kopia lustrzana https://github.com/shoelace-style/shoelace
75 wiersze
2.3 KiB
TypeScript
75 wiersze
2.3 KiB
TypeScript
type GenericCallback = (this: unknown, ...args: unknown[]) => unknown;
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type MethodOf<T, K extends keyof T> = T[K] extends GenericCallback ? T[K] : never;
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const debounce = <T extends GenericCallback>(fn: T, delay: number) => {
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let timerId = 0;
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return function (this: unknown, ...args: unknown[]) {
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window.clearTimeout(timerId);
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timerId = window.setTimeout(() => {
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fn.call(this, ...args);
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}, delay);
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};
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};
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const decorate = <T, M extends keyof T>(
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proto: T,
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method: M,
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decorateFn: (this: unknown, superFn: T[M], ...args: unknown[]) => unknown
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) => {
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const superFn = proto[method] as MethodOf<T, M>;
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proto[method] = function (this: unknown, ...args: unknown[]) {
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superFn.call(this, ...args);
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decorateFn.call(this, superFn, ...args);
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} as MethodOf<T, M>;
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};
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const isSupported = 'onscrollend' in window;
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if (!isSupported) {
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const pointers = new Set();
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const scrollHandlers = new WeakMap<EventTarget, EventListenerOrEventListenerObject>();
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const handlePointerDown = (event: PointerEvent) => {
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pointers.add(event.pointerId);
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};
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const handlePointerUp = (event: PointerEvent) => {
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pointers.delete(event.pointerId);
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};
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document.addEventListener('pointerdown', handlePointerDown);
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document.addEventListener('pointerup', handlePointerUp);
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decorate(EventTarget.prototype, 'addEventListener', function (this: EventTarget, addEventListener, type) {
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if (type !== 'scroll') return;
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const handleScrollEnd = debounce(() => {
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if (!pointers.size) {
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// If no pointer is active in the scroll area then the scroll has ended
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this.dispatchEvent(new Event('scrollend'));
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} else {
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// otherwise let's wait a bit more
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handleScrollEnd();
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}
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}, 100);
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addEventListener.call(this, 'scroll', handleScrollEnd, { passive: true });
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scrollHandlers.set(this, handleScrollEnd);
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});
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decorate(EventTarget.prototype, 'removeEventListener', function (this: EventTarget, removeEventListener, type) {
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if (type !== 'scroll') return;
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const scrollHandler = scrollHandlers.get(this);
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if (scrollHandler) {
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removeEventListener.call(this, 'scroll', scrollHandler, { passive: true } as unknown as EventListenerOptions);
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}
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});
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}
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// Without an import or export, TypeScript sees vars in this file as global
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export {};
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