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perf: prevent layout thrashing on document drag (#86)
Swaps the order of DOM reads (getBoundingClientRect) and writes (classList.add) in the dragging onMove handler to prevent forced synchronous layouts. Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
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1 changed files with 7 additions and 7 deletions
14
src/main.ts
14
src/main.ts
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@ -112,13 +112,6 @@ function setupDocInteraction(el: HTMLElement, doc: DocMeta, list: HTMLElement, d
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const startY = e.clientY;
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let cachedItems: { el: HTMLElement, top: number, bottom: number }[] | null = null;
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const onMove = (ev: MouseEvent) => {
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if (!dragging) {
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if (Math.abs(ev.clientY - startY) < 4) return;
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dragging = true;
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suppressClick = true;
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el.classList.add("dragging");
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document.body.style.cursor = "grabbing";
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}
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if (!cachedItems) {
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const domItems = [...list.querySelectorAll<HTMLElement>(".doc-item")];
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cachedItems = domItems.map((item) => {
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@ -126,6 +119,13 @@ function setupDocInteraction(el: HTMLElement, doc: DocMeta, list: HTMLElement, d
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return { el: item, top: rect.top, bottom: rect.bottom };
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});
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}
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if (!dragging) {
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if (Math.abs(ev.clientY - startY) < 4) return;
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dragging = true;
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suppressClick = true;
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el.classList.add("dragging");
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document.body.style.cursor = "grabbing";
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}
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let over: HTMLElement | undefined;
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for (const item of cachedItems) {
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item.el.classList.remove("drag-over");
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