Add gdk_frame_timings_get_predicted_presentation_time()

For an operation like synchronizing audio to video playback, we need to
be able to predict the time that a frame will be presented. The details
of this depend on the windowing system, so make the backend predict
a presentation time for ::begin-frame and set it on the GdkFrameTimings.

The timing algorithm of GdkFrameClockIdle is adjusted to give predictable
presentation times for frames that are not throttled by the windowing
system.

Helper functions:

 gdk_frame_clock_get_current_frame_timings()
 gdk_frame_clock_get_refresh_info()

are added for operations that would otherwise be needed multiple times
in different locations.

https://bugzilla.gnome.org/show_bug.cgi?id=685460

1 files changed, 9 insertions, 2 deletions

diff --git a/gdk/gdkframeclock.h b/gdk/gdkframeclock.h
index 03b04304cd..8d79f90a96 100644
--- a/gdk/gdkframeclock.h
+++ b/gdk/gdkframeclock.h
@@ -78,7 +78,7 @@ struct _GdkFrameClockInterface
 {
   GTypeInterface		   base_iface;
 
-  guint64  (* get_frame_time)      (GdkFrameClock *clock);
+  guint64  (* get_frame_time)            (GdkFrameClock *clock);
 
   void               (* request_phase) (GdkFrameClock      *clock,
                                         GdkFrameClockPhase  phase);
@@ -102,7 +102,7 @@ struct _GdkFrameClockInterface
 
 GType    gdk_frame_clock_get_type             (void) G_GNUC_CONST;
 
-guint64  gdk_frame_clock_get_frame_time      (GdkFrameClock *clock);
+guint64  gdk_frame_clock_get_frame_time            (GdkFrameClock *clock);
 
 void               gdk_frame_clock_request_phase (GdkFrameClock      *clock,
                                                   GdkFrameClockPhase  phase);
@@ -117,6 +117,13 @@ GdkFrameHistory *gdk_frame_clock_get_history (GdkFrameClock *clock);
 void  gdk_frame_clock_get_frame_time_val (GdkFrameClock  *clock,
                                           GTimeVal       *timeval);
 
+void gdk_frame_clock_get_refresh_info (GdkFrameClock *clock,
+                                       gint64         base_time,
+                                       gint64        *refresh_interval_return,
+                                       gint64        *presentation_time_return);
+
+GdkFrameTimings *gdk_frame_clock_get_current_frame_timings (GdkFrameClock *clock);
+
 /* Signal emitters (used in frame clock implementations) */
 void     gdk_frame_clock_frame_requested     (GdkFrameClock *clock);