react-native/Libraries/Pressability/HoverState.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 * @format
 */

'use strict';

import Platform from '../Utilities/Platform';

let isEnabled = false;

if (Platform.OS === 'web') {
  const canUseDOM = Boolean(
    typeof window !== 'undefined' &&
      window.document &&
      window.document.createElement,
  );

  if (canUseDOM) {
    /**
     * Web browsers emulate mouse events (and hover states) after touch events.
     * This code infers when the currently-in-use modality supports hover
     * (including for multi-modality devices) and considers "hover" to be enabled
     * if a mouse movement occurs more than 1 second after the last touch event.
     * This threshold is long enough to account for longer delays between the
     * browser firing touch and mouse events on low-powered devices.
     */
    const HOVER_THRESHOLD_MS = 1000;
    let lastTouchTimestamp = 0;

    const enableHover = () => {
      if (isEnabled || Date.now() - lastTouchTimestamp < HOVER_THRESHOLD_MS) {
        return;
      }
      isEnabled = true;
    };

    const disableHover = () => {
      lastTouchTimestamp = Date.now();
      if (isEnabled) {
        isEnabled = false;
      }
    };

    document.addEventListener('touchstart', disableHover, true);
    document.addEventListener('touchmove', disableHover, true);
    document.addEventListener('mousemove', enableHover, true);
  }
}

export function isHoverEnabled(): boolean {
  return isEnabled;
}