function screen_get(container)
{
	var nodes = $(container).childNodes;
	for (var i = 0; i < nodes.length; i++) {
		var node = nodes[i];
		if (node.tagName == 'A')
			return node;
	}
	return undefined;
}

function screen_push(container, node)
{
	var cont = $(container);
	if (cont.childNodes.length)
		cont.insertBefore(node, cont.childNodes[0]);
	else
		cont.appendChild(node);
}

function screen_update()
{
	var btn = $('screen-left');
	if (screen_get('screenshots-left')) {
		btn.src = '/st/index/v3/screen-left.gif';
		btn.style.cursor = 'pointer';
	} else {
		btn.src = '/st/interface/null.gif';
		btn.style.cursor = '';
	}
	var btn = $('screen-right');
	if (screen_get('screenshots-right')) {
		btn.src = '/st/index/v3/screen-right.gif';
		btn.style.cursor = 'pointer';
	} else {
		btn.src = '/st/interface/null.gif';
		btn.style.cursor = '';
	}
}

function screenshots_visible()
{
	var lst = new Array();
	var nodes = $('screenshots').childNodes;
	for (var i = 0; i < nodes.length; i++) {
		var node = nodes[i];
		if (node.tagName == 'A')
			lst.push(node);
	}
	return lst;
}

function screen_right()
{
	var node = screen_get('screenshots-right');
	if (node) {
		var vis = screenshots_visible();
		var old = vis[0];
		old.parentNode.removeChild(old);
		screen_push('screenshots-left', old);
		vis[1].className = 'screen-1';
		node.className = 'screen-2';
		vis[1].parentNode.insertBefore(node, vis[1].nextSibling);
	}
	screen_update();
}

function screen_left()
{
	var node = screen_get('screenshots-left');
	if (node) {
		var vis = screenshots_visible();
		var old = vis[1];
		old.parentNode.removeChild(old);
		screen_push('screenshots-right', old);
		vis[0].className = 'screen-2';
		node.className = 'screen-1';
		vis[0].parentNode.insertBefore(node, vis[0]);
	}
	screen_update();
}