It sure does
for every application that proposes a plugin system. I have
been programing maya plugins profesionally and having the ability to use any
toolkit I want for my GUI certainely counts. Same goes for photoshop
plugins, FCP plugins, etc... I know the sort answer to this question from
unix people is always "you can't do this", period. Browser plugins have the
same problem too, in fact the lack of flexibility prevented people from
doing it but I'm pretty sure they would have done it a lot more if it was
available.
the point here is that not that there is any problem with XWindow. if
you are willing to use Xlib directly, you can do all this stuff with
no problems at all. the problems all arise from toolkits being too
egocentric and thinking that they will inevitably control the event
loop. if you cut toolkits out of the picture, and scribble on XWindows
and XDrawables using XDraw* functions and stuff like that, the
problems all go away. the problem is, nobody really wants to work at
that level, it seems.
and to put this a different way, you are also fine if you use a
"drawing kit" (such as OpenGL). these don't have event loops per se -
they just provide ways to draw things on an XDrawable.
--p