/**
 * Resize Events
 * @version 0.7
 * This extension is based on the 'text resize' events work of Lawrence Carvalho http://www.alistapart.com/articles/fontresizing/.
 * @author Lawrence Carvalho <carvalho@uk.yahoo-inc.com>
 * @author Andrew Ramsden <http://irama.org/>
 * @see http://irama.org/web/dhtml/resize-events/
 * @license GNU GENERAL PUBLIC LICENSE (GPL) <http://www.gnu.org/licenses/gpl.html>
 * @requires jQuery (tested with 1.4.2) <http://jquery.com/>
 */
var ResizeEvents = {
    baseTextHeight      : null,
    currentTextHeight   : null,
    baseWindowWidth     : null,
    baseWindowHeight    : null,
    currentWindowWidth  : null,
    currentWindowHeight : null,
    initialised         : false,
    intervalReference   : null,
    textSizeTestElement : null,
    eventElement        : $(document),
    conf                : {
        textResizeEvent          : 'x-text-resize',
        windowResizeEvent        : 'x-window-resize',
        windowWidthResizeEvent   : 'x-window-width-resize',
        windowHeightResizeEvent  : 'x-window-height-resize',
        initialResizeEvent       : 'x-initial-sizes',
        pollFrequency            : 500,
        textSizeTestElId         : 'text-resize'
    }
};
 // start closure (protects variables from global scope)
(function($){
    
    
    /**
     * A simple way to add a listener for resize events.
     * 
     * @param String events A space delimited list of events that should trigger this handler.
     * @param function handler The handler function to be called when an event occurs.
     */
    ResizeEvents.bind = function (events, handler) {
        
        // on DOMReady
            $(function(){
                // initialise if it hasn't happened already
                    if (ResizeEvents.initialised !== true) {
                        ResizeEvents.initialise();
                    }
            });
        
        ResizeEvents.eventElement.bind(
            events,
            handler
        );
    };
    
    /**
     * Initialisation
     */
    ResizeEvents.initialise = function () {
        
        if (ResizeEvents.initialised === true) {
            return; // already initialised
        }
        
        // create text resize control element, and push it offscreen
            ResizeEvents.textSizeTestElement = $(
                '<span id="'+ResizeEvents.conf.textSizeTestElId+'" style="position: absolute; left: -9999px; '+
                'font-size: 100%; font-family: Courier New, mono; margin: 0; padding: 0;">&nbsp;</span>'
            ).get(0);
            
        // append control element
            $('body').append(ResizeEvents.textSizeTestElement);
        
        // initialise variables
            windowWidthNow = $(window).width();
            windowHeightNow = $(window).height();
            textHeightNow = getTextHeight();
            ResizeEvents.baseTextHeight = textHeightNow;
            ResizeEvents.currentTextHeight = textHeightNow;
            ResizeEvents.baseWindowWidth = windowWidthNow;
            ResizeEvents.currentWindowWidth = windowWidthNow;
            ResizeEvents.baseWindowHeight = windowHeightNow;
            ResizeEvents.currentWindowHeight = windowHeightNow;
        
        // start polling
            if (ResizeEvents.intervalReference == null) {
                ResizeEventsPoll();
                ResizeEvents.intervalReference = window.setInterval('ResizeEventsPoll()', ResizeEvents.conf.pollFrequency);
            }
        
        // trigger onload
            ResizeEvents.eventElement.trigger(ResizeEvents.conf.initialResizeEvent, [emPixelNow, textHeightNow, windowWidthNow, windowHeightNow]);
                
        // flag initialisation complete
            ResizeEvents.initialised = true;
        
        
    };
    
    /**
     * This function is called a number of times each second to check if text size 
     * or window size has changed
     */
    ResizeEventsPoll = function () {
        
        // get current values
            windowWidthNow = $(window).width();
            windowHeightNow = $(window).height();
            textHeightNow = getTextHeight();
            emPixelNow = windowWidthNow/textHeightNow;
            widthChanged = false;
        
        // test for window width change
            if (ResizeEvents.currentWindowWidth != windowWidthNow) {
                // Send custom event
                    ResizeEvents.eventElement.trigger(ResizeEvents.conf.windowWidthResizeEvent, [emPixelNow, textHeightNow, windowWidthNow, windowHeightNow]);
                    ResizeEvents.eventElement.trigger(ResizeEvents.conf.windowResizeEvent, [emPixelNow, textHeightNow, windowWidthNow, windowHeightNow]);
                // update current height
                    ResizeEvents.currentWindowWidth = windowWidthNow;
                    widthChanged = true;
            }
        
        // test for window height change
            if (ResizeEvents.currentWindowHeight != windowHeightNow) {
                // Send custom event
                    ResizeEvents.eventElement.trigger(ResizeEvents.conf.windowHeightResizeEvent, [emPixelNow, textHeightNow, windowWidthNow, windowHeightNow]);
                    if (!widthChanged) { // don't send window-resize event twice
                        ResizeEvents.eventElement.trigger(ResizeEvents.conf.windowResizeEvent, [emPixelNow, textHeightNow, windowWidthNow, windowHeightNow]);
                    }
                // update current height
                    ResizeEvents.currentWindowHeight = windowHeightNow;
            }
        
        
        // test for text size change
            if (ResizeEvents.currentTextHeight != textHeightNow) {
                // Send custom event (with new text size)
                    ResizeEvents.eventElement.trigger(ResizeEvents.conf.textResizeEvent, [emPixelNow, textHeightNow, windowWidthNow, windowHeightNow]);
                // update current height
                    ResizeEvents.currentTextHeight = textHeightNow;
            }
    };
    
    /**
     * @return The current text height in pixels
     */
    getTextHeight = function () {
        return ResizeEvents.textSizeTestElement.offsetHeight+'';
    };
    
})(jQuery); /* end closure */