/*	Script: element.pin.js
		Extends the Mootools <Window> and <Element> classes to allow fixed positioning for an element.

		Dependencies:
		mootools = <Element.js>, <Window.js> and all their dependencies
	
		Class: window
		This extends the <window> class from the <http://mootools.net> library.
	*/
window.extend({
/*	Property: supportsPositionFixed
		Returns true if the browser supports fixed positioning; must be called after DomReady (or it returns null);
	*/
	supportsPositionFixed: function(){
		if(!window.loaded) return null;
		var test = new Element('div').setStyles({
			position: 'fixed',
			top: '0px',
			right: '0px'
		}).injectInside(document.body);
		var supported = (test.offsetTop === 0);
		test.remove();
		return supported;
	}
});

/*	Class: Element
		Extends the <Element> class from the <http://mootools.net> library.
	*/
Element.extend({
/*	Property: pin
		Affixes an element at its current position, even if the window is scrolled.
		
		Arguments: 
		pin - (boolean) true: pin, false: release pin. See also <Element.unpin>.
	*/
	pin: function(enable){
		var p = this.getPosition();
		if(enable!==false) {
			if(!this.pinned) {
				var pos = {
					top: (p.y - window.getScrollTop())+'px',
					left: (p.x - window.getScrollLeft())+'px'
				};
				if(window.supportsPositionFixed()) {
					this.setStyle('position','fixed').setStyles(pos);
				} else {
					this.setStyles({
						position: 'absolute',
						top: p.y+'px',
						left: p.x+'px'
					});
					window.addEvent('scroll', function(){
						if(this.pinned) {
							var to = {
								top: (pos.top.toInt() + window.getScrollTop())+'px',
								left: (pos.left.toInt() + window.getScrollLeft())+'px'
							};
							this.setStyles(to);
						}
					}.bind(this));
				}
				this.pinned = true;
			}
		} else {
			this.pinned = false;
			var reposition = (window.supportsPositionFixed())?
				{
					top: (p.y + window.getScrollTop())+'px',
					left: (p.x + window.getScrollLeft())+'px'
				}:
				{
					top: (p.y)+'px',
					left: (p.x)+'px'
				};
			this.setStyles($merge(reposition, {position: 'absolute'}));
		}
		return this;
	},
/*	Property: unpin
		Un-pins an element at its current position (see <Element.pin>).
	*/
	unpin: function(){
		return this.pin(false);
	},
/*	Property: togglepin
		Toggles the pin state of the element.
	*/
	togglepin: function(){
		this.pin(!this.pinned);
	}
});