'infogulch has it right. A damage region is a way of saying "this region of pixels hasn't changed," but you can also say that for a scene graph, attributes of w

'infogulch has it right. A damage region is a way of saying "this region of pixels hasn't changed," but you can also say that for a scene graph, attributes of widgets, layout, the view tree, and other things. Ideally you press a key and the CPU does only a tiny amount of work figuring out what changed, followed by the GPU doing a tiny amount of work rerendering the changed pixels.