[PATCH] Flush the wl_display at the end of SwapBuffers

[Kristian Høgsberg]

On Wed, Dec 04, 2013 at 02:36:05PM +0000, Neil Roberts wrote:
> I think this is a good idea. Imagine a simple game main loop like this:
> 
> while (TRUE) {
> 	do_some_game_logic();
>         redraw();
>         eglSwapBuffers();
> }
> 
> In that case it wouldn't flush the commit until the right at the
> beginning of each call to eglSwapBuffers when it waits for the frame
> callback. Then it would have to block waiting for the compositor to
> finish rendering before it receives the frame callback. If we dispatch
> after the swap buffers then in this case the compositor could start
> rendering while the game is in do_some_game_logic().
> 
> There was a similar patch proposed on the Mesa-dev mailing list here:
> 
> http://lists.freedesktop.org/archives/mesa-dev/2013-August/043697.html
> 
> That also points out the additional problem case where the rendering is
> done in a separate thread. After the rendering is done potentially
> nothing would wake up the main loop thread and cause a dispatch.
> 
> That patch also moves the call to dri2_dpy->flush->flush further up. I'm
> not sure if that is necessary. It also adds a pointer to the wl_display
> in struct dri2_egl_surface which definitely looks unnecessary. So I
> think Axel's patch makes more sense.
> 
> Reviewed-by: Neil Roberts <neil at linux.intel.com>

Yup, let's do it then.  I pushed the path to mesa master, with a Cc to
the 10.0 branch.

Kristian

> Regards,
> - Neil
> 
> Axel Davy <axel.davy at ens.fr> writes:
> 
> > We would like the compositor to receive the commited buffer
> > as soon as possible, so it has the time to treat it, and 
> > release old ones. We shouldn't rely on the client
> > to flush the queue for us.
> >
> > Signed-off-by: Axel Davy <axel.davy at ens.fr>
> > ---
> > We flush the wl_display after we flush the drawable.
> >
> >  src/egl/drivers/dri2/platform_wayland.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/src/egl/drivers/dri2/platform_wayland.c b/src/egl/drivers/dri2/platform_wayland.c
> > index 7e3733b..8c3d1f1 100644
> > --- a/src/egl/drivers/dri2/platform_wayland.c
> > +++ b/src/egl/drivers/dri2/platform_wayland.c
> > @@ -627,6 +627,8 @@ dri2_swap_buffers_with_damage(_EGLDriver *drv,
> >        (*dri2_dpy->flush->flush)(dri2_surf->dri_drawable);
> >     (*dri2_dpy->flush->invalidate)(dri2_surf->dri_drawable);
> >  
> > +   wl_display_flush(dri2_dpy->wl_dpy);
> > +
> >     return EGL_TRUE;
> >  }
> >  
> > -- 
> > 1.8.1.2
> >
> > _______________________________________________
> > wayland-devel mailing list
> > wayland-devel at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/wayland-devel



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