/**
 * @license Copyright (c) 2003-2018, CKSource - Frederico Knabben. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
 */

/**
 * @fileOverview Defines the {@link CKEDITOR.dom.element} class, which
 *		represents a DOM element.
 */

/**
 * Represents a DOM element.
 *
 *		// Create a new <span> element.
 *		var element = new CKEDITOR.dom.element( 'span' );
 *
 *		// Create an element based on a native DOM element.
 *		var element = new CKEDITOR.dom.element( document.getElementById( 'myId' ) );
 *
 * @class
 * @extends CKEDITOR.dom.node
 * @constructor Creates an element class instance.
 * @param {Object/String} element A native DOM element or the element name for
 * new elements.
 * @param {CKEDITOR.dom.document} [ownerDocument] The document that will contain
 * the element in case of element creation.
 */
CKEDITOR.dom.element = function( element, ownerDocument ) {
	if ( typeof element == 'string' )
		element = ( ownerDocument ? ownerDocument.$ : document ).createElement( element );

	// Call the base constructor (we must not call CKEDITOR.dom.node).
	CKEDITOR.dom.domObject.call( this, element );
};

// PACKAGER_RENAME( CKEDITOR.dom.element )
/**
 * The the {@link CKEDITOR.dom.element} representing and element. If the
 * element is a native DOM element, it will be transformed into a valid
 * CKEDITOR.dom.element object.
 *
 *		var element = new CKEDITOR.dom.element( 'span' );
 *		alert( element == CKEDITOR.dom.element.get( element ) ); // true
 *
 *		var element = document.getElementById( 'myElement' );
 *		alert( CKEDITOR.dom.element.get( element ).getName() ); // (e.g.) 'p'
 *
 * @static
 * @param {String/Object} element Element's id or name or native DOM element.
 * @returns {CKEDITOR.dom.element} The transformed element.
 */
CKEDITOR.dom.element.get = function( element ) {
	var el = typeof element == 'string' ? document.getElementById( element ) || document.getElementsByName( element )[ 0 ] : element;

	return el && ( el.$ ? el : new CKEDITOR.dom.element( el ) );
};

CKEDITOR.dom.element.prototype = new CKEDITOR.dom.node();

/**
 * Creates an instance of the {@link CKEDITOR.dom.element} class based on the
 * HTML representation of an element.
 *
 *		var element = CKEDITOR.dom.element.createFromHtml( '<strong class="anyclass">My element</strong>' );
 *		alert( element.getName() ); // 'strong'
 *
 * @static
 * @param {String} html The element HTML. It should define only one element in
 * the "root" level. The "root" element can have child nodes, but not siblings.
 * @returns {CKEDITOR.dom.element} The element instance.
 */
CKEDITOR.dom.element.createFromHtml = function( html, ownerDocument ) {
	var temp = new CKEDITOR.dom.element( 'div', ownerDocument );
	temp.setHtml( html );

	// When returning the node, remove it from its parent to detach it.
	return temp.getFirst().remove();
};

/**
 * Sets {@link CKEDITOR.dom.element#setCustomData custom data} on an element in a way that it is later
 * possible to {@link #clearAllMarkers clear all data} set on all elements sharing the same database.
 *
 * This mechanism is very useful when processing some portion of DOM. All markers can later be removed
 * by calling the {@link #clearAllMarkers} method, hence markers will not leak to second pass of this algorithm.
 *
 *		var database = {};
 *		CKEDITOR.dom.element.setMarker( database, element1, 'foo', 'bar' );
 *		CKEDITOR.dom.element.setMarker( database, element2, 'oof', [ 1, 2, 3 ] );
 *
 *		element1.getCustomData( 'foo' ); // 'bar'
 *		element2.getCustomData( 'oof' ); // [ 1, 2, 3 ]
 *
 *		CKEDITOR.dom.element.clearAllMarkers( database );
 *
 *		element1.getCustomData( 'foo' ); // null
 *
 * @static
 * @param {Object} database
 * @param {CKEDITOR.dom.element} element
 * @param {String} name
 * @param {Object} value
 * @returns {CKEDITOR.dom.element} The element.
 */
CKEDITOR.dom.element.setMarker = function( database, element, name, value ) {
	var id = element.getCustomData( 'list_marker_id' ) || ( element.setCustomData( 'list_marker_id', CKEDITOR.tools.getNextNumber() ).getCustomData( 'list_marker_id' ) ),
		markerNames = element.getCustomData( 'list_marker_names' ) || ( element.setCustomData( 'list_marker_names', {} ).getCustomData( 'list_marker_names' ) );
	database[ id ] = element;
	markerNames[ name ] = 1;

	return element.setCustomData( name, value );
};

/**
 * Removes all markers added using this database. See the {@link #setMarker} method for more information.
 *
 * @param {Object} database
 * @static
 */
CKEDITOR.dom.element.clearAllMarkers = function( database ) {
	for ( var i in database )
		CKEDITOR.dom.element.clearMarkers( database, database[ i ], 1 );
};

/**
 * Removes all markers added to this element and removes it from the database if
 * `removeFromDatabase` was passed. See the {@link #setMarker} method for more information.
 *
 *		var database = {};
 *		CKEDITOR.dom.element.setMarker( database, element1, 'foo', 'bar' );
 *		CKEDITOR.dom.element.setMarker( database, element2, 'oof', [ 1, 2, 3 ] );
 *
 *		element1.getCustomData( 'foo' ); // 'bar'
 *		element2.getCustomData( 'oof' ); // [ 1, 2, 3 ]
 *
 *		CKEDITOR.dom.element.clearMarkers( database, element1, true );
 *
 *		element1.getCustomData( 'foo' ); // null
 *		element2.getCustomData( 'oof' ); // [ 1, 2, 3 ]
 *
 * @param {Object} database
 * @static
 */
CKEDITOR.dom.element.clearMarkers = function( database, element, removeFromDatabase ) {
	var names = element.getCustomData( 'list_marker_names' ),
		id = element.getCustomData( 'list_marker_id' );
	for ( var i in names )
		element.removeCustomData( i );
	element.removeCustomData( 'list_marker_names' );
	if ( removeFromDatabase ) {
		element.removeCustomData( 'list_marker_id' );
		delete database[ id ];
	}
};

( function() {
	var elementsClassList = document.createElement( '_' ).classList,
		supportsClassLists = typeof elementsClassList !== 'undefined' && String( elementsClassList.add ).match( /\[Native code\]/gi ) !== null,
		rclass = /[\n\t\r]/g;

	function hasClass( classNames, className ) {
		// Source: jQuery.
		return ( ' ' + classNames + ' ' ).replace( rclass, ' ' ).indexOf( ' ' + className + ' ' ) > -1;
	}

	CKEDITOR.tools.extend( CKEDITOR.dom.element.prototype, {
		/**
		 * The node type. This is a constant value set to {@link CKEDITOR#NODE_ELEMENT}.
		 *
		 * @readonly
		 * @property {Number} [=CKEDITOR.NODE_ELEMENT]
		 */
		type: CKEDITOR.NODE_ELEMENT,

		/**
		 * Adds a CSS class to the element. It appends the class to the
		 * already existing names.
		 *
		 *		var element = new CKEDITOR.dom.element( 'div' );
		 *		element.addClass( 'classA' ); // <div class="classA">
		 *		element.addClass( 'classB' ); // <div class="classA classB">
		 *		element.addClass( 'classA' ); // <div class="classA classB">
		 *
		 * **Note:** Since CKEditor 4.5 this method cannot be used with multiple classes (`'classA classB'`).
		 *
		 * @chainable
		 * @method addClass
		 * @param {String} className The name of the class to be added.
		 */
		addClass: supportsClassLists ?
			function( className ) {
				this.$.classList.add( className );

				return this;
			} : function( className ) {
				var c = this.$.className;
				if ( c ) {
					if ( !hasClass( c, className ) )
						c += ' ' + className;
				}
				this.$.className = c || className;

				return this;
			},

		/**
		 * Removes a CSS class name from the elements classes. Other classes
		 * remain untouched.
		 *
		 *		var element = new CKEDITOR.dom.element( 'div' );
		 *		element.addClass( 'classA' );		// <div class="classA">
		 *		element.addClass( 'classB' );		// <div class="classA classB">
		 *		element.removeClass( 'classA' );	// <div class="classB">
		 *		element.removeClass( 'classB' );	// <div>
		 *
		 * @chainable
		 * @method removeClass
		 * @param {String} className The name of the class to remove.
		 */
		removeClass: supportsClassLists ?
			function( className ) {
				var $ = this.$;
				$.classList.remove( className );

				if ( !$.className )
					$.removeAttribute( 'class' );

				return this;
			} : function( className ) {
				var c = this.getAttribute( 'class' );
				if ( c && hasClass( c, className ) ) {
					c = c
						.replace( new RegExp( '(?:^|\\s+)' + className + '(?=\\s|$)' ), '' )
						.replace( /^\s+/, '' );

					if ( c )
						this.setAttribute( 'class', c );
					else
						this.removeAttribute( 'class' );
				}

				return this;
			},

		/**
		 * Checks if element has class name.
		 *
		 * @param {String} className
		 * @returns {Boolean}
		 */
		hasClass: function( className ) {
			return hasClass( this.$.className, className );
		},

		/**
		 * Append a node as a child of this element.
		 *
		 *		var p = new CKEDITOR.dom.element( 'p' );
		 *
		 *		var strong = new CKEDITOR.dom.element( 'strong' );
		 *		p.append( strong );
		 *
		 *		var em = p.append( 'em' );
		 *
		 *		// Result: '<p><strong></strong><em></em></p>'
		 *
		 * @param {CKEDITOR.dom.node/String} node The node or element name to be appended.
		 * @param {Boolean} [toStart=false] Indicates that the element is to be appended at the start.
		 * @returns {CKEDITOR.dom.node} The appended node.
		 */
		append: function( node, toStart ) {
			if ( typeof node == 'string' )
				node = this.getDocument().createElement( node );

			if ( toStart )
				this.$.insertBefore( node.$, this.$.firstChild );
			else
				this.$.appendChild( node.$ );

			return node;
		},

		/**
		 * Append HTML as a child(ren) of this element.
		 *
		 * @param {String} html
		 */
		appendHtml: function( html ) {
			if ( !this.$.childNodes.length )
				this.setHtml( html );
			else {
				var temp = new CKEDITOR.dom.element( 'div', this.getDocument() );
				temp.setHtml( html );
				temp.moveChildren( this );
			}
		},

		/**
		 * Append text to this element.
		 *
		 *		var p = new CKEDITOR.dom.element( 'p' );
		 *		p.appendText( 'This is' );
		 *		p.appendText( ' some text' );
		 *
		 *		// Result: '<p>This is some text</p>'
		 *
		 * @param {String} text The text to be appended.
		 */
		appendText: function( text ) {
			// On IE8 it is impossible to append node to script tag, so we use its text.
			// On the contrary, on Safari the text property is unpredictable in links. (https://dev.ckeditor.com/ticket/13232)
			if ( this.$.text != null && CKEDITOR.env.ie && CKEDITOR.env.version < 9 )
				this.$.text += text;
			else
				this.append( new CKEDITOR.dom.text( text ) );
		},

		/**
		 * Appends a `<br>` filler element to this element if the filler is not present already.
		 * By default filler is appended only if {@link CKEDITOR.env#needsBrFiller} is `true`,
		 * however when `force` is set to `true` filler will be appended regardless of the environment.
		 *
		 * @param {Boolean} [force] Append filler regardless of the environment.
		 */
		appendBogus: function( force ) {
			if ( !force && !CKEDITOR.env.needsBrFiller )
				return;

			var lastChild = this.getLast();

			// Ignore empty/spaces text.
			while ( lastChild && lastChild.type == CKEDITOR.NODE_TEXT && !CKEDITOR.tools.rtrim( lastChild.getText() ) )
				lastChild = lastChild.getPrevious();
			if ( !lastChild || !lastChild.is || !lastChild.is( 'br' ) ) {
				var bogus = this.getDocument().createElement( 'br' );

				CKEDITOR.env.gecko && bogus.setAttribute( 'type', '_moz' );

				this.append( bogus );
			}
		},

		/**
		 * Breaks one of the ancestor element in the element position, moving
		 * this element between the broken parts.
		 *
		 *		// Before breaking:
		 *		//		<b>This <i>is some<span /> sample</i> test text</b>
		 *		// If "element" is <span /> and "parent" is <i>:
		 *		//		<b>This <i>is some</i><span /><i> sample</i> test text</b>
		 *		element.breakParent( parent );
		 *
		 *		// Before breaking:
		 *		//		<b>This <i>is some<span /> sample</i> test text</b>
		 *		// If "element" is <span /> and "parent" is <b>:
		 *		//		<b>This <i>is some</i></b><span /><b><i> sample</i> test text</b>
		 *		element.breakParent( parent );
		 *
		 * @param {CKEDITOR.dom.element} parent The anscestor element to get broken.
		 * @param {Boolean} [cloneId=false] Whether to preserve ancestor ID attributes while breaking.
		 */
		breakParent: function( parent, cloneId ) {
			var range = new CKEDITOR.dom.range( this.getDocument() );

			// We'll be extracting part of this element, so let's use our
			// range to get the correct piece.
			range.setStartAfter( this );
			range.setEndAfter( parent );

			// Extract it.
			var docFrag = range.extractContents( false, cloneId || false ),
				tmpElement,
				current;

			// Move the element outside the broken element.
			range.insertNode( this.remove() );

			// In case of Internet Explorer, we must check if there is no background-color
			// added to the element. In such case, we have to overwrite it to prevent "switching it off"
			// by a browser (https://dev.ckeditor.com/ticket/14667).
			if ( CKEDITOR.env.ie && !CKEDITOR.env.edge ) {
				tmpElement = new CKEDITOR.dom.element( 'div' );

				while ( current = docFrag.getFirst() ) {
					if ( current.$.style.backgroundColor ) {
						// This is a necessary hack to make sure that IE will track backgroundColor CSS property, see
						// https://dev.ckeditor.com/ticket/14667#comment:8 for more details.
						current.$.style.backgroundColor = current.$.style.backgroundColor;
					}

					tmpElement.append( current );
				}

				// Re-insert the extracted piece after the element.
				tmpElement.insertAfter( this );
				tmpElement.remove( true );
			} else {
				// Re-insert the extracted piece after the element.
				docFrag.insertAfterNode( this );
			}
		},

		/**
		 * Checks if this element contains given node.
		 *
		 * @method
		 * @param {CKEDITOR.dom.node} node
		 * @returns {Boolean}
		 */
		contains: !document.compareDocumentPosition ?
			function( node ) {
				var $ = this.$;

				return node.type != CKEDITOR.NODE_ELEMENT ? $.contains( node.getParent().$ ) : $ != node.$ && $.contains( node.$ );
			} : function( node ) {
				return !!( this.$.compareDocumentPosition( node.$ ) & 16 );
			},

		/**
		 * Moves the selection focus to this element.
		 *
		 *		var element = CKEDITOR.document.getById( 'myTextarea' );
		 *		element.focus();
		 *
		 * @method
		 * @param  {Boolean} defer Whether to asynchronously defer the
		 * execution by 100 ms.
		 */
		focus: ( function() {
			function exec() {
				// IE throws error if the element is not visible.
				try {
					this.$.focus();
				} catch ( e ) {}
			}

			return function( defer ) {
				if ( defer )
					CKEDITOR.tools.setTimeout( exec, 100, this );
				else
					exec.call( this );
			};
		} )(),

		/**
		 * Gets the inner HTML of this element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div><b>Example</b></div>' );
		 *		alert( element.getHtml() ); // '<b>Example</b>'
		 *
		 * @returns {String} The inner HTML of this element.
		 */
		getHtml: function() {
			var retval = this.$.innerHTML;
			// Strip <?xml:namespace> tags in IE. (https://dev.ckeditor.com/ticket/3341).
			return CKEDITOR.env.ie ? retval.replace( /<\?[^>]*>/g, '' ) : retval;
		},

		/**
		 * Gets the outer (inner plus tags) HTML of this element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div class="bold"><b>Example</b></div>' );
		 *		alert( element.getOuterHtml() ); // '<div class="bold"><b>Example</b></div>'
		 *
		 * @returns {String} The outer HTML of this element.
		 */
		getOuterHtml: function() {
			if ( this.$.outerHTML ) {
				// IE includes the <?xml:namespace> tag in the outerHTML of
				// namespaced element. So, we must strip it here. (https://dev.ckeditor.com/ticket/3341)
				return this.$.outerHTML.replace( /<\?[^>]*>/, '' );
			}

			var tmpDiv = this.$.ownerDocument.createElement( 'div' );
			tmpDiv.appendChild( this.$.cloneNode( true ) );
			return tmpDiv.innerHTML;
		},

		/**
		 * Retrieve the bounding rectangle of the current element, in pixels,
		 * relative to the upper-left corner of the browser's client area.
		 *
		 * Since 4.10.0 you can pass an additional parameter if the function should return an absolute element position that can be used for
		 * positioning elements inside scrollable areas.
		 *
		 * For example, you can use this function with the {@link CKEDITOR.dom.window#getFrame editor's window frame} to
		 * calculate the absolute rectangle of the visible area of the editor viewport.
		 * The retrieved absolute rectangle can be used to position elements like toolbars or notifications (elements outside the editor)
		 * to always keep them inside the editor viewport independently from the scroll position.
		 *
		 * ```javascript
		 * var frame = editor.window.getFrame();
		 * frame.getClientRect( true );
		 * ```
		 *
		 * @param {Boolean} [isAbsolute=false] The function will retrieve an absolute rectangle of the element, i.e. the position relative
		 * to the upper-left corner of the topmost viewport. This option is available since 4.10.0.
		 * @returns {CKEDITOR.dom.rect} The dimensions of the DOM element.
		 */
		getClientRect: function( isAbsolute ) {
			// http://help.dottoro.com/ljvmcrrn.php
			var elementRect = CKEDITOR.tools.extend( {}, this.$.getBoundingClientRect() );

			!elementRect.width && ( elementRect.width = elementRect.right - elementRect.left );
			!elementRect.height && ( elementRect.height = elementRect.bottom - elementRect.top );

			if ( !isAbsolute ) {
				return elementRect;
			}

			return CKEDITOR.tools.getAbsoluteRectPosition( this.getWindow(), elementRect );
		},

		/**
		 * Sets the inner HTML of this element.
		 *
		 *		var p = new CKEDITOR.dom.element( 'p' );
		 *		p.setHtml( '<b>Inner</b> HTML' );
		 *
		 *		// Result: '<p><b>Inner</b> HTML</p>'
		 *
		 * @method
		 * @param {String} html The HTML to be set for this element.
		 * @returns {String} The inserted HTML.
		 */
		setHtml: ( CKEDITOR.env.ie && CKEDITOR.env.version < 9 ) ?
			// old IEs throws error on HTML manipulation (through the "innerHTML" property)
			// on the element which resides in an DTD invalid position,  e.g. <span><div></div></span>
			// fortunately it can be worked around with DOM manipulation.
			function( html ) {
				try {
					var $ = this.$;

					// Fix the case when setHtml is called on detached element.
					// HTML5 shiv used for document in which this element was created
					// won't affect that detached element. So get document fragment with
					// all HTML5 elements enabled and set innerHTML while this element is appended to it.
					if ( this.getParent() )
						return ( $.innerHTML = html );
					else {
						var $frag = this.getDocument()._getHtml5ShivFrag();
						$frag.appendChild( $ );
						$.innerHTML = html;
						$frag.removeChild( $ );

						return html;
					}
				}
				catch ( e ) {
					this.$.innerHTML = '';

					var temp = new CKEDITOR.dom.element( 'body', this.getDocument() );
					temp.$.innerHTML = html;

					var children = temp.getChildren();
					while ( children.count() )
						this.append( children.getItem( 0 ) );

					return html;
				}
			} : function( html ) {
				return ( this.$.innerHTML = html );
			},

		/**
		 * Sets the element contents as plain text.
		 *
		 *		var element = new CKEDITOR.dom.element( 'div' );
		 *		element.setText( 'A > B & C < D' );
		 *		alert( element.innerHTML ); // 'A &gt; B &amp; C &lt; D'
		 *
		 * @param {String} text The text to be set.
		 * @returns {String} The inserted text.
		 */
		setText: ( function() {
			var supportsTextContent = document.createElement( 'p' );
			supportsTextContent.innerHTML = 'x';
			supportsTextContent = supportsTextContent.textContent;

			return function( text ) {
				this.$[ supportsTextContent ? 'textContent' : 'innerText' ] = text;
			};
		} )(),

		/**
		 * Gets the value of an element attribute.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<input type="text" />' );
		 *		alert( element.getAttribute( 'type' ) ); // 'text'
		 *
		 * @method
		 * @param {String} name The attribute name.
		 * @returns {String} The attribute value or null if not defined.
		 */
		getAttribute: ( function() {
			var standard = function( name ) {
					return this.$.getAttribute( name, 2 );
				};

			if ( CKEDITOR.env.ie && ( CKEDITOR.env.ie7Compat || CKEDITOR.env.quirks ) ) {
				return function( name ) {
					switch ( name ) {
						case 'class':
							name = 'className';
							break;

						case 'http-equiv':
							name = 'httpEquiv';
							break;

						case 'name':
							return this.$.name;

						case 'tabindex':
							var tabIndex = standard.call( this, name );

							// IE returns tabIndex=0 by default for all
							// elements. For those elements,
							// getAtrribute( 'tabindex', 2 ) returns 32768
							// instead. So, we must make this check to give a
							// uniform result among all browsers.
							if ( tabIndex !== 0 && this.$.tabIndex === 0 )
								tabIndex = null;

							return tabIndex;

						case 'checked':
							var attr = this.$.attributes.getNamedItem( name ),
								attrValue = attr.specified ? attr.nodeValue // For value given by parser.
								: this.$.checked; // For value created via DOM interface.

							return attrValue ? 'checked' : null;

						case 'hspace':
						case 'value':
							return this.$[ name ];

						case 'style':
							// IE does not return inline styles via getAttribute(). See https://dev.ckeditor.com/ticket/2947.
							return this.$.style.cssText;

						case 'contenteditable':
						case 'contentEditable':
							return this.$.attributes.getNamedItem( 'contentEditable' ).specified ? this.$.getAttribute( 'contentEditable' ) : null;
					}

					return standard.call( this, name );
				};
			} else {
				return standard;
			}
		} )(),

		/**
		 * Gets the values of all element attributes.
		 *
		 * @param {Array} exclude The names of attributes to be excluded from the returned object.
		 * @return {Object} An object containing all element attributes with their values.
		 */
		getAttributes: function( exclude ) {
			var attributes = {},
				attrDefs = this.$.attributes,
				i;

			exclude = CKEDITOR.tools.isArray( exclude ) ? exclude : [];

			for ( i = 0; i < attrDefs.length; i++ ) {
				if ( CKEDITOR.tools.indexOf( exclude, attrDefs[ i ].name ) === -1 ) {
					attributes[ attrDefs[ i ].name ] = attrDefs[ i ].value;
				}
			}

			return attributes;
		},

		/**
		 * Gets the nodes list containing all children of this element.
		 *
		 * @returns {CKEDITOR.dom.nodeList}
		 */
		getChildren: function() {
			return new CKEDITOR.dom.nodeList( this.$.childNodes );
		},

		/**
		 * Gets the current computed value of one of the element CSS style
		 * properties.
		 *
		 *		var element = new CKEDITOR.dom.element( 'span' );
		 *		alert( element.getComputedStyle( 'display' ) ); // 'inline'
		 *
		 * @method
		 * @param {String} propertyName The style property name.
		 * @returns {String} The property value.
		 */
		getComputedStyle: ( document.defaultView && document.defaultView.getComputedStyle ) ?
				function( propertyName ) {
					var style = this.getWindow().$.getComputedStyle( this.$, null );

					// Firefox may return null if we call the above on a hidden iframe. (https://dev.ckeditor.com/ticket/9117)
					return style ? style.getPropertyValue( propertyName ) : '';
				} : function( propertyName ) {
					return this.$.currentStyle[ CKEDITOR.tools.cssStyleToDomStyle( propertyName ) ];
				},

		/**
		 * Gets the DTD entries for this element.
		 *
		 * @returns {Object} An object containing the list of elements accepted
		 * by this element.
		 */
		getDtd: function() {
			var dtd = CKEDITOR.dtd[ this.getName() ];

			this.getDtd = function() {
				return dtd;
			};

			return dtd;
		},

		/**
		 * Gets all this element's descendants having given tag name.
		 *
		 * @method
		 * @param {String} tagName
		 */
		getElementsByTag: CKEDITOR.dom.document.prototype.getElementsByTag,

		/**
		 * Gets the computed tabindex for this element.
		 *
		 *		var element = CKEDITOR.document.getById( 'myDiv' );
		 *		alert( element.getTabIndex() ); // (e.g.) '-1'
		 *
		 * @method
		 * @returns {Number} The tabindex value.
		 */
		getTabIndex: function() {
			var tabIndex = this.$.tabIndex;

			// IE returns tabIndex=0 by default for all elements. In
			// those cases we must check that the element really has
			// the tabindex attribute set to zero, or it is one of
			// those element that should have zero by default.
			if ( tabIndex === 0 && !CKEDITOR.dtd.$tabIndex[ this.getName() ] && parseInt( this.getAttribute( 'tabindex' ), 10 ) !== 0 )
				return -1;

			return tabIndex;
		},

		/**
		 * Gets the text value of this element.
		 *
		 * Only in IE (which uses innerText), `<br>` will cause linebreaks,
		 * and sucessive whitespaces (including line breaks) will be reduced to
		 * a single space. This behavior is ok for us, for now. It may change
		 * in the future.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div>Sample <i>text</i>.</div>' );
		 *		alert( <b>element.getText()</b> ); // 'Sample text.'
		 *
		 * @returns {String} The text value.
		 */
		getText: function() {
			return this.$.textContent || this.$.innerText || '';
		},

		/**
		 * Gets the window object that contains this element.
		 *
		 * @returns {CKEDITOR.dom.window} The window object.
		 */
		getWindow: function() {
			return this.getDocument().getWindow();
		},

		/**
		 * Gets the value of the `id` attribute of this element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<p id="myId"></p>' );
		 *		alert( element.getId() ); // 'myId'
		 *
		 * @returns {String} The element id, or null if not available.
		 */
		getId: function() {
			return this.$.id || null;
		},

		/**
		 * Gets the value of the `name` attribute of this element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<input name="myName"></input>' );
		 *		alert( <b>element.getNameAtt()</b> ); // 'myName'
		 *
		 * @returns {String} The element name, or null if not available.
		 */
		getNameAtt: function() {
			return this.$.name || null;
		},

		/**
		 * Gets the element name (tag name). The returned name is guaranteed to
		 * be always full lowercased.
		 *
		 *		var element = new CKEDITOR.dom.element( 'span' );
		 *		alert( element.getName() ); // 'span'
		 *
		 * @returns {String} The element name.
		 */
		getName: function() {
			// Cache the lowercased name inside a closure.
			var nodeName = this.$.nodeName.toLowerCase();

			if ( CKEDITOR.env.ie && ( document.documentMode <= 8 ) ) {
				var scopeName = this.$.scopeName;
				if ( scopeName != 'HTML' )
					nodeName = scopeName.toLowerCase() + ':' + nodeName;
			}

			this.getName = function() {
				return nodeName;
			};

			return this.getName();
		},

		/**
		 * Gets the value set to this element. This value is usually available
		 * for form field elements.
		 *
		 * @returns {String} The element value.
		 */
		getValue: function() {
			return this.$.value;
		},

		/**
		 * Gets the first child node of this element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div><b>Example</b></div>' );
		 *		var first = element.getFirst();
		 *		alert( first.getName() ); // 'b'
		 *
		 * @param {Function} evaluator Filtering the result node.
		 * @returns {CKEDITOR.dom.node} The first child node or null if not available.
		 */
		getFirst: function( evaluator ) {
			var first = this.$.firstChild,
				retval = first && new CKEDITOR.dom.node( first );
			if ( retval && evaluator && !evaluator( retval ) )
				retval = retval.getNext( evaluator );

			return retval;
		},

		/**
		 * See {@link #getFirst}.
		 *
		 * @param {Function} evaluator Filtering the result node.
		 * @returns {CKEDITOR.dom.node}
		 */
		getLast: function( evaluator ) {
			var last = this.$.lastChild,
				retval = last && new CKEDITOR.dom.node( last );
			if ( retval && evaluator && !evaluator( retval ) )
				retval = retval.getPrevious( evaluator );

			return retval;
		},

		/**
		 * Gets CSS style value.
		 *
		 * @param {String} name The CSS property name.
		 * @returns {String} Style value.
		 */
		getStyle: function( name ) {
			return this.$.style[ CKEDITOR.tools.cssStyleToDomStyle( name ) ];
		},

		/**
		 * Checks if the element name matches the specified criteria.
		 *
		 *		var element = new CKEDITOR.element( 'span' );
		 *		alert( element.is( 'span' ) );			// true
		 *		alert( element.is( 'p', 'span' ) );		// true
		 *		alert( element.is( 'p' ) );				// false
		 *		alert( element.is( 'p', 'div' ) );		// false
		 *		alert( element.is( { p:1,span:1 } ) );	// true
		 *
		 * @param {String.../Object} name One or more names to be checked, or a {@link CKEDITOR.dtd} object.
		 * @returns {Boolean} `true` if the element name matches any of the names.
		 */
		is: function() {
			var name = this.getName();

			// Check against the specified DTD liternal.
			if ( typeof arguments[ 0 ] == 'object' )
				return !!arguments[ 0 ][ name ];

			// Check for tag names
			for ( var i = 0; i < arguments.length; i++ ) {
				if ( arguments[ i ] == name )
					return true;
			}
			return false;
		},

		/**
		 * Decide whether one element is able to receive cursor.
		 *
		 * @param {Boolean} [textCursor=true] Only consider element that could receive text child.
		 */
		isEditable: function( textCursor ) {
			var name = this.getName();

			if ( this.isReadOnly() || this.getComputedStyle( 'display' ) == 'none' ||
				this.getComputedStyle( 'visibility' ) == 'hidden' ||
				CKEDITOR.dtd.$nonEditable[ name ] ||
				CKEDITOR.dtd.$empty[ name ] ||
				( this.is( 'a' ) &&
					( this.data( 'cke-saved-name' ) || this.hasAttribute( 'name' ) ) &&
					!this.getChildCount()
				) ) {
				return false;
			}

			if ( textCursor !== false ) {
				// Get the element DTD (defaults to span for unknown elements).
				var dtd = CKEDITOR.dtd[ name ] || CKEDITOR.dtd.span;
				// In the DTD # == text node.
				return !!( dtd && dtd[ '#' ] );
			}

			return true;
		},

		/**
		 * Compare this element's inner html, tag name, attributes, etc. with other one.
		 *
		 * See [W3C's DOM Level 3 spec - node#isEqualNode](http://www.w3.org/TR/DOM-Level-3-Core/core.html#Node3-isEqualNode)
		 * for more details.
		 *
		 * @param {CKEDITOR.dom.element} otherElement Element to compare.
		 * @returns {Boolean}
		 */
		isIdentical: function( otherElement ) {
			// do shallow clones, but with IDs
			var thisEl = this.clone( 0, 1 ),
				otherEl = otherElement.clone( 0, 1 );

			// Remove distractions.
			thisEl.removeAttributes( [ '_moz_dirty', 'data-cke-expando', 'data-cke-saved-href', 'data-cke-saved-name' ] );
			otherEl.removeAttributes( [ '_moz_dirty', 'data-cke-expando', 'data-cke-saved-href', 'data-cke-saved-name' ] );

			// Native comparison available.
			if ( thisEl.$.isEqualNode ) {
				// Styles order matters.
				thisEl.$.style.cssText = CKEDITOR.tools.normalizeCssText( thisEl.$.style.cssText );
				otherEl.$.style.cssText = CKEDITOR.tools.normalizeCssText( otherEl.$.style.cssText );
				return thisEl.$.isEqualNode( otherEl.$ );
			} else {
				thisEl = thisEl.getOuterHtml();
				otherEl = otherEl.getOuterHtml();

				// Fix tiny difference between link href in older IEs.
				if ( CKEDITOR.env.ie && CKEDITOR.env.version < 9 && this.is( 'a' ) ) {
					var parent = this.getParent();
					if ( parent.type == CKEDITOR.NODE_ELEMENT ) {
						var el = parent.clone();
						el.setHtml( thisEl ), thisEl = el.getHtml();
						el.setHtml( otherEl ), otherEl = el.getHtml();
					}
				}

				return thisEl == otherEl;
			}
		},

		/**
		 * Checks if this element is visible. May not work if the element is
		 * child of an element with visibility set to `hidden`, but works well
		 * on the great majority of cases.
		 *
		 * @returns {Boolean} True if the element is visible.
		 */
		isVisible: function() {
			var isVisible = ( this.$.offsetHeight || this.$.offsetWidth ) && this.getComputedStyle( 'visibility' ) != 'hidden',
				elementWindow, elementWindowFrame;

			// Webkit and Opera report non-zero offsetHeight despite that
			// element is inside an invisible iframe. (https://dev.ckeditor.com/ticket/4542)
			if ( isVisible && CKEDITOR.env.webkit ) {
				elementWindow = this.getWindow();

				if ( !elementWindow.equals( CKEDITOR.document.getWindow() ) && ( elementWindowFrame = elementWindow.$.frameElement ) )
					isVisible = new CKEDITOR.dom.element( elementWindowFrame ).isVisible();

			}

			return !!isVisible;
		},

		/**
		 * Whether it's an empty inline elements which has no visual impact when removed.
		 *
		 * @returns {Boolean}
		 */
		isEmptyInlineRemoveable: function() {
			if ( !CKEDITOR.dtd.$removeEmpty[ this.getName() ] )
				return false;

			var children = this.getChildren();
			for ( var i = 0, count = children.count(); i < count; i++ ) {
				var child = children.getItem( i );

				if ( child.type == CKEDITOR.NODE_ELEMENT && child.data( 'cke-bookmark' ) )
					continue;

				if ( child.type == CKEDITOR.NODE_ELEMENT && !child.isEmptyInlineRemoveable() || child.type == CKEDITOR.NODE_TEXT && CKEDITOR.tools.trim( child.getText() ) )
					return false;

			}
			return true;
		},

		/**
		 * Checks if the element has any defined attributes.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div title="Test">Example</div>' );
		 *		alert( element.hasAttributes() ); // true
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div>Example</div>' );
		 *		alert( element.hasAttributes() ); // false
		 *
		 * @method
		 * @returns {Boolean} True if the element has attributes.
		 */
		hasAttributes: CKEDITOR.env.ie && ( CKEDITOR.env.ie7Compat || CKEDITOR.env.quirks ) ?
			function() {
				var attributes = this.$.attributes;

				for ( var i = 0; i < attributes.length; i++ ) {
					var attribute = attributes[ i ];

					switch ( attribute.nodeName ) {
						case 'class':
							// IE has a strange bug. If calling removeAttribute('className'),
							// the attributes collection will still contain the "class"
							// attribute, which will be marked as "specified", even if the
							// outerHTML of the element is not displaying the class attribute.
							// Note : I was not able to reproduce it outside the editor,
							// but I've faced it while working on the TC of https://dev.ckeditor.com/ticket/1391.
							if ( this.getAttribute( 'class' ) ) {
								return true;
							}

						// Attributes to be ignored.
						/* falls through */
						case 'data-cke-expando':
							continue;


						/* falls through */
						default:
							if ( attribute.specified ) {
								return true;
							}
					}
				}

				return false;
			} : function() {
				var attrs = this.$.attributes,
					attrsNum = attrs.length;

				// The _moz_dirty attribute might get into the element after pasting (https://dev.ckeditor.com/ticket/5455)
				var execludeAttrs = { 'data-cke-expando': 1, _moz_dirty: 1 };

				return attrsNum > 0 && ( attrsNum > 2 || !execludeAttrs[ attrs[ 0 ].nodeName ] || ( attrsNum == 2 && !execludeAttrs[ attrs[ 1 ].nodeName ] ) );
			},

		/**
		 * Checks if the specified attribute is defined for this element.
		 *
		 * @method
		 * @param {String} name The attribute name.
		 * @returns {Boolean} `true` if the specified attribute is defined.
		 */
		hasAttribute: ( function() {
			function ieHasAttribute( name ) {
				var $attr = this.$.attributes.getNamedItem( name );

				if ( this.getName() == 'input' ) {
					switch ( name ) {
						case 'class':
							return this.$.className.length > 0;
						case 'checked':
							return !!this.$.checked;
						case 'value':
							var type = this.getAttribute( 'type' );
							return type == 'checkbox' || type == 'radio' ? this.$.value != 'on' : !!this.$.value;
					}
				}

				if ( !$attr )
					return false;

				return $attr.specified;
			}

			if ( CKEDITOR.env.ie ) {
				if ( CKEDITOR.env.version < 8 ) {
					return function( name ) {
						// On IE < 8 the name attribute cannot be retrieved
						// right after the element creation and setting the
						// name with setAttribute.
						if ( name == 'name' )
							return !!this.$.name;

						return ieHasAttribute.call( this, name );
					};
				} else {
					return ieHasAttribute;
				}
			} else {
				return function( name ) {
					// On other browsers specified property is deprecated and return always true,
					// but fortunately $.attributes contains only specified attributes.
					return !!this.$.attributes.getNamedItem( name );
				};
			}
		} )(),

		/**
		 * Hides this element (sets `display: none`).
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.hide();
		 */
		hide: function() {
			this.setStyle( 'display', 'none' );
		},

		/**
		 * Moves this element's children to the target element.
		 *
		 * @param {CKEDITOR.dom.element} target
		 * @param {Boolean} [toStart=false] Insert moved children at the
		 * beginning of the target element.
		 */
		moveChildren: function( target, toStart ) {
			var $ = this.$;
			target = target.$;

			if ( $ == target )
				return;

			var child;

			if ( toStart ) {
				while ( ( child = $.lastChild ) )
					target.insertBefore( $.removeChild( child ), target.firstChild );
			} else {
				while ( ( child = $.firstChild ) )
					target.appendChild( $.removeChild( child ) );
			}
		},

		/**
		 * Merges sibling elements that are identical to this one.
		 *
		 * Identical child elements are also merged. For example:
		 *
		 *		<b><i></i></b><b><i></i></b> => <b><i></i></b>
		 *
		 * @method
		 * @param {Boolean} [inlineOnly=true] Allow only inline elements to be merged.
		 */
		mergeSiblings: ( function() {
			function mergeElements( element, sibling, isNext ) {
				if ( sibling && sibling.type == CKEDITOR.NODE_ELEMENT ) {
					// Jumping over bookmark nodes and empty inline elements, e.g. <b><i></i></b>,
					// queuing them to be moved later. (https://dev.ckeditor.com/ticket/5567)
					var pendingNodes = [];

					while ( sibling.data( 'cke-bookmark' ) || sibling.isEmptyInlineRemoveable() ) {
						pendingNodes.push( sibling );
						sibling = isNext ? sibling.getNext() : sibling.getPrevious();
						if ( !sibling || sibling.type != CKEDITOR.NODE_ELEMENT )
							return;
					}

					if ( element.isIdentical( sibling ) ) {
						// Save the last child to be checked too, to merge things like
						// <b><i></i></b><b><i></i></b> => <b><i></i></b>
						var innerSibling = isNext ? element.getLast() : element.getFirst();

						// Move pending nodes first into the target element.
						while ( pendingNodes.length )
							pendingNodes.shift().move( element, !isNext );

						sibling.moveChildren( element, !isNext );
						sibling.remove();

						// Now check the last inner child (see two comments above).
						if ( innerSibling && innerSibling.type == CKEDITOR.NODE_ELEMENT )
							innerSibling.mergeSiblings();
					}
				}
			}

			return function( inlineOnly ) {
				// Merge empty links and anchors also. (https://dev.ckeditor.com/ticket/5567)
				if ( !( inlineOnly === false || CKEDITOR.dtd.$removeEmpty[ this.getName() ] || this.is( 'a' ) ) ) {
					return;
				}

				mergeElements( this, this.getNext(), true );
				mergeElements( this, this.getPrevious() );
			};
		} )(),

		/**
		 * Shows this element (displays it).
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.show();
		 */
		show: function() {
			this.setStyles( {
				display: '',
				visibility: ''
			} );
		},

		/**
		 * Sets the value of an element attribute.
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.setAttribute( 'class', 'myClass' );
		 *		element.setAttribute( 'title', 'This is an example' );
		 *
		 * @method
		 * @param {String} name The name of the attribute.
		 * @param {String} value The value to be set to the attribute.
		 * @returns {CKEDITOR.dom.element} This element instance.
		 */
		setAttribute: ( function() {
			var standard = function( name, value ) {
					this.$.setAttribute( name, value );
					return this;
				};

			if ( CKEDITOR.env.ie && ( CKEDITOR.env.ie7Compat || CKEDITOR.env.quirks ) ) {
				return function( name, value ) {
					if ( name == 'class' )
						this.$.className = value;
					else if ( name == 'style' )
						this.$.style.cssText = value;
					else if ( name == 'tabindex' ) // Case sensitive.
					this.$.tabIndex = value;
					else if ( name == 'checked' )
						this.$.checked = value;
					else if ( name == 'contenteditable' )
						standard.call( this, 'contentEditable', value );
					else
						standard.apply( this, arguments );
					return this;
				};
			} else if ( CKEDITOR.env.ie8Compat && CKEDITOR.env.secure ) {
				return function( name, value ) {
					// IE8 throws error when setting src attribute to non-ssl value. (https://dev.ckeditor.com/ticket/7847)
					if ( name == 'src' && value.match( /^http:\/\// ) ) {
						try {
							standard.apply( this, arguments );
						} catch ( e ) {}
					} else {
						standard.apply( this, arguments );
					}
					return this;
				};
			} else {
				return standard;
			}
		} )(),

		/**
		 * Sets the value of several element attributes.
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.setAttributes( {
		 *			'class':	'myClass',
		 *			title:		'This is an example'
		 *		} );
		 *
		 * @chainable
		 * @param {Object} attributesPairs An object containing the names and
		 * values of the attributes.
		 * @returns {CKEDITOR.dom.element} This element instance.
		 */
		setAttributes: function( attributesPairs ) {
			for ( var name in attributesPairs )
				this.setAttribute( name, attributesPairs[ name ] );
			return this;
		},

		/**
		 * Sets the element value. This function is usually used with form
		 * field element.
		 *
		 * @chainable
		 * @param {String} value The element value.
		 * @returns {CKEDITOR.dom.element} This element instance.
		 */
		setValue: function( value ) {
			this.$.value = value;
			return this;
		},

		/**
		 * Removes an attribute from the element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div class="classA"></div>' );
		 *		element.removeAttribute( 'class' );
		 *
		 * @method
		 * @param {String} name The attribute name.
		 */
		removeAttribute: ( function() {
			var standard = function( name ) {
					this.$.removeAttribute( name );
				};

			if ( CKEDITOR.env.ie && ( CKEDITOR.env.ie7Compat || CKEDITOR.env.quirks ) ) {
				return function( name ) {
					if ( name == 'class' )
						name = 'className';
					else if ( name == 'tabindex' )
						name = 'tabIndex';
					else if ( name == 'contenteditable' )
						name = 'contentEditable';
					standard.call( this, name );
				};
			} else {
				return standard;
			}
		} )(),

		/**
		 * Removes all element's attributes or just given ones.
		 *
		 * @param {Array} [attributes] The array with attributes names.
		 */
		removeAttributes: function( attributes ) {
			if ( CKEDITOR.tools.isArray( attributes ) ) {
				for ( var i = 0; i < attributes.length; i++ ) {
					this.removeAttribute( attributes[ i ] );
				}
			} else {
				attributes = attributes || this.getAttributes();

				for ( var attr in attributes ) {
					attributes.hasOwnProperty( attr ) && this.removeAttribute( attr );
				}
			}
		},

		/**
		 * Removes a style from the element.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div style="display:none"></div>' );
		 *		element.removeStyle( 'display' );
		 *
		 * @method
		 * @param {String} name The style name.
		 */
		removeStyle: function( name ) {
			// Removes the specified property from the current style object.
			var $ = this.$.style;

			// "removeProperty" need to be specific on the following styles.
			if ( !$.removeProperty && ( name == 'border' || name == 'margin' || name == 'padding' ) ) {
				var names = expandedRules( name );
				for ( var i = 0 ; i < names.length ; i++ )
					this.removeStyle( names[ i ] );
				return;
			}

			$.removeProperty ? $.removeProperty( name ) : $.removeAttribute( CKEDITOR.tools.cssStyleToDomStyle( name ) );

			// Eventually remove empty style attribute.
			if ( !this.$.style.cssText )
				this.removeAttribute( 'style' );
		},

		/**
		 * Sets the value of an element style.
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.setStyle( 'background-color', '#ff0000' );
		 *		element.setStyle( 'margin-top', '10px' );
		 *		element.setStyle( 'float', 'right' );
		 *
		 * @param {String} name The name of the style. The CSS naming notation
		 * must be used (e.g. `background-color`).
		 * @param {String} value The value to be set to the style.
		 * @returns {CKEDITOR.dom.element} This element instance.
		 */
		setStyle: function( name, value ) {
			this.$.style[ CKEDITOR.tools.cssStyleToDomStyle( name ) ] = value;
			return this;
		},

		/**
		 * Sets the value of several element styles.
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.setStyles( {
		 *			position:	'absolute',
		 *			float:		'right'
		 *		} );
		 *
		 * @param {Object} stylesPairs An object containing the names and
		 * values of the styles.
		 * @returns {CKEDITOR.dom.element} This element instance.
		 */
		setStyles: function( stylesPairs ) {
			for ( var name in stylesPairs )
				this.setStyle( name, stylesPairs[ name ] );
			return this;
		},

		/**
		 * Sets the opacity of an element.
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.setOpacity( 0.75 );
		 *
		 * @param {Number} opacity A number within the range `[0.0, 1.0]`.
		 */
		setOpacity: function( opacity ) {
			if ( CKEDITOR.env.ie && CKEDITOR.env.version < 9 ) {
				opacity = Math.round( opacity * 100 );
				this.setStyle( 'filter', opacity >= 100 ? '' : 'progid:DXImageTransform.Microsoft.Alpha(opacity=' + opacity + ')' );
			} else {
				this.setStyle( 'opacity', opacity );
			}
		},

		/**
		 * Makes the element and its children unselectable.
		 *
		 *		var element = CKEDITOR.document.getById( 'myElement' );
		 *		element.unselectable();
		 *
		 * @method
		 */
		unselectable: function() {
			// CSS unselectable.
			this.setStyles( CKEDITOR.tools.cssVendorPrefix( 'user-select', 'none' ) );

			// For IE/Opera which doesn't support for the above CSS style,
			// the unselectable="on" attribute only specifies the selection
			// process cannot start in the element itself, and it doesn't inherit.
			if ( CKEDITOR.env.ie ) {
				this.setAttribute( 'unselectable', 'on' );

				var element,
					elements = this.getElementsByTag( '*' );

				for ( var i = 0, count = elements.count() ; i < count ; i++ ) {
					element = elements.getItem( i );
					element.setAttribute( 'unselectable', 'on' );
				}
			}
		},

		/**
		 * Gets closest positioned (`position != static`) ancestor.
		 *
		 * @returns {CKEDITOR.dom.element} Positioned ancestor or `null`.
		 */
		getPositionedAncestor: function() {
			var current = this;
			while ( current.getName() != 'html' ) {
				if ( current.getComputedStyle( 'position' ) != 'static' )
					return current;

				current = current.getParent();
			}
			return null;
		},

		/**
		 * Gets this element's position in document.
		 *
		 * @param {CKEDITOR.dom.document} [refDocument]
		 * @returns {Object} Element's position.
		 * @returns {Number} return.x
		 * @returns {Number} return.y
		 * @todo refDocument
		 */
		getDocumentPosition: function( refDocument ) {
			var x = 0,
				y = 0,
				doc = this.getDocument(),
				body = doc.getBody(),
				quirks = doc.$.compatMode == 'BackCompat';

			if ( document.documentElement.getBoundingClientRect &&
				( CKEDITOR.env.ie ? CKEDITOR.env.version !== 8 : true ) ) {
				var box = this.$.getBoundingClientRect(),
					$doc = doc.$,
					$docElem = $doc.documentElement;

				var clientTop = $docElem.clientTop || body.$.clientTop || 0,
					clientLeft = $docElem.clientLeft || body.$.clientLeft || 0,
					needAdjustScrollAndBorders = true;

				// https://dev.ckeditor.com/ticket/3804: getBoundingClientRect() works differently on IE and non-IE
				// browsers, regarding scroll positions.
				//
				// On IE, the top position of the <html> element is always 0, no matter
				// how much you scrolled down.
				//
				// On other browsers, the top position of the <html> element is negative
				// scrollTop.
				if ( CKEDITOR.env.ie ) {
					var inDocElem = doc.getDocumentElement().contains( this ),
						inBody = doc.getBody().contains( this );

					needAdjustScrollAndBorders = ( quirks && inBody ) || ( !quirks && inDocElem );
				}

				// https://dev.ckeditor.com/ticket/12747.
				if ( needAdjustScrollAndBorders ) {
					var scrollRelativeLeft,
						scrollRelativeTop;

					// See https://dev.ckeditor.com/ticket/12758 to know more about document.(documentElement|body).scroll(Left|Top) in Webkit.
					if ( CKEDITOR.env.webkit || ( CKEDITOR.env.ie && CKEDITOR.env.version >= 12 ) ) {
						scrollRelativeLeft = body.$.scrollLeft || $docElem.scrollLeft;
						scrollRelativeTop = body.$.scrollTop || $docElem.scrollTop;
					} else {
						var scrollRelativeElement = quirks ? body.$ : $docElem;

						scrollRelativeLeft = scrollRelativeElement.scrollLeft;
						scrollRelativeTop = scrollRelativeElement.scrollTop;
					}

					x = box.left + scrollRelativeLeft - clientLeft;
					y = box.top + scrollRelativeTop - clientTop;
				}
			} else {
				var current = this,
					previous = null,
					offsetParent;
				while ( current && !( current.getName() == 'body' || current.getName() == 'html' ) ) {
					x += current.$.offsetLeft - current.$.scrollLeft;
					y += current.$.offsetTop - current.$.scrollTop;

					// Opera includes clientTop|Left into offsetTop|Left.
					if ( !current.equals( this ) ) {
						x += ( current.$.clientLeft || 0 );
						y += ( current.$.clientTop || 0 );
					}

					var scrollElement = previous;
					while ( scrollElement && !scrollElement.equals( current ) ) {
						x -= scrollElement.$.scrollLeft;
						y -= scrollElement.$.scrollTop;
						scrollElement = scrollElement.getParent();
					}

					previous = current;
					current = ( offsetParent = current.$.offsetParent ) ? new CKEDITOR.dom.element( offsetParent ) : null;
				}
			}

			if ( refDocument ) {
				var currentWindow = this.getWindow(),
					refWindow = refDocument.getWindow();

				if ( !currentWindow.equals( refWindow ) && currentWindow.$.frameElement ) {
					var iframePosition = ( new CKEDITOR.dom.element( currentWindow.$.frameElement ) ).getDocumentPosition( refDocument );

					x += iframePosition.x;
					y += iframePosition.y;
				}
			}

			if ( !document.documentElement.getBoundingClientRect ) {
				// In Firefox, we'll endup one pixel before the element positions,
				// so we must add it here.
				if ( CKEDITOR.env.gecko && !quirks ) {
					x += this.$.clientLeft ? 1 : 0;
					y += this.$.clientTop ? 1 : 0;
				}
			}

			return { x: x, y: y };
		},

		/**
		 * Make any page element visible inside the browser viewport.
		 *
		 * @param {Boolean} [alignToTop=false]
		 */
		scrollIntoView: function( alignToTop ) {
			var parent = this.getParent();
			if ( !parent )
				return;

			// Scroll the element into parent container from the inner out.
			do {
				// Check ancestors that overflows.
				var overflowed =
					parent.$.clientWidth && parent.$.clientWidth < parent.$.scrollWidth ||
					parent.$.clientHeight && parent.$.clientHeight < parent.$.scrollHeight;

				// Skip body element, which will report wrong clientHeight when containing
				// floated content. (https://dev.ckeditor.com/ticket/9523)
				if ( overflowed && !parent.is( 'body' ) )
					this.scrollIntoParent( parent, alignToTop, 1 );

				// Walk across the frame.
				if ( parent.is( 'html' ) ) {
					var win = parent.getWindow();

					// Avoid security error.
					try {
						var iframe = win.$.frameElement;
						iframe && ( parent = new CKEDITOR.dom.element( iframe ) );
					} catch ( er ) {}
				}
			}
			while ( ( parent = parent.getParent() ) );
		},

		/**
		 * Make any page element visible inside one of the ancestors by scrolling the parent.
		 *
		 * @param {CKEDITOR.dom.element/CKEDITOR.dom.window} parent The container to scroll into.
		 * @param {Boolean} [alignToTop] Align the element's top side with the container's
		 * when `true` is specified; align the bottom with viewport bottom when
		 * `false` is specified. Otherwise scroll on either side with the minimum
		 * amount to show the element.
		 * @param {Boolean} [hscroll] Whether horizontal overflow should be considered.
		 */
		scrollIntoParent: function( parent, alignToTop, hscroll ) {
			!parent && ( parent = this.getWindow() );

			var doc = parent.getDocument();
			var isQuirks = doc.$.compatMode == 'BackCompat';

			// On window <html> is scrolled while quirks scrolls <body>.
			if ( parent instanceof CKEDITOR.dom.window )
				parent = isQuirks ? doc.getBody() : doc.getDocumentElement();

			// Scroll the parent by the specified amount.
			function scrollBy( x, y ) {
				// Webkit doesn't support "scrollTop/scrollLeft"
				// on documentElement/body element.
				if ( /body|html/.test( parent.getName() ) )
					parent.getWindow().$.scrollBy( x, y );
				else {
					parent.$.scrollLeft += x;
					parent.$.scrollTop += y;
				}
			}

			// Figure out the element position relative to the specified window.
			function screenPos( element, refWin ) {
				var pos = { x: 0, y: 0 };

				if ( !( element.is( isQuirks ? 'body' : 'html' ) ) ) {
					var box = element.$.getBoundingClientRect();
					pos.x = box.left, pos.y = box.top;
				}

				var win = element.getWindow();
				if ( !win.equals( refWin ) ) {
					var outerPos = screenPos( CKEDITOR.dom.element.get( win.$.frameElement ), refWin );
					pos.x += outerPos.x, pos.y += outerPos.y;
				}

				return pos;
			}

			// calculated margin size.
			function margin( element, side ) {
				return parseInt( element.getComputedStyle( 'margin-' + side ) || 0, 10 ) || 0;
			}

			// [WebKit] Reset stored scrollTop value to not break scrollIntoView() method flow.
			// Scrolling breaks when range.select() is used right after element.scrollIntoView(). (https://dev.ckeditor.com/ticket/14659)
			if ( CKEDITOR.env.webkit ) {
				var editor = this.getEditor( false );

				if ( editor ) {
					editor._.previousScrollTop = null;
				}
			}

			var win = parent.getWindow();

			var thisPos = screenPos( this, win ),
				parentPos = screenPos( parent, win ),
				eh = this.$.offsetHeight,
				ew = this.$.offsetWidth,
				ch = parent.$.clientHeight,
				cw = parent.$.clientWidth,
				lt, br;

			// Left-top margins.
			lt = {
				x: thisPos.x - margin( this, 'left' ) - parentPos.x || 0,
				y: thisPos.y - margin( this, 'top' ) - parentPos.y || 0
			};

			// Bottom-right margins.
			br = {
				x: thisPos.x + ew + margin( this, 'right' ) - ( ( parentPos.x ) + cw ) || 0,
				y: thisPos.y + eh + margin( this, 'bottom' ) - ( ( parentPos.y ) + ch ) || 0
			};

			// 1. Do the specified alignment as much as possible;
			// 2. Otherwise be smart to scroll only the minimum amount;
			// 3. Never cut at the top;
			// 4. DO NOT scroll when already visible.
			if ( lt.y < 0 || br.y > 0 )
				scrollBy( 0, alignToTop === true ? lt.y : alignToTop === false ? br.y : lt.y < 0 ? lt.y : br.y );

			if ( hscroll && ( lt.x < 0 || br.x > 0 ) )
				scrollBy( lt.x < 0 ? lt.x : br.x, 0 );
		},

		/**
		 * Switch the `class` attribute to reflect one of the triple states of an
		 * element in one of {@link CKEDITOR#TRISTATE_ON}, {@link CKEDITOR#TRISTATE_OFF}
		 * or {@link CKEDITOR#TRISTATE_DISABLED}.
		 *
		 *		link.setState( CKEDITOR.TRISTATE_ON );
		 *		// <a class="cke_on" aria-pressed="true">...</a>
		 *		link.setState( CKEDITOR.TRISTATE_OFF );
		 *		// <a class="cke_off">...</a>
		 *		link.setState( CKEDITOR.TRISTATE_DISABLED );
		 *		// <a class="cke_disabled" aria-disabled="true">...</a>
		 *
		 *		span.setState( CKEDITOR.TRISTATE_ON, 'cke_button' );
		 *		// <span class="cke_button_on">...</span>
		 *
		 * @param {Number} state Indicate the element state. One of {@link CKEDITOR#TRISTATE_ON},
		 * {@link CKEDITOR#TRISTATE_OFF}, {@link CKEDITOR#TRISTATE_DISABLED}.
		 * @param [base='cke'] The prefix apply to each of the state class name.
		 * @param [useAria=true] Whether toggle the ARIA state attributes besides of class name change.
		 */
		setState: function( state, base, useAria ) {
			base = base || 'cke';

			switch ( state ) {
				case CKEDITOR.TRISTATE_ON:
					this.addClass( base + '_on' );
					this.removeClass( base + '_off' );
					this.removeClass( base + '_disabled' );
					useAria && this.setAttribute( 'aria-pressed', true );
					useAria && this.removeAttribute( 'aria-disabled' );
					break;

				case CKEDITOR.TRISTATE_DISABLED:
					this.addClass( base + '_disabled' );
					this.removeClass( base + '_off' );
					this.removeClass( base + '_on' );
					useAria && this.setAttribute( 'aria-disabled', true );
					useAria && this.removeAttribute( 'aria-pressed' );
					break;

				default:
					this.addClass( base + '_off' );
					this.removeClass( base + '_on' );
					this.removeClass( base + '_disabled' );
					useAria && this.removeAttribute( 'aria-pressed' );
					useAria && this.removeAttribute( 'aria-disabled' );
					break;
			}
		},

		/**
		 * Returns the inner document of this `<iframe>` element.
		 *
		 * @returns {CKEDITOR.dom.document} The inner document.
		 */
		getFrameDocument: function() {
			var $ = this.$;

			try {
				// In IE, with custom document.domain, it may happen that
				// the iframe is not yet available, resulting in "Access
				// Denied" for the following property access.
				$.contentWindow.document;
			} catch ( e ) {
				// Trick to solve this issue, forcing the iframe to get ready
				// by simply setting its "src" property.
				$.src = $.src;
			}

			return $ && new CKEDITOR.dom.document( $.contentWindow.document );
		},

		/**
		 * Copy all the attributes from one node to the other, kinda like a clone
		 * skipAttributes is an object with the attributes that must **not** be copied.
		 *
		 * @param {CKEDITOR.dom.element} dest The destination element.
		 * @param {Object} skipAttributes A dictionary of attributes to skip.
		 */
		copyAttributes: function( dest, skipAttributes ) {
			var attributes = this.$.attributes;
			skipAttributes = skipAttributes || {};

			for ( var n = 0; n < attributes.length; n++ ) {
				var attribute = attributes[ n ];

				// Lowercase attribute name hard rule is broken for
				// some attribute on IE, e.g. CHECKED.
				var attrName = attribute.nodeName.toLowerCase(),
					attrValue;

				// We can set the type only once, so do it with the proper value, not copying it.
				if ( attrName in skipAttributes )
					continue;

				if ( attrName == 'checked' && ( attrValue = this.getAttribute( attrName ) ) )
					dest.setAttribute( attrName, attrValue );
				// IE contains not specified attributes in $.attributes so we need to check
				// if elements attribute is specified using hasAttribute.
				else if ( !CKEDITOR.env.ie || this.hasAttribute( attrName ) ) {
					attrValue = this.getAttribute( attrName );
					if ( attrValue === null )
						attrValue = attribute.nodeValue;

					dest.setAttribute( attrName, attrValue );
				}
			}

			// The style:
			if ( this.$.style.cssText !== '' )
				dest.$.style.cssText = this.$.style.cssText;
		},

		/**
		 * Changes the tag name of the current element.
		 *
		 * @param {String} newTag The new tag for the element.
		 */
		renameNode: function( newTag ) {
			// If it's already correct exit here.
			if ( this.getName() == newTag )
				return;

			var doc = this.getDocument();

			// Create the new node.
			var newNode = new CKEDITOR.dom.element( newTag, doc );

			// Copy all attributes.
			this.copyAttributes( newNode );

			// Move children to the new node.
			this.moveChildren( newNode );

			// Replace the node.
			this.getParent( true ) && this.$.parentNode.replaceChild( newNode.$, this.$ );
			newNode.$[ 'data-cke-expando' ] = this.$[ 'data-cke-expando' ];
			this.$ = newNode.$;
			// Bust getName's cache. (https://dev.ckeditor.com/ticket/8663)
			delete this.getName;
		},

		/**
		 * Gets a DOM tree descendant under the current node.
		 *
		 *		var strong = p.getChild( 0 );
		 *
		 * @method
		 * @param {Array/Number} indices The child index or array of child indices under the node.
		 * @returns {CKEDITOR.dom.node} The specified DOM child under the current node. Null if child does not exist.
		 */
		getChild: ( function() {
			function getChild( rawNode, index ) {
				var childNodes = rawNode.childNodes;

				if ( index >= 0 && index < childNodes.length )
					return childNodes[ index ];
			}

			return function( indices ) {
				var rawNode = this.$;

				if ( !indices.slice )
					rawNode = getChild( rawNode, indices );
				else {
					indices = indices.slice();
					while ( indices.length > 0 && rawNode )
						rawNode = getChild( rawNode, indices.shift() );
				}

				return rawNode ? new CKEDITOR.dom.node( rawNode ) : null;
			};
		} )(),

		/**
		 * Gets number of element's children.
		 *
		 * @returns {Number}
		 */
		getChildCount: function() {
			return this.$.childNodes.length;
		},

		/**
		 * Disables browser's context menu in this element.
		 */
		disableContextMenu: function() {
			this.on( 'contextmenu', function( evt ) {
				// Cancel the browser context menu.
				if ( !evt.data.getTarget().getAscendant( enablesContextMenu, true ) )
					evt.data.preventDefault();
			} );

			function enablesContextMenu( node ) {
				return node.type == CKEDITOR.NODE_ELEMENT && node.hasClass( 'cke_enable_context_menu' );
			}
		},

		/**
		 * Gets element's direction. Supports both CSS `direction` prop and `dir` attr.
		 */
		getDirection: function( useComputed ) {
			if ( useComputed ) {
				return this.getComputedStyle( 'direction' ) ||
						this.getDirection() ||
						this.getParent() && this.getParent().getDirection( 1 ) ||
						this.getDocument().$.dir ||
						'ltr';
			}
			else {
				return this.getStyle( 'direction' ) || this.getAttribute( 'dir' );
			}
		},

		/**
		 * Gets, sets and removes custom data to be stored as HTML5 data-* attributes.
		 *
		 *		element.data( 'extra-info', 'test' );	// Appended the attribute data-extra-info="test" to the element.
		 *		alert( element.data( 'extra-info' ) );	// 'test'
		 *		element.data( 'extra-info', false );	// Remove the data-extra-info attribute from the element.
		 *
		 * @param {String} name The name of the attribute, excluding the `data-` part.
		 * @param {String} [value] The value to set. If set to false, the attribute will be removed.
		 */
		data: function( name, value ) {
			name = 'data-' + name;
			if ( value === undefined )
				return this.getAttribute( name );
			else if ( value === false )
				this.removeAttribute( name );
			else
				this.setAttribute( name, value );

			return null;
		},

		/**
		 * Retrieves an editor instance which is based on this element (if any).
		 * It basically loops over {@link CKEDITOR#instances} in search for an instance
		 * that uses the element.
		 *
		 *		var element = new CKEDITOR.dom.element( 'div' );
		 *		element.appendTo( CKEDITOR.document.getBody() );
		 *		CKEDITOR.replace( element );
		 *		alert( element.getEditor().name ); // 'editor1'
		 *
		 * By default this method considers only original DOM elements upon which the editor
		 * was created. Setting `optimized` parameter to `false` will consider editor editable
		 * and its children.
		 *
		 * @param {Boolean} [optimized=true] If set to `false` it will scan every editor editable.
		 * @returns {CKEDITOR.editor} An editor instance or null if nothing has been found.
		 */
		getEditor: function( optimized ) {
			var instances = CKEDITOR.instances,
				name, instance, editable;

			optimized = optimized || optimized === undefined;

			for ( name in instances ) {
				instance = instances[ name ];

				if ( instance.element.equals( this ) && instance.elementMode != CKEDITOR.ELEMENT_MODE_APPENDTO )
					return instance;

				if ( !optimized ) {
					editable = instance.editable();

					if ( editable && ( editable.equals( this ) || editable.contains( this ) ) ) {
						return instance;
					}
				}
			}

			return null;
		},

		/**
		 * Returns list of elements within this element that match specified `selector`.
		 *
		 * **Notes:**
		 *
		 *	* Not available in IE7.
		 *	* Returned list is not a live collection (like a result of native `querySelectorAll`).
		 *	* Unlike native `querySelectorAll` this method ensures selector contextualization. This is:
		 *
		 *			HTML:		'<body><div><i>foo</i></div></body>'
		 *			Native:		div.querySelectorAll( 'body i' ) // ->		[ <i>foo</i> ]
		 *			Method:		div.find( 'body i' ) // ->					[]
		 *						div.find( 'i' ) // ->						[ <i>foo</i> ]
		 *
		 * @since 4.3
		 * @param {String} selector
		 * @returns {CKEDITOR.dom.nodeList}
		 */
		find: function( selector ) {
			var removeTmpId = createTmpId( this ),
				list = new CKEDITOR.dom.nodeList(
					this.$.querySelectorAll( getContextualizedSelector( this, selector ) )
				);

			removeTmpId();

			return list;
		},

		/**
		 * Returns first element within this element that matches specified `selector`.
		 *
		 * **Notes:**
		 *
		 *	* Not available in IE7.
		 *	* Unlike native `querySelectorAll` this method ensures selector contextualization. This is:
		 *
		 *			HTML:		'<body><div><i>foo</i></div></body>'
		 *			Native:		div.querySelector( 'body i' ) // ->			<i>foo</i>
		 *			Method:		div.findOne( 'body i' ) // ->				null
		 *						div.findOne( 'i' ) // ->					<i>foo</i>
		 *
		 * @since 4.3
		 * @param {String} selector
		 * @returns {CKEDITOR.dom.element}
		 */
		findOne: function( selector ) {
			var removeTmpId = createTmpId( this ),
				found = this.$.querySelector( getContextualizedSelector( this, selector ) );

			removeTmpId();

			return found ? new CKEDITOR.dom.element( found ) : null;
		},

		/**
		 * Traverse the DOM of this element (inclusive), executing a callback for
		 * each node.
		 *
		 *		var element = CKEDITOR.dom.element.createFromHtml( '<div><p>foo<b>bar</b>bom</p></div>' );
		 *		element.forEach( function( node ) {
		 *			console.log( node );
		 *		} );
		 *		// Will log:
		 *		// 1. <div> element,
		 *		// 2. <p> element,
		 *		// 3. "foo" text node,
		 *		// 4. <b> element,
		 *		// 5. "bar" text node,
		 *		// 6. "bom" text node.
		 *
		 * @since 4.3
		 * @param {Function} callback Function to be executed on every node.
		 * If `callback` returns `false` descendants of the node will be ignored.
		 * @param {CKEDITOR.htmlParser.node} callback.node Node passed as argument.
		 * @param {Number} [type] If specified `callback` will be executed only on
		 * nodes of this type.
		 * @param {Boolean} [skipRoot] Don't execute `callback` on this element.
		 */
		forEach: function( callback, type, skipRoot ) {
			if ( !skipRoot && ( !type || this.type == type ) )
					var ret = callback( this );

			// Do not filter children if callback returned false.
			if ( ret === false )
				return;

			var children = this.getChildren(),
				node,
				i = 0;

			// We do not cache the size, because the live list of nodes may be changed by the callback.
			for ( ; i < children.count(); i++ ) {
				node = children.getItem( i );
				if ( node.type == CKEDITOR.NODE_ELEMENT )
					node.forEach( callback, type );
				else if ( !type || node.type == type )
					callback( node );
			}
		}
	} );

	function createTmpId( element ) {
		var hadId = true;

		if ( !element.$.id ) {
			element.$.id = 'cke_tmp_' + CKEDITOR.tools.getNextNumber();
			hadId = false;
		}

		return function() {
			if ( !hadId )
				element.removeAttribute( 'id' );
		};
	}

	function getContextualizedSelector( element, selector ) {
		var id = CKEDITOR.tools.escapeCss( element.$.id );
		return '#' + id + ' ' + selector.split( /,\s*/ ).join( ', #' + id + ' ' );
	}

	var sides = {
		width: [ 'border-left-width', 'border-right-width', 'padding-left', 'padding-right' ],
		height: [ 'border-top-width', 'border-bottom-width', 'padding-top', 'padding-bottom' ]
	};

	// Generate list of specific style rules, applicable to margin/padding/border.
	function expandedRules( style ) {
		var sides = [ 'top', 'left', 'right', 'bottom' ], components;

		if ( style == 'border' )
				components = [ 'color', 'style', 'width' ];

		var styles = [];
		for ( var i = 0 ; i < sides.length ; i++ ) {

			if ( components ) {
				for ( var j = 0 ; j < components.length ; j++ )
					styles.push( [ style, sides[ i ], components[ j ] ].join( '-' ) );
			} else {
				styles.push( [ style, sides[ i ] ].join( '-' ) );
			}
		}

		return styles;
	}

	function marginAndPaddingSize( type ) {
		var adjustment = 0;
		for ( var i = 0, len = sides[ type ].length; i < len; i++ )
			adjustment += parseFloat( this.getComputedStyle( sides[ type ][ i ] ) || 0, 10 ) || 0;
		return adjustment;
	}

	/**
	 * Sets the element size considering the box model.
	 *
	 * @param {'width'/'height'} type The dimension to set.
	 * @param {Number} size The length unit in px.
	 * @param {Boolean} isBorderBox Apply the size based on the border box model.
	 */
	CKEDITOR.dom.element.prototype.setSize = function( type, size, isBorderBox ) {
		if ( typeof size == 'number' ) {
			if ( isBorderBox && !( CKEDITOR.env.ie && CKEDITOR.env.quirks ) )
				size -= marginAndPaddingSize.call( this, type );

			this.setStyle( type, size + 'px' );
		}
	};

	/**
	 * Gets the element size, possibly considering the box model.
	 *
	 * @param {'width'/'height'} type The dimension to get.
	 * @param {Boolean} isBorderBox Get the size based on the border box model.
	 */
	CKEDITOR.dom.element.prototype.getSize = function( type, isBorderBox ) {
		var size = Math.max( this.$[ 'offset' + CKEDITOR.tools.capitalize( type ) ], this.$[ 'client' + CKEDITOR.tools.capitalize( type ) ] ) || 0;

		if ( isBorderBox )
			size -= marginAndPaddingSize.call( this, type );

		return size;
	};
} )();
