util.js

/**
 * @license
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Stores result from supportsCssVariables to avoid redundant processing to detect CSS custom variable support.
 * @private {boolean|undefined}
 */
let supportsCssVariables_;

/**
 * Stores result from applyPassive to avoid redundant processing to detect passive event listener support.
 * @private {boolean|undefined}
 */
let supportsPassive_;

/**
 * @param {!Window} windowObj
 * @return {boolean}
 */
function detectEdgePseudoVarBug(windowObj) {
  // Detect versions of Edge with buggy var() support
  // See: https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/11495448/
  const document = windowObj.document;
  const node = document.createElement('div');
  node.className = 'mdc-ripple-surface--test-edge-var-bug';
  document.body.appendChild(node);

  // The bug exists if ::before style ends up propagating to the parent element.
  // Additionally, getComputedStyle returns null in iframes with display: "none" in Firefox,
  // but Firefox is known to support CSS custom properties correctly.
  // See: https://bugzilla.mozilla.org/show_bug.cgi?id=548397
  const computedStyle = windowObj.getComputedStyle(node);
  const hasPseudoVarBug = computedStyle !== null && computedStyle.borderTopStyle === 'solid';
  node.remove();
  return hasPseudoVarBug;
}

/**
 * @param {!Window} windowObj
 * @param {boolean=} forceRefresh
 * @return {boolean|undefined}
 */

function supportsCssVariables(windowObj, forceRefresh = false) {
  if (typeof supportsCssVariables_ === 'boolean' && !forceRefresh) {
    return supportsCssVariables_;
  }

  const supportsFunctionPresent = windowObj.CSS && typeof windowObj.CSS.supports === 'function';
  if (!supportsFunctionPresent) {
    return;
  }

  const explicitlySupportsCssVars = windowObj.CSS.supports('--css-vars', 'yes');
  // See: https://bugs.webkit.org/show_bug.cgi?id=154669
  // See: README section on Safari
  const weAreFeatureDetectingSafari10plus = (
    windowObj.CSS.supports('(--css-vars: yes)') &&
    windowObj.CSS.supports('color', '#00000000')
  );

  if (explicitlySupportsCssVars || weAreFeatureDetectingSafari10plus) {
    supportsCssVariables_ = !detectEdgePseudoVarBug(windowObj);
  } else {
    supportsCssVariables_ = false;
  }
  return supportsCssVariables_;
}

//
/**
 * Determine whether the current browser supports passive event listeners, and if so, use them.
 * @param {!Window=} globalObj
 * @param {boolean=} forceRefresh
 * @return {boolean|{passive: boolean}}
 */
function applyPassive(globalObj = window, forceRefresh = false) {
  if (supportsPassive_ === undefined || forceRefresh) {
    let isSupported = false;
    try {
      globalObj.document.addEventListener('test', null, {get passive() {
        isSupported = true;
      }});
    } catch (e) { }

    supportsPassive_ = isSupported;
  }

  return supportsPassive_ ? {passive: true} : false;
}

/**
 * @param {!Object} HTMLElementPrototype
 * @return {!Array<string>}
 */
function getMatchesProperty(HTMLElementPrototype) {
  return [
    'webkitMatchesSelector', 'msMatchesSelector', 'matches',
  ].filter((p) => p in HTMLElementPrototype).pop();
}

/**
 * @param {!Event} ev
 * @param {!{x: number, y: number}} pageOffset
 * @param {!ClientRect} clientRect
 * @return {!{x: number, y: number}}
 */
function getNormalizedEventCoords(ev, pageOffset, clientRect) {
  const {x, y} = pageOffset;
  const documentX = x + clientRect.left;
  const documentY = y + clientRect.top;

  let normalizedX;
  let normalizedY;
  // Determine touch point relative to the ripple container.
  if (ev.type === 'touchstart') {
    normalizedX = ev.changedTouches[0].pageX - documentX;
    normalizedY = ev.changedTouches[0].pageY - documentY;
  } else {
    normalizedX = ev.pageX - documentX;
    normalizedY = ev.pageY - documentY;
  }

  return {x: normalizedX, y: normalizedY};
}

export {supportsCssVariables, applyPassive, getMatchesProperty, getNormalizedEventCoords};