When I try to programmatically change the size of my window (using the FOX toolkit, with a call to XReconfigureWMWindow), it fails unless the old motif style hints have been specified that the window may resize (MWM_FUNC_RESIZE). This seems wrong, since the Motif hints should only apply to user actions, not to the programmers actions. At least, that's what I'm guessing what is going wrong. Changing the position in the call of XReconfigureWMWindow seem to work fine.
I do not see this in the code, but feel free to point me to where you think this is wrong.
In clientComputeWidth/clientComputeHight it checks against PMaxSize/PMinSize which are set by FOX if no resizing should be allowed. these are not updated by FOX, so they still contain the old values, therefore, resizing will fail. I believe the WM should just quietly update these values... I'll ask the FOX author and see what he thinks..
PMaxSize/PMinSize are not updated by the the WM, this is normal behaviour and it looks like a toolkit bug to me. BTW, this is totally unrelated to MWM hints, so this looks like to another different toolkit bug.
Ok, I've talked to the FOX author. He will fix the issue of not updating the size hints. I'll leave it up to you whether or not have a workaround in xfwm for other possible broken toolkits.
Closing as invalid, the bug is not in the WM