Function initMoveObserver

packages/rrweb/src/record/observer.ts:106–190

({
  mousemoveCb,
  sampling,
  doc,
  mirror,
}: observerParam)

}

function initMoveObserver({
  mousemoveCb,
  sampling,
  doc,
  mirror,
}: observerParam): listenerHandler {
  if (sampling.mousemove === false) {
    return () => {
      //
    };
  }

  const threshold =
    typeof sampling.mousemove === 'number' ? sampling.mousemove : 50;
  const callbackThreshold =
    typeof sampling.mousemoveCallback === 'number'
      ? sampling.mousemoveCallback
      : 500;

  let positions: mousePosition[] = [];
  let timeBaseline: number | null;
  const wrappedCb = throttle(
    callbackWrapper(
      (
        source:
          | IncrementalSource.MouseMove
          | IncrementalSource.TouchMove
          | IncrementalSource.Drag,
      ) => {
        const totalOffset = Date.now() - timeBaseline!;
        mousemoveCb(
          positions.map((p) => {
            p.timeOffset -= totalOffset;
            return p;
          }),
          source,
        );
        positions = [];
        timeBaseline = null;
      },
    ),
    callbackThreshold,
  );
  const updatePosition = callbackWrapper(
    throttle<MouseEvent | TouchEvent | DragEvent>(
      callbackWrapper((evt) => {
        const target = getEventTarget(evt);
        // 'legacy' here as we could switch to https://developer.mozilla.org/en-US/docs/Web/API/Element/pointermove_event
        const { clientX, clientY } = legacy_isTouchEvent(evt)
          ? evt.changedTouches[0]
          : evt;
        if (!timeBaseline) {
          timeBaseline = nowTimestamp();
        }
        positions.push({
          x: clientX,
          y: clientY,
          id: mirror.getId(target as Node),