If we do this there is a short window where we think there is a grab, and
if we generate a client side pointer motion event in this time (e.g. from
a window move) we could be delivering that according to the grab. But in
the Xserver that grab is infinitely short as it sends Press and then
Release immediately.
To see a problem from this, try using the scrollwheel to quickly scroll
in the testgtk list of buttons.
This is basically the same fix as was done for
gdk_window_move_resize_internal. We make sure not to move the native
child window contents twice and we don't copy data that was overwritten
by the moving of the native child windows.
Whenever a native window is moved this causes an immediate change in
the window (the window content is copied). This change conflicts can
conflict with outstanding moves or other cached changed, so we need
to flush all outstanding moves in the related windows.
To simplify the code for window move/resize the toplevel version was
split out to its own function.
Move native windows after recomputing so that we get the right new
shape before moving (and the implied copy). This means we're not
copying too much data.
Take into account the area of a moved window that contains native
subwindows, as these affect things in two ways:
First of all we shouldn't copy the original window location, as that
is copied by the native window move.
Secondly, we can't copy things that would end up copying from the
native window move destination, as the data that used to be there is
now destroyed by the native window move.
It can happen that another native window is re-shaped over the region to
be moved, this will not destroy the data (since we're unsetting the background
when we reshape), but it will mean we need to read from this window.
We already used INCLUDE_INFERIORS, but that only handle subwindows. We fix
this by doing the copy on the toplevel, offsetting the copy to compensate for
this.
All the calls that unset private->parent failed if that was
not a native window (impl), instead we need to find the impl window
for the parent. Add some helper functions for this and use them.
For move/resize of child windows, we really need to recursively unset
on the parent, because moving the window could expose other native
children of the parent.
In do_shape_combine_region, only unset background if we're changing
the bounding shape (i.e. not the input shape)
There is no need to do all these computations when moving toplevels
as that can't really change any visible regions. Nor will it cause
any exposes we need to handle.
