At kMaxShapedRuns (8192) UIRenderer::ShapeText did a full shapedRuns_.clear().
A stream of unique strings (FPS counters, timers) alongside many stable labels
periodically nuked every stable entry, forcing a full-UI reshape the next frame.
Track recency with an auxiliary std::list<const ShapedRunKey*> (front = most
recently used) holding pointers to the keys owned by the node-based map. A hit
splices its entry to the front; an overflow pops the least-recently-used entry
from the back and erases just that one — both O(1). The hot set of labels,
reshaped every frame, stays at the front and survives, so the churn of unique
strings only recycles the cold tail. Output is byte-identical either way.
InvalidateFont now drops matching entries from both the map and the LRU list.
Adds ShapedRunCacheSize()/IsShapedRunCached() introspection hooks (the policy
isn't observable through output or atlas.dirty) and a ShapeTextCache test that
asserts the cache plateaus at a fixed cap (evict-one, not clear-all), the hot
label survives a churn past the cap, and an untouched cold string is evicted.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
ShapeText re-decoded UTF-8, re-looked-up every glyph, and recomputed
layout every frame for static strings (DrawText / EmitCenteredLabel run
inside per-frame onBuild). DrawText and EmitCenteredLabel also did a
second full pass over the glyphs to apply alignment.
Memoize the shaped run, keyed by (Font*, pxSize, color, utf8), as an
origin-relative vector<GlyphItem>. A cache hit skips decode/lookup/layout
and just translates the cached run into the output buffer by
(x + alignShift, baselineY). The alignment shift (Center = -advance/2,
Right = -advance) is folded into ShapeText's single pass, dropping the
second loop in both callers. TextAlign moves to the :UI partition so
ShapeText can take it.
Pure CPU memoization — the glyph buffer is fully rewritten and re-flushed
every frame, so a hit is byte-equivalent. A miss still calls Ensure so new
glyphs rasterise and dirty the atlas; hits don't (atlas entries are never
evicted). InvalidateFont drops a font's runs before it is destroyed (the
cache, like FontAtlas's glyph cache, keys on the Font pointer). A soft cap
bounds memory against pathological per-frame-unique text.
Adds the ShapeTextCache test (15 checks): hit == miss byte-for-byte, hits
don't touch the atlas, translate/alignment/truncation/InvalidateFont.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
