Make sure we're looking at the right location. The frame could have
received a motion event from a pointer from a different wl_seat, but
under X it looks like our core pointer moved. Move the frame pointer
to the button press location before deciding what to do.
If we're going to move or resize an xwayland surface, we used to just
pick the first seat in the list for doing the move/resize. Ideally we
can map from the XInput device doing the click to the corresponding
weston_seat, but that requires using xcb xinput, which isn't well supported.
Instead, lets use a simple heuristic that just picks the pointer that
most recently delivered a button event to the window in question.
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=73807
Set up X windows that are transient for another window as transient
surfaces in shell.c. This keeps the transient windows on top of their
parent as windows are raised, lowered for fullscreened.
https://bugs.freedesktop.org/show_bug.cgi?id=69443
