Created attachment 36487 [details]
Three windows, Firefox, pidgin and gnome-terminal. Pidgin (chat window) has focus, firefox is behind it, and gnome-terminal is at the back (but still visible which is wrong)

When I connect an external screen (1680x1050) next to my normal laptop screen (1280x800) window stacking is wrong.

What happens is:
I have 2 windows A and B, window A is bigger, and  window B is at the same position as window A. So normally you expect when A has focus you cant see B (its hidden by A), and the other way around, when B has foucs, you can only see part of A.

This does not happen. What happens is
Window A has focus: window B is not visible, but a large dark shadow at its position is, also a lighter shadow is completely above A
Window B has focus: window B visible, A still has the lighter shadow

If B is a gnome-terminal (which in my case uses transparancy in its main window, so probably other "transparent" apps behave the same)
Window A has focus: window B is visible, with shadow. A has shadow
window B has focus: window B is visible without shadow, A has shadow

Also normal windows (= not gnome-terminal) have a shadow above them (even when they are not overlapped by or overlapping another window)

This is only with metacity with compositing enabled. (I havent tried compiz, or another compositing window manager)

When I connect the same external screen at the same position of my laptop screen (so total screen size is 1680x1050 and not (1680+1280)x1050) these problems do not appear.

I'm using latest xorg-edgers PPA on intel 950. (wich has xorg-intel-driver 2.12, and latest drm fix)