49 lines
1.3 KiB
TypeScript
49 lines
1.3 KiB
TypeScript
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import { type TimelineState, xToTime } from './renderer';
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export type { TimelineState };
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const MIN_VISIBLE_RANGE = 0.1;
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const MIN_ZOOM = 1;
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export function clampZoom(zoom: number, duration: number): number {
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const maxZoom = duration / MIN_VISIBLE_RANGE;
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return Math.max(MIN_ZOOM, Math.min(zoom, maxZoom));
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}
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export function computeZoom(
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state: TimelineState,
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anchorTime: number,
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factor: number,
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duration: number
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): { visibleStart: number; visibleEnd: number; zoom: number } {
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const currentRange = state.visibleEnd - state.visibleStart;
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const newRange = currentRange / factor;
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const clampedRange = Math.max(MIN_VISIBLE_RANGE, Math.min(newRange, duration));
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const anchorRatio = (anchorTime - state.visibleStart) / currentRange;
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let newStart = anchorTime - anchorRatio * clampedRange;
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let newEnd = newStart + clampedRange;
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if (newStart < 0) {
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newStart = 0;
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newEnd = clampedRange;
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}
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if (newEnd > duration) {
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newEnd = duration;
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newStart = Math.max(0, newEnd - clampedRange);
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}
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const newZoom = clampZoom(duration / clampedRange, duration);
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return { visibleStart: newStart, visibleEnd: newEnd, zoom: newZoom };
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}
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export function handleClick(
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x: number,
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state: TimelineState,
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duration: number
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): number {
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const time = xToTime(x, state);
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return Math.max(0, Math.min(time, duration));
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}
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