The Present code sends the idle notification event to the client after
xwl_present_flush returns. If we don't flush our GPU work here, the
client may race to draw another frame to the same buffer, so we may end
up copying (parts of) that new frame instead of the one we meant to.
Fixes https://gitlab.freedesktop.org/xorg/xserver/issues/835
Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>
(Cherry picked from commit 2a2234ad1a)
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
The X server accepts requests from client applications to create windows,
which are (normally rectangular) "virtual screens" that the client program
can draw into.
Windows are then composed on the actual screen by the X server
(or by a separate composite manager) as directed by the window manager,
which usually communicates with the user via graphical controls such as buttons
and draggable titlebars and borders.
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