25 lines
1023 B
TypeScript
25 lines
1023 B
TypeScript
import type { ViewportTransform } from "@/types/canvas";
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const MIN_VIEWPORT_SCALE = 0.05;
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const MIN_PREVIEW_RATIO = 0.85;
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const MAX_PREVIEW_RATIO = 1.25;
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export function calculateCanvasPreviewTransform(viewport: ViewportTransform, rasterViewport: ViewportTransform) {
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const ratio = viewport.k / Math.max(rasterViewport.k, MIN_VIEWPORT_SCALE);
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// 将旧 backing store 的屏幕坐标映射到实时视口，避免缩放手势逐帧触发矢量重绘。
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return {
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ratio,
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x: viewport.x - rasterViewport.x * ratio,
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y: viewport.y - rasterViewport.y * ratio,
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};
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}
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export function shouldRebaseCanvasRaster(viewport: ViewportTransform, rasterViewport: ViewportTransform) {
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const { ratio } = calculateCanvasPreviewTransform(viewport, rasterViewport);
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return ratio < MIN_PREVIEW_RATIO || ratio > MAX_PREVIEW_RATIO;
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}
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export function sameCanvasViewport(left: ViewportTransform, right: ViewportTransform) {
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return left.x === right.x && left.y === right.y && left.k === right.k;
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}
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