http://bugs.winehq.org/show_bug.cgi?id=12640
--- Comment #12 from Giuseppe Bilotta giuseppe.bilotta@gmail.com 2008-04-20 02:34:46 --- The situation seems to be more complicated than that: for example, The Bat! has no minimize button, but it has a maximize button and I can resize it. Its taskbar button has a minimize command, but the maximize and shade commands are disabled.
Doing something like minimizing and restoring restores the functionality. I think this happens because something happens to the zero-sized control window although it's marked non-resizable (this is, however, something that deserves a different bug report because it happened even before the 'disappearing taskbar button' bug).
Also, there are lots of focusing problems because while for example clicking on the taskbar button brings the visible non-zero-sized window to front, it doesn't give it focus, which causes problems with e.g. dead keys. Also changing focus via alt-tab gives lots of strange problems. Not to mention that the app window comes up with the ugly <2> specifier that WMs put to disambiguate windows with the same name.
IMO, mapping the zero-sized window was not the best way fix for the disappearing taskbar, precisely because of all these problems (the patch I proposed to fix bug 12264 does not present this problem, AFAICS): we should just accept the fact that X window managers can't handle the zero-sized control window properly, and get done with it.