At present, we ship a program called metacity-dialog, which is often to be found as the sole occupant of /usr/lib/metacity, and it gets spawned on the rare occasions when Metacity needs to ask the user a question. For example, if you attempt to close a window, Metacity asks the permission of the program which owns it; if nothing is heard back from that program within a reasonable time, Metacity spawns metacity-dialog to ask the user whether the window should be closed by force.
There are only three occasions when Metacity needs to ask such questions, and metacity-dialog has ad hoc code for each, with the usual problems attendant on ad hoc code. When there’s any difficulty with metacity-dialog (see, for example, Debian bug 427406), reproducing the fault can be pretty difficult.
GNOME also includes another program called zenity, whose purpose is to pop up and ask questions in just this way. Zenity is stable, polished, and well-understood. With the closing of GNOME bug 335763, zenity’s abilities are now a superset of metacity-dialog’s. It would be a simple matter to remove metacity-dialog from the codebase, and use zenity instead.
The only difficulty I can see is that in some distros it may not always be true that if Metacity is installed, zenity will be too, and it may be difficult to add this as a dependency. Of course, they can always patch and keep metacity-dialog; what do you folks think?
Photo by Dave Spellman; cc-by-nc.