For me this concept of expose/damage/paint event which bubbles through the window hierarchy is what defines the retained mode. In theory in immediate mode widg

For me this concept of expose/damage/paint event which bubbles through the window hierarchy is what defines the retained mode. In theory in immediate mode widget library you can have global state that defines which part of screen has to be repainted if any, but there is not that much of performance benefit because you still end up doing most of the processing for each frame and when there is any damaged region you still in effect redraw everything and clip it to the region.