51 lines
1.7 KiB
TypeScript
51 lines
1.7 KiB
TypeScript
// Trackpad / pointer gesture primitives shared across canvas + DOM surfaces.
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//
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// macOS quirk (Chromium/Electron): both pinch-zoom and "smart zoom" arrive as
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// `wheel` events with `ctrlKey` synthetically set — there is no dedicated DOM
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// event for either. They're disambiguated by their deltas:
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// - pinch-to-zoom: ctrlKey + a non-zero delta
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// - smart zoom: ctrlKey + zero deltas (the two-finger double-tap)
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// Plain two-finger scroll has ctrlKey === false. Centralising this here keeps
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// every zoom/pan surface from re-deriving the same OS trivia (and getting it
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// wrong, which makes smart-zoom read as a zoom-in).
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export interface WheelLike {
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ctrlKey: boolean
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deltaX: number
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deltaY: number
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}
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/** macOS "smart zoom" (two-finger double-tap): a ctrl-wheel with no delta. */
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export function isSmartZoomWheel(e: WheelLike): boolean {
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return e.ctrlKey && e.deltaX === 0 && e.deltaY === 0
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}
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/** Pinch-to-zoom (or ctrl + mouse wheel): a ctrl-wheel carrying a delta. */
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export function isPinchZoomWheel(e: WheelLike): boolean {
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return e.ctrlKey && (e.deltaX !== 0 || e.deltaY !== 0)
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}
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export const DOUBLE_TAP_MS = 300
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/**
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* Stateful double-tap detector for surfaces where a real `dblclick` may never
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* fire (e.g. a trackpad with tap-to-click off). Call it once per discrete tap;
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* it returns true when two taps land within `thresholdMs` of each other, then
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* resets so a third tap starts a fresh pair.
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*/
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export function createDoubleTapDetector(thresholdMs: number = DOUBLE_TAP_MS): (now?: number) => boolean {
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let last = 0
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return (now: number = Date.now()): boolean => {
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if (now - last < thresholdMs) {
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last = 0
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return true
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}
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last = now
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return false
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}
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}
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