/* 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: 2009-10-21 16:47:45 +0200 (Mi, 21 Okt 2009) $
 * $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);