Catcrafts/Crafter.Graphics
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perf(ui): transparent shaped-run cache lookup, no string copy on hit (#122)

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ShapeText built ShapedRunKey{..., std::string(utf8)} before find()
unconditionally — even on cache hits, on the per-frame onBuild path.
N labels meant N string copies + hashes (+ frees for non-SSO strings)
every frame, partially defeating the run cache.

Add is_transparent hash + equality functors on shapedRuns_ and probe
with a borrowing ShapedRunViewKey {const Font*, float, array<float,4>,
string_view}. The owning std::string is now materialised only on a
miss, for emplace. Cache hits copy and hash no string.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
catbot 2026-06-18 13:19:11 +00:00
commit c8495f548b
2 changed files with 51 additions and 9 deletions
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8
implementations/Crafter.Graphics-UI-Shared.cpp
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@ -75,8 +75,11 @@ std::uint32_t UIRenderer::ShapeText(Font& font, float pxSize,
// the pen starting at x=0, baseline=0 so a cache hit only needs the
// translate below. The whole string is shaped (no outCapacity limit) so
// a later call with a larger buffer still gets the full run.
ShapedRunKey key{&font, pxSize, color, std::string(utf8)};
auto it = shapedRuns_.find(key);
// Probe with a borrowing view key (text is a string_view onto utf8) so a
// cache hit copies and hashes no string. The owning std::string is only
// built on a miss, below, for the emplace.
ShapedRunViewKey viewKey{&font, pxSize, color, utf8};
auto it = shapedRuns_.find(viewKey);
if (it == shapedRuns_.end()) {
// Miss: shape from scratch. Ensure() each glyph so brand-new ones
// rasterise into the atlas and mark it dirty for the next upload —
@ -110,6 +113,7 @@ std::uint32_t UIRenderer::ShapeText(Font& font, float pxSize,
run.advance = cursor;
if (shapedRuns_.size() >= kMaxShapedRuns) shapedRuns_.clear();
ShapedRunKey key{&font, pxSize, color, std::string(utf8)};
it = shapedRuns_.emplace(std::move(key), std::move(run)).first;
}