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// Copyright 2014 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 This event wrapper will dispatch an event when the user uses
* the wheel on an element. The event provides details of the unit type (pixel /
* line / page) and deltas in those units in up to 3 dimensions. Additionally,
* simplified pixel deltas are provided for code that doesn't need to handle the
* different units differently. This is not to be confused with the scroll
* event, where an element in the dom can report that it was scrolled.
*
* This class aims to smooth out inconsistencies between browser platforms with
* regards to wheel events, but we do not cover every possible software/hardware
* combination out there, some of which occasionally produce very large deltas
* in wheel events, especially when the device supports acceleration.
*
* Relevant standard:
* http://www.w3.org/TR/2014/WD-DOM-Level-3-Events-20140925/#interface-WheelEvent
*
* Clients of this code should be aware that some input devices only fire a few
* discrete events (such as a mouse wheel without acceleration) whereas some can
* generate a large number of events for a single interaction (such as a
* touchpad with acceleration). There is no signal in the events to reliably
* distinguish between these.
*
* @author arv@google.com (Erik Arvidsson)
* @see ../demos/wheelhandler.html
*/
goog.provide('goog.events.WheelHandler');
goog.require('goog.dom');
goog.require('goog.events');
goog.require('goog.events.EventTarget');
goog.require('goog.events.WheelEvent');
goog.require('goog.style');
goog.require('goog.userAgent');
goog.require('goog.userAgent.product');
goog.require('goog.userAgent.product.isVersion');
/**
* This event handler allows you to catch wheel events in a consistent manner.
* @param {!Element|!Document} element The element to listen to the wheel event
* on.
* @param {boolean=} opt_capture Whether to handle the wheel event in capture
* phase.
* @constructor
* @extends {goog.events.EventTarget}
*/
goog.events.WheelHandler = function(element, opt_capture) {
goog.events.WheelHandler.base(this, 'constructor');
/**
* This is the element that we will listen to the real wheel events on.
* @private {!Element|!Document}
*/
this.element_ = element;
var rtlElement = goog.dom.isElement(this.element_) ?
/** @type {!Element} */ (this.element_) :
/** @type {!Document} */ (this.element_).body;
/**
* True if the element exists and is RTL, false otherwise.
* @private {boolean}
*/
this.isRtl_ = !!rtlElement && goog.style.isRightToLeft(rtlElement);
/**
* The key returned from the goog.events.listen.
* @private {goog.events.Key}
*/
this.listenKey_ = goog.events.listen(
this.element_, goog.events.WheelHandler.getDomEventType(), this,
opt_capture);
};
goog.inherits(goog.events.WheelHandler, goog.events.EventTarget);
/**
* Returns the dom event type.
* @return {string} The dom event type.
*/
goog.events.WheelHandler.getDomEventType = function() {
// Prefer to use wheel events whenever supported.
if (goog.userAgent.GECKO && goog.userAgent.isVersionOrHigher(17) ||
goog.userAgent.IE && goog.userAgent.isVersionOrHigher(9) ||
goog.userAgent.product.CHROME && goog.userAgent.product.isVersion(31)) {
return 'wheel';
}
// Legacy events. Still the best we have on Opera and Safari.
return goog.userAgent.GECKO ? 'DOMMouseScroll' : 'mousewheel';
};
/**
* Handles the events on the element.
* @param {!goog.events.BrowserEvent} e The underlying browser event.
*/
goog.events.WheelHandler.prototype.handleEvent = function(e) {
var deltaMode = goog.events.WheelEvent.DeltaMode.PIXEL;
var deltaX = 0;
var deltaY = 0;
var deltaZ = 0;
var be = e.getBrowserEvent();
if (be.type == 'wheel') {
deltaMode = be.deltaMode;
deltaX = be.deltaX;
deltaY = be.deltaY;
deltaZ = be.deltaZ;
} else if (be.type == 'mousewheel') {
// Assume that these are still comparable to pixels. This may not be true
// for all old browsers.
if (goog.isDef(be.wheelDeltaX)) {
deltaX = -be.wheelDeltaX;
deltaY = -be.wheelDeltaY;
} else {
deltaY = -be.wheelDelta;
}
} else { // Historical Gecko
// Gecko returns multiple of 3 (representing the number of lines)
deltaMode = goog.events.WheelEvent.DeltaMode.LINE;
// Firefox 3.1 adds an axis field to the event to indicate axis.
if (goog.isDef(be.axis) && be.axis === be.HORIZONTAL_AXIS) {
deltaX = be.detail;
} else {
deltaY = be.detail;
}
}
// For horizontal deltas we need to flip the value for RTL grids.
if (this.isRtl_) {
deltaX = -deltaX;
}
var newEvent =
new goog.events.WheelEvent(be, deltaMode, deltaX, deltaY, deltaZ);
this.dispatchEvent(newEvent);
};
/** @override */
goog.events.WheelHandler.prototype.disposeInternal = function() {
goog.events.WheelHandler.superClass_.disposeInternal.call(this);
goog.events.unlistenByKey(this.listenKey_);
this.listenKey_ = null;
};
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