“In essence, CoreUI is a low-level framework that – ultimately – will be responsible for drawing all the user interface widgets in OS X. Among other things, CoreUI will define the look and feel of the Aqua interface. I say ‘will’ and ‘ultimately’ because at the time of writing CoreUI is still something of a work in progress. Some folks have reported that CoreUI isn’t used at all in Leopard, unless you change the scale factor from its default value of 1.0, but this is simplistic. By default, CoreUI is used for drawing a number of user interface elements in Leopard.”
