586 lines
17 KiB
JavaScript
586 lines
17 KiB
JavaScript
// Copyright 2008 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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* @fileoverview Class for making an element detach and float to remain
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* visible when otherwise it would have scrolled up out of view.
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* <p>
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* The element remains at its normal position in the layout until scrolling
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* would cause its top edge to scroll off the top of the viewport; at that
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* point, the element is replaced with an invisible placeholder (to keep the
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* layout stable), reattached in the dom tree to a new parent (the body element
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* by default), and set to "fixed" positioning (emulated for IE < 7) so that it
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* remains at its original X position while staying fixed to the top of the
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* viewport in the Y dimension.
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* <p>
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* When the window is scrolled up past the point where the original element
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* would be fully visible again, the element snaps back into place, replacing
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* the placeholder.
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*
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* @see ../demos/scrollfloater.html
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*
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* Adapted from http://go/elementfloater.js
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*/
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goog.provide('goog.ui.ScrollFloater');
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goog.provide('goog.ui.ScrollFloater.EventType');
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goog.require('goog.array');
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goog.require('goog.dom');
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goog.require('goog.dom.classes');
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goog.require('goog.events.EventType');
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goog.require('goog.style');
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goog.require('goog.ui.Component');
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goog.require('goog.userAgent');
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/**
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* Creates a ScrollFloater; see file overview for details.
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*
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* @param {Element=} opt_parentElement Where to attach the element when it's
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* floating. Default is the document body. If the floating element
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* contains form inputs, it will be necessary to attach it to the
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* corresponding form element, or to an element in the DOM subtree under
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* the form element.
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* @param {goog.dom.DomHelper=} opt_domHelper Optional DOM helper.
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* @constructor
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* @extends {goog.ui.Component}
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*/
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goog.ui.ScrollFloater = function(opt_parentElement, opt_domHelper) {
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// If a parentElement is supplied, we want to use its domHelper,
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// ignoring the caller-supplied one.
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var domHelper = opt_parentElement ?
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goog.dom.getDomHelper(opt_parentElement) : opt_domHelper;
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goog.base(this, domHelper);
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/**
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* The element to which the scroll-floated element will be attached
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* when it is floating.
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* @type {Element}
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* @private
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*/
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this.parentElement_ =
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opt_parentElement || this.getDomHelper().getDocument().body;
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/**
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* The original styles applied to the element before it began floating;
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* used to restore those styles when the element stops floating.
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* @type {Object}
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* @private
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*/
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this.originalStyles_ = {};
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/**
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* A vertical offset from which to start floating the element. This is
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* useful in cases when there are 'position:fixed' elements covering up
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* part of the viewport.
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* @type {number}
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* @private
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*/
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this.viewportTopOffset_ = 0;
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/**
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* An element used to define the boundaries within which the floater can
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* be positioned.
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* @type {Element}
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* @private
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*/
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this.containerElement_ = null;
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/**
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* Container element's bounding rectangle.
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* @type {goog.math.Rect}
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* @private
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*/
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this.containerBounds_ = null;
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/**
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* Element's original bounding rectangle.
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* @type {goog.math.Rect}
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* @private
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*/
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this.originalBounds_ = null;
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/**
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* The placeholder element dropped in to hold the layout for
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* the floated element.
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* @type {Element}
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* @private
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*/
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this.placeholder_ = null;
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/**
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* Whether scrolling is enabled for this element; true by default.
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* The {@link #setScrollingEnabled} method can be used to change this value.
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* @type {boolean}
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* @private
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*/
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this.scrollingEnabled_ = true;
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/**
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* A flag indicating whether this instance is currently pinned to the bottom
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* of the container element.
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* @type {boolean}
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* @private
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*/
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this.pinned_ = false;
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/**
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* A flag indicating whether this instance is currently floating.
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* @type {boolean}
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* @private
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*/
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this.floating_ = false;
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};
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goog.inherits(goog.ui.ScrollFloater, goog.ui.Component);
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/**
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* Events dispatched by this component.
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* @enum {string}
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*/
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goog.ui.ScrollFloater.EventType = {
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/**
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* Dispatched when the component starts floating. The event is
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* cancellable.
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*/
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FLOAT: 'float',
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/**
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* Dispatched when the component returns to its original state.
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* The event is cancellable.
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*/
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DOCK: 'dock',
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/**
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* Dispatched when the component gets pinned to the bottom of the
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* container element. This event is cancellable.
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*/
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PIN: 'pin'
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};
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/**
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* The style properties which are stored when we float an element, so they
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* can be restored when it 'docks' again.
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* @type {Array.<string>}
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* @private
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*/
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goog.ui.ScrollFloater.STORED_STYLE_PROPS_ = [
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'position', 'top', 'left', 'width', 'cssFloat'];
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/**
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* The style elements managed for the placeholder object.
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* @type {Array.<string>}
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* @private
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*/
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goog.ui.ScrollFloater.PLACEHOLDER_STYLE_PROPS_ = [
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'position', 'top', 'left', 'display', 'cssFloat',
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'marginTop', 'marginLeft', 'marginRight', 'marginBottom'];
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/**
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* The class name applied to the floating element.
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* @type {string}
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* @private
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*/
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goog.ui.ScrollFloater.CSS_CLASS_ = goog.getCssName('goog-scrollfloater');
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/**
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* Delegates dom creation to superclass, then constructs and
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* decorates required DOM elements.
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* @override
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*/
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goog.ui.ScrollFloater.prototype.createDom = function() {
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goog.base(this, 'createDom');
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this.decorateInternal(this.getElement());
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};
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/**
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* Decorates the floated element with the standard ScrollFloater CSS class.
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* @param {Element} element The element to decorate.
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* @override
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*/
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goog.ui.ScrollFloater.prototype.decorateInternal = function(element) {
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goog.base(this, 'decorateInternal', element);
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goog.dom.classes.add(element, goog.ui.ScrollFloater.CSS_CLASS_);
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};
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/** @override */
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goog.ui.ScrollFloater.prototype.enterDocument = function() {
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goog.base(this, 'enterDocument');
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if (!this.placeholder_) {
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this.placeholder_ =
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this.getDomHelper().createDom('div', {'style': 'visibility:hidden'});
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}
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this.update();
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this.setScrollingEnabled(this.scrollingEnabled_);
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var win = this.getDomHelper().getWindow();
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this.getHandler().
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listen(win, goog.events.EventType.SCROLL, this.handleScroll_).
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listen(win, goog.events.EventType.RESIZE, this.update);
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};
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/**
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* Forces the component to update the cached element positions and sizes and
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* to re-evaluate whether the the component should be docked, floated or
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* pinned.
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*/
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goog.ui.ScrollFloater.prototype.update = function() {
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if (!this.isInDocument()) {
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return;
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}
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// These values can only be calculated when the element is in its original
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// state, so we dock first, and then re-evaluate.
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this.dock_();
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if (this.containerElement_) {
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this.containerBounds_ = goog.style.getBounds(this.containerElement_);
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}
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this.originalBounds_ = goog.style.getBounds(this.getElement());
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this.handleScroll_();
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};
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/** @override */
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goog.ui.ScrollFloater.prototype.disposeInternal = function() {
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goog.base(this, 'disposeInternal');
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this.placeholder_ = null;
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};
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/**
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* Sets whether the element should be floated if it scrolls out of view.
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* @param {boolean} enable Whether floating is enabled for this element.
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*/
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goog.ui.ScrollFloater.prototype.setScrollingEnabled = function(enable) {
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this.scrollingEnabled_ = enable;
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if (enable) {
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this.applyIeBgHack_();
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this.handleScroll_();
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} else {
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this.dock_();
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}
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};
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/**
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* @return {boolean} Whether the component is enabled for scroll-floating.
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*/
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goog.ui.ScrollFloater.prototype.isScrollingEnabled = function() {
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return this.scrollingEnabled_;
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};
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/**
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* @return {boolean} Whether the component is currently scroll-floating.
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*/
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goog.ui.ScrollFloater.prototype.isFloating = function() {
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return this.floating_;
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};
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/**
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* @return {boolean} Whether the component is currently pinned to the bottom
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* of the container.
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*/
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goog.ui.ScrollFloater.prototype.isPinned = function() {
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return this.pinned_;
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};
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/**
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* @param {number} offset A vertical offset from the top of the viewport, from
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* which to start floating the element. Default is 0. This is useful in cases
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* when there are 'position:fixed' elements covering up part of the viewport.
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*/
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goog.ui.ScrollFloater.prototype.setViewportTopOffset = function(offset) {
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this.viewportTopOffset_ = offset;
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this.update();
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};
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/**
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* @param {Element} container An element used to define the boundaries within
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* which the floater can be positioned. If not specified, scrolling the page
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* down far enough may result in the floated element extending past the
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* containing element as it is being scrolled out of the viewport. In some
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* cases, such as a list with a sticky header, this may be undesirable. If
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* the container element is specified and the floated element extends past
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* the bottom of the container, the element will be pinned to the bottom of
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* the container.
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*/
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goog.ui.ScrollFloater.prototype.setContainerElement = function(container) {
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this.containerElement_ = container;
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this.update();
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};
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/**
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* When a scroll event occurs, compares the element's position to the current
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* document scroll position, and stops or starts floating behavior if needed.
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* @param {goog.events.Event=} opt_e The event, which is ignored.
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* @private
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*/
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goog.ui.ScrollFloater.prototype.handleScroll_ = function(opt_e) {
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if (this.scrollingEnabled_) {
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var scrollTop = this.getDomHelper().getDocumentScroll().y;
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if (this.originalBounds_.top - scrollTop >= this.viewportTopOffset_) {
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this.dock_();
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return;
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}
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// If the element extends past the container, we need to pin it instead.
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if (this.containerElement_) {
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var containerBottom = this.containerBounds_.top +
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this.containerBounds_.height;
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var effectiveElementHeight = this.originalBounds_.height +
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this.viewportTopOffset_;
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if (scrollTop > containerBottom - effectiveElementHeight) {
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this.pin_();
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return;
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}
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}
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this.float_();
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}
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};
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/**
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* Pins the element to the bottom of the container, making as much of the
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* element visible as possible without extending past it.
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* @private
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*/
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goog.ui.ScrollFloater.prototype.pin_ = function() {
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if (this.floating_ && !this.dock_()) {
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return;
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}
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// Ignore if the component is pinned or the PIN event is cancelled.
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if (this.pinned_ ||
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!this.dispatchEvent(goog.ui.ScrollFloater.EventType.PIN)) {
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return;
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}
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var elem = this.getElement();
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this.storeOriginalStyles_();
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elem.style.position = 'relative';
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elem.style.top = this.containerBounds_.height - this.originalBounds_.height -
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this.originalBounds_.top + this.containerBounds_.top + 'px';
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this.pinned_ = true;
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};
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/**
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* Begins floating behavior, making the element position:fixed (or IE hacked
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* equivalent) and inserting a placeholder where it used to be to keep the
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* layout from shifting around.
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* @private
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*/
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goog.ui.ScrollFloater.prototype.float_ = function() {
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if (this.pinned_ && !this.dock_()) {
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return;
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}
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// Ignore if the component is floating or the FLOAT event is cancelled.
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if (this.floating_ ||
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!this.dispatchEvent(goog.ui.ScrollFloater.EventType.FLOAT)) {
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return;
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}
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var elem = this.getElement();
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var doc = this.getDomHelper().getDocument();
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// Read properties of element before modifying it.
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var originalLeft_ = goog.style.getPageOffsetLeft(elem);
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var originalWidth_ = goog.style.getContentBoxSize(elem).width;
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this.storeOriginalStyles_();
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goog.style.setSize(this.placeholder_, elem.offsetWidth, elem.offsetHeight);
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// Make element float.
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goog.style.setStyle(elem, {
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'left': originalLeft_ + 'px',
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'width': originalWidth_ + 'px',
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'cssFloat': 'none'
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});
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// If parents are the same, avoid detaching and reattaching elem.
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// This prevents Flash embeds from being reloaded, for example.
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if (elem.parentNode == this.parentElement_) {
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elem.parentNode.insertBefore(this.placeholder_, elem);
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} else {
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elem.parentNode.replaceChild(this.placeholder_, elem);
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this.parentElement_.appendChild(elem);
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}
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// Versions of IE below 7-in-standards-mode don't handle 'position: fixed',
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// so we must emulate it using an IE-specific idiom for JS-based calculated
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// style values.
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if (this.needsIePositionHack_()) {
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elem.style.position = 'absolute';
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elem.style.setExpression('top',
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'document.compatMode=="CSS1Compat"?' +
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'documentElement.scrollTop:document.body.scrollTop');
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} else {
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elem.style.position = 'fixed';
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elem.style.top = this.viewportTopOffset_ + 'px';
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}
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this.floating_ = true;
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};
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/**
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* Stops floating behavior, returning element to its original state.
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* @return {boolean} True if the the element has been docked. False if the
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* element is already docked or the event was cancelled.
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* @private
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*/
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goog.ui.ScrollFloater.prototype.dock_ = function() {
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// Ignore if the component is docked or the DOCK event is cancelled.
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if (!(this.floating_ || this.pinned_) ||
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!this.dispatchEvent(goog.ui.ScrollFloater.EventType.DOCK)) {
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return false;
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}
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var elem = this.getElement();
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if (this.floating_) {
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this.restoreOriginalStyles_();
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if (this.needsIePositionHack_()) {
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elem.style.removeExpression('top');
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}
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// If placeholder_ was inserted and didn't replace elem then elem has
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// the right parent already, no need to replace (which removes elem before
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// inserting it).
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if (this.placeholder_.parentNode == this.parentElement_) {
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this.placeholder_.parentNode.removeChild(this.placeholder_);
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} else {
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this.placeholder_.parentNode.replaceChild(elem, this.placeholder_);
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}
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}
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if (this.pinned_) {
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this.restoreOriginalStyles_();
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}
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this.floating_ = this.pinned_ = false;
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return true;
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};
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/**
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* @private
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*/
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goog.ui.ScrollFloater.prototype.storeOriginalStyles_ = function() {
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var elem = this.getElement();
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this.originalStyles_ = {};
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// Store styles while not floating so we can restore them when the
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// element stops floating.
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goog.array.forEach(goog.ui.ScrollFloater.STORED_STYLE_PROPS_,
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function(property) {
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this.originalStyles_[property] = elem.style[property];
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},
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this);
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// Copy relevant styles to placeholder so it will be layed out the same
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// as the element that's about to be floated.
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goog.array.forEach(goog.ui.ScrollFloater.PLACEHOLDER_STYLE_PROPS_,
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function(property) {
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this.placeholder_.style[property] =
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elem.style[property] ||
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goog.style.getCascadedStyle(elem, property) ||
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goog.style.getComputedStyle(elem, property);
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},
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this);
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};
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/**
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* @private
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*/
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goog.ui.ScrollFloater.prototype.restoreOriginalStyles_ = function() {
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var elem = this.getElement();
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for (var prop in this.originalStyles_) {
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elem.style[prop] = this.originalStyles_[prop];
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}
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};
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/**
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* Determines whether we need to apply the position hack to emulated position:
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* fixed on this browser.
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* @return {boolean} Whether the current browser needs the position hack.
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* @private
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*/
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goog.ui.ScrollFloater.prototype.needsIePositionHack_ = function() {
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return goog.userAgent.IE &&
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!(goog.userAgent.isVersionOrHigher('7') &&
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this.getDomHelper().isCss1CompatMode());
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};
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/**
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* Sets some magic CSS properties that make float-scrolling work smoothly
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* in IE6 (and IE7 in quirks mode). Without this hack, the floating element
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* will appear jumpy when you scroll the document. This involves modifying
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* the background of the HTML element (or BODY in quirks mode). If there's
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* already a background image in use this is not required.
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* For further reading, see
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* http://annevankesteren.nl/2005/01/position-fixed-in-ie
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* @private
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*/
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goog.ui.ScrollFloater.prototype.applyIeBgHack_ = function() {
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if (this.needsIePositionHack_()) {
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var doc = this.getDomHelper().getDocument();
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var topLevelElement = goog.style.getClientViewportElement(doc);
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if (topLevelElement.currentStyle.backgroundImage == 'none') {
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// Using an https URL if the current windowbp is https avoids an IE
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// "This page contains a mix of secure and nonsecure items" warning.
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topLevelElement.style.backgroundImage =
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this.getDomHelper().getWindow().location.protocol == 'https:' ?
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'url(https:///)' : 'url(about:blank)';
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topLevelElement.style.backgroundAttachment = 'fixed';
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}
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}
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|
};
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