Visible contents is quite ugly with pseudo-transparency terminals when moving
and with complex hight-level widget layouts when resizing.
So there is an option for disable this, but when I move or resize windows
everything stops : no gkrellm update, no song title scrolling with xmms and
even no music at all if I wait.
When release the mouse button, apps start again.
I use a 2.6 kernel with debian's xfce package.
The WM needs to grab the X server (display) when using xored ops to draw on
screen, like when it draws the windows frame.
That's unavoidable. Now why xmms stop playing when the display is grabbed is
yet another problem that resides in xmms, not xfwm.
I therefore shall close this call.
display must be grabbed when using xor draw. That's not a bug.