mark.lin@Eng 1998-02-02

When you tell a component to repaint itself, the RepaintManager paints it using paintImmediately which will:

 "Paint the specified region in this component and all of its descendants that overlap the region, immediately."

This means that any component getting draw will also have to draw any descendants which overlap it's bounds.

For example, in our app, we have two internal frames added to a desktop pane. Now suppose I place one internal frame over the other, such that the second internal frame cannot be seen. If I do something to cause the first internal frame to repaint itself, note that the internal frame underneath it (which isn't even visible) will get a call to repaint itself also.

This is because since the RepaintManager tells the first internal frame to paintImmediately, the internal frame tells it's parent, the desktop pane, to paint itself also. However, this will cause the desktop pane to paint any of it's children which are in the graphics's clip area. Since this area includes the second internal frame, that will get painted also, even though it is completely hidden!

It seems unnecessary for the repaint manager to paint a component starting from it's topmost parent. If I have a fast drawing component on top of a slow drawing component, the faster drawing component will take just as long to draw itself as the slower one because the RepaintManager ends up calling paintImmediately, which forces the slower one to get drawn also.

-Mark