var g_menu_imageCache;

function menu_load()
{
	// cache menu images, etc.
	var menuEle = document.getElementById( 'menu' );
	if( !menuEle )
		return;
	
	g_menu_imageCache = new Array();
	
	var imgList = menuEle.getElementsByTagName( 'img' );
	for( var i = 0; i < imgList.length; ++i )
	{
		var img = imgList[ i ];
		var src = img.src;
		var lastDot = src.lastIndexOf( '.' );
		var pre_src = src.substr( 0, lastDot );
		var post_src = src.substr( lastDot );
		
		img.onmouseover = menu_createOverHandler( img, pre_src, post_src );
		img.onmouseout = menu_createOutHandler( img, pre_src, post_src );
		
		// Cache the image.
		var imgObj = new Image();
		imgObj.src = pre_src + '_over' + post_src;
		g_menu_imageCache.push( imgObj );
	}
}

function menu_createOverHandler( img, pre_src, post_src )
{
	return function()
	{
		img.src = pre_src + '_over' + post_src;
	};
}

function menu_createOutHandler( img, pre_src, post_src )
{
	return function()
	{
		img.src = pre_src + post_src;
	};
}

function menu_unload()
{
	var menuEle = document.getElementById( 'menu' );
	if( !menuEle )
		return;
	
	var imgList = menuEle.getElementsByTagName( 'img' );
	for( var i = 0; i < imgList.length; ++i )
	{
		var img = imgList[ i ];
		img.onmouseover = null;
		img.onmouseout = null;
	}
	
	g_menu_imageCache = null;
}