/*! Copyright (c) 2008 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.
 *
 * Version 2.1.2-pre
 */

(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);