 3
+wait 8000 w.txt
+stable 700 20000
+# a second pane in the RIGHT column
+key c-w l
+stable 400 5000
+key a-n
+stable 700 15000
+snap right-split
+# hover col 1's corner: the v hint runs full height AND col 1's h hint lights,
+# from col 51 rightward. Before this that row was dark on the handle — only the
+# hovered column's seam lit, and the hovered cell belongs to col 0
+motion 50 5
+stable 400 5000
+snap hover-corner
+# CONTROL: col 0's own seam is still a left-column corner, its h hint drawn
+# through the handle from col 1 to the handle itself, unchanged
+motion 50 16
+stable 400 5000
+snap hover-left-corner
+# grab col 1's corner and drag down-left: the column preview and col 1's row
+# preview both follow the one mouse, the row dashes lying to the RIGHT of the v
+# line because they are the right column's
+press left 50 5
+drag left 30 12
+stable 400 5000
+snap corner-drag
+release left 30 12
+motion 45 25
+stable 500 8000
+snap corner-done
diff --git a/test/snapshots/grep.golden b/test/snapshots/grep.golden
index 846ab703..af4c4708 100644
--- a/test/snapshots/grep.golden
+++ b/test/snapshots/grep.golden
@@ -153,7 +153,7 @@
 |     2 a.txt:3:6-11 last TARGET line
 |     3 sub/b.txt:2:1-6 TARGET inside sub
 |     4
-== snap nomatch grid=180x30 cursor=37,28
+== snap nomatch grid=180x30 cursor=62,3
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
 |  /tmp/pardes-snap/grep/cwd/a.txt Save New Del                /tmp/pardes-snap/grep/cwd      New Del                      /tmp/pardes-snap/grep/cwd      New Del
 |     1 hello TARGET one                                       ls                                                          ls
diff --git a/test/snapshots/grep.snap b/test/snapshots/grep.snap
index 1d3efc9e..ab708a25 100644
--- a/test/snapshots/grep.snap
+++ b/test/snapshots/grep.snap
@@ -6,7 +6,8 @@
 # looking it SELECTS the hit — with the path RELATIVE to the directory
 # of the pane that asked — the same directory its results buffer is named in,
 # so the short name resolves; only a hit from outside that tree stays absolute.
-# n/N SELECT the next/prev row like any other result list and open nothing;
+# n/N SELECT the next/prev row like any other result list and open nothing —
+# one press per row, the location at its head, never the matched text after it;
 # Enter looks what they leave selected, and a row pointing into a file nothing
 # has open yet opens it.
 dirmk sub
@@ -62,10 +63,12 @@ wait 10000 TARGET inside sub
 stable 700 15000
 snap opened-hit
 # a pattern nothing holds: an empty list of its own, with nothing in it for n
-# to stop on — so the ring carries that step back into the TARGET list. The
-# look above is why both of those read the way they do: it left the cursor in
-# sub/b.txt, so the empty list is named in sub/ rather than cwd/, and it left
-# the hit SELECTED there (a ranged result row is one a look selects).
+# to stop on — so the ring carries that step out of it and on round. It lands
+# in the SHELL, whose `ls` row is free text and steps word by word: the TARGET
+# list is standing on its last row, and a row-grained walk has nothing left in
+# it to offer. The look above is why these read the way they do: it left the
+# cursor in sub/b.txt, so the empty list is named in sub/ rather than cwd/, and
+# it left the hit SELECTED there (a ranged result row is one a look selects).
 #   Armed from the LEADER, not the topbar word, because of that selection: a
 # topbar execute chords whatever is selected into its argument, so a
 # middle-click here would run `Grep TARGET` and never ask for a pattern at
diff --git a/test/snapshots/jumps.snap b/test/snapshots/jumps.snap
index db131bd4..d7d44967 100644
--- a/test/snapshots/jumps.snap
+++ b/test/snapshots/jumps.snap
@@ -64,19 +64,20 @@ snap last-back
 key space j l
 stable 700 15000
 snap jumplist
-# n/N select the next/prev look-able span and Enter looks it, exactly as they
-# do a +Search: the stepped span is selected in the buffer (snapstyle) and the
-# Enter after it moves the pane the row names. Row 1 is the shell (no path, so
+# n/N select the next/prev row and Enter looks it, exactly as they do a
+# +Search: the stepped span is selected in the buffer (snapstyle) and the Enter
+# after it moves the pane the row names. Row 1 is the shell (no path, so
 # `@pN`), row 2 the file at line 1, row 4 the file at line 100 — so the body
 # visibly rides the list.
 #
-# SPANS, not rows, and this buffer is the one place in the suite where the two
-# differ: an `@pN` row's trailing text is the pane's DIRECTORY, which is a
-# look-able word of its own, so row 1 and row 3 each hold TWO stops and
-# reaching the next row takes two steps. A file row's text is its content line
-# (`line 1`), which resolves to nothing, so those hold one. Stepping words
-# rather than rows is what makes the walk the same motion in a results buffer
-# and in the middle of a paragraph, and this is the price of that.
+# ONE PRESS PER ROW, and this buffer is where that rule earns itself: an `@pN`
+# row's trailing text is the pane's DIRECTORY, which is a look-able word of its
+# own, so rows 1 and 3 used to hold TWO stops each and reaching the next row
+# took two steps. A results buffer is a LIST — its rows are locations, and the
+# text after one says what is THERE rather than naming another place to go — so
+# the walk takes the location at the head of a row and moves on to the next row
+# (output_pane.Grain.line). Free text still steps every word: that is the
+# terminal walk in ttylook, and it is why the two goldens differ.
 #
 # An `@pN` row moves focus like any other, which it did not use to: the STEP
 # only selects now, and the look Enter runs goes to the pane by the same route
@@ -86,26 +87,20 @@ key enter
 stable 700 15000
 snap step1-shell
 snapstyle step1-shell
-# past the directory on row 1, then onto row 2
-key n
-stable 400 5000
+# on to row 2 — one press, the directory on row 1 is no longer a stop of its own
 key n
 key enter
 stable 700 15000
 snap step2-file
-# row 3 is the shell again, both its spans, and then row 4
-key n
-stable 400 5000
+# row 3 is the shell again, then row 4
 key n
 stable 400 5000
 key n
 key enter
 stable 700 15000
 snap step4-line100
-# N is the exact inverse: the same two spans of row 3 in the other order, so
-# two presses land back on its location and Enter follows it to the shell
-key N
-stable 400 5000
+# N is the exact inverse: one press back onto row 3's location, and Enter
+# follows it to the shell
 key N
 key enter
 stable 700 15000
diff --git a/test/snapshots/stepgrain.golden b/test/snapshots/stepgrain.golden
new file mode 100644
index 00000000..f269c865
--- /dev/null
+++ b/test/snapshots/stepgrain.golden
@@ -0,0 +1,310 @@
+== snap results grid=150x30 cursor=7,2
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 a.txt:1:7-12 hello ZQMARK one
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
+== snap step-row1 grid=150x30 cursor=7,27
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 a.txt:1:7-12 hello ZQMARK one
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
+== style step-row1
+|0: 0-56 #949494,#121212, 57-149 d,#121212,
+|1: 0-1 #ffffff,#262626, 2-129 #949494,#121212, 130-149 d,#121212,
+|2: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-22 #bdbdbd,#080808, 23-149 d,#080808,
+|3: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-39 #bdbdbd,#080808, 40-149 d,#080808,
+|4: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|5: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|6: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|7: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|8: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|9: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|10: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|11: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|12: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|13: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|14: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|15: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|16: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|17: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|18: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|19: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|20: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|21: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|22: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|23: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|24: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|25: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|26: 0-1 #ffffff,#626262, 2-129 #949494,#121212, 130-149 d,#121212,
+|27: 0-0 d,#444444, 1-1 d,#080808, 2-6 #949494,#121212, 7-18 #080808,#80a0ff, 19-35 #bdbdbd,#080808, 36-149 d,#080808,
+|28: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-53 #bdbdbd,#080808, 54-149 d,#080808,
+|29: 0-0 d,#121212, 1-1 d,#080808, 2-6 #626262,#080808, 7-39 #bdbdbd,#080808, 40-149 d,#080808,
+== snap step-row2 grid=150x30 cursor=7,28
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 a.txt:1:7-12 hello ZQMARK one
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
+== style step-row2
+|0: 0-56 #949494,#121212, 57-149 d,#121212,
+|1: 0-1 #ffffff,#262626, 2-129 #949494,#121212, 130-149 d,#121212,
+|2: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-22 #bdbdbd,#080808, 23-149 d,#080808,
+|3: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-39 #bdbdbd,#080808, 40-149 d,#080808,
+|4: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|5: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|6: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|7: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|8: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|9: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|10: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|11: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|12: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|13: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|14: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|15: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|16: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|17: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|18: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|19: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|20: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|21: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|22: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|23: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|24: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|25: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|26: 0-1 #ffffff,#626262, 2-129 #949494,#121212, 130-149 d,#121212,
+|27: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-35 #bdbdbd,#080808, 36-149 d,#080808,
+|28: 0-0 d,#444444, 1-1 d,#080808, 2-6 #949494,#121212, 7-19 #080808,#80a0ff, 20-53 #bdbdbd,#080808, 54-149 d,#080808,
+|29: 0-0 d,#121212, 1-1 d,#080808, 2-6 #626262,#080808, 7-39 #bdbdbd,#080808, 40-149 d,#080808,
+== snap step-row3 grid=150x30 cursor=7,28
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
+|     4
+== snap step-wrap grid=150x30 cursor=7,27
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
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+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 a.txt:1:7-12 hello ZQMARK one
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
+== snap blank-in-path grid=150x30 cursor=7,25
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 two words.txt
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 a.txt:1:7-12 hello ZQMARK one
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
+== style blank-in-path
+|0: 0-56 #949494,#121212, 57-149 d,#121212,
+|1: 0-1 #ffffff,#262626, 2-129 #949494,#121212, 130-149 d,#121212,
+|2: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-22 #bdbdbd,#080808, 23-149 d,#080808,
+|3: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-39 #bdbdbd,#080808, 40-149 d,#080808,
+|4: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|5: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|6: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|7: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|8: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|9: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|10: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|11: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|12: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|13: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|14: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|15: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|16: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|17: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|18: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|19: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|20: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|21: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|22: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|23: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-149 d,#080808,
+|24: 0-1 #ffffff,#626262, 2-129 #949494,#121212, 130-149 d,#121212,
+|25: 0-0 d,#444444, 1-1 d,#080808, 2-6 #949494,#121212, 7-19 #080808,#80a0ff, 20-149 d,#080808,
+|26: 0-1 #ffffff,#262626, 2-129 #949494,#121212, 130-149 d,#121212,
+|27: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-18 #080808,#80a0ff, 19-35 #bdbdbd,#080808, 36-149 d,#080808,
+|28: 0-0 d,#444444, 1-1 d,#080808, 2-6 #626262,#080808, 7-53 #bdbdbd,#080808, 54-149 d,#080808,
+|29: 0-0 d,#121212, 1-1 d,#080808, 2-6 #626262,#080808, 7-39 #bdbdbd,#080808, 40-149 d,#080808,
+== snap blank-opened grid=150x30 cursor=7,14
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/stepgrain/cwd/a.txt                                                                                Save New Del
+|     1 hello ZQMARK one
+|     2 see also sub/b.txt for ZQMARK two
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/two words.txt                                                                        Save New Del
+|     1
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 two words.txt
+|  /tmp/pardes-snap/stepgrain/cwd/+Search                                                                                   New Del
+|     1 a.txt:1:7-12 hello ZQMARK one
+|     2 a.txt:2:24-29 see also sub/b.txt for ZQMARK two
+|     3 sub/b.txt:1:1-6 ZQMARK inside sub
diff --git a/test/snapshots/stepgrain.snap b/test/snapshots/stepgrain.snap
new file mode 100644
index 00000000..a12d7bbd
--- /dev/null
+++ b/test/snapshots/stepgrain.snap
@@ -0,0 +1,77 @@
+# WHAT ONE PRESS OF `n` TAKES, and why that is not one answer. A pane's rows
+# decide it (output_pane.Grain, read in Pardes.lookSpanIn):
+#
+#   free text — a terminal, a file, a PDF — is stepped WORD by word, several
+#   stops to a line, because a line of it may name several places at once (the
+#   `ls` row in ttylook.snap hops big.txt -> plain.txt -> sub);
+#
+#   a RESULTS BUFFER is stepped ROW by row, on the location at the head of the
+#   row, because a row there IS one location and the words after it are the
+#   MATCHED TEXT — the same hit, spelled out. That text is full of look-able
+#   words, and stopping on them was stopping on the same result twice.
+#
+# This script is the second rule. Row 2 below matched on a line that mentions
+# `sub/b.txt`, so the old word-grained walk stopped there before it ever
+# reached row 3; now `n` presses and rows correspond one to one, and the fourth
+# press wraps the ring back to row 1.
+#
+# LARGEST from the head, so a path with a BLANK in it is one span rather than
+# the word in front of it: `two words.txt` selects whole and opens.
+dirmk sub
+file a.txt hello ZQMARK one\nsee also sub/b.txt for ZQMARK two
+file sub/b.txt ZQMARK inside sub
+run touch 'two words.txt'
+start 30 150 a.txt
+wait 8000 hello ZQMARK
+stable 700 20000
+# Grep from the leader: three hits, sorted by path, the empty file contributing
+# none. Row 2 is the one whose TEXT holds a path.
+key space
+key f
+key g
+stable 400 5000
+text ZQMARK
+key enter
+wait 10000 sub/b.txt:1:1
+stable 700 15000
+snap results
+# one press, one row: the head of row 1...
+key n
+stable 400 5000
+snap step-row1
+snapstyle step-row1
+# ...the head of row 2, and NOT the `sub/b.txt` sitting in its matched text —
+# the cursor column is the assertion
+key n
+stable 400 5000
+snap step-row2
+snapstyle step-row2
+# ...row 3, and then the ring comes round to row 1 again
+key n
+stable 400 5000
+snap step-row3
+key n
+stable 400 5000
+snap step-wrap
+# Back into the file, so the Find below is asked from a pane that is not a
+# results buffer (fillResults never refills the buffer it was asked from).
+press left 8 3
+release left 8 3
+stable 400 5000
+# A path with a blank in it: the row is one span from its first cell, because
+# the walk asks about the LONGEST run of the row first and the filesystem is
+# what vouches for it. Enter then opens exactly what is selected.
+key space
+key f
+key f
+text words
+key enter
+wait 10000 two words.txt
+stable 700 15000
+key n
+stable 400 5000
+snap blank-in-path
+snapstyle blank-in-path
+key enter
+stable 700 15000
+snap blank-opened
diff --git a/test/snapshots/ttytaken.golden b/test/snapshots/ttytaken.golden
new file mode 100644
index 00000000..960081d1
--- /dev/null
+++ b/test/snapshots/ttytaken.golden
@@ -0,0 +1,124 @@
+== snap opened grid=100x30 cursor=7,2
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/ttytaken/cwd/cmd.txt Save New D  /tmp/pardes-snap/ttytaken/cwd New Del
+|     1 echo TAKEN''ONE                              ls
+|     2 echo TAKEN''TWO                              big.txt  cmd.txt
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+== snap at-prompt grid=100x30 cursor=7,2
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/ttytaken/cwd/cmd.txt Save New D  /tmp/pardes-snap/ttytaken/cwd New Del
+|     1 echo TAKEN''ONE                              ls
+|     2 echo TAKEN''TWO                              big.txt  cmd.txt
+|                                                    echo TAKEN''ONE
+|                                                    TAKENONE
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+== snap paging grid=100x30 cursor=59,29
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/ttytaken/cwd/cmd.txt Save New D$ /tmp/pardes-snap/ttytaken/cwd New Del
+|     1 echo TAKEN''ONE                              line 1
+|     2 echo TAKEN''TWO                              line 2
+|                                                    line 3
+|                                                    line 4
+|                                                    line 5
+|                                                    line 6
+|                                                    line 7
+|                                                    line 8
+|                                                    line 9
+|                                                    line 10
+|                                                    line 11
+|                                                    line 12
+|                                                    line 13
+|                                                    line 14
+|                                                    line 15
+|                                                    line 16
+|                                                    line 17
+|                                                    line 18
+|                                                    line 19
+|                                                    line 20
+|                                                    line 21
+|                                                    line 22
+|                                                    line 23
+|                                                    line 24
+|                                                    line 25
+|                                                    line 26
+|                                                    line 27
+|                                                    big.txt
+== snap spawned grid=100x30 cursor=53,25
+|New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
+|  /tmp/pardes-snap/ttytaken/cwd/cmd.txt Save New D$ /tmp/pardes-snap/ttytaken/cwd New Del
+|     1 echo TAKEN''ONE                              line 1
+|     2 echo TAKEN''TWO                              line 2
+|                                                    line 3
+|                                                    line 4
+|                                                    line 5
+|                                                    line 6
+|                                                    line 7
+|                                                    line 8
+|                                                    line 9
+|                                                    line 10
+|                                                    line 11
+|                                                    line 12
+|                                                    line 13
+|                                                    line 14
+|                                                    line 15
+|                                                    line 16
+|                                                    line 17
+|                                                    line 18
+|                                                    line 19
+|                                                    line 20
+|                                                    line 21
+|                                                    line 22
+|                                                    line 23
+|                                                    :
+|                                                    /tmp/pardes-snap/ttytaken/cwd New Del
+|                                                    echo TAKEN''TWO
+|                                                    TAKENTWO
+|
diff --git a/test/snapshots/ttytaken.snap b/test/snapshots/ttytaken.snap
new file mode 100644
index 00000000..6505fc63
--- /dev/null
+++ b/test/snapshots/ttytaken.snap
@@ -0,0 +1,43 @@
+# Process monitoring, end to end. A pane whose tty is held by a full-screen
+# program is not somewhere a command line may be typed: the SAME middle-drag
+# Exec goes into the shell while it sits at its prompt, and into a NEW shell
+# beside it once `less` owns the terminal — where it runs, instead of becoming
+# keystrokes the pager would eat. Nothing about the pager's screen changes.
+file cmd.txt echo TAKEN''ONE\necho TAKEN''TWO
+lines big.txt 40
+start 30 100 -n 1
+wait 8000 cmd.txt
+stable 700 20000
+# open the command file by looking its name in the greeting `ls`
+press right 14 4
+release right 14 4
+wait 10000 echo TAKEN
+stable 700 20000
+snap opened
+# at the prompt: the drag runs in the shell that is already on this directory
+press middle 8 3
+drag middle 22 3
+release middle 22 3
+wait 10000 TAKENONE
+stable 700 20000
+snap at-prompt
+# ...and now a pager owns that terminal. Ctrl-b is raw tty (config.tty_toggle),
+# which is how a script types AT the shell instead of into the pane's own edit
+# buffer — the same way exec.snap runs a command line.
+press left 60 8
+release left 60 8
+stable 400 5000
+key c-b
+stable 400 5000
+text env LESS= less big.txt
+key enter
+wait 10000 line 1
+stable 700 20000
+snap paging
+# the same gesture on the second line: a new shell, not `less` keystrokes
+press middle 8 4
+drag middle 22 4
+release middle 22 4
+wait 10000 TAKENTWO
+stable 700 20000
+snap spawned