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// Copyright 2007 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 Utility class that monitors viewport size changes.
*
* @author attila@google.com (Attila Bodis)
* @see ../demos/viewportsizemonitor.html
*/
goog.provide('goog.dom.ViewportSizeMonitor');
goog.require('goog.dom');
goog.require('goog.events');
goog.require('goog.events.EventTarget');
goog.require('goog.events.EventType');
goog.require('goog.math.Size');
goog.require('goog.userAgent');
/**
* This class can be used to monitor changes in the viewport size. Instances
* dispatch a {@link goog.events.EventType.RESIZE} event when the viewport size
* changes. Handlers can call {@link goog.dom.ViewportSizeMonitor#getSize} to
* get the new viewport size.
*
* Use this class if you want to execute resize/reflow logic each time the
* user resizes the browser window. This class is guaranteed to only dispatch
* {@code RESIZE} events when the pixel dimensions of the viewport change.
* (Internet Explorer fires resize events if any element on the page is resized,
* even if the viewport dimensions are unchanged, which can lead to infinite
* resize loops.)
*
* Example usage:
* <pre>
* var vsm = new goog.dom.ViewportSizeMonitor();
* goog.events.listen(vsm, goog.events.EventType.RESIZE, function(e) {
* alert('Viewport size changed to ' + vsm.getSize());
* });
* </pre>
*
* Manually verified on IE6, IE7, FF2, Opera 9, and WebKit. {@code getSize}
* doesn't always return the correct viewport height on Safari 2.0.4.
*
* @param {Window=} opt_window The window to monitor; defaults to the window in
* which this code is executing.
* @constructor
* @extends {goog.events.EventTarget}
*/
goog.dom.ViewportSizeMonitor = function(opt_window) {
goog.events.EventTarget.call(this);
// Default the window to the current window if unspecified.
this.window_ = opt_window || window;
// Listen for window resize events.
this.listenerKey_ = goog.events.listen(this.window_,
goog.events.EventType.RESIZE, this.handleResize_, false, this);
// Set the initial size.
this.size_ = goog.dom.getViewportSize(this.window_);
if (this.isPollingRequired_()) {
this.windowSizePollInterval_ = window.setInterval(
goog.bind(this.checkForSizeChange_, this),
goog.dom.ViewportSizeMonitor.WINDOW_SIZE_POLL_RATE);
}
};
goog.inherits(goog.dom.ViewportSizeMonitor, goog.events.EventTarget);
/**
* Returns a viewport size monitor for the given window. A new one is created
* if it doesn't exist already. This prevents the unnecessary creation of
* multiple spooling monitors for a window.
* @param {Window=} opt_window The window to monitor; defaults to the window in
* which this code is executing.
* @return {goog.dom.ViewportSizeMonitor} Monitor for the given window.
*/
goog.dom.ViewportSizeMonitor.getInstanceForWindow = function(opt_window) {
var currentWindow = opt_window || window;
var uid = goog.getUid(currentWindow);
return goog.dom.ViewportSizeMonitor.windowInstanceMap_[uid] =
goog.dom.ViewportSizeMonitor.windowInstanceMap_[uid] ||
new goog.dom.ViewportSizeMonitor(currentWindow);
};
/**
* Removes and disposes a viewport size monitor for the given window if one
* exists.
* @param {Window=} opt_window The window whose monitor should be removed;
* defaults to the window in which this code is executing.
*/
goog.dom.ViewportSizeMonitor.removeInstanceForWindow = function(opt_window) {
var uid = goog.getUid(opt_window || window);
goog.dispose(goog.dom.ViewportSizeMonitor.windowInstanceMap_[uid]);
delete goog.dom.ViewportSizeMonitor.windowInstanceMap_[uid];
};
/**
* Map of window hash code to viewport size monitor for that window, if
* created.
* @type {Object.<number,goog.dom.ViewportSizeMonitor>}
* @private
*/
goog.dom.ViewportSizeMonitor.windowInstanceMap_ = {};
/**
* Rate in milliseconds at which to poll the window size on browsers that
* need polling.
* @type {number}
*/
goog.dom.ViewportSizeMonitor.WINDOW_SIZE_POLL_RATE = 500;
/**
* Event listener key for window the window resize handler, as returned by
* {@link goog.events.listen}.
* @type {?number}
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.listenerKey_ = null;
/**
* The window to monitor. Defaults to the window in which the code is running.
* @type {Window}
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.window_ = null;
/**
* The most recently recorded size of the viewport, in pixels.
* @type {goog.math.Size?}
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.size_ = null;
/**
* Identifier for the interval used for polling the window size on Windows
* Safari.
* @type {?number}
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.windowSizePollInterval_ = null;
/**
* Checks if polling is required for this user agent. Opera only requires
* polling when the page is loaded within an IFRAME.
* @return {boolean} Whether polling is required.
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.isPollingRequired_ = function() {
return goog.userAgent.WEBKIT && goog.userAgent.WINDOWS ||
goog.userAgent.OPERA && this.window_.self != this.window_.top;
};
/**
* Returns the most recently recorded size of the viewport, in pixels. May
* return null if no window resize event has been handled yet.
* @return {goog.math.Size} The viewport dimensions, in pixels.
*/
goog.dom.ViewportSizeMonitor.prototype.getSize = function() {
// Return a clone instead of the original to preserve encapsulation.
return this.size_ ? this.size_.clone() : null;
};
/** @override */
goog.dom.ViewportSizeMonitor.prototype.disposeInternal = function() {
goog.dom.ViewportSizeMonitor.superClass_.disposeInternal.call(this);
if (this.listenerKey_) {
goog.events.unlistenByKey(this.listenerKey_);
this.listenerKey_ = null;
}
if (this.windowSizePollInterval_) {
window.clearInterval(this.windowSizePollInterval_);
this.windowSizePollInterval_ = null;
}
this.window_ = null;
this.size_ = null;
};
/**
* Handles window resize events by measuring the dimensions of the
* viewport and dispatching a {@link goog.events.EventType.RESIZE} event if the
* current dimensions are different from the previous ones.
* @param {goog.events.Event} event The window resize event to handle.
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.handleResize_ = function(event) {
this.checkForSizeChange_();
};
/**
* Measures the dimensions of the viewport and dispatches a
* {@link goog.events.EventType.RESIZE} event if the current dimensions are
* different from the previous ones.
* @private
*/
goog.dom.ViewportSizeMonitor.prototype.checkForSizeChange_ = function() {
var size = goog.dom.getViewportSize(this.window_);
if (!goog.math.Size.equals(size, this.size_)) {
this.size_ = size;
this.dispatchEvent(goog.events.EventType.RESIZE);
}
};
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