compositor: set presentation.presented flags

compositor: set presentation.presented flags

Change weston_output_finish_frame() signature so that backends are
required to set the flags, that will be reported on the Presentation
'presented' event. This is meant for output-wide feedback flags. Flags
that vary per wl_surface are subject for the following patch.

All start_repaint_loop functions use the special private flag
PRESENTATION_FEEDBACK_INVALID to mark, that this call of
weston_output_finish_frame() cannot trigger the 'presented' event. If it
does, we now hit an assert, and should then investigate why a fake update
triggered Presentation feedback.

DRM:

Page flip is always vsync'd, and always gets the completion timestamp
from the kernel which should correspond well to hardware. Completion is
triggered by the kernel/hardware.

Vblank handler is only used with the broken planes path, therefore do
not report VSYNC, because we cannot guarantee all the planes updated at
the same time. We cannot set the INVALID, because it would abort the
compositor if the broken planes path was ever used.  This is a hack that
will get fixed with nuclear pageflip support in the future.

fbdev:

No vsync, update done by copy, no completion event from hardware, and
completion time is totally fake.

headless:

No real output to update.

RDP:

Guessing that maybe no vsync, fake time, and copy make sense (pixels
sent over network). Also no event that the pixels have been shown?

RPI:

Presumably Dispmanx updates are vsync'd. We get a completion event from
the driver, but need to read the clock ourselves, so the completion time
is somewhat unreliable. Zero-copy flag not implemented though it would
be theoretically possible with EGL clients (zero-copy is a per-surface
flag anyway, so in this patch).

Wayland:

No information how the host compositor is doing updates, so make a safe
guess without assuming vsync or hardware completion event. While we do
get some timestamp from the host compositor, it is not the completion
time. Would need to hook to the Presentation extension of the host
compositor to get more accurate flags.

X11:

No idea about vsync, completion event, or copying. Also the timestamp is
a fake.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Tested-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Acked-by: Mario Kleiner <mario.kleiner.de@gmail.com>