Codeman maintainer 1082724db9 perf(zerolag): rebuild only the changed overlay line, one paint layer per line ...

The local echo overlay rebuilt every character of the prompt on each
keystroke, one absolutely positioned span per character, so a keystroke
cost O(prompt length) in DOM work, style, layout and paint. Every
positioned span was also its own paint layer, so the browser re-layerized
and repainted thousands of them per frame. In headless Chromium with a 6x
CPU slowdown, a ~4,100-character prompt ran at a median 813 ms per frame,
and ~300 characters already missed 60 fps (54 ms).

renderOverlay() now keeps a per-container record of the line elements it
drew and rebuilds only lines whose text, position or composition range
changed. It starts over when the font, colour, cell size or Unicode
version changes, or when something else emptied or edited the container.

makeLine() lays the spans out in a flex row instead of positioning each
one, and sets the shared font styles once on the line. Cell edges are
snapped to a quarter pixel, which Blink, WebKit and Gecko all store
exactly, so the widths add up to the grid without drift and every edge
stays within 1/8 px of col * cellW. Same prompt: 17 ms per frame.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

2026-10-25 06:07:34 +01:00

..

gesture-control

feat(tiles): move tiles by hand, and detach a tile into its own window

2026-10-10 07:17:26 +02:00

xterm-zerolag-input

perf(zerolag): rebuild only the changed overlay line, one paint layer per line

2026-10-25 06:07:34 +01:00