var fch_change = 3;
var fontsize_changes = [1, 2, 3, 7, 13];

function fch_go(dir, sel, min, max) {
	var newval = Math.min(max, Math.max(min, fch_change + dir));
	if (newval == fch_change) return;

	var diff = fontsize_changes[newval - 1] - fontsize_changes[fch_change - 1];
	fch_change = newval;
	
	var fs = 0;

	$$('*').each(function(el) {
		if (fs = el.getStyle('font-size').toInt()) {
			el.setStyle('font-size', (fs + diff) + 'px');
		}
	});

	$(sel).src='fileadmin/widgets/i/fs_display_'+fch_change+'.png';

}