[cp-patches] FYI: JComponent painting optimization

[Roman Kennke]

I checked in a neat little optimization for painting overlapping
children. Up to now we always painted the whole stack of components for
a given clip, from the bottom up to the top. This is really not
necessary if one of the components spans the whole clip. In this case we
don't need to paint the underlying components. I added this checking in
JComponent.paintChildren as well as the implementation of the
isPaintingTile() method.

This should significantly improve performance for all overlapping
components like menus, JLayeredPanes, Popups, JTabbedPanes, etc.

2005-10-10  Roman Kennke  <address@hidden>

        * javax/swing/JComponent.java
        (paintingTile): New field.
        (isPaintingTile): Implemented.
        (paintChildren): Optimized painting of overlapping children.

/Roman

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