var gbLoaded = false;
var ggbLoaded = false;
var gImages, gNav;

function OnLoad(param) {
	gbLoaded = true;

	gNav = new LinkImage("img/nav-1.png", "img/nav-0.png");

	if (param == "groups") {
		OnLoadGroups();
	}
}

function OnLoadGroups() {
	ggbLoaded = true;

	//initialize global array for link images
	gImages = new Array(
		//images for group links
		new LinkImage("img/link-eruptions-1.jpg", "img/link-eruptions-0.jpg"),
		new LinkImage("img/link-flashflood-1.jpg", "img/link-flashflood-0.jpg"),
		new LinkImage("img/link-hurricanes-1.jpg", "img/link-hurricanes-0.jpg"),
		new LinkImage("img/link-meteorstrike-1.jpg", "img/link-meteorstrike-0.jpg"),
		new LinkImage("img/link-monsoon-1.jpg", "img/link-monsoon-0.jpg"),
		new LinkImage("img/link-mudslides-1.jpg", "img/link-mudslides-0.jpg"),
		new LinkImage("img/link-plague-1.jpg", "img/link-plague-0.jpg"),
		new LinkImage("img/link-prairiefire-1.jpg", "img/link-prairiefire-0.jpg"),
		new LinkImage("img/link-quake-1.jpg", "img/link-quake-0.jpg"),
		new LinkImage("img/link-tsunami-1.jpg", "img/link-tsunami-0.jpg"),
		new LinkImage("img/link-planning-1.jpg", "img/link-planning-0.jpg")
		);
}

//constructor for link image object
function LinkImage(imgOn, imgOff) {
	this.imgOn = new Image();
	this.imgOn.src = imgOn;

	this.imgOff = new Image();
	this.imgOff.src = imgOff;
}


/*
functions for changing images:
*/

//switches a link image to the "on" image
function on(num) {
	eval("document.img" + num + ".src = gImages[" + num + "].imgOn.src;");
}

//switches a link image to the "off" image
function off(num) {
	eval("document.img" + num + ".src = gImages[" + num + "].imgOff.src;");
}


/*
functions for navbar images
*/

function onNav(num) {
	eval("document.nav" + num + ".src = gNav.imgOn.src;");
}

function offNav(num) {
	eval("document.nav" + num + ".src = gNav.imgOff.src;");
}