[fix] [sdf] Sdf text alpha double multiplication#2
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May 11, 2026
Three changes covering the hot update path for x/y changes on simple nodes (no rotation/scale/mount): 1. CoreNode.update Global block: when both the node is simple and the parent's global is translate-only, the resulting global is also translate-only and collapses to two adds on tx/ty — bypassing the 6-field Matrix3d.copy + 2 mul-add translate. Tracked with a per-node _globalIsTranslate flag that propagates down the tree. RTT chains conservatively opt out. 2. updateLocalTransform simple path: localTransform is guaranteed to be identity-shape (ta=1, tb=0, tc=0, td=1), so only tx/ty need to change between frames. _localIsTranslate tracks whether the matrix is still in identity-shape so a non-simple -> simple transition correctly restores it. 3. updateBoundingRect: fix `||` -> `&&` on the axis-aligned-fast-path check. With `||`, a matrix with one zero shear component and the other non-zero (e.g. tb=0, tc=-0.5) wrongly took the diagonal fast path and produced incorrect bounds. Now matches calculateRenderCoords semantics. Adds setTranslate() helper to Matrix3d for the in-place tx/ty + mutation flag write used by both #1 and #2. Adds 12 unit tests covering simple-path reuse, non-simple -> simple transitions, translate-only propagation through grandchildren, fast-path opt-out when parent has rotation, and the bounding-rect axis check. Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
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The text color was being premultiplied by alpha twice:
v_color.rgb * opacityThis resulted in a double moltiplication of alpha channel, leading to wrong transparency results.
Solution: Removed the CPU-side premultiplication in
addSdfQuads(). The color is now packed as straight (non-premultiplied) RGBA into the vertex attribute, and the SDF fragment shader remains the single point where premultiplied alpha blending is applied.