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, 11 insertions, 4 deletions

diff --git a/src/Output.zig b/src/Output.zig
index b8dd5e34..6ea81924 100644
--- a/src/Output.zig
+++ b/src/Output.zig
@@ -54,10 +54,17 @@ const RowDecoration = struct {
     mark_end: usize = 0,
     severity: enum { none, err, warning, info, hint } = .none,
 
-    pub fn styleAt(row: RowDecoration, p: *const Pardes, byte: usize) ?pardes.CellStyle {
-        // Body paper changes immediately, so its ink must change with it
-        // even while the surrounding tags are still fading.
-        const chrome = pardes.ChromeTheme.fromTheme(p.theme());
+    /// Nothing in the row is decorated: most rows of most files.
+    pub fn plain(row: RowDecoration) bool {
+        return !row.declaration and row.location_end == 0 and row.prefix_end == 0 and row.mark_end <= row.mark_start;
+    }
+
+    /// `chrome` is the theme's own (Pardes.bodyChrome): body paper changes
+    /// immediately, so its ink must change with it even while the
+    /// surrounding tags are still fading. Once a frame, never a grapheme:
+    /// working it out takes the contrast searches' pow calls.
+    pub fn styleAt(row: RowDecoration, chrome: *const pardes.ChromeTheme, byte: usize) ?pardes.CellStyle {
+        if (row.plain()) return null;
         if (row.declaration or byte < @max(row.location_end, row.prefix_end))
             return .{ .fg = .{ .rgb = chrome.lineno } };
         if (byte < row.mark_start or byte >= row.mark_end) return null;