[PATCH weston] compositor-wayland: ignore frame callback's time

[Derek Foreman]

Makes sense, fixes the problem for me.

Reviewed-by: Derek Foreman <derekf at osg.samsung.com>

On 02/04/15 08:54 AM, Pekka Paalanen wrote:
> From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> 
> Weston running the Wayland backend is nested. The parent compositor uses
> an unknown clock for the frame callback timestamps. This is quite likely
> a different clock from what the nested Weston chose as its presentation
> clock.
> 
> This means we cannot reasonably read the presentation clock and assume
> it has any relation to the timestamp got from the frame callback. In
> fact, this was seen to cause absurd repaint delays, trigger the insanity
> check, reduce fraterate, etc. problems, because we assume we can read
> the clock and compute the remaining repaint delay.
> 
> As we can't use the timestamp, ignore it, and read our own presentation
> clock instead.
> 
> The X11 backend does not suffer from this, because there the parent
> window system never provides us any timestamps, so we always read our
> own clock.
> 
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> Cc: Derek Foreman <derekf at osg.samsung.com>
> Cc: Giulio Camuffo <giuliocamuffo at gmail.com>
> ---
>  src/compositor-wayland.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/src/compositor-wayland.c b/src/compositor-wayland.c
> index 7e59ecd..6c33361 100644
> --- a/src/compositor-wayland.c
> +++ b/src/compositor-wayland.c
> @@ -312,8 +312,15 @@ frame_done(void *data, struct wl_callback *callback, uint32_t time)
>  	wl_callback_destroy(callback);
>  
>  	/* XXX: use the presentation extension for proper timings */
> -	ts.tv_sec = time / 1000;
> -	ts.tv_nsec = (time % 1000) * 1000000;
> +
> +	/*
> +	 * This is the fallback case, where Presentation extension is not
> +	 * available from the parent compositor. We do not know the base for
> +	 * 'time', so we cannot feed it to finish_frame(). Do the only thing
> +	 * we can, and pretend finish_frame time is when we process this
> +	 * event.
> +	 */
> +	weston_compositor_read_presentation_clock(output->compositor, &ts);
>  	weston_output_finish_frame(output, &ts, 0);
>  }
>  
>