this is a pretty basic question and I'm a bit embarrassed to admit that I don't know the answer to it but... here it goes.
I've noticed that in many examples, you make use of the setControlImage and setCellImage methods of UI Controls to set an image. This is great, but there's one thing that's got me puzzled. Take the following example:
from some Class reference page. I've searched my entire ActiveWidgets tree for an image called "favorites.png, .gif. .jpeg" whatever. Nothing. The image just seems to be coming from outer space. Is it coming from the browser's chrome? If so, is there a place where I can inspect what images are available there? Does anyone have any links?