clutter/frame-clock: Add notify_ready()

In constrast to notify_presented(), notify_ready() also returns the
state machine to the idle state, but without providing new frame
information, as no frame was actually presented.

This will happen for example with the simple KMS impl backend will do a
cursor movement, which will trigger a symbolic "page flip" reply in
order to emulate atomic KMS behavior. When this happen, we should just
try to reschedule again.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>

clutter/clutter/clutter-frame-clock.c

@@ -215,6 +215,24 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     }
 }
 
+void
+clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock)
+{
+  switch (frame_clock->state)
+    {
+    case CLUTTER_FRAME_CLOCK_STATE_INIT:
+    case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+      g_warn_if_reached ();
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
+    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
+      maybe_reschedule_update (frame_clock);
+      break;
+    }
+}
+
 static void
 calculate_next_update_time_us (ClutterFrameClock *frame_clock,
                                int64_t           *out_next_update_time_us,

clutter/clutter/clutter-frame-clock.h

@@ -66,6 +66,9 @@ CLUTTER_EXPORT
 void clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
                                            ClutterFrameInfo  *frame_info);
 
+CLUTTER_EXPORT
+void clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock);
+
 CLUTTER_EXPORT
 void clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock);
 

src/tests/clutter/conform/frame-clock.c

@@ -747,6 +747,78 @@ frame_clock_destroy_signal (void)
   g_object_unref (frame_clock_backup);
 }
 
+static gboolean
+notify_ready_and_schedule_update_idle (gpointer user_data)
+{
+  ClutterFrameClock *frame_clock = user_data;
+
+  clutter_frame_clock_notify_ready (frame_clock);
+  clutter_frame_clock_schedule_update (frame_clock);
+
+  return G_SOURCE_REMOVE;
+}
+
+static ClutterFrameResult
+frame_clock_ready_frame (ClutterFrameClock *frame_clock,
+                         int64_t            frame_count,
+                         int64_t            time_us,
+                         gpointer           user_data)
+{
+  GMainLoop *main_loop = user_data;
+
+  g_assert_cmpint (frame_count, ==, expected_frame_count);
+
+  expected_frame_count++;
+
+  if (test_frame_count == 0)
+    {
+      g_main_loop_quit (main_loop);
+      return CLUTTER_FRAME_RESULT_IDLE;
+    }
+
+  test_frame_count--;
+
+  g_idle_add (notify_ready_and_schedule_update_idle, frame_clock);
+
+  return CLUTTER_FRAME_RESULT_PENDING_PRESENTED;
+}
+
+static const ClutterFrameListenerIface frame_clock_ready_listener_iface = {
+  .frame = frame_clock_ready_frame,
+};
+
+static void
+frame_clock_notify_ready (void)
+{
+  GMainLoop *main_loop;
+  ClutterFrameClock *frame_clock;
+  int64_t before_us;
+  int64_t after_us;
+
+  test_frame_count = 10;
+  expected_frame_count = 0;
+
+  main_loop = g_main_loop_new (NULL, FALSE);
+  frame_clock = clutter_frame_clock_new (refresh_rate,
+                                         &frame_clock_ready_listener_iface,
+                                         main_loop);
+
+  before_us = g_get_monotonic_time ();
+
+  clutter_frame_clock_schedule_update (frame_clock);
+  g_main_loop_run (main_loop);
+
+  after_us = g_get_monotonic_time ();
+
+  /* The initial frame will only be delayed by 2 ms, so we are checking one
+   * less.
+   */
+  g_assert_cmpint (after_us - before_us, >, 8 * refresh_interval_us);
+
+  g_main_loop_unref (main_loop);
+  clutter_frame_clock_destroy (frame_clock);
+}
+
 CLUTTER_TEST_SUITE (
   CLUTTER_TEST_UNIT ("/frame-clock/schedule-update", frame_clock_schedule_update)
   CLUTTER_TEST_UNIT ("/frame-clock/immediate-present", frame_clock_immediate_present)
@@ -757,4 +829,5 @@ CLUTTER_TEST_SUITE (
   CLUTTER_TEST_UNIT ("/frame-clock/inhibit", frame_clock_inhibit)
   CLUTTER_TEST_UNIT ("/frame-clock/reschedule-on-idle", frame_clock_reschedule_on_idle)
   CLUTTER_TEST_UNIT ("/frame-clock/destroy-signal", frame_clock_destroy_signal)
+  CLUTTER_TEST_UNIT ("/frame-clock/notify-ready", frame_clock_notify_ready)
 )