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, 25 insertions, 2 deletions

diff --git a/src/gui/Post.zig b/src/gui/Post.zig
index 06310b7f..602b2790 100644
--- a/src/gui/Post.zig
+++ b/src/gui/Post.zig
@@ -94,6 +94,8 @@ pub const Pass = struct {
     pipeline: ?*Pipeline = null,
     /// The SPIR-V revision `pipeline` was made from (shader_build.Pass).
     revision: u32 = 0,
+    /// It moves on its own (shader_build.Pass).
+    animated: bool = false,
 };
 
 passes: [max]Pass = @splat(.{}),
@@ -140,7 +142,7 @@ pub fn sync(post: *Post, gpa: std.mem.Allocator, device: *c.SDL_GPUDevice, forma
                 post.bloom_down = makePipeline(device, bloom_format, bloom_down_spv, 1, 1) catch null;
                 post.bloom_up = makePipeline(device, bloom_format, bloom_up_spv, 1, 1) catch null;
             }
-            next[i] = .{ .scene = scene, .level = entry.level, .pipeline = post.bundled.get(scene) };
+            next[i] = .{ .scene = scene, .level = entry.level, .pipeline = post.bundled.get(scene), .animated = entry.animated };
             continue;
         }
         // A file already in the chain keeps its pipeline and its path.
@@ -151,6 +153,7 @@ pub fn sync(post: *Post, gpa: std.mem.Allocator, device: *c.SDL_GPUDevice, forma
             break;
         } else next[i] = .{ .path = gpa.dupe(u8, entry.path) catch &.{} };
         const pass = &next[i];
+        pass.animated = entry.animated;
         if (pass.revision == entry.revision or entry.spirv.len == 0) continue;
         pass.revision = entry.revision;
         const made = makePipeline(device, format, entry.spirv, 1, 4) catch {
@@ -200,8 +203,14 @@ pub fn ready(post: *const Post) bool {
 }
 
 /// The chain redraws on its own (level A) as ShaderAnimation says.
+/// Only a pass that moves on its own (shader_build.Pass.animated) asks for
+/// frames while idle: a still one (Bloom, Vignette, Grain, a file that reads
+/// no clock) is drawn again only with a frame of the core's.
 pub fn animating(post: *const Post, mode: pardes.config.Runtime.ShaderAnimation) bool {
-    return post.ready() and switch (mode) {
+    const moving = for (post.passes[0..post.len]) |pass| {
+        if (pass.pipeline != null and pass.animated) break true;
+    } else false;
+    return moving and switch (mode) {
         .off => false,
         .on => post.uniforms.focus != 0,
         .always => true,
@@ -664,3 +673,17 @@ test "a moved cursor becomes the previous one, stamped with the time of the move
     try std.testing.expectEqual([4]f32{ 1.0 / 255.0, 2.0 / 255.0, 3.0 / 255.0, 1 }, post.uniforms.selection_foreground_color);
 }
 
+
+test "a still pass asks for no idle frames; one that reads the clock does" {
+    var post: Post = .{};
+    const fake: *Pipeline = @ptrFromInt(0x1000);
+    post.passes[0] = .{ .scene = .bloom, .level = 2, .pipeline = fake };
+    post.len = 1;
+    try std.testing.expect(!post.animating(.on) and !post.animating(.always));
+    post.passes[1] = .{ .scene = .crt, .level = 2, .pipeline = fake, .animated = true };
+    post.len = 2;
+    try std.testing.expect(post.animating(.on) and post.animating(.always) and !post.animating(.off));
+    // Unfocused, `on` rests.
+    post.uniforms.focus = 0;
+    try std.testing.expect(!post.animating(.on) and post.animating(.always));
+}