IdealGraphVisualizer: work around a Swing/NetBeans tree UI problem that occurs when mouse events are handled while the tree model is changing, e.g. when using IGV while it still receives graphs from a compiler. BasicTreeUI attempts to get the boundaries for the node associated with the location on screen, but fails and tries to access a null Rectangle, causing a user-visible NullPointerException. By implementing equals() for GraphNode, nodes for graphs that are already in the tree are not removed and re-added when updating groups, and the exception can no longer be reproduced. This potentially also resolves some redraw issues.

Lukas Stadler (stadler@ssw.jku.at)
* July - September 2010: Initial feature-complete implementation, remote compilation
* Since April 2011: New IR design

Gilles Duboscq (gilles.duboscq@oracle.com)
* Since April 2011: New IR design

Peter Hofer (hofer@ssw.jku.at)
* Since May 2011: Graphviz visualization

Thomas Wuerthinger (thomas.wuerthinger@oracle.com)
* June 2011: Initial prototype
* October 2010 - January 2011: Bug fixes (all DaCapo's pass), better performance on SciMark than C1
* Since April 2011: New IR design