summaryrefslogtreecommitdiff
path: root/gdk/gdkframeclock.c
blob: 9787be59b97565508bfa63b1a146e844665d81f8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
/* GDK - The GIMP Drawing Kit
 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Modified by the GTK+ Team and others 1997-2010.  See the AUTHORS
 * file for a list of people on the GTK+ Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
 */

#include "config.h"

#include "gdkframeclockprivate.h"

/**
 * GdkFrameClock:
 *
 * A `GdkFrameClock` tells the application when to update and repaint
 * a surface.
 *
 * This may be synced to the vertical refresh rate of the monitor, for example.
 * Even when the frame clock uses a simple timer rather than a hardware-based
 * vertical sync, the frame clock helps because it ensures everything paints at
 * the same time (reducing the total number of frames).
 *
 * The frame clock can also automatically stop painting when it knows the frames
 * will not be visible, or scale back animation framerates.
 *
 * `GdkFrameClock` is designed to be compatible with an OpenGL-based implementation
 * or with mozRequestAnimationFrame in Firefox, for example.
 *
 * A frame clock is idle until someone requests a frame with
 * [method@Gdk.FrameClock.request_phase]. At some later point that makes sense
 * for the synchronization being implemented, the clock will process a frame and
 * emit signals for each phase that has been requested. (See the signals of the
 * `GdkFrameClock` class for documentation of the phases.
 * %GDK_FRAME_CLOCK_PHASE_UPDATE and the [signal@Gdk.FrameClock::update] signal
 * are most interesting for application writers, and are used to update the
 * animations, using the frame time given by [method@Gdk.FrameClock.get_frame_time].
 *
 * The frame time is reported in microseconds and generally in the same
 * timescale as g_get_monotonic_time(), however, it is not the same
 * as g_get_monotonic_time(). The frame time does not advance during
 * the time a frame is being painted, and outside of a frame, an attempt
 * is made so that all calls to [method@Gdk.FrameClock.get_frame_time] that
 * are called at a “similar” time get the same value. This means that
 * if different animations are timed by looking at the difference in
 * time between an initial value from [method@Gdk.FrameClock.get_frame_time]
 * and the value inside the [signal@Gdk.FrameClock::update] signal of the clock,
 * they will stay exactly synchronized.
 */

enum {
  FLUSH_EVENTS,
  BEFORE_PAINT,
  UPDATE,
  LAYOUT,
  PAINT,
  AFTER_PAINT,
  RESUME_EVENTS,
  LAST_SIGNAL
};

static guint signals[LAST_SIGNAL];

static guint fps_counter;

#define FRAME_HISTORY_MAX_LENGTH 128

struct _GdkFrameClockPrivate
{
  gint64 frame_counter;
  int n_timings;
  int current;
  GdkFrameTimings *timings[FRAME_HISTORY_MAX_LENGTH];
  int n_freeze_inhibitors;
};

G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (GdkFrameClock, gdk_frame_clock, G_TYPE_OBJECT)

static void
_gdk_frame_clock_freeze (GdkFrameClock *clock);

static void
gdk_frame_clock_finalize (GObject *object)
{
  GdkFrameClockPrivate *priv = GDK_FRAME_CLOCK (object)->priv;
  int i;

  for (i = 0; i < FRAME_HISTORY_MAX_LENGTH; i++)
    if (priv->timings[i] != 0)
      gdk_frame_timings_unref (priv->timings[i]);

  G_OBJECT_CLASS (gdk_frame_clock_parent_class)->finalize (object);
}

static void
gdk_frame_clock_constructed (GObject *object)
{
  G_OBJECT_CLASS (gdk_frame_clock_parent_class)->constructed (object);

  _gdk_frame_clock_freeze (GDK_FRAME_CLOCK (object));
}

static void
gdk_frame_clock_class_init (GdkFrameClockClass *klass)
{
  GObjectClass *gobject_class = (GObjectClass*) klass;

  gobject_class->finalize     = gdk_frame_clock_finalize;
  gobject_class->constructed  = gdk_frame_clock_constructed;

  /**
   * GdkFrameClock::flush-events:
   * @clock: the frame clock emitting the signal
   *
   * Used to flush pending motion events that are being batched up and
   * compressed together.
   *
   * Applications should not handle this signal.
   */
  signals[FLUSH_EVENTS] =
    g_signal_new (g_intern_static_string ("flush-events"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * GdkFrameClock::before-paint:
   * @clock: the frame clock emitting the signal
   *
   * Begins processing of the frame.
   *
   * Applications should generally not handle this signal.
   */
  signals[BEFORE_PAINT] =
    g_signal_new (g_intern_static_string ("before-paint"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * GdkFrameClock::update:
   * @clock: the frame clock emitting the signal
   *
   * Emitted as the first step of toolkit and application processing
   * of the frame.
   *
   * Animations should be updated using [method@Gdk.FrameClock.get_frame_time].
   * Applications can connect directly to this signal, or use
   * [method@Gtk.Widget.add_tick_callback] as a more convenient interface.
   */
  signals[UPDATE] =
    g_signal_new (g_intern_static_string ("update"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * GdkFrameClock::layout:
   * @clock: the frame clock emitting the signal
   *
   * Emitted as the second step of toolkit and application processing
   * of the frame.
   *
   * Any work to update sizes and positions of application elements
   * should be performed. GTK normally handles this internally.
   */
  signals[LAYOUT] =
    g_signal_new (g_intern_static_string ("layout"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * GdkFrameClock::paint:
   * @clock: the frame clock emitting the signal
   *
   * Emitted as the third step of toolkit and application processing
   * of the frame.
   *
   * The frame is repainted. GDK normally handles this internally and
   * emits [signal@Gdk.Surface::render] signals which are turned into
   * [signal@Gtk.Widget::snapshot] signals by GTK.
   */
  signals[PAINT] =
    g_signal_new (g_intern_static_string ("paint"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * GdkFrameClock::after-paint:
   * @clock: the frame clock emitting the signal
   *
   * This signal ends processing of the frame.
   *
   * Applications should generally not handle this signal.
   */
  signals[AFTER_PAINT] =
    g_signal_new (g_intern_static_string ("after-paint"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * GdkFrameClock::resume-events:
   * @clock: the frame clock emitting the signal
   *
   * Emitted after processing of the frame is finished.
   *
   * This signal is handled internally by GTK to resume normal
   * event processing. Applications should not handle this signal.
   */
  signals[RESUME_EVENTS] =
    g_signal_new (g_intern_static_string ("resume-events"),
                  GDK_TYPE_FRAME_CLOCK,
                  G_SIGNAL_RUN_LAST,
                  0,
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);
}

static void
gdk_frame_clock_init (GdkFrameClock *clock)
{
  GdkFrameClockPrivate *priv;

  clock->priv = priv = gdk_frame_clock_get_instance_private (clock);

  priv->frame_counter = -1;
  priv->current = FRAME_HISTORY_MAX_LENGTH - 1;

  if (fps_counter == 0)
    fps_counter = gdk_profiler_define_counter ("fps", "Frames per Second");
}

/**
 * gdk_frame_clock_get_frame_time:
 * @frame_clock: a `GdkFrameClock`
 *
 * Gets the time that should currently be used for animations.
 *
 * Inside the processing of a frame, it’s the time used to compute the
 * animation position of everything in a frame. Outside of a frame, it's
 * the time of the conceptual “previous frame,” which may be either
 * the actual previous frame time, or if that’s too old, an updated
 * time.
 *
 * Returns: a timestamp in microseconds, in the timescale of
 *  of g_get_monotonic_time().
 */
gint64
gdk_frame_clock_get_frame_time (GdkFrameClock *frame_clock)
{
  g_return_val_if_fail (GDK_IS_FRAME_CLOCK (frame_clock), 0);

  return GDK_FRAME_CLOCK_GET_CLASS (frame_clock)->get_frame_time (frame_clock);
}

/**
 * gdk_frame_clock_request_phase:
 * @frame_clock: a `GdkFrameClock`
 * @phase: the phase that is requested
 *
 * Asks the frame clock to run a particular phase.
 *
 * The signal corresponding the requested phase will be emitted the next
 * time the frame clock processes. Multiple calls to
 * gdk_frame_clock_request_phase() will be combined together
 * and only one frame processed. If you are displaying animated
 * content and want to continually request the
 * %GDK_FRAME_CLOCK_PHASE_UPDATE phase for a period of time,
 * you should use [method@Gdk.FrameClock.begin_updating] instead,
 * since this allows GTK to adjust system parameters to get maximally
 * smooth animations.
 */
void
gdk_frame_clock_request_phase (GdkFrameClock      *frame_clock,
                               GdkFrameClockPhase  phase)
{
  g_return_if_fail (GDK_IS_FRAME_CLOCK (frame_clock));

  GDK_FRAME_CLOCK_GET_CLASS (frame_clock)->request_phase (frame_clock, phase);
}

/**
 * gdk_frame_clock_begin_updating:
 * @frame_clock: a `GdkFrameClock`
 *
 * Starts updates for an animation.
 *
 * Until a matching call to [method@Gdk.FrameClock.end_updating] is made,
 * the frame clock will continually request a new frame with the
 * %GDK_FRAME_CLOCK_PHASE_UPDATE phase. This function may be called multiple
 * times and frames will be requested until gdk_frame_clock_end_updating()
 * is called the same number of times.
 */
void
gdk_frame_clock_begin_updating (GdkFrameClock *frame_clock)
{
  g_return_if_fail (GDK_IS_FRAME_CLOCK (frame_clock));

  GDK_FRAME_CLOCK_GET_CLASS (frame_clock)->begin_updating (frame_clock);
}

/**
 * gdk_frame_clock_end_updating:
 * @frame_clock: a `GdkFrameClock`
 *
 * Stops updates for an animation.
 *
 * See the documentation for [method@Gdk.FrameClock.begin_updating].
 */
void
gdk_frame_clock_end_updating (GdkFrameClock *frame_clock)
{
  g_return_if_fail (GDK_IS_FRAME_CLOCK (frame_clock));

  GDK_FRAME_CLOCK_GET_CLASS (frame_clock)->end_updating (frame_clock);
}

static void
_gdk_frame_clock_freeze (GdkFrameClock *clock)
{
  g_return_if_fail (GDK_IS_FRAME_CLOCK (clock));

  GDK_FRAME_CLOCK_GET_CLASS (clock)->freeze (clock);
}

static void
_gdk_frame_clock_thaw (GdkFrameClock *clock)
{
  g_return_if_fail (GDK_IS_FRAME_CLOCK (clock));

  GDK_FRAME_CLOCK_GET_CLASS (clock)->thaw (clock);
}

void
_gdk_frame_clock_inhibit_freeze (GdkFrameClock *clock)
{
  GdkFrameClockPrivate *priv;

  g_return_if_fail (GDK_IS_FRAME_CLOCK (clock));

  priv = clock->priv;

  priv->n_freeze_inhibitors++;
  if (priv->n_freeze_inhibitors == 1)
    _gdk_frame_clock_thaw (clock);
}

void
_gdk_frame_clock_uninhibit_freeze (GdkFrameClock *clock)
{
  GdkFrameClockPrivate *priv;

  g_return_if_fail (GDK_IS_FRAME_CLOCK (clock));

  priv = clock->priv;

  priv->n_freeze_inhibitors--;
  if (priv->n_freeze_inhibitors == 0)
    _gdk_frame_clock_freeze (clock);
}

/**
 * gdk_frame_clock_get_frame_counter:
 * @frame_clock: a `GdkFrameClock`
 *
 * `GdkFrameClock` maintains a 64-bit counter that increments for
 * each frame drawn.
 *
 * Returns: inside frame processing, the value of the frame counter
 *   for the current frame. Outside of frame processing, the frame
 *   counter for the last frame.
 */
gint64
gdk_frame_clock_get_frame_counter (GdkFrameClock *frame_clock)
{
  GdkFrameClockPrivate *priv;

  g_return_val_if_fail (GDK_IS_FRAME_CLOCK (frame_clock), 0);

  priv = frame_clock->priv;

  return priv->frame_counter;
}

/**
 * gdk_frame_clock_get_history_start:
 * @frame_clock: a `GdkFrameClock`
 *
 * Returns the frame counter for the oldest frame available in history.
 *
 * `GdkFrameClock` internally keeps a history of `GdkFrameTimings`
 * objects for recent frames that can be retrieved with
 * [method@Gdk.FrameClock.get_timings]. The set of stored frames
 * is the set from the counter values given by
 * [method@Gdk.FrameClock.get_history_start] and
 * [method@Gdk.FrameClock.get_frame_counter], inclusive.
 *
 * Returns: the frame counter value for the oldest frame
 *  that is available in the internal frame history of the
 *  `GdkFrameClock`
 */
gint64
gdk_frame_clock_get_history_start (GdkFrameClock *frame_clock)
{
  GdkFrameClockPrivate *priv;

  g_return_val_if_fail (GDK_IS_FRAME_CLOCK (frame_clock), 0);

  priv = frame_clock->priv;

  return priv->frame_counter + 1 - priv->n_timings;
}

void
_gdk_frame_clock_begin_frame (GdkFrameClock *frame_clock)
{
  GdkFrameClockPrivate *priv;

  g_return_if_fail (GDK_IS_FRAME_CLOCK (frame_clock));

  priv = frame_clock->priv;

  priv->frame_counter++;
  priv->current = (priv->current + 1) % FRAME_HISTORY_MAX_LENGTH;

  /* Try to steal the previous frame timing instead of discarding
   * and allocating a new one.
   */
  if G_LIKELY (priv->n_timings == FRAME_HISTORY_MAX_LENGTH &&
               _gdk_frame_timings_steal (priv->timings[priv->current],
                                         priv->frame_counter))
    return;

  if (priv->n_timings < FRAME_HISTORY_MAX_LENGTH)
    priv->n_timings++;
  else
    gdk_frame_timings_unref (priv->timings[priv->current]);

  priv->timings[priv->current] = _gdk_frame_timings_new (priv->frame_counter);
}

/**
 * gdk_frame_clock_get_timings:
 * @frame_clock: a `GdkFrameClock`
 * @frame_counter: the frame counter value identifying the frame to
 *  be received
 *
 * Retrieves a `GdkFrameTimings` object holding timing information
 * for the current frame or a recent frame.
 *
 * The `GdkFrameTimings` object may not yet be complete: see
 * [method@Gdk.FrameTimings.get_complete] and
 * [method@Gdk.FrameClock.get_history_start].
 *
 * Returns: (nullable) (transfer none): the `GdkFrameTimings` object
 *   for the specified frame, or %NULL if it is not available
 */
GdkFrameTimings *
gdk_frame_clock_get_timings (GdkFrameClock *frame_clock,
                             gint64         frame_counter)
{
  GdkFrameClockPrivate *priv;
  int pos;

  g_return_val_if_fail (GDK_IS_FRAME_CLOCK (frame_clock), NULL);

  priv = frame_clock->priv;

  if (frame_counter > priv->frame_counter)
    return NULL;

  if (frame_counter <= priv->frame_counter - priv->n_timings)
    return NULL;

  pos = (priv->current - (priv->frame_counter - frame_counter) + FRAME_HISTORY_MAX_LENGTH) % FRAME_HISTORY_MAX_LENGTH;

  return priv->timings[pos];
}

/**
 * gdk_frame_clock_get_current_timings:
 * @frame_clock: a `GdkFrameClock`
 *
 * Gets the frame timings for the current frame.
 *
 * Returns: (nullable) (transfer none): the `GdkFrameTimings` for the
 *   frame currently being processed, or even no frame is being
 *   processed, for the previous frame. Before any frames have been
 *   processed, returns %NULL.
 */
GdkFrameTimings *
gdk_frame_clock_get_current_timings (GdkFrameClock *frame_clock)
{
  GdkFrameClockPrivate *priv;

  g_return_val_if_fail (GDK_IS_FRAME_CLOCK (frame_clock), 0);

  priv = frame_clock->priv;

  return gdk_frame_clock_get_timings (frame_clock, priv->frame_counter);
}


#ifdef G_ENABLE_DEBUG
void
_gdk_frame_clock_debug_print_timings (GdkFrameClock   *clock,
                                      GdkFrameTimings *timings)
{
  GString *str;

  gint64 previous_frame_time = 0;
  gint64 previous_smoothed_frame_time = 0;
  GdkFrameTimings *previous_timings = gdk_frame_clock_get_timings (clock,
                                                                   timings->frame_counter - 1);

  if (previous_timings != NULL)
    {
      previous_frame_time = previous_timings->frame_time;
      previous_smoothed_frame_time = previous_timings->smoothed_frame_time;
    }

  str = g_string_new ("");

  g_string_append_printf (str, "%5" G_GINT64_FORMAT ":", timings->frame_counter);
  if (previous_frame_time != 0)
    {
      g_string_append_printf (str, " interval=%-4.1f", (timings->frame_time - previous_frame_time) / 1000.);
      g_string_append_printf (str, timings->slept_before ?  " (sleep)" : "        ");
      g_string_append_printf (str, " smoothed=%4.1f / %-4.1f",
                              (timings->smoothed_frame_time - timings->frame_time) / 1000.,
                              (timings->smoothed_frame_time - previous_smoothed_frame_time) / 1000.);
    }
  if (timings->layout_start_time != 0)
    g_string_append_printf (str, " layout_start=%-4.1f", (timings->layout_start_time - timings->frame_time) / 1000.);
  if (timings->paint_start_time != 0)
    g_string_append_printf (str, " paint_start=%-4.1f", (timings->paint_start_time - timings->frame_time) / 1000.);
  if (timings->frame_end_time != 0)
    g_string_append_printf (str, " frame_end=%-4.1f", (timings->frame_end_time - timings->frame_time) / 1000.);
  if (timings->drawn_time != 0)
    g_string_append_printf (str, " drawn=%-4.1f", (timings->drawn_time - timings->frame_time) / 1000.);
  if (timings->presentation_time != 0)
    g_string_append_printf (str, " present=%-4.1f", (timings->presentation_time - timings->frame_time) / 1000.);
  if (timings->predicted_presentation_time != 0)
    g_string_append_printf (str, " predicted=%-4.1f", (timings->predicted_presentation_time - timings->frame_time) / 1000.);
  if (timings->refresh_interval != 0)
    g_string_append_printf (str, " refresh_interval=%-4.1f", timings->refresh_interval / 1000.);

  g_message ("%s", str->str);
  g_string_free (str, TRUE);
}
#endif /* G_ENABLE_DEBUG */

#define DEFAULT_REFRESH_INTERVAL 16667 /* 16.7ms (1/60th second) */
#define MAX_HISTORY_AGE 150000         /* 150ms */

/**
 * gdk_frame_clock_get_refresh_info:
 * @frame_clock: a `GdkFrameClock`
 * @base_time: base time for determining a presentaton time
 * @refresh_interval_return: (out) (optional): a location to store the
 *   determined refresh interval, or %NULL. A default refresh interval of
 *   1/60th of a second will be stored if no history is present.
 * @presentation_time_return: (out): a location to store the next
 *   candidate presentation time after the given base time.
 *   0 will be will be stored if no history is present.
 *
 * Predicts a presentation time, based on history.
 *
 * Using the frame history stored in the frame clock, finds the last
 * known presentation time and refresh interval, and assuming that
 * presentation times are separated by the refresh interval,
 * predicts a presentation time that is a multiple of the refresh
 * interval after the last presentation time, and later than @base_time.
 */
void
gdk_frame_clock_get_refresh_info (GdkFrameClock *frame_clock,
                                  gint64         base_time,
                                  gint64        *refresh_interval_return,
                                  gint64        *presentation_time_return)
{
  gint64 frame_counter;
  gint64 default_refresh_interval = DEFAULT_REFRESH_INTERVAL;

  g_return_if_fail (GDK_IS_FRAME_CLOCK (frame_clock));

  frame_counter = gdk_frame_clock_get_frame_counter (frame_clock);

  while (TRUE)
    {
      GdkFrameTimings *timings = gdk_frame_clock_get_timings (frame_clock, frame_counter);
      gint64 presentation_time;
      gint64 refresh_interval;

      if (timings == NULL)
        break;

      refresh_interval = timings->refresh_interval;
      presentation_time = timings->presentation_time;

      if (refresh_interval == 0)
        refresh_interval = default_refresh_interval;
      else
        default_refresh_interval = refresh_interval;

      if (presentation_time != 0)
        {
          if (presentation_time > base_time - MAX_HISTORY_AGE &&
              presentation_time_return)
            {
              if (refresh_interval_return)
                *refresh_interval_return = refresh_interval;

              while (presentation_time < base_time)
                presentation_time += refresh_interval;

              if (presentation_time_return)
                *presentation_time_return = presentation_time;

              return;
            }

          break;
        }

      frame_counter--;
    }

  if (presentation_time_return)
    *presentation_time_return = 0;
  if (refresh_interval_return)
    *refresh_interval_return = default_refresh_interval;
}

void
_gdk_frame_clock_emit_flush_events (GdkFrameClock *frame_clock)
{
  g_signal_emit (frame_clock, signals[FLUSH_EVENTS], 0);
}

void
_gdk_frame_clock_emit_before_paint (GdkFrameClock *frame_clock)
{
  g_signal_emit (frame_clock, signals[BEFORE_PAINT], 0);
}

void
_gdk_frame_clock_emit_update (GdkFrameClock *frame_clock)
{
  gint64 before G_GNUC_UNUSED;

  before = GDK_PROFILER_CURRENT_TIME;

  g_signal_emit (frame_clock, signals[UPDATE], 0);

  gdk_profiler_end_mark (before, "frameclock update", NULL);
}

void
_gdk_frame_clock_emit_layout (GdkFrameClock *frame_clock)
{
  gint64 before G_GNUC_UNUSED;

  before = GDK_PROFILER_CURRENT_TIME;

  g_signal_emit (frame_clock, signals[LAYOUT], 0);

  gdk_profiler_end_mark (before, "frameclock layout", NULL);
}

void
_gdk_frame_clock_emit_paint (GdkFrameClock *frame_clock)
{
  gint64 before G_GNUC_UNUSED;

  before = GDK_PROFILER_CURRENT_TIME;

  g_signal_emit (frame_clock, signals[PAINT], 0);

  gdk_profiler_end_mark (before, "frameclock paint", NULL);
}

void
_gdk_frame_clock_emit_after_paint (GdkFrameClock *frame_clock)
{
  g_signal_emit (frame_clock, signals[AFTER_PAINT], 0);
}

void
_gdk_frame_clock_emit_resume_events (GdkFrameClock *frame_clock)
{
  g_signal_emit (frame_clock, signals[RESUME_EVENTS], 0);
}

static gint64
guess_refresh_interval (GdkFrameClock *frame_clock)
{
  gint64 interval;
  gint64 i;

  interval = G_MAXINT64;

  for (i = gdk_frame_clock_get_history_start (frame_clock);
       i < gdk_frame_clock_get_frame_counter (frame_clock);
       i++)
    {
      GdkFrameTimings *t, *before;
      gint64 ts, before_ts;

      t = gdk_frame_clock_get_timings (frame_clock, i);
      before = gdk_frame_clock_get_timings (frame_clock, i - 1);
      if (t == NULL || before == NULL)
        continue;

      ts = gdk_frame_timings_get_frame_time (t);
      before_ts = gdk_frame_timings_get_frame_time (before);
      if (ts == 0 || before_ts == 0)
        continue;

      interval = MIN (interval, ts - before_ts);
    }

  if (interval == G_MAXINT64)
    return 0;

  return interval;
}

/**
 * gdk_frame_clock_get_fps:
 * @frame_clock: a `GdkFrameClock`
 *
 * Calculates the current frames-per-second, based on the
 * frame timings of @frame_clock.
 *
 * Returns: the current fps, as a `double`
 */
double
gdk_frame_clock_get_fps (GdkFrameClock *frame_clock)
{
  GdkFrameTimings *start, *end;
  gint64 start_counter, end_counter;
  gint64 start_timestamp, end_timestamp;
  gint64 interval;

  start_counter = gdk_frame_clock_get_history_start (frame_clock);
  end_counter = gdk_frame_clock_get_frame_counter (frame_clock);
  start = gdk_frame_clock_get_timings (frame_clock, start_counter);
  for (end = gdk_frame_clock_get_timings (frame_clock, end_counter);
       end_counter > start_counter && end != NULL && !gdk_frame_timings_get_complete (end);
       end = gdk_frame_clock_get_timings (frame_clock, end_counter))
    end_counter--;
  if (end_counter - start_counter < 4)
    return 0.0;

  start_timestamp = gdk_frame_timings_get_presentation_time (start);
  end_timestamp = gdk_frame_timings_get_presentation_time (end);
  if (start_timestamp == 0 || end_timestamp == 0)
    {
      start_timestamp = gdk_frame_timings_get_frame_time (start);
      end_timestamp = gdk_frame_timings_get_frame_time (end);
    }
  interval = gdk_frame_timings_get_refresh_interval (end);
  if (interval == 0)
    {
      interval = guess_refresh_interval (frame_clock);
      if (interval == 0)
        return 0.0;
    }

  return ((double) end_counter - start_counter) * G_USEC_PER_SEC / (end_timestamp - start_timestamp);
}

void
_gdk_frame_clock_add_timings_to_profiler (GdkFrameClock   *clock,
                                          GdkFrameTimings *timings)
{
  if (timings->drawn_time != 0)
    {
      gdk_profiler_add_mark (1000 * timings->drawn_time, 0, "drawn window", NULL);
    }

  if (timings->presentation_time != 0)
    {
      gdk_profiler_add_mark (1000 * timings->presentation_time, 0, "presented window", NULL);
    }

  gdk_profiler_set_counter (fps_counter, gdk_frame_clock_get_fps (clock));
}