/* Copyright (c) 2006 Brandon Aaron (http://brandonaaron.net)
* Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php) 
* and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses.
*
* $LastChangedDate: 2007-07-21 18:44:59 -0500 (Sat, 21 Jul 2007) $
* $Rev: 2446 $
*
* Version 2.1.1
*/

(function($) {

	/**
	* The bgiframe is chainable and applies the iframe hack to get 
	* around zIndex issues in IE6. It will only apply itself in IE6 
	* and adds a class to the iframe called 'bgiframe'. The iframe
	* is appeneded as the first child of the matched element(s) 
	* with a tabIndex and zIndex of -1.
	* 
	* By default the plugin will take borders, sized with pixel units,
	* into account. If a different unit is used for the border's width,
	* then you will need to use the top and left settings as explained below.
	*
	* NOTICE: This plugin has been reported to cause perfromance problems
	* when used on elements that change properties (like width, height and
	* opacity) a lot in IE6. Most of these problems have been caused by 
	* the expressions used to calculate the elements width, height and 
	* borders. Some have reported it is due to the opacity filter. All 
	* these settings can be changed if needed as explained below.
	*
	* @example $('div').bgiframe();
	* @before <div><p>Paragraph</p></div>
	* @result <div><iframe class="bgiframe".../><p>Paragraph</p></div>
	*
	* @param Map settings Optional settings to configure the iframe.
	* @option String|Number top The iframe must be offset to the top
	* 		by the width of the top border. This should be a negative 
	*      number representing the border-top-width. If a number is 
	* 		is used here, pixels will be assumed. Otherwise, be sure
	*		to specify a unit. An expression could also be used. 
	* 		By default the value is "auto" which will use an expression 
	* 		to get the border-top-width if it is in pixels.
	* @option String|Number left The iframe must be offset to the left
	* 		by the width of the left border. This should be a negative 
	*      number representing the border-left-width. If a number is 
	* 		is used here, pixels will be assumed. Otherwise, be sure
	*		to specify a unit. An expression could also be used. 
	* 		By default the value is "auto" which will use an expression 
	* 		to get the border-left-width if it is in pixels.
	* @option String|Number width This is the width of the iframe. If
	*		a number is used here, pixels will be assume. Otherwise, be sure
	* 		to specify a unit. An experssion could also be used.
	*		By default the value is "auto" which will use an experssion
	* 		to get the offsetWidth.
	* @option String|Number height This is the height of the iframe. If
	*		a number is used here, pixels will be assume. Otherwise, be sure
	* 		to specify a unit. An experssion could also be used.
	*		By default the value is "auto" which will use an experssion
	* 		to get the offsetHeight.
	* @option Boolean opacity This is a boolean representing whether or not
	* 		to use opacity. If set to true, the opacity of 0 is applied. If
	*		set to false, the opacity filter is not applied. Default: true.
	* @option String src This setting is provided so that one could change 
	*		the src of the iframe to whatever they need.
	*		Default: "javascript:false;"
	*
	* @name bgiframe
	* @type jQuery
	* @cat Plugins/bgiframe
	* @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
	*/
	$.fn.bgIframe = $.fn.bgiframe = function(s) {
		// This is only for IE6
		if ($.browser.msie && /6.0/.test(navigator.userAgent)) {
			s = $.extend({
				top: 'auto', // auto == .currentStyle.borderTopWidth
				left: 'auto', // auto == .currentStyle.borderLeftWidth
				width: 'auto', // auto == offsetWidth
				height: 'auto', // auto == offsetHeight
				opacity: true,
				src: 'javascript:false;'
			}, s || {});
			var prop = function(n) { return n && n.constructor == Number ? n + 'px' : n; },
		    html = '<iframe class="bgiframe"frameborder="0"tabindex="-1"src="' + s.src + '"' +
		               'style="display:block;position:absolute;z-index:-1;' +
			               (s.opacity !== false ? 'filter:Alpha(Opacity=\'0\');' : '') +
					       'top:' + (s.top == 'auto' ? 'expression(((parseInt(this.parentNode.currentStyle.borderTopWidth)||0)*-1)+\'px\')' : prop(s.top)) + ';' +
					       'left:' + (s.left == 'auto' ? 'expression(((parseInt(this.parentNode.currentStyle.borderLeftWidth)||0)*-1)+\'px\')' : prop(s.left)) + ';' +
					       'width:' + (s.width == 'auto' ? 'expression(this.parentNode.offsetWidth+\'px\')' : prop(s.width)) + ';' +
					       'height:' + (s.height == 'auto' ? 'expression(this.parentNode.offsetHeight+\'px\')' : prop(s.height)) + ';' +
					'"/>';
			return this.each(function() {
				if ($('> iframe.bgiframe', this).length == 0)
					this.insertBefore(document.createElement(html), this.firstChild);
			});
		}
		return this;
	};

})(jQuery);