In Merlin, JToolBar now supports rollover toolbar buttons. This functionality was exclusive to metal in earlier versions but has been refactored into Basic so that the new Windows LAF now supports this feature.

Turning this feature on or off is hidden away in an obscure client property on the JToolBar instance:

toolbar.putClientProperty("JToolBar.isRollover"), Boolean.TRUE);

This feature would be much more promenent if there was a specific APIon JToolBar which would call the above client property:

void setRollover(boolean);

boolean isRollover();