fix: bordered shaders precision with asymmetric borders#21
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Port upstream lightning-js/renderer#751: adjust u_borderWidth via `u_borderWidth - 1.0 + clamp(u_borderWidth, -1.0, 1.0)` so asymmetric border-diff math (borderRight - borderLeft, etc.) renders correctly for sub-pixel and zero-on-one-side cases. Values >= 1 are unchanged. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Summary
u_borderWidth.xyzwwithvec4 adjustedBorderWidth = u_borderWidth - 1.0 + clamp(u_borderWidth, -1.0, 1.0)before splitting into top/right/bottom/left.Why
The asymmetric border math (
borderRight - borderLeft,borderBottom - borderTop) was losing precision for sub-pixel borders and zero-on-one-side cases. The clamp-based adjustment keeps values>= 1unchanged but shifts the diff math so asymmetric borders render correctly.Files
src/core/shaders/webgl/Border.tssrc/core/shaders/webgl/RoundedWithBorder.tssrc/core/shaders/webgl/RoundedWithBorderAndShadow.tsTest plan
pnpm buildpassesborderTop: 4, borderBottom: 0) render with correct edgespnpm test:visual— review any diffs in border-related snapshots🤖 Generated with Claude Code