function RegisterPopupDismissal( dismissFunc, elemIgnore, bNoGuard )
{
	var dismissHandler = {
		guard: bNoGuard ? 0 : 1,
		dismiss: function( event ) {
			if ( this.elemIgnore )
			{
				var elem = Event.element( event );
				if ( elem.up( '#' + elemIgnore.id ) )
					return;
			}
			// ignore the first click- assume it's the one starting the popup
			if ( this.guard-- > 0 )
				return;
			this.regFunc();
			this.unregister();
		},
		unregister: function() {
			Event.stopObserving( document, 'click', this.boundHandler );
			Event.stopObserving( document, 'keydown', this.boundHandler );
		}
	};
	dismissHandler.regFunc = dismissFunc;
	dismissHandler.elemIgnore = elemIgnore || null;
	dismissHandler.boundHandler = dismissHandler.dismiss.bindAsEventListener( dismissHandler );
	Event.observe( document, 'click', dismissHandler.boundHandler );
	Event.observe( document, 'keydown', dismissHandler.boundHandler );
	
	return dismissHandler;
	
}
  function ShowMenu( elemLink, elemPopup, align, valign )
{
	var elemLink = $(elemLink);
	var elemPopup = $(elemPopup);
	
	AlignMenu( elemLink, elemPopup, align, valign );
	
	ShowWithFade( elemPopup );
	elemLink.addClassName('focus');
	RegisterPopupDismissal( function() { HideWithFade( elemPopup ); elemLink.removeClassName('focus'); }, elemPopup );
}
function ShowWithFade( elem )
{
	var elem = $(elem);

	if ( !elem.visible() || elem.hiding )
	{
		elem.hiding = false;
		if ( elem.effect )
			elem.effect.cancel();
		
		if ( Prototype.Browser.IE )
		{
			elem.addClassName( 'suppress_shadow' );
			elem.effect = new Effect.Appear( elem, { duration: 0.5, afterFinish: function() { elem.removeClassName( 'suppress_shadow' ); } } );
		}
		else
		{
			elem.effect = new Effect.Appear( elem, { duration: 0.5 } );
		}
	}
}

function HideWithFade( elem )
{
	var elem = $(elem);
	
	if ( elem.visible() && !elem.hiding )
	{
		if ( elem.effect && !elem.hiding )
			elem.effect.cancel();
		elem.hiding = true;

		if ( Prototype.Browser.IE )
		{
			elem.addClassName( 'suppress_shadow' );
		}
		elem.effect = new Effect.Fade( elem, { duration: 0.5 } );
	}
}
function AlignMenu( elemLink, elemPopup, align, valign )
{
	var align = align ? align : 'left';
	
	if ( !valign )
	{
		//if there's not enough room between our spot and the top of the document, we definitely want to drop down
		if ( document.viewport.getScrollOffsets().top + elemLink.viewportOffset().top < nPopupHeight )
			valign = 'bottom'; 
		else
		{			
			// add a little bit of padding so we don't position it flush to an edge if possible
			var nPopupHeight = elemPopup.getHeight() + 8;
			var nSpaceAbove = elemLink.viewportOffset().top;
			var nSpaceBelow = document.viewport.getHeight() - elemLink.viewportOffset().top;
			//otherwise we only want to drop down if we've got enough space below us (measured based on view area)
			// or if there's not enough space above to pop in either direction and there's more space below
			if ( nSpaceBelow > nPopupHeight || ( nSpaceAbove < nPopupHeight && nSpaceBelow > nSpaceAbove ) )
				valign = 'bottom'; 
			else
				valign = 'top';
			
		}
	}

	if ( align == 'left' )
	{
		elemPopup.style.left = ( elemLink.positionedOffset()[0] - 13 ) + 'px';
	} 
	else if ( align == 'right' )
	{
		elemPopup.style.left = ( elemLink.positionedOffset()[0] + elemLink.getWidth() - elemPopup.getWidth() + 14 ) + 'px';
	}
	
	if ( valign == 'bottom' ) 
	{
		elemPopup.style.top = ( elemLink.positionedOffset()[1] + elemLink.getHeight() - 12 ) + 'px';
	}
	else if ( valign == 'top' )
	{
		elemPopup.style.top = ( elemLink.positionedOffset()[1] - elemPopup.getHeight() + 12 ) + 'px';
	}
}