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