import { Subscription } from '../Subscription';
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interface AnimationFrameProvider {
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schedule(callback: FrameRequestCallback): Subscription;
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requestAnimationFrame: typeof requestAnimationFrame;
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cancelAnimationFrame: typeof cancelAnimationFrame;
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delegate:
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| {
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requestAnimationFrame: typeof requestAnimationFrame;
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cancelAnimationFrame: typeof cancelAnimationFrame;
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}
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| undefined;
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}
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export const animationFrameProvider: AnimationFrameProvider = {
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// When accessing the delegate, use the variable rather than `this` so that
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// the functions can be called without being bound to the provider.
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schedule(callback) {
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let request = requestAnimationFrame;
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let cancel: typeof cancelAnimationFrame | undefined = cancelAnimationFrame;
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const { delegate } = animationFrameProvider;
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if (delegate) {
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request = delegate.requestAnimationFrame;
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cancel = delegate.cancelAnimationFrame;
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}
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const handle = request((timestamp) => {
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// Clear the cancel function. The request has been fulfilled, so
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// attempting to cancel the request upon unsubscription would be
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// pointless.
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cancel = undefined;
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callback(timestamp);
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});
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return new Subscription(() => cancel?.(handle));
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},
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requestAnimationFrame(...args) {
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const { delegate } = animationFrameProvider;
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return (delegate?.requestAnimationFrame || requestAnimationFrame)(...args);
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},
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cancelAnimationFrame(...args) {
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const { delegate } = animationFrameProvider;
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return (delegate?.cancelAnimationFrame || cancelAnimationFrame)(...args);
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},
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delegate: undefined,
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};
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