Qooxdoo change global application font size

setFontSize: function(size)
{
	var doc         = this.getRoot();  
	var manager     = qx.theme.manager.Font.getInstance();  
	var defaultFont = manager.resolve(doc.getFont());
	var newFont     = defaultFont.clone().setSize(parseInt(size));
	doc.setFont(newFont);
},