perf: sort main-pass SDF text writes for fewer draw calls - #865
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wouterlucas wants to merge 3 commits into
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perf: sort main-pass SDF text writes for fewer draw calls#865wouterlucas wants to merge 3 commits into
wouterlucas wants to merge 3 commits into
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Render SDF glyphs into renderer-owned shared vertex buffers (one plain 6f + one rich 7f per-vertex layout) backed by per-node CPU vertex caches. Consecutive text nodes that share a layout, font atlas, and clip merge into a single draw call, and unchanged nodes skip GPU uploads entirely via a cache-hit mem-copy path. - add SdfBuffer (cursor/growth/change tracking) and SdfRenderOp (contiguous-range drawElements with scissor-only clipping) - rewrite SdfShader to feed pre-transformed position, per-vertex color, distance range, and style as vertex attributes; remove the per-node u_transform/u_size/u_color/u_distanceRange uniforms - extend WebGlShaderProgram.bindRenderOp to bind SdfRenderOps through the normal uniform path; drop the legacy onSdfBind hook and isSdfRenderOp flag - move CoreTextNode onto a shared SdfVertexCache; track lastStartQuad and lastWriteDirty so a render-list reorder marks the shared buffer dirty and re-uploads instead of leaving stale GPU bytes at shifted offsets - add the text-stress-sdf example (interleaved vs grouped render order) and unit tests for the buffer, bind path, and offset-tracking fix
Add certified visual baselines for the SDF text stress example.
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What
Defer main-pass SDF text rendering into a scene-wide sorted list instead of writing interleaved glyph runs inline during the traversal.
SDF text already batches into a shared GPU buffer, but only consecutive writes sharing a vertex layout (plain 6f vs rich 7f), glyph atlas (per font family) and scissor clip rect merge into one
drawElements. Apps that interleave plain/rich text (cards, rails) forced a draw call per region. This sorts the visible SDF text nodes by batch key at render-list build time so each (layout, atlas, clip) group becomes one contiguous range and merges into a single draw call, with zero app-side grouping.Changes
lib/utils.ts— newSdfBatchKeytype andcompareSdfBatchKeystotal ordering (matches the merge key inWebGlRenderer.finalizeSdfBatch: layout, atlas, clip rect incl. radius).CoreNode.getSdfBatchKey()— virtual returningnull;CoreTextNodeoverrides it to return the key for main-pass SDF text,nullfor canvas text, un-laid-out text, and text inside render-to-texture subtrees.Stage—buildRenderListcollects main-pass SDF text nodes (scene order) instead of writing inline;sortRenderListSdfTextNodessorts them with a stable sort (equal keys keep scene order / relative z), cached across frames;writeRenderListSdfTextemits them after the main list on every frame. RTT traversal and all non-SDF nodes keep the inline path.getSdfBatchKeytests inCoreTextNode.test.ts; 12 Stage tests covering comparator order, deferral, sorted emission, inline paths (images, rounded clips, RTT), visibility skips, stable equal-keys, and cached replay.Correctness
The sort is best-effort:
finalizeSdfBatchstill keys off actual write-time values, so a stale cached order (e.g. afontFamily/clip change without a structural rebuild) only costs extra draw calls, never wrong output.Verification
pnpm test272/272,tsc --build, prettier, eslint clean.chromium-local).