/**
* @license
* Copyright The Closure Library Authors.
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview Class for making an element detach and float to remain visible
* even when the viewport has been scrolled.
* <p>
* The element remains at its normal position in the layout until scrolling
* would cause its top edge to scroll off the top of the viewport; at that
* point, the element is replaced with an invisible placeholder (to keep the
* layout stable), reattached in the dom tree to a new parent (the body element
* by default), and set to "fixed" positioning (emulated for IE < 7) so that it
* remains at its original X position while staying fixed to the top of the
* viewport in the Y dimension.
* <p>
* When the window is scrolled up past the point where the original element
* would be fully visible again, the element snaps back into place, replacing
* the placeholder.
*
* @see ../demos/scrollfloater.html
*
* Adapted from http://go/elementfloater.js
*/
goog.provide('goog.ui.ScrollFloater');
goog.provide('goog.ui.ScrollFloater.EventType');
goog.require('goog.asserts');
goog.require('goog.dom');
goog.require('goog.dom.TagName');
goog.require('goog.dom.classlist');
goog.require('goog.events.EventType');
goog.require('goog.style');
goog.require('goog.ui.Component');
goog.require('goog.userAgent');
goog.requireType('goog.events.Event');
goog.requireType('goog.math.Rect');
/**
* Creates a ScrollFloater; see file overview for details.
*
* @param {Element=} opt_parentElement Where to attach the element when it's
* floating. Default is the document body. If the floating element
* contains form inputs, it will be necessary to attach it to the
* corresponding form element, or to an element in the DOM subtree under
* the form element.
* @param {goog.dom.DomHelper=} opt_domHelper Optional DOM helper.
* @constructor
* @extends {goog.ui.Component}
*/
goog.ui.ScrollFloater = function(opt_parentElement, opt_domHelper) {
'use strict';
// If a parentElement is supplied, we want to use its domHelper,
// ignoring the caller-supplied one.
var domHelper = opt_parentElement ? goog.dom.getDomHelper(opt_parentElement) :
opt_domHelper;
goog.ui.ScrollFloater.base(this, 'constructor', domHelper);
/**
* The element to which the scroll-floated element will be attached
* when it is floating.
* @type {Element}
* @private
*/
this.parentElement_ =
opt_parentElement || this.getDomHelper().getDocument().body;
/**
* The original styles applied to the element before it began floating;
* used to restore those styles when the element stops floating.
* @type {Object}
* @private
*/
this.originalStyles_ = {};
/**
* A vertical offset from which to start floating the element. This is
* useful in cases when there are 'position:fixed' elements covering up
* part of the viewport.
* @type {number}
* @private
*/
this.viewportTopOffset_ = 0;
/**
* An element used to define the boundaries within which the floater can
* be positioned.
* @type {?Element}
* @private
*/
this.containerElement_ = null;
/**
* Container element's bounding rectangle.
* @type {?goog.math.Rect}
* @private
*/
this.containerBounds_ = null;
/**
* Element's original bounding rectangle.
* @type {?goog.math.Rect}
* @private
*/
this.originalBounds_ = null;
/**
* Element's top offset when it's not floated or pinned.
* @type {number}
* @private
*/
this.originalTopOffset_ = 0;
/**
* Element's left offset when it's not floated or pinned.
* @type {number}
* @private
*/
this.originalLeftOffset_ = 0;
/**
* The placeholder element dropped in to hold the layout for
* the floated element.
* @type {?Element}
* @private
*/
this.placeholder_ = null;
/**
* Whether scrolling is enabled for this element; true by default.
* The {@link #setScrollingEnabled} method can be used to change this value.
* @type {boolean}
* @private
*/
this.scrollingEnabled_ = true;
/**
* A flag indicating whether this instance is currently pinned to the bottom
* of the container element.
* @type {boolean}
* @private
*/
this.pinned_ = false;
/**
* A flag indicating whether this instance is currently floating.
* @type {boolean}
* @private
*/
this.floating_ = false;
};
goog.inherits(goog.ui.ScrollFloater, goog.ui.Component);
/**
* Events dispatched by this component.
* @enum {string}
*/
goog.ui.ScrollFloater.EventType = {
/**
* Dispatched when the component starts floating. The event is
* cancellable.
*/
FLOAT: 'float',
/**
* Dispatched when the component returns to its original state.
* The event is cancellable.
*/
DOCK: 'dock',
/**
* Dispatched when the component gets pinned to the bottom of the
* container element. This event is cancellable.
*/
PIN: 'pin'
};
/**
* The element can float at different positions on the page.
* @enum {number}
* @private
*/
goog.ui.ScrollFloater.FloatMode_ = {
TOP: 0,
BOTTOM: 1
};
/**
* The style properties which are stored when we float an element, so they
* can be restored when it 'docks' again.
* @type {Array<string>}
* @private
*/
goog.ui.ScrollFloater.STORED_STYLE_PROPS_ =
['position', 'top', 'left', 'width', 'cssFloat'];
/**
* The style elements managed for the placeholder object.
* @type {Array<string>}
* @private
*/
goog.ui.ScrollFloater.PLACEHOLDER_STYLE_PROPS_ = [
'position', 'top', 'left', 'display', 'cssFloat', 'marginTop', 'marginLeft',
'marginRight', 'marginBottom'
];
/**
* The class name applied to the floating element.
* @type {string}
* @private
*/
goog.ui.ScrollFloater.CSS_CLASS_ = goog.getCssName('goog-scrollfloater');
/**
* Delegates dom creation to superclass, then constructs and
* decorates required DOM elements.
* @override
*/
goog.ui.ScrollFloater.prototype.createDom = function() {
'use strict';
goog.ui.ScrollFloater.base(this, 'createDom');
this.decorateInternal(this.getElement());
};
/**
* Decorates the floated element with the standard ScrollFloater CSS class.
* @param {Element} element The element to decorate.
* @override
*/
goog.ui.ScrollFloater.prototype.decorateInternal = function(element) {
'use strict';
goog.ui.ScrollFloater.base(this, 'decorateInternal', element);
goog.asserts.assert(element);
goog.dom.classlist.add(element, goog.ui.ScrollFloater.CSS_CLASS_);
};
/** @override */
goog.ui.ScrollFloater.prototype.enterDocument = function() {
'use strict';
goog.ui.ScrollFloater.base(this, 'enterDocument');
if (!this.placeholder_) {
this.placeholder_ = this.getDomHelper().createDom(
goog.dom.TagName.DIV, {'style': 'visibility:hidden'});
}
this.update();
this.setScrollingEnabled(this.scrollingEnabled_);
var win = this.getDomHelper().getWindow();
this.getHandler()
.listen(win, goog.events.EventType.SCROLL, this.handleScroll_)
.listen(win, goog.events.EventType.RESIZE, this.update);
};
/**
* Forces the component to update the cached element positions and sizes and
* to re-evaluate whether the component should be docked, floated or pinned.
*/
goog.ui.ScrollFloater.prototype.update = function() {
'use strict';
if (!this.isInDocument()) {
return;
}
// These values can only be calculated when the element is in its original
// state, so we dock first, and then re-evaluate.
this.dock_();
if (this.containerElement_) {
this.containerBounds_ = goog.style.getBounds(this.containerElement_);
}
var pageOffset_ = goog.style.getPageOffset(this.getElement());
this.originalBounds_ = goog.style.getBounds(this.getElement());
this.originalTopOffset_ = pageOffset_.y;
this.originalLeftOffset_ = pageOffset_.x;
this.handleScroll_();
};
/** @override */
goog.ui.ScrollFloater.prototype.disposeInternal = function() {
'use strict';
goog.ui.ScrollFloater.base(this, 'disposeInternal');
this.placeholder_ = null;
};
/**
* Sets whether the element should be floated if it scrolls out of view.
* @param {boolean} enable Whether floating is enabled for this element.
*/
goog.ui.ScrollFloater.prototype.setScrollingEnabled = function(enable) {
'use strict';
this.scrollingEnabled_ = enable;
if (enable) {
this.applyIeBgHack_();
this.handleScroll_();
} else {
this.dock_();
}
};
/**
* @return {boolean} Whether the component is enabled for scroll-floating.
*/
goog.ui.ScrollFloater.prototype.isScrollingEnabled = function() {
'use strict';
return this.scrollingEnabled_;
};
/**
* @return {boolean} Whether the component is currently scroll-floating.
*/
goog.ui.ScrollFloater.prototype.isFloating = function() {
'use strict';
return this.floating_;
};
/**
* @return {boolean} Whether the component is currently pinned to the bottom
* of the container.
*/
goog.ui.ScrollFloater.prototype.isPinned = function() {
'use strict';
return this.pinned_;
};
/**
* @param {number} offset A vertical offset from the top of the viewport, from
* which to start floating the element. Default is 0. This is useful in cases
* when there are 'position:fixed' elements covering up part of the viewport.
*/
goog.ui.ScrollFloater.prototype.setViewportTopOffset = function(offset) {
'use strict';
this.viewportTopOffset_ = offset;
this.update();
};
/**
* @param {Element} container An element used to define the boundaries within
* which the floater can be positioned. If not specified, scrolling the page
* down far enough may result in the floated element extending past the
* containing element as it is being scrolled out of the viewport. In some
* cases, such as a list with a sticky header, this may be undesirable. If
* the container element is specified and the floated element extends past
* the bottom of the container, the element will be pinned to the bottom of
* the container.
*/
goog.ui.ScrollFloater.prototype.setContainerElement = function(container) {
'use strict';
this.containerElement_ = container;
this.update();
};
/**
* When a scroll event occurs, compares the element's position to the current
* document scroll position, and stops or starts floating behavior if needed.
* @param {goog.events.Event=} opt_e The event, which is ignored.
* @private
*/
goog.ui.ScrollFloater.prototype.handleScroll_ = function(opt_e) {
'use strict';
if (this.scrollingEnabled_) {
var scrollTop = this.getDomHelper().getDocumentScroll().y;
if (this.originalBounds_.top - scrollTop >= this.viewportTopOffset_) {
this.dock_();
return;
}
var effectiveElementHeight =
this.originalBounds_.height + this.viewportTopOffset_;
// If the element extends past the container, we need to pin it instead.
if (this.containerElement_) {
var containerBottom =
this.containerBounds_.top + this.containerBounds_.height;
if (scrollTop > containerBottom - effectiveElementHeight) {
this.pin_();
return;
}
}
var windowHeight = this.getDomHelper().getViewportSize().height;
// If the element is shorter than the window or the user uses IE < 7,
// float it at the top.
if (this.needsIePositionHack_() || effectiveElementHeight < windowHeight) {
this.float_(goog.ui.ScrollFloater.FloatMode_.TOP);
return;
}
// If the element is taller than the window and is extending past the
// bottom, allow it scroll with the page until the bottom of the element is
// fully visible.
if (this.originalBounds_.height + this.originalTopOffset_ >
windowHeight + scrollTop) {
this.dock_();
} else {
// Pin the element to the bottom of the page since the user has scrolled
// past it.
this.float_(goog.ui.ScrollFloater.FloatMode_.BOTTOM);
}
}
};
/**
* Pins the element to the bottom of the container, making as much of the
* element visible as possible without extending past it.
* @private
*/
goog.ui.ScrollFloater.prototype.pin_ = function() {
'use strict';
if (this.floating_ && !this.dock_()) {
return;
}
// Ignore if the component is pinned or the PIN event is cancelled.
if (this.pinned_ ||
!this.dispatchEvent(goog.ui.ScrollFloater.EventType.PIN)) {
return;
}
var elem = this.getElement();
this.storeOriginalStyles_();
elem.style.position = 'relative';
elem.style.top = this.containerBounds_.height - this.originalBounds_.height -
this.originalBounds_.top + this.containerBounds_.top + 'px';
this.pinned_ = true;
};
/**
* Begins floating behavior, making the element position:fixed (or IE hacked
* equivalent) and inserting a placeholder where it used to be to keep the
* layout from shifting around. For IE < 7 users, we only support floating at
* the top.
* @param {goog.ui.ScrollFloater.FloatMode_} floatMode The position at which we
* should float.
* @private
*/
goog.ui.ScrollFloater.prototype.float_ = function(floatMode) {
'use strict';
var isTop = floatMode == goog.ui.ScrollFloater.FloatMode_.TOP;
if (this.pinned_ && !this.dock_()) {
return;
}
// Ignore if the FLOAT event is cancelled.
if (!this.dispatchEvent(goog.ui.ScrollFloater.EventType.FLOAT)) {
return;
}
// If the component is already floating, only update the left position.
var newWindowLeftOffset_ = goog.dom.getDocumentScroll().x;
if (this.floating_) {
this.updateFloatingLeftPosition_();
return;
}
var elem = /** @type {!HTMLElement} */ (this.getElement());
// Read properties of element before modifying it.
var originalLeft_ = goog.style.getPageOffsetLeft(elem);
var originalWidth_ = goog.style.getContentBoxSize(elem).width;
this.storeOriginalStyles_();
goog.style.setSize(this.placeholder_, elem.offsetWidth, elem.offsetHeight);
// Make element float.
goog.style.setStyle(elem, {
'left': (originalLeft_ - newWindowLeftOffset_) + 'px',
'width': originalWidth_ + 'px',
'cssFloat': 'none'
});
// If parents are the same, avoid detaching and reattaching elem.
// This prevents Flash embeds from being reloaded, for example.
if (elem.parentNode == this.parentElement_) {
elem.parentNode.insertBefore(
/** @type {!Node} */ (this.placeholder_), elem);
} else {
elem.parentNode.replaceChild(
/** @type {!Node} */ (this.placeholder_), elem);
this.parentElement_.appendChild(elem);
}
// Versions of IE below 7-in-standards-mode don't handle 'position: fixed',
// so we must emulate it using an IE-specific idiom for JS-based calculated
// style values. These users will only ever float at the top (bottom floating
// not supported.) Also checked in handleScroll_.
if (this.needsIePositionHack_()) {
elem.style.position = 'absolute';
elem.style.setExpression(
'top', 'document.compatMode=="CSS1Compat"?' +
'documentElement.scrollTop:document.body.scrollTop');
} else {
elem.style.position = 'fixed';
if (isTop) {
elem.style.top = this.viewportTopOffset_ + 'px';
elem.style.bottom = 'auto';
} else {
elem.style.top = 'auto';
elem.style.bottom = '0';
}
}
this.floating_ = true;
};
/**
* Stops floating behavior, returning element to its original state.
* @return {boolean} True if the element has been docked. False if the
* element is already docked or the event was cancelled.
* @private
*/
goog.ui.ScrollFloater.prototype.dock_ = function() {
'use strict';
// Ignore if the component is docked or the DOCK event is cancelled.
if (!(this.floating_ || this.pinned_) ||
!this.dispatchEvent(goog.ui.ScrollFloater.EventType.DOCK)) {
return false;
}
var elem = this.getElement();
if (this.floating_) {
this.restoreOriginalStyles_();
if (this.needsIePositionHack_()) {
elem.style.removeExpression('top');
}
// If placeholder_ was inserted and didn't replace elem then elem has
// the right parent already, no need to replace (which removes elem before
// inserting it).
if (this.placeholder_.parentNode == this.parentElement_) {
this.placeholder_.parentNode.removeChild(this.placeholder_);
} else {
this.placeholder_.parentNode.replaceChild(
/** @type {!Node} */ (elem), this.placeholder_);
}
}
if (this.pinned_) {
this.restoreOriginalStyles_();
}
this.floating_ = this.pinned_ = false;
return true;
};
/**
* Handle horizontal scroll events by updating the left offset position. This
* cannot change the floating or docked state and is only valid while the
* element is floating.
* @private
*/
goog.ui.ScrollFloater.prototype.updateFloatingLeftPosition_ = function() {
'use strict';
goog.asserts.assert(this.floating_);
var newWindowLeftOffset_ = goog.dom.getDocumentScroll().x;
goog.style.setStyle(
this.getElement(),
{'left': (this.originalLeftOffset_ - newWindowLeftOffset_) + 'px'});
};
/**
* @private
*/
goog.ui.ScrollFloater.prototype.storeOriginalStyles_ = function() {
'use strict';
var elem = this.getElement();
this.originalStyles_ = {};
// Store styles while not floating so we can restore them when the
// element stops floating.
goog.ui.ScrollFloater.STORED_STYLE_PROPS_.forEach(function(property) {
'use strict';
this.originalStyles_[property] = elem.style[property];
}, this);
// Copy relevant styles to placeholder so it will be laid out the same
// as the element that's about to be floated.
goog.ui.ScrollFloater.PLACEHOLDER_STYLE_PROPS_.forEach(function(property) {
'use strict';
this.placeholder_.style[property] = elem.style[property] ||
goog.style.getCascadedStyle(elem, property) ||
goog.style.getComputedStyle(elem, property);
}, this);
};
/**
* @private
*/
goog.ui.ScrollFloater.prototype.restoreOriginalStyles_ = function() {
'use strict';
var elem = this.getElement();
for (var prop in this.originalStyles_) {
elem.style[prop] = this.originalStyles_[prop];
}
};
/**
* Determines whether we need to apply the position hack to emulated position:
* fixed on this browser.
* @return {boolean} Whether the current browser needs the position hack.
* @private
*/
goog.ui.ScrollFloater.prototype.needsIePositionHack_ = function() {
'use strict';
return goog.userAgent.IE && !this.getDomHelper().isCss1CompatMode();
};
/**
* Sets some magic CSS properties that make float-scrolling work smoothly
* in IE6 (and IE7 in quirks mode). Without this hack, the floating element
* will appear jumpy when you scroll the document. This involves modifying
* the background of the HTML element (or BODY in quirks mode). If there's
* already a background image in use this is not required.
* For further reading, see
* http://annevankesteren.nl/2005/01/position-fixed-in-ie
* @private
*/
goog.ui.ScrollFloater.prototype.applyIeBgHack_ = function() {
'use strict';
if (this.needsIePositionHack_()) {
var doc = this.getDomHelper().getDocument();
var topLevelElement = goog.style.getClientViewportElement(doc);
if (topLevelElement.currentStyle.backgroundImage == 'none') {
// Using an https URL if the current windowbp is https avoids an IE
// "This page contains a mix of secure and nonsecure items" warning.
topLevelElement.style.backgroundImage =
this.getDomHelper().getWindow().location.protocol == 'https:' ?
'url(https:///)' :
'url(about:blank)';
topLevelElement.style.backgroundAttachment = 'fixed';
}
}
};
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