The incorrect values could result in the new pixmap's contents
getting corrupted down the line.
v2:
* Guard screen_x/y lines by #ifdef COMPOSITE
Bugzilla: https://bugs.freedesktop.org/106841
Fixes: 029608dd80 "present: Add window flip mode"
Reviewed-by: Adam Jackson <ajax@redhat.com> # v1
Reviewed-by: Keith Packard <keithp@keithp.com> # v1
Reviewed-by: Roman Gilg <subdiff@gmail.com>
Tested-by: Olivier Fourdan <ofourdan@redhat.com> # v1