I've done some research into the problem and also contacted the AWT developers. Here is the situation: the low-level AWT code is completely broken and needs big rework. It is unlikely that it gets fixed before JDK7 (and there are no guarantees, because this is formally a low-priority bug: non-reparenting WMs are not officially supported), although AWT developers are trying to improve the situation in background.
<br><br>Recently (in JDK 1.6u1) they added support for Compiz and LG3D WMs which don&#39;t do reparenting. Thus it is possible to make Xmonad pretend that it is one of these WMs, and thus workaround the problem. However pretending to be Compiz doesn&#39;t help (because of another AWT bug, cf. the insets problem). For LG3D there is a special branch which resets the insets to zero, which happens to be just what we need. Setting WM name to &quot;LG3D&quot; fixes gray-rectangle-instead-of-a-window problem.
<br><br>The patch adds a new XMonadContrib module. One should make a key-binding which executes the (setWMName &quot;LG3D&quot;), which should be used before running Java GUI programs. It is okay to execute this action several times, it takes care not to leak windows.
<br><br>Ivan<br>