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// Copyright 2010 The Closure Library Authors. 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.
/**
* @fileoverview Browser capability checks for the events package.
*
*/
goog.provide('goog.events.BrowserFeature');
goog.require('goog.userAgent');
goog.scope(function() {
/**
* Enum of browser capabilities.
* @enum {boolean}
*/
goog.events.BrowserFeature = {
/**
* Whether the button attribute of the event is W3C compliant. False in
* Internet Explorer prior to version 9; document-version dependent.
*/
HAS_W3C_BUTTON:
!goog.userAgent.IE || goog.userAgent.isDocumentModeOrHigher(9),
/**
* Whether the browser supports full W3C event model.
*/
HAS_W3C_EVENT_SUPPORT:
!goog.userAgent.IE || goog.userAgent.isDocumentModeOrHigher(9),
/**
* To prevent default in IE7-8 for certain keydown events we need set the
* keyCode to -1.
*/
SET_KEY_CODE_TO_PREVENT_DEFAULT:
goog.userAgent.IE && !goog.userAgent.isVersionOrHigher('9'),
/**
* Whether the {@code navigator.onLine} property is supported.
*/
HAS_NAVIGATOR_ONLINE_PROPERTY:
!goog.userAgent.WEBKIT || goog.userAgent.isVersionOrHigher('528'),
/**
* Whether HTML5 network online/offline events are supported.
*/
HAS_HTML5_NETWORK_EVENT_SUPPORT:
goog.userAgent.GECKO && goog.userAgent.isVersionOrHigher('1.9b') ||
goog.userAgent.IE && goog.userAgent.isVersionOrHigher('8') ||
goog.userAgent.OPERA && goog.userAgent.isVersionOrHigher('9.5') ||
goog.userAgent.WEBKIT && goog.userAgent.isVersionOrHigher('528'),
/**
* Whether HTML5 network events fire on document.body, or otherwise the
* window.
*/
HTML5_NETWORK_EVENTS_FIRE_ON_BODY:
goog.userAgent.GECKO && !goog.userAgent.isVersionOrHigher('8') ||
goog.userAgent.IE && !goog.userAgent.isVersionOrHigher('9'),
/**
* Whether touch is enabled in the browser.
*/
TOUCH_ENABLED:
('ontouchstart' in goog.global ||
!!(goog.global['document'] && document.documentElement &&
'ontouchstart' in document.documentElement) ||
// IE10 uses non-standard touch events, so it has a different check.
!!(goog.global['navigator'] &&
goog.global['navigator']['msMaxTouchPoints'])),
/**
* Whether addEventListener supports {passive: true}.
* https://developers.google.com/web/updates/2016/06/passive-event-listeners
*/
PASSIVE_EVENTS: purify(function() {
// If we're in a web worker or other custom environment, we can't tell.
if (!goog.global.addEventListener || !Object.defineProperty) { // IE 8
return false;
}
var passive = false;
var options = Object.defineProperty({}, 'passive', {
get: function() {
passive = true;
}
});
goog.global.addEventListener('test', goog.nullFunction, options);
goog.global.removeEventListener('test', goog.nullFunction, options);
return passive;
})
};
/**
* Tricks Closure Compiler into believing that a function is pure. The compiler
* assumes that any `valueOf` function is pure, without analyzing its contents.
*
* @param {function(): T} fn
* @return {T}
* @template T
*/
function purify(fn) {
return ({valueOf: fn}).valueOf();
}
}); // goog.scope
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