perf: optimize render-to-output text writing using replaceAt#124
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perf: optimize render-to-output text writing using replaceAt#124jacob314 wants to merge 2 commits into
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- Fix bug where zero-width characters (e.g., zero-width space) at the start of a chunk would consume a visual column and cause layout shifts. - Optimize `clearRange` by using `StyledLine.empty(len)` for spaces without background colors. - Add regression tests and update snapshots for zero-width characters.
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cocosheng-g
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Apr 15, 2026
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| const left = this.slice(0, start); | ||
| const right = this.slice(end); | ||
| const combined = left.combine(slicedChars, right); |
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these create 3 new instances, maybe more efficient by directly mutate this.charData and this.spans using splice or direct index updates?
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This commit introduces performance optimizations for the renderer by using
replaceAtandcombineinOutputto reduce string allocations andlooping overhead. With these optimizations, the frame rate for
examples/nested-static/increases from 12 to 15 FPS.Additional fixes and optimizations:
applyWritewherezero-width characters (e.g., zero-width spaces, combining characters) at
the start of a slice chunk would incorrectly consume a visual column and
cause a layout shift.
clearRange: Leverages theStyledLine.empty(len)cache whenclearing spaces without a background color, avoiding unnecessary
allocations and looping.
(
test.serial) intest/multi-char-text.tsxto prevent race conditionscaused by global
currentStringWidthstate mutations.