mirrors
/
weston
mirror of https://gitlab.freedesktop.org/wayland/weston.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

protocol: add Presentation feedback flags 

Add the missing feedback flags to the Presentation extension protocol
specification.

These flags are slightly different from the previous RFCv3.1 definition:
http://lists.freedesktop.org/archives/wayland-devel/2014-March/013598.html

Now, all compositors are safe to use 0 as the flags if they don't bother
setting them properly. 0 is the "worst case" with the least guarantees.

The meaning of ZERO_COPY is not exactly the opposite of the old COPY
flag. ZERO_COPY is more strict, but applies only to that one surface.
Therefore it can be used to verify a zero-copy video playback pipeline,
also to a hardware overlay.

There is no longer a flag to clearly indicate if the final presentation
was done by a copy or a page flip. ZERO_COPY forbids the copy, but VSYNC
alone does allow copy in case it cannot tear.  It is possible to have
first a compositing pass, and then another copy into the frontbuffer,
and still set VSYNC if it cannot tear.  Usually "cannot tear" is too
hard to guarantee with a copy, so it often implies a page flip.

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>
This commit is contained in:
Pekka Paalanen 2014-12-17 16:20:39 +02:00 committed by Bryce Harrington
parent 050c1ba729
commit 0de22a38e6
1 changed files with 39 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
protocol/presentation_timing.xml
View File

@ -164,11 +164,47 @@
<enum name="kind">
<description summary="bitmask of flags in presented event">
Currently no flags are defined. Some flags will be added
into presentation_feedback version 1 before it is released.
These flags provide information about how the presentation of
the related content update was done. The intent is to help
clients assess the reliability of the feedback and the visual
quality with respect to possible tearing and timings. The
flags are:
VSYNC:
The presentation was synchronized to the "vertical retrace" by
the display hardware such that tearing does not happen.
Relying on user space scheduling is not acceptable for this
flag. If presentation is done by a copy to the active
frontbuffer, then it must guarantee that tearing cannot
happen.
HW_CLOCK:
The display hardware provided measurements that the hardware
driver converted into a presentation timestamp. Sampling a
clock in user space is not acceptable for this flag.
HW_COMPLETION:
The display hardware signalled that it started using the new
image content. The opposite of this is e.g. a timer being used
to guess when the display hardware has switched to the new
image content.
ZERO_COPY:
The presentation of this update was done zero-copy. This means
the buffer from the client was given to display hardware as
is, without copying it. Compositing with OpenGL counts as
copying, even if textured directly from the client buffer.
Possible zero-copy cases include direct scanout of a
fullscreen surface and a surface on a hardware overlay.
</description>
<entry name="dummy" value="0"/>
<entry name="vsync" value="0x1" summary="presentation was vsync'd"/>
<entry name="hw_clock" value="0x2"
summary="hardware provided the presentation timestamp"/>
<entry name="hw_completion" value="0x4"
summary="hardware signalled the start of the presentation"/>
<entry name="zero_copy" value="0x8"
summary="presentation was done zero-copy"/>
</enum>
<event name="presented">