Fix race condition between ConfigureNotify and PresentCompleteNotify

* compositor.h: Update prototypes.
* frame_clock.c (struct _FrameClock): New fields for keeping
track of configure events.
(FreezeForValue): If the freeze is outdated, bring the counter
up to date now.
(XLFrameClockHandleFrameEvent): Set the number of configure
events that should have been considered by the frame clock upon
processing.
(XLFrameClockNoteConfigure): New function.
* picture_renderer.c (SwapBackBuffers): Remove outdated comment.
* xdg_surface.c (NoteConfigure, XLXdgRoleReconstrain):
* xdg_toplevel.c (NoteWindowResized): Note frame clock
configure.

compositor.h

@@ -1288,6 +1288,7 @@ extern void XLFrameClockDisablePredictRefresh (FrameClock *);
 extern void XLFrameClockSetFreezeCallback (FrameClock *, void (*) (void *),
 					   void *);
 extern uint64_t XLFrameClockGetFrameTime (FrameClock *);
+extern void XLFrameClockNoteConfigure (FrameClock *);
 extern void *XLAddCursorClockCallback (void (*) (void *, struct timespec),
 				       void *);
 extern void XLStopCursorClockCallback (void *);

frame_clock.c

@@ -109,6 +109,11 @@ struct _FrameClock
   /* The delay between the start of vblank and the redraw point.  */
   uint32_t frame_delay;
 
+  /* The number of configure events received affecting freeze, and the
+     number of configure events that should be received after a freeze
+     is put in place.  */
+  uint32_t got_configure_count, pending_configure_count;
+
   /* Whether or not configury is in progress, and whether or not this
      is frozen, and whether or not the frame shouldn't actually be
      unfrozen until EndFrame.  */
@@ -239,18 +244,31 @@ HandleEndFrame (Timer *timer, void *data, struct timespec time)
     EndFrame (clock);
 }
 
-/* Forward declaration.  */
+/* Forward declarations.  */
+
 static void RunFrameCallbacks (FrameClock *);
+static Bool StartFrame (FrameClock *, Bool, Bool);
 
 static void
 FreezeForValue (FrameClock *clock, uint64_t counter_value)
 {
+  Bool need_empty_frame;
+
   /* If it took too long (1 second at 60fps) to obtain the counter
      value, and said value is now out of date, don't do anything.  */
 
   if (clock->next_frame_id > counter_value)
     return;
 
+  need_empty_frame = False;
+
+  /* If ending a frame waits for PresentCompleteNotify, then the
+     configure event after this freeze may have been put into effect
+     by the time the freeze itself.  Start a new frame to bring up to
+     date contents to the display.  */
+  if (clock->pending_configure_count <= clock->got_configure_count)
+    need_empty_frame = True;
+
   /* The frame clock is now frozen, and we will have to wait for a
      client to ack_configure and then commit something.  */
 
@@ -278,7 +296,20 @@ FreezeForValue (FrameClock *clock, uint64_t counter_value)
   clock->in_frame = False;
   clock->need_configure = True;
   clock->configure_id = counter_value;
+
+  if (need_empty_frame)
+    {
+      /* Request a new frame and don't allow starting frames until it
+	 finishes.  See above for why.  clock->in_frame is False for
+	 now to really force the frame to happen.  */
+
+      StartFrame (clock, True, False);
+      EndFrame (clock);
+    }
+  else
     clock->frozen = True;
+
+  return;
 }
 
 static void
@@ -408,6 +439,10 @@ StartFrame (FrameClock *clock, Bool urgent, Bool predict)
     {
       clock->next_frame_id = clock->configure_id;
       clock->finished_frame_id = 0;
+
+      /* Don't start the end frame timer if this frame is being drawn
+	 in response to configury.  */
+      predict = True;
     }
 
   clock->in_frame = True;
@@ -700,6 +735,11 @@ XLFrameClockHandleFrameEvent (FrameClock *clock, XEvent *event)
       if (value % 2)
 	value += 1;
 
+      /* Set the number of configure events that should be received by
+	 the time the freeze is put into effect.  */
+      clock->pending_configure_count
+	= clock->got_configure_count + 1;
+
       /* If a frame is in progress, postpone this frame
 	 synchronization message.  */
       if (clock->in_frame && !clock->end_frame_called)
@@ -861,6 +901,13 @@ XLFrameClockGetFrameTime (FrameClock *clock)
   return clock->last_frame_time;
 }
 
+void
+XLFrameClockNoteConfigure (FrameClock *clock)
+{
+  /* This value is to track resize event validity.  */
+  clock->got_configure_count += 1;
+}
+
 
 /* Cursor animation clock-related functions.  */
 

picture_renderer.c

@@ -804,7 +804,6 @@ SwapBackBuffers (PictureTarget *target, pixman_region32_t *damage)
   if (!present_serial)
     present_serial++;
 
-  /* TODO: handle completion correctly.  */
   XPresentPixmap (compositor.display, target->window,
 		  back_buffer->pixmap, present_serial,
 		  None, region, 0, 0, None, None, fence,

xdg_surface.c

@@ -1064,6 +1064,11 @@ NoteConfigure (XdgRole *role, XEvent *event)
 					  event->xconfigure.y);
     }
 
+  /* Tell the frame clock how many WM-generated configure events have
+     arrived.  */
+  XLFrameClockNoteConfigure (role->clock);
+
+  /* Run reconstrain callbacks.  */
   RunReconstrainCallbacksForXEvent (role, event);
 }
 
@@ -1956,6 +1961,10 @@ XLXdgRoleReconstrain (Role *role, XEvent *event)
 
   xdg_role = XdgRoleFromRole (role);
   RunReconstrainCallbacksForXEvent (xdg_role, event);
+
+  /* If event is a configure event, tell the frame clock about it.  */
+  if (event->type == ConfigureNotify)
+    XLFrameClockNoteConfigure (xdg_role->clock);
 }
 
 void

xdg_toplevel.c

@@ -1660,6 +1660,8 @@ NoteWindowResized (Role *role, XdgRoleImplementation *impl,
 
       if (event.xconfigure.send_event)
 	XLXdgRoleNoteConfigure (toplevel->role, &event);
+      else
+	XLXdgRoleReconstrain (toplevel->role, &event);
 
       RecordStateSize (toplevel);
     }