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Andrew Clark
8c67bbf183
* [scheduler] Deadline object -> shouldYield Instead of using a requestIdleCallback-style deadline object, expose a method Scheduler.shouldYield that returns true if there's a higher priority event in the queue. * Nits
57 lines
1.7 KiB
JavaScript
57 lines
1.7 KiB
JavaScript
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow
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*/
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const hasNativePerformanceNow =
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typeof performance === 'object' && typeof performance.now === 'function';
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const now = hasNativePerformanceNow
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? () => performance.now()
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: () => Date.now();
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let scheduledCallback: (() => mixed) | null = null;
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let frameDeadline: number = 0;
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function setTimeoutCallback() {
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// TODO (bvaughn) Hard-coded 5ms unblocks initial async testing.
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// React API probably changing to boolean rather than time remaining.
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// Longer-term plan is to rewrite this using shared memory,
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// And just return the value of the bit as the boolean.
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frameDeadline = now() + 5;
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const callback = scheduledCallback;
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scheduledCallback = null;
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if (callback !== null) {
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callback();
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}
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}
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// RN has a poor polyfill for requestIdleCallback so we aren't using it.
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// This implementation is only intended for short-term use anyway.
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// We also don't implement cancel functionality b'c Fiber doesn't currently need it.
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function scheduleDeferredCallback(
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callback: () => mixed,
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options?: {timeout: number},
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): number {
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// We assume only one callback is scheduled at a time b'c that's how Fiber works.
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scheduledCallback = callback;
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const timeoutId = setTimeout(setTimeoutCallback, 1);
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return (timeoutId: any); // Timeouts are always numbers on RN
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}
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function cancelDeferredCallback(callbackID: number) {
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scheduledCallback = null;
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clearTimeout((callbackID: any)); // Timeouts are always numbers on RN
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}
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function shouldYield() {
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return frameDeadline <= now();
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}
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export {now, scheduleDeferredCallback, cancelDeferredCallback, shouldYield};
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