code: function measure() {
  			if (!tw || !th) {
  				var wrapper = $('.plupload_file:eq(0)', self.filelist);
  				tw = wrapper.outerWidth(true);
  				th = wrapper.outerHeight(true);
  			}
  
  			var aw = self.content.width(), ah = self.content.height();
  			cols = Math.floor(aw / tw);
  			num =  cols * (Math.ceil(ah / th) + 1);
  		}
docs: calculate number of simultaneously visible thumbs