window.onload = load_function;
window.onresize = resize_function;

function load_function() {
	dynamic_layout();
}

function resize_function() {
	deleteCookie("center_margin")
	dynamic_layout();
}

function obj_height(id) {
	return(document.getElementById(id).offsetHeight);
}

function obj_width(id) {
	return(document.getElementById(id).offsetWidth);
}

function use(id) {
	return(document.getElementById(id));
}

/*
   name - name of the cookie
   value - value of the cookie
   [expires] - expiration date of the cookie
     (defaults to end of current session)
   [path] - path for which the cookie is valid
     (defaults to path of calling document)
   [domain] - domain for which the cookie is valid
     (defaults to domain of calling document)
   [secure] - Boolean value indicating if the cookie transmission requires
     a secure transmission
   * an argument defaults when it is assigned null as a placeholder
   * a null placeholder is not required for trailing omitted arguments
*/
function setCookie(name, value, expires, path, domain, secure) {
    expires_date = new Date(new Date().getTime() + expires)

	var curCookie = name + "=" + escape(value) +
		((expires) ? "; expires=" + expires_date.toGMTString() : "") +
		((path) ? "; path=" + path : "") +
		((domain) ? "; domain=" + domain : "") +
		((secure) ? "; secure" : "");

	document.cookie = curCookie;
}

/*
  name - name of the desired cookie
  return string containing value of specified cookie or null
  if cookie does not exist
*/
function getCookie(name) {
	var dc = document.cookie;
	var prefix = name + "=";
	var begin = dc.indexOf("; " + prefix);

	if (begin == -1) {
		begin = dc.indexOf(prefix);
	
		if (begin != 0) return null;
	} else
	    begin += 2;

		var end = document.cookie.indexOf(";", begin);

		if (end == -1)
			end = dc.length;

	return unescape(dc.substring(begin + prefix.length, end));
}

/*
   name - name of the cookie
   [path] - path of the cookie (must be same as path used to create cookie)
   [domain] - domain of the cookie (must be same as domain used to
     create cookie)
   path and domain default if assigned null or omitted if no explicit
     argument proceeds
*/
function deleteCookie(name, path, domain) {
	if (getCookie(name)) {
		document.cookie = name + "=" +
			((path) ? "; path=" + path : "") +
			((domain) ? "; domain=" + domain : "") +
			"; expires=Thu, 01-Jan-70 00:00:01 GMT";
	}
}

function dynamic_layout() {
	var cookie_margin = getCookie("center_margin");

	if(! cookie_margin) {
		var browser_width = document.documentElement.clientWidth;
		var margin = Math.floor((browser_width - obj_width('middle')) / 2);

		if(margin < 0) {
			margin = 0;
		}

		use('left').style.width = margin + "px";
		use('right').style.width = margin + "px";

		setCookie("center_margin", margin, 6048000000);
	} else {
		var browser_width = document.documentElement.clientWidth;
		var margin = Math.floor((browser_width - obj_width('middle')) / 2);

		if(margin < 0) {
			margin = 0;
		}

		use('left').style.width = margin + "px";
		use('right').style.width = margin + "px";
	}

	use('middle').style.height = obj_height('content') + 220 + "px";
}

function show_sub(id) {
	use(id).style.visibility = 'visible';
}

function hide_sub(id) {
	use(id).style.visibility = 'hidden';
}

function toggle(id) {
	use('slideshow_img').src = "afbeelding_img.php?table=afbeeldingen&column=grote_thumbnail&key=pkAfbeeldingID&value=" + id;
}