44 lines
1.3 KiB
TypeScript
44 lines
1.3 KiB
TypeScript
import { useEffect } from "react";
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export function useHiDPICanvas(
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imgRef: React.RefObject<HTMLImageElement | null>,
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canvasRef: React.RefObject<HTMLCanvasElement | null>
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) {
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const sync = () => {
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const img = imgRef.current,
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cvs = canvasRef.current;
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if (!img || !cvs) return;
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const dpr = window.devicePixelRatio || 1;
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const w = img.clientWidth || img.naturalWidth || 0;
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const h = img.clientHeight || img.naturalHeight || 0;
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// CSS size
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cvs.style.width = `${w}px`;
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cvs.style.height = `${h}px`;
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// backing store size (scaled for HiDPI)
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const W = Math.max(1, Math.round(w * dpr));
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const H = Math.max(1, Math.round(h * dpr));
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if (cvs.width !== W || cvs.height !== H) {
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cvs.width = W;
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cvs.height = H;
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const ctx = cvs.getContext("2d");
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if (ctx) ctx.setTransform(dpr, 0, 0, dpr, 0, 0); // draw in CSS px
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}
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};
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useEffect(() => {
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const ro = new ResizeObserver(sync); // reacts to image size changes
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if (imgRef.current) ro.observe(imgRef.current);
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const onResize = () => sync();
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window.addEventListener("resize", onResize);
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return () => {
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ro.disconnect();
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window.removeEventListener("resize", onResize);
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};
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}, []); // eslint-disable-line react-hooks/exhaustive-deps
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return { sync };
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}
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