@smui/common/src/dom/events.ts

Svelte Material UI - Common

/**
 * @license
 * Copyright 2019 Google Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/**
 * Determine whether the current browser supports passive event listeners, and
 * if so, use them.
 */
export function applyPassive(
  globalObj: Window = window,
): boolean | EventListenerOptions {
  return supportsPassiveOption(globalObj)
    ? ({ passive: true } as AddEventListenerOptions)
    : false;
}

function supportsPassiveOption(globalObj: Window = window): boolean {
  // See
  // https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener
  let passiveSupported = false;

  try {
    const options = {
      // This function will be called when the browser
      // attempts to access the passive property.
      get passive() {
        passiveSupported = true;
        return false;
      },
    };

    const handler = () => {};
    globalObj.document.addEventListener('test', handler, options);
    globalObj.document.removeEventListener(
      'test',
      handler,
      options as EventListenerOptions,
    );
  } catch (err) {
    passiveSupported = false;
  }

  return passiveSupported;
}