Calculate next-frame target time in absolute space

Rather than determining the time until next-frame repaint in relative
space (time until repaint), determine it first in absolute space, and
then later convert this to relative.

This will later allow us to store these per-output, so we can have a
single idle timer which will allow us to aggregate multiple repaints
together when timing allows.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

diff --git a/libweston/compositor.c b/libweston/compositor.c
index 2a9f476d4c96b2683f49cf09bc74f10fdd4c4799..e7c3b2df30707356438d6e2140f1264793e3288b 100644 (file)
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -2376,8 +2376,9 @@ weston_output_finish_frame(struct weston_output *output,
        struct weston_compositor *compositor = output->compositor;
        int32_t refresh_nsec;
        struct timespec now;
-       struct timespec gone;
-       int msec;
+       struct timespec next;
+       struct timespec remain;
+       int msec_rel = 0;
 
        TL_POINT("core_repaint_finished", TLP_OUTPUT(output),
                 TLP_VBLANK(stamp), TLP_END);
@@ -2389,34 +2390,35 @@ weston_output_finish_frame(struct weston_output *output,
                                                  presented_flags);
 
        output->frame_time = timespec_to_msec(stamp);
-
        weston_compositor_read_presentation_clock(compositor, &now);
-       timespec_sub(&gone, &now, stamp);
-       msec = (refresh_nsec - timespec_to_nsec(&gone)) / 1000000; /* floor */
-       msec -= compositor->repaint_msec;
 
-       if (msec < -1000 || msec > 1000) {
+       timespec_add_nsec(&next, stamp, refresh_nsec);
+       timespec_add_msec(&next, &next, -compositor->repaint_msec);
+       timespec_sub(&remain, &next, &now);
+       msec_rel = timespec_to_msec(&remain);
+
+       if (msec_rel < -1000 || msec_rel > 1000) {
                static bool warned;
 
                if (!warned)
                        weston_log("Warning: computed repaint delay is "
-                                  "insane: %d msec\n", msec);
+                                  "insane: %d msec\n", msec_rel);
                warned = true;
 
-               msec = 0;
+               msec_rel = 0;
        }
 
        /* Called from restart_repaint_loop and restart happens already after
         * the deadline given by repaint_msec? In that case we delay until
         * the deadline of the next frame, to give clients a more predictable
         * timing of the repaint cycle to lock on. */
-       if (presented_flags == WP_PRESENTATION_FEEDBACK_INVALID && msec < 0)
-               msec += refresh_nsec / 1000000;
+       if (presented_flags == WP_PRESENTATION_FEEDBACK_INVALID && msec_rel < 0)
+               msec_rel += refresh_nsec / 1000000;
 
-       if (msec < 1)
+       if (msec_rel < 1)
                output_repaint_timer_handler(output);
        else
-               wl_event_source_timer_update(output->repaint_timer, msec);
+               wl_event_source_timer_update(output->repaint_timer, msec_rel);
 }
 
 static void