gistfile1.js

// determine if an element is COMPLETELY inside the current viewport.
// surely, there must be an easier way

$.expr[':']['in-viewport'] = function(element){
	var $win = $(window), $el = $(element),

		// element calculations
		offset = $el.offset(),
		outerWidth = $el.outerWidth(),
		outerHeight = $el.outerHeight(),
		offsetLeft = offset.left + outerWidth,
		offsetTop = offset.top + outerHeight,
	
		// window calculations
		winScrollTop = $win.scrollTop(), 
		winScrollLeft = $win.scrollLeft(),
		winViewportTop = $win.height() + winScrollTop,
		winViewportLeft = $win.width() + winScrollLeft;

	// so... is it in the viewport?

	return offsetLeft >= winScrollLeft 
		&& offsetLeft <= (winViewportLeft + outerWidth)
		&& offsetTop >= winScrollTop 
		&& offsetTop <= (winViewportTop + outerHeight)
		? true : false;
}