Performance

What runsCopy Anchor Link

• One MutationObserver that watches for shadcn parts appearing and changing state
• Two listeners in the capture phase, pointerdown and keydown, that remember the last press
• Animations of transform, opacity and filter only, which the browser runs off the main thread where it can
• Ghosts, the copies of leaving elements, which are removed as soon as their animation ends or is cancelled

Nothing runs while nothing changes.

SizeCopy Anchor Link

The layer is about 7 KB gzipped once your bundler minifies it: cuts.tsx, its stylesheet and the engine. Each helper adds about 1.5–2.5 KB.

ListsCopy Anchor Link

ListCut measures its items once per render, in a layout effect. Only items in or near the viewport animate, so a list of thousands stays fast. Key items by a stable id, and avoid re-rendering the whole list on every keystroke elsewhere on the page.

Slow devicesCopy Anchor Link

Blur is the most expensive part of a rack focus. If you target low-end phones, turn it off:

:root {
  --kf-blur: 0px;
}