119 lines
3.1 KiB
JavaScript
Executable File
119 lines
3.1 KiB
JavaScript
Executable File
/**
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* @license
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* Copyright The Closure Library Authors.
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @fileoverview Browser capability checks for the events package.
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*/
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goog.module('goog.events.BrowserFeature');
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goog.module.declareLegacyNamespace();
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/**
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* Tricks Closure Compiler into believing that a function is pure. The compiler
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* assumes that any `valueOf` function is pure, without analyzing its contents.
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*
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* @param {function(): T} fn
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* @return {T}
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* @template T
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*/
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const purify = (fn) => {
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return ({valueOf: fn}).valueOf();
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};
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/**
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* Enum of browser capabilities.
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* @enum {boolean}
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*/
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exports = {
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/**
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* Whether the button attribute of the event is W3C compliant. False in
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* Internet Explorer prior to version 9; document-version dependent.
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*/
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HAS_W3C_BUTTON: true,
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/**
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* Whether the browser supports full W3C event model.
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*/
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HAS_W3C_EVENT_SUPPORT: true,
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/**
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* To prevent default in IE7-8 for certain keydown events we need set the
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* keyCode to -1.
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*/
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SET_KEY_CODE_TO_PREVENT_DEFAULT: false,
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/**
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* Whether the `navigator.onLine` property is supported.
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*/
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HAS_NAVIGATOR_ONLINE_PROPERTY: true,
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/**
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* Whether HTML5 network online/offline events are supported.
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*/
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HAS_HTML5_NETWORK_EVENT_SUPPORT: true,
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/**
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* Whether HTML5 network events fire on document.body, or otherwise the
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* window.
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*/
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HTML5_NETWORK_EVENTS_FIRE_ON_BODY: false,
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/**
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* Whether touch is enabled in the browser.
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*/
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TOUCH_ENABLED:
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('ontouchstart' in goog.global ||
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!!(goog.global['document'] && document.documentElement &&
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'ontouchstart' in document.documentElement) ||
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// IE10 uses non-standard touch events, so it has a different check.
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!!(goog.global['navigator'] &&
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(goog.global['navigator']['maxTouchPoints'] ||
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goog.global['navigator']['msMaxTouchPoints']))),
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/**
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* Whether addEventListener supports W3C standard pointer events.
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* http://www.w3.org/TR/pointerevents/
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*/
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POINTER_EVENTS: ('PointerEvent' in goog.global),
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/**
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* Whether addEventListener supports MSPointer events (only used in IE10).
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* http://msdn.microsoft.com/en-us/library/ie/hh772103(v=vs.85).aspx
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* http://msdn.microsoft.com/library/hh673557(v=vs.85).aspx
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*/
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MSPOINTER_EVENTS:
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('MSPointerEvent' in goog.global &&
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!!(goog.global['navigator'] &&
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goog.global['navigator']['msPointerEnabled'])),
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/**
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* Whether addEventListener supports {passive: true}.
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* https://developers.google.com/web/updates/2016/06/passive-event-listeners
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*/
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PASSIVE_EVENTS: purify(function() {
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// If we're in a web worker or other custom environment, we can't tell.
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if (!goog.global.addEventListener || !Object.defineProperty) { // IE 8
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return false;
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}
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var passive = false;
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var options = Object.defineProperty({}, 'passive', {
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get: function() {
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passive = true;
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}
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});
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try {
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goog.global.addEventListener('test', goog.nullFunction, options);
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goog.global.removeEventListener('test', goog.nullFunction, options);
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} catch (e) {
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}
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return passive;
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})
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};
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