react-native-worklets/lib/module/runLoop/uiRuntime/requestAnimationFrame.js

The React Native multithreading library

'use strict';

import { callMicrotasks } from '../../threads';
export function setupRequestAnimationFrame() {
  'worklet';

  const nativeRequestAnimationFrame = globalThis.requestAnimationFrame;
  let queuedCallbacks = [];
  let queuedCallbacksBegin = 0;
  let queuedCallbacksEnd = 0;
  let flushedCallbacks = queuedCallbacks;
  let flushedCallbacksBegin = 0;
  let flushedCallbacksEnd = 0;
  let flushRequested = false;
  globalThis.__flushAnimationFrame = timestamp => {
    flushedCallbacks = queuedCallbacks;
    queuedCallbacks = [];
    flushedCallbacksBegin = queuedCallbacksBegin;
    flushedCallbacksEnd = queuedCallbacksEnd;
    queuedCallbacksBegin = queuedCallbacksEnd;
    for (const callback of flushedCallbacks) {
      callback(timestamp);
    }
    flushedCallbacksBegin = flushedCallbacksEnd;
    callMicrotasks();
  };
  globalThis.requestAnimationFrame = callback => {
    const handle = queuedCallbacksEnd++;
    queuedCallbacks.push(callback);
    if (!flushRequested) {
      flushRequested = true;
      nativeRequestAnimationFrame(timestamp => {
        flushRequested = false;
        globalThis.__frameTimestamp = timestamp;
        globalThis.__flushAnimationFrame(timestamp);
        globalThis.__frameTimestamp = undefined;
      });
    }
    return handle;
  };
  globalThis.cancelAnimationFrame = handle => {
    if (handle < flushedCallbacksBegin || handle >= queuedCallbacksEnd) {
      return;
    }
    if (handle < flushedCallbacksEnd) {
      flushedCallbacks[handle - flushedCallbacksBegin] = () => {};
    } else {
      queuedCallbacks[handle - queuedCallbacksBegin] = () => {};
    }
  };
}
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