http://spdsupport.org/forum/jscripts/popup_menu.js?ver=1400

1var PopupMenu = Class.create();
2
3PopupMenu.prototype = {
4
5	initialize: function(id, options)
6	{
7		document.currentMenu = "";
8
9		if(!$(id))
10		{
11			return false;
12		}
13		this.id = id;
14		var element = $(id);
15		
16		var popupMenu = element.id+"_popup";
17		if(!$(popupMenu))
18		{
19			return false;
20		}
21		
22		this.menu = $(popupMenu);
23		this.menu.style.display = "none";
24		element.onclick = this.openMenu.bindAsEventListener(this);
25	},
26	
27	openMenu: function(e)
28	{
29		Event.stop(e);
30		if(document.currentMenu && document.currentMenu == this.id)
31		{
32			this.closeMenu();
33			return false;
34		}
35		else if(document.currentMenu != "")
36		{
37			this.closeMenu();
38		}
39		
40		offsetTop = offsetLeft = 0;
41		var element = $(this.id);
42		do
43		{
44			offsetTop += element.offsetTop || 0;
45			offsetLeft += element.offsetLeft || 0;
46			element = element.offsetParent;
47			if(element)
48			{
49				if(Element.getStyle(element, 'position') == 'relative' || Element.getStyle(element, 'position') == 'absolute') break;
50			}
51		} while(element);
52		offsetTopReal = offsetTop;
53		offsetLeftReal = offsetLeft;
54		if(element) // will be true if we broke off the last loop
55		{
56			// calculate the true top/left position relative to page borders (this is used for checking whether the popup menu will be displayed within the page)
57			do
58			{
59				offsetTopReal += element.offsetTop || 0;
60				offsetLeftReal += element.offsetLeft || 0;
61			} while(element = element.offsetParent);
62		}
63		element = $(this.id);
64		element.blur();
65		this.menu.style.position = "absolute";
66		this.menu.style.zIndex = 100;
67		this.menu.style.top = (offsetTop+element.offsetHeight-1)+"px";
68		// Bad browser detection - yes, only choice - yes.
69		if(MyBB.browser == "opera" || MyBB.browser == "safari")
70		{
71			this.menu.style.top = (parseInt(this.menu.style.top)-2)+"px";
72		}
73		this.menu.style.left = offsetLeft+"px";
74		this.menu.style.visibility = 'hidden';
75		this.menu.style.display = 'block';
76		if(this.menu.style.width)
77		{
78			menuWidth = parseInt(this.menu.style.width);
79		}
80		else
81		{
82			menuWidth = this.menu.offsetWidth;
83		}
84		pageSize = DomLib.getPageSize();
85		if(offsetLeftReal+menuWidth >= pageSize[0])
86		{
87			this.menu.style.left = (offsetLeft-menuWidth+element.offsetWidth)+"px";
88		}
89		this.menu.style.display = 'block';	
90		this.menu.style.visibility = 'visible';
91
92		document.currentMenu = element.id;
93		Event.observe(document, 'click', this.closeMenu.bindAsEventListener(this));
94	},
95	
96	closeMenu: function()
97	{
98		if(!document.currentMenu)
99		{
100			return;
101		}
102		var menu = document.currentMenu;
103		menu = $(menu+"_popup");
104		menu.style.display = "none";
105		document.currentMenu = "";
106		document.onclick = function() { };
107	}
108};