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File _service:download_url:1441.patch of Package mutter (Revision fe666f4b081f3a009fd6da0a71057b0f)

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From 133ef8334d4a904222a0e0111d2cdcb934c53289 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 17 Sep 2021 17:48:20 +0800
Subject: [PATCH 01/30] cogl/onscreen: Add function
 cogl_onscreen_count_pending_frames

---
 cogl/cogl/cogl-onscreen-private.h | 3 +++
 cogl/cogl/cogl-onscreen.c         | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/cogl/cogl/cogl-onscreen-private.h b/cogl/cogl/cogl-onscreen-private.h
index 959a60533b3..785f67aca16 100644
--- a/cogl/cogl/cogl-onscreen-private.h
+++ b/cogl/cogl/cogl-onscreen-private.h
@@ -79,3 +79,6 @@ cogl_onscreen_peek_tail_frame_info (CoglOnscreen *onscreen);
 
 COGL_EXPORT CoglFrameInfo *
 cogl_onscreen_pop_head_frame_info (CoglOnscreen *onscreen);
+
+COGL_EXPORT unsigned int
+cogl_onscreen_count_pending_frames (CoglOnscreen *onscreen);
diff --git a/cogl/cogl/cogl-onscreen.c b/cogl/cogl/cogl-onscreen.c
index 71a9367224d..b2d6e98e7ea 100644
--- a/cogl/cogl/cogl-onscreen.c
+++ b/cogl/cogl/cogl-onscreen.c
@@ -494,6 +494,14 @@ cogl_onscreen_pop_head_frame_info (CoglOnscreen *onscreen)
   return g_queue_pop_head (&priv->pending_frame_infos);
 }
 
+unsigned int
+cogl_onscreen_count_pending_frames (CoglOnscreen *onscreen)
+{
+  CoglOnscreenPrivate *priv = cogl_onscreen_get_instance_private (onscreen);
+
+  return g_queue_get_length (&priv->pending_frame_infos);
+}
+
 CoglFrameClosure *
 cogl_onscreen_add_frame_callback (CoglOnscreen *onscreen,
                                   CoglFrameCallback callback,
-- 
GitLab

From 5971d5398f9ee84b9b425035d0e7938b630da102 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Mon, 12 Feb 2024 17:16:03 +0800
Subject: [PATCH 02/30] cogl/onscreen: Indent declaration parameters to align
 with above/below

This fixes warnings from check-code-style.
---
 cogl/cogl/cogl-onscreen-private.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cogl/cogl/cogl-onscreen-private.h b/cogl/cogl/cogl-onscreen-private.h
index 785f67aca16..86d8ea2d5ff 100644
--- a/cogl/cogl/cogl-onscreen-private.h
+++ b/cogl/cogl/cogl-onscreen-private.h
@@ -78,7 +78,7 @@ COGL_EXPORT CoglFrameInfo *
 cogl_onscreen_peek_tail_frame_info (CoglOnscreen *onscreen);
 
 COGL_EXPORT CoglFrameInfo *
-cogl_onscreen_pop_head_frame_info (CoglOnscreen *onscreen);
+cogl_onscreen_pop_head_frame_info  (CoglOnscreen *onscreen);
 
 COGL_EXPORT unsigned int
 cogl_onscreen_count_pending_frames (CoglOnscreen *onscreen);
-- 
GitLab

From 752469c592c87951d2aae5c65ec91ec623654ff6 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 20 Apr 2022 18:33:43 +0800
Subject: [PATCH 03/30] kms: Keep a shutting_down flag

---
 src/backends/native/meta-kms.c | 9 +++++++++
 src/backends/native/meta-kms.h | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/src/backends/native/meta-kms.c b/src/backends/native/meta-kms.c
index 32f3a0088e7..d7d6a4001e8 100644
--- a/src/backends/native/meta-kms.c
+++ b/src/backends/native/meta-kms.c
@@ -66,6 +66,8 @@ struct _MetaKms
   int kernel_thread_inhibit_count;
 
   MetaKmsCursorManager *cursor_manager;
+
+  gboolean shutting_down;
 };
 
 G_DEFINE_TYPE (MetaKms, meta_kms, META_TYPE_THREAD)
@@ -367,6 +369,7 @@ static void
 on_prepare_shutdown (MetaBackend *backend,
                      MetaKms     *kms)
 {
+  kms->shutting_down = TRUE;
   meta_kms_run_impl_task_sync (kms, prepare_shutdown_in_impl, NULL, NULL);
   meta_thread_flush_callbacks (META_THREAD (kms));
 
@@ -428,6 +431,12 @@ meta_kms_new (MetaBackend   *backend,
   return kms;
 }
 
+gboolean
+meta_kms_is_shutting_down (MetaKms *kms)
+{
+  return kms->shutting_down;
+}
+
 static void
 meta_kms_finalize (GObject *object)
 {
diff --git a/src/backends/native/meta-kms.h b/src/backends/native/meta-kms.h
index 74340140639..f6b19520bec 100644
--- a/src/backends/native/meta-kms.h
+++ b/src/backends/native/meta-kms.h
@@ -60,6 +60,8 @@ MetaKmsDevice * meta_kms_create_device (MetaKms            *kms,
                                         MetaKmsDeviceFlag   flags,
                                         GError            **error);
 
+gboolean meta_kms_is_shutting_down (MetaKms *kms);
+
 MetaKms * meta_kms_new (MetaBackend   *backend,
                         MetaKmsFlags   flags,
                         GError       **error);
-- 
GitLab

From 2a58ae16db1ad0152b853307447db9a4bc10eea1 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 26 Oct 2021 18:50:50 +0800
Subject: [PATCH 04/30] renderer/native: Avoid requeuing the same onscreen for
 a power save flip

This is a case that triple buffering will encounter. We don't want it
to queue the same onscreen multiple times because that would represent
multiple flips occurring simultaneously.

It's a linear search but the list length is typically only 1 or 2 so
no need for anything fancier yet.
---
 src/backends/native/meta-renderer-native.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index b818faf6f52..0aeb050e560 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -748,6 +748,9 @@ meta_renderer_native_queue_power_save_page_flip (MetaRendererNative *renderer_na
 {
   const unsigned int timeout_ms = 100;
 
+  if (g_list_find (renderer_native->power_save_page_flip_onscreens, onscreen))
+    return;
+
   if (!renderer_native->power_save_page_flip_source_id)
     {
       renderer_native->power_save_page_flip_source_id =
-- 
GitLab

From 3515cf3ef65e4cdab22850683aa9f2827a64b8b6 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Mon, 1 Nov 2021 19:35:34 +0800
Subject: [PATCH 05/30] renderer/native: Steal the power save flip list before
 iterating over it

Because a single iteration might also grow the list again.
---
 src/backends/native/meta-renderer-native.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 0aeb050e560..02d1e3e0c06 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -731,12 +731,18 @@ static gboolean
 dummy_power_save_page_flip_cb (gpointer user_data)
 {
   MetaRendererNative *renderer_native = user_data;
+  GList *old_list =
+    g_steal_pointer (&renderer_native->power_save_page_flip_onscreens);
 
-  g_list_foreach (renderer_native->power_save_page_flip_onscreens,
+  g_list_foreach (old_list,
                   (GFunc) meta_onscreen_native_dummy_power_save_page_flip,
                   NULL);
-  g_clear_list (&renderer_native->power_save_page_flip_onscreens,
+  g_clear_list (&old_list,
                 g_object_unref);
+
+  if (renderer_native->power_save_page_flip_onscreens != NULL)
+    return G_SOURCE_CONTINUE;
+
   renderer_native->power_save_page_flip_source_id = 0;
 
   return G_SOURCE_REMOVE;
-- 
GitLab

From 793aa4e687cf7a20b7835d632f26afefe6db47de Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 10 Dec 2021 16:40:58 +0800
Subject: [PATCH 06/30] onscreen/native: Log swapbuffers and N-buffering when
 MUTTER_DEBUG=kms

---
 src/backends/native/meta-onscreen-native.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 8a25fca8cc4..7e539923ff5 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1294,6 +1294,19 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   COGL_TRACE_BEGIN_SCOPED (MetaRendererNativeSwapBuffers,
                            "Meta::OnscreenNative::swap_buffers_with_damage()");
 
+  if (meta_is_topic_enabled (META_DEBUG_KMS))
+    {
+      unsigned int frames_pending =
+        cogl_onscreen_count_pending_frames (onscreen);
+
+      meta_topic (META_DEBUG_KMS,
+                  "Swap buffers: %u frames pending (%s-buffering)",
+                  frames_pending,
+                  frames_pending == 1 ? "double" :
+                  frames_pending == 2 ? "triple" :
+                  "?");
+    }
+
   secondary_gpu_fb =
     update_secondary_gpu_state_pre_swap_buffers (onscreen,
                                                  rectangles,
-- 
GitLab

From 811f428e2656ed3d1c07e015b7b94e10611e756e Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 28 Jul 2021 16:35:56 +0800
Subject: [PATCH 07/30] onscreen/native: Replace an assertion that double
 buffering is the maximum

Because it soon won't be the maximum. But we do want to verify that the
frame info queue is not empty, to avoid NULL dereferencing and catch logic
errors.
---
 src/backends/native/meta-onscreen-native.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 7e539923ff5..0591b67cb7b 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -192,7 +192,7 @@ meta_onscreen_native_notify_frame_complete (CoglOnscreen *onscreen)
 
   info = cogl_onscreen_pop_head_frame_info (onscreen);
 
-  g_assert (!cogl_onscreen_peek_head_frame_info (onscreen));
+  g_return_if_fail (info);
 
   _cogl_onscreen_notify_frame_sync (onscreen, info);
   _cogl_onscreen_notify_complete (onscreen, info);
-- 
GitLab

From 34f5515058550cf1de1e1f7ecf588d45214e0d82 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 16 Sep 2021 16:26:25 +0800
Subject: [PATCH 08/30] onscreen/native: Deduplicate calls to
 clutter_frame_set_result

All paths out of `meta_onscreen_native_swap_buffers_with_damage` from
here onward would set the same `CLUTTER_FRAME_RESULT_PENDING_PRESENTED`
(or terminate with `g_assert_not_reached`).

Even failed posts set this result because they will do a
`meta_onscreen_native_notify_frame_complete` in
`page_flip_feedback_discarded`.
---
 src/backends/native/meta-onscreen-native.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 0591b67cb7b..9e83bd01d5d 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1405,6 +1405,9 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
 #endif
     }
 
+  clutter_frame_set_result (frame,
+                            CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
+
   /*
    * If we changed EGL context, cogl will have the wrong idea about what is
    * current, making it fail to set it when it needs to. Avoid that by making
@@ -1441,8 +1444,6 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
     {
       meta_renderer_native_queue_power_save_page_flip (renderer_native,
                                                        onscreen);
-      clutter_frame_set_result (frame,
-                                CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
       return;
     }
 
@@ -1462,8 +1463,6 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
           kms_update = meta_frame_native_steal_kms_update (frame_native);
           meta_renderer_native_queue_mode_set_update (renderer_native,
                                                       kms_update);
-          clutter_frame_set_result (frame,
-                                    CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
           return;
         }
       else if (meta_renderer_native_has_pending_mode_set (renderer_native))
@@ -1477,8 +1476,6 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
 
           meta_frame_native_steal_kms_update (frame_native);
           meta_renderer_native_post_mode_set_updates (renderer_native);
-          clutter_frame_set_result (frame,
-                                    CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
           return;
         }
       break;
@@ -1494,8 +1491,6 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
                                                       kms_update);
 
           meta_renderer_native_post_mode_set_updates (renderer_native);
-          clutter_frame_set_result (frame,
-                                    CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
           return;
         }
       break;
@@ -1510,7 +1505,6 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   kms_update = meta_frame_native_steal_kms_update (frame_native);
   meta_kms_device_post_update (kms_device, kms_update,
                                META_KMS_UPDATE_FLAG_NONE);
-  clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
 }
 
 gboolean
-- 
GitLab

From 4c04e1240aa27a3291d892d8cb7c64a4e3490dfc Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 28 Jul 2021 16:29:27 +0800
Subject: [PATCH 09/30] onscreen/native: Split swap_buffers_with_damage into
 two functions

1. The EGL part: meta_onscreen_native_swap_buffers_with_damage
2. The KMS part: post_latest_swap
---
 src/backends/native/meta-onscreen-native.c | 69 ++++++++++++++++------
 1 file changed, 51 insertions(+), 18 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 9e83bd01d5d..fca37321f9c 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -97,6 +97,8 @@ struct _MetaOnscreenNative
 
   ClutterFrame *presented_frame;
   ClutterFrame *next_frame;
+  int *next_rectangles;  /* 4 x n_rectangles */
+  int next_n_rectangles;
 
   struct {
     struct gbm_surface *surface;
@@ -131,6 +133,9 @@ G_DEFINE_TYPE (MetaOnscreenNative, meta_onscreen_native,
 
 static GQuark blit_source_quark = 0;
 
+static void
+post_latest_swap (CoglOnscreen *onscreen);
+
 static gboolean
 init_secondary_gpu_state (MetaRendererNative  *renderer_native,
                           CoglOnscreen        *onscreen,
@@ -1267,29 +1272,21 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   CoglRendererEGL *cogl_renderer_egl = cogl_renderer->winsys;
   MetaRendererNativeGpuData *renderer_gpu_data = cogl_renderer_egl->platform;
   MetaRendererNative *renderer_native = renderer_gpu_data->renderer_native;
-  MetaRenderer *renderer = META_RENDERER (renderer_native);
-  MetaBackend *backend = meta_renderer_get_backend (renderer);
-  MetaMonitorManager *monitor_manager =
-    meta_backend_get_monitor_manager (backend);
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
   MetaOnscreenNativeSecondaryGpuState *secondary_gpu_state;
   MetaGpuKms *render_gpu = onscreen_native->render_gpu;
   MetaDeviceFile *render_device_file;
   ClutterFrame *frame = user_data;
-  MetaFrameNative *frame_native = meta_frame_native_from_frame (frame);
-  MetaKmsUpdate *kms_update;
   CoglOnscreenClass *parent_class;
   gboolean create_timestamp_query = TRUE;
   gboolean egl_context_changed = FALSE;
-  MetaPowerSave power_save_mode;
   g_autoptr (GError) error = NULL;
   MetaDrmBufferFlags buffer_flags;
   MetaDrmBufferGbm *buffer_gbm;
   g_autoptr (MetaDrmBuffer) primary_gpu_fb = NULL;
   g_autoptr (MetaDrmBuffer) secondary_gpu_fb = NULL;
   g_autoptr (MetaDrmBuffer) buffer = NULL;
-  MetaKmsCrtc *kms_crtc;
-  MetaKmsDevice *kms_device;
+  size_t rectangles_size;
 
   COGL_TRACE_BEGIN_SCOPED (MetaRendererNativeSwapBuffers,
                            "Meta::OnscreenNative::swap_buffers_with_damage()");
@@ -1378,13 +1375,11 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
                                  primary_gpu_fb,
                                  secondary_gpu_fb);
 
-  g_warn_if_fail (!onscreen_native->next_frame);
-  onscreen_native->next_frame = clutter_frame_ref (frame);
-
   switch (renderer_gpu_data->mode)
     {
     case META_RENDERER_NATIVE_MODE_GBM:
-      meta_frame_native_set_buffer (frame_native, buffer);
+      meta_frame_native_set_buffer (meta_frame_native_from_frame (frame),
+                                    buffer);
 
       if (!meta_drm_buffer_ensure_fb_id (buffer, &error))
         {
@@ -1417,12 +1412,47 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   if (egl_context_changed)
     _cogl_winsys_egl_ensure_current (cogl_display);
 
-  kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (onscreen_native->crtc));
-  kms_device = meta_kms_crtc_get_device (kms_crtc);
+  rectangles_size = n_rectangles * 4 * sizeof (int);
+  onscreen_native->next_rectangles =
+    g_realloc (onscreen_native->next_rectangles, rectangles_size);
+  memcpy (onscreen_native->next_rectangles, rectangles, rectangles_size);
+  onscreen_native->next_n_rectangles = n_rectangles;
+
+  g_warn_if_fail (!onscreen_native->next_frame);
+  g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
+  onscreen_native->next_frame = clutter_frame_ref (frame);
+
+  post_latest_swap (onscreen);
+}
+
+static void
+post_latest_swap (CoglOnscreen *onscreen)
+{
+  CoglFramebuffer *framebuffer = COGL_FRAMEBUFFER (onscreen);
+  CoglContext *cogl_context = cogl_framebuffer_get_context (framebuffer);
+  CoglRenderer *cogl_renderer = cogl_context->display->renderer;
+  CoglRendererEGL *cogl_renderer_egl = cogl_renderer->winsys;
+  MetaRendererNativeGpuData *renderer_gpu_data = cogl_renderer_egl->platform;
+  MetaRendererNative *renderer_native = renderer_gpu_data->renderer_native;
+  MetaRenderer *renderer = META_RENDERER (renderer_native);
+  MetaBackend *backend = meta_renderer_get_backend (renderer);
+  MetaMonitorManager *monitor_manager =
+    meta_backend_get_monitor_manager (backend);
+  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
+  MetaPowerSave power_save_mode;
+  MetaCrtcKms *crtc_kms = META_CRTC_KMS (onscreen_native->crtc);
+  MetaKmsCrtc *kms_crtc = meta_crtc_kms_get_kms_crtc (crtc_kms);
+  MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);
+  MetaKmsUpdate *kms_update;
+  g_autoptr (MetaKmsFeedback) kms_feedback = NULL;
+  ClutterFrame *frame = onscreen_native->next_frame;
+  MetaFrameNative *frame_native;
 
   power_save_mode = meta_monitor_manager_get_power_save_mode (monitor_manager);
   if (power_save_mode == META_POWER_SAVE_ON)
     {
+      frame_native = meta_frame_native_from_frame (frame);
+
       kms_update = meta_frame_native_ensure_kms_update (frame_native,
                                                         kms_device);
       meta_kms_update_add_result_listener (kms_update,
@@ -1437,8 +1467,8 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
                                       onscreen_native->crtc,
                                       kms_update,
                                       META_KMS_ASSIGN_PLANE_FLAG_NONE,
-                                      rectangles,
-                                      n_rectangles);
+                                      onscreen_native->next_rectangles,
+                                      onscreen_native->next_n_rectangles);
     }
   else
     {
@@ -1448,7 +1478,7 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
     }
 
   COGL_TRACE_BEGIN_SCOPED (MetaRendererNativePostKmsUpdate,
-                           "Meta::OnscreenNative::swap_buffers_with_damage#post_pending_update()");
+                           "Meta::OnscreenNative::post_latest_swap#post_pending_update()");
 
   switch (renderer_gpu_data->mode)
     {
@@ -2825,6 +2855,9 @@ meta_onscreen_native_dispose (GObject *object)
   g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
   g_clear_pointer (&onscreen_native->presented_frame, clutter_frame_unref);
 
+  g_clear_pointer (&onscreen_native->next_rectangles, g_free);
+  onscreen_native->next_n_rectangles = 0;
+
   renderer_gpu_data =
     meta_renderer_native_get_gpu_data (renderer_native,
                                        onscreen_native->render_gpu);
-- 
GitLab

From 7ff78e378c2c9c9791d051c42ff69303859e57de Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 5 Dec 2023 17:50:44 +0800
Subject: [PATCH 10/30] onscreen/native: Insert a 'posted' frame between 'next'
 and 'presented'

This will allow us to keep track of up to two buffers that have been
swapped but not yet scanning out, for triple buffering.

This commit replaces mutter!1968
---
 src/backends/native/meta-onscreen-native.c | 36 +++++++++++++---------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index fca37321f9c..83f50dff12d 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -96,6 +96,7 @@ struct _MetaOnscreenNative
   MetaOnscreenNativeSecondaryGpuState *secondary_gpu_state;
 
   ClutterFrame *presented_frame;
+  ClutterFrame *posted_frame;
   ClutterFrame *next_frame;
   int *next_rectangles;  /* 4 x n_rectangles */
   int next_n_rectangles;
@@ -146,20 +147,20 @@ meta_onscreen_native_swap_drm_fb (CoglOnscreen *onscreen)
 {
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
 
-  if (!onscreen_native->next_frame)
+  if (!onscreen_native->posted_frame)
     return;
 
   g_clear_pointer (&onscreen_native->presented_frame, clutter_frame_unref);
   onscreen_native->presented_frame =
-    g_steal_pointer (&onscreen_native->next_frame);
+    g_steal_pointer (&onscreen_native->posted_frame);
 }
 
 static void
-meta_onscreen_native_clear_next_fb (CoglOnscreen *onscreen)
+meta_onscreen_native_clear_posted_fb (CoglOnscreen *onscreen)
 {
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
 
-  g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
+  g_clear_pointer (&onscreen_native->posted_frame, clutter_frame_unref);
 }
 
 static void
@@ -288,7 +289,7 @@ page_flip_feedback_ready (MetaKmsCrtc *kms_crtc,
   frame_info = cogl_onscreen_peek_head_frame_info (onscreen);
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
-  g_warn_if_fail (!onscreen_native->next_frame);
+  g_warn_if_fail (!onscreen_native->posted_frame);
 
   meta_onscreen_native_notify_frame_complete (onscreen);
 }
@@ -340,7 +341,7 @@ page_flip_feedback_discarded (MetaKmsCrtc  *kms_crtc,
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
   meta_onscreen_native_notify_frame_complete (onscreen);
-  meta_onscreen_native_clear_next_fb (onscreen);
+  meta_onscreen_native_clear_posted_fb (onscreen);
 }
 
 static const MetaKmsPageFlipListenerVtable page_flip_listener_vtable = {
@@ -489,7 +490,7 @@ meta_onscreen_native_flip_crtc (CoglOnscreen           *onscreen,
 {
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
   MetaRendererNative *renderer_native = onscreen_native->renderer_native;
-  ClutterFrame *frame = onscreen_native->next_frame;
+  g_autoptr (ClutterFrame) frame = NULL;
   MetaFrameNative *frame_native;
   MetaGpuKms *render_gpu = onscreen_native->render_gpu;
   MetaCrtcKms *crtc_kms = META_CRTC_KMS (crtc);
@@ -505,6 +506,7 @@ meta_onscreen_native_flip_crtc (CoglOnscreen           *onscreen,
   COGL_TRACE_BEGIN_SCOPED (MetaOnscreenNativeFlipCrtcs,
                            "Meta::OnscreenNative::flip_crtc()");
 
+  frame = g_steal_pointer (&onscreen_native->next_frame);
   g_return_if_fail (frame);
 
   gpu_kms = META_GPU_KMS (meta_crtc_get_gpu (crtc));
@@ -566,6 +568,10 @@ meta_onscreen_native_flip_crtc (CoglOnscreen           *onscreen,
 #endif
     }
 
+  g_warn_if_fail (!onscreen_native->posted_frame);
+  g_clear_pointer (&onscreen_native->posted_frame, clutter_frame_unref);
+  onscreen_native->posted_frame = g_steal_pointer (&frame);
+
   meta_kms_update_add_page_flip_listener (kms_update,
                                           kms_crtc,
                                           &page_flip_listener_vtable,
@@ -1251,7 +1257,7 @@ swap_buffer_result_feedback (const MetaKmsFeedback *kms_feedback,
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
   meta_onscreen_native_notify_frame_complete (onscreen);
-  meta_onscreen_native_clear_next_fb (onscreen);
+  meta_onscreen_native_clear_posted_fb (onscreen);
 }
 
 static const MetaKmsResultListenerVtable swap_buffer_result_listener_vtable = {
@@ -1445,12 +1451,13 @@ post_latest_swap (CoglOnscreen *onscreen)
   MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);
   MetaKmsUpdate *kms_update;
   g_autoptr (MetaKmsFeedback) kms_feedback = NULL;
-  ClutterFrame *frame = onscreen_native->next_frame;
+  g_autoptr (ClutterFrame) frame = NULL;
   MetaFrameNative *frame_native;
 
   power_save_mode = meta_monitor_manager_get_power_save_mode (monitor_manager);
   if (power_save_mode == META_POWER_SAVE_ON)
     {
+      frame = clutter_frame_ref (onscreen_native->next_frame);
       frame_native = meta_frame_native_from_frame (frame);
 
       kms_update = meta_frame_native_ensure_kms_update (frame_native,
@@ -1602,11 +1609,11 @@ scanout_result_feedback (const MetaKmsFeedback *kms_feedback,
                         G_IO_ERROR_PERMISSION_DENIED))
     {
       ClutterStageView *view = CLUTTER_STAGE_VIEW (onscreen_native->view);
-      ClutterFrame *next_frame = onscreen_native->next_frame;
-      MetaFrameNative *next_frame_native =
-        meta_frame_native_from_frame (next_frame);
+      ClutterFrame *posted_frame = onscreen_native->posted_frame;
+      MetaFrameNative *posted_frame_native =
+        meta_frame_native_from_frame (posted_frame);
       CoglScanout *scanout =
-        meta_frame_native_get_scanout (next_frame_native);
+        meta_frame_native_get_scanout (posted_frame_native);
 
       g_warning ("Direct scanout page flip failed: %s", error->message);
 
@@ -1619,7 +1626,7 @@ scanout_result_feedback (const MetaKmsFeedback *kms_feedback,
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
   meta_onscreen_native_notify_frame_complete (onscreen);
-  meta_onscreen_native_clear_next_fb (onscreen);
+  meta_onscreen_native_clear_posted_fb (onscreen);
 }
 
 static const MetaKmsResultListenerVtable scanout_result_listener_vtable = {
@@ -2853,6 +2860,7 @@ meta_onscreen_native_dispose (GObject *object)
   meta_onscreen_native_detach (onscreen_native);
 
   g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
+  g_clear_pointer (&onscreen_native->posted_frame, clutter_frame_unref);
   g_clear_pointer (&onscreen_native->presented_frame, clutter_frame_unref);
 
   g_clear_pointer (&onscreen_native->next_rectangles, g_free);
-- 
GitLab

From cb4de661c02386a9c838ec2e7c4e8307b0680ecc Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 17 Sep 2021 17:59:28 +0800
Subject: [PATCH 11/30] onscreen/native: Defer posting if there's already a
 post in progress

And when the number of pending posts decreases we know it's safe to submit
a new one. Since KMS generally only supports one outstanding post right now,
"decreases" means equal to zero.
---
 src/backends/native/meta-onscreen-native.c | 198 ++++++++++++++++++---
 1 file changed, 172 insertions(+), 26 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 83f50dff12d..93451ff2c3b 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -97,6 +97,7 @@ struct _MetaOnscreenNative
 
   ClutterFrame *presented_frame;
   ClutterFrame *posted_frame;
+  ClutterFrame *stalled_frame;
   ClutterFrame *next_frame;
   int *next_rectangles;  /* 4 x n_rectangles */
   int next_n_rectangles;
@@ -127,6 +128,10 @@ struct _MetaOnscreenNative
   gulong privacy_screen_changed_handler_id;
   gulong color_space_changed_handler_id;
   gulong hdr_metadata_changed_handler_id;
+
+  gboolean needs_flush;
+
+  unsigned int swaps_pending;
 };
 
 G_DEFINE_TYPE (MetaOnscreenNative, meta_onscreen_native,
@@ -135,7 +140,11 @@ G_DEFINE_TYPE (MetaOnscreenNative, meta_onscreen_native,
 static GQuark blit_source_quark = 0;
 
 static void
-post_latest_swap (CoglOnscreen *onscreen);
+try_post_latest_swap (CoglOnscreen *onscreen);
+
+static void
+post_finish_frame (MetaOnscreenNative *onscreen_native,
+                   MetaKmsUpdate      *kms_update);
 
 static gboolean
 init_secondary_gpu_state (MetaRendererNative  *renderer_native,
@@ -234,6 +243,7 @@ notify_view_crtc_presented (MetaRendererView *view,
 
   meta_onscreen_native_notify_frame_complete (onscreen);
   meta_onscreen_native_swap_drm_fb (onscreen);
+  try_post_latest_swap (onscreen);
 }
 
 static void
@@ -283,15 +293,13 @@ page_flip_feedback_ready (MetaKmsCrtc *kms_crtc,
   CoglFramebuffer *framebuffer =
     clutter_stage_view_get_onscreen (CLUTTER_STAGE_VIEW (view));
   CoglOnscreen *onscreen = COGL_ONSCREEN (framebuffer);
-  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
   CoglFrameInfo *frame_info;
 
   frame_info = cogl_onscreen_peek_head_frame_info (onscreen);
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
-  g_warn_if_fail (!onscreen_native->posted_frame);
-
   meta_onscreen_native_notify_frame_complete (onscreen);
+  try_post_latest_swap (onscreen);
 }
 
 static void
@@ -342,6 +350,7 @@ page_flip_feedback_discarded (MetaKmsCrtc  *kms_crtc,
 
   meta_onscreen_native_notify_frame_complete (onscreen);
   meta_onscreen_native_clear_posted_fb (onscreen);
+  try_post_latest_swap (onscreen);
 }
 
 static const MetaKmsPageFlipListenerVtable page_flip_listener_vtable = {
@@ -402,18 +411,36 @@ custom_egl_stream_page_flip (gpointer custom_page_flip_data,
 }
 #endif /* HAVE_EGL_DEVICE */
 
-void
-meta_onscreen_native_dummy_power_save_page_flip (CoglOnscreen *onscreen)
+static void
+drop_stalled_swap (CoglOnscreen *onscreen)
 {
   CoglFrameInfo *frame_info;
+  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
 
-  meta_onscreen_native_swap_drm_fb (onscreen);
+  if (onscreen_native->swaps_pending <= 1)
+    return;
+
+  onscreen_native->swaps_pending--;
+
+  g_clear_pointer (&onscreen_native->stalled_frame, clutter_frame_unref);
 
   frame_info = cogl_onscreen_peek_tail_frame_info (onscreen);
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
   meta_onscreen_native_notify_frame_complete (onscreen);
 }
 
+void
+meta_onscreen_native_dummy_power_save_page_flip (CoglOnscreen *onscreen)
+{
+  drop_stalled_swap (onscreen);
+
+  /* If the monitor just woke up and the shell is fully idle (has nothing
+   * more to swap) then we just woke to an indefinitely black screen. Let's
+   * fix that using the last swap (which is never classified as "stalled").
+   */
+  try_post_latest_swap (onscreen);
+}
+
 static void
 apply_transform (MetaCrtcKms            *crtc_kms,
                  MetaKmsPlaneAssignment *kms_plane_assignment,
@@ -1254,12 +1281,38 @@ swap_buffer_result_feedback (const MetaKmsFeedback *kms_feedback,
     g_warning ("Page flip failed: %s", error->message);
 
   frame_info = cogl_onscreen_peek_head_frame_info (onscreen);
-  frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
-  meta_onscreen_native_notify_frame_complete (onscreen);
+  /* After resuming from suspend, drop_stalled_swap might have done this
+   * already and emptied the frame_info queue.
+   */
+  if (frame_info)
+    {
+      frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
+      meta_onscreen_native_notify_frame_complete (onscreen);
+    }
+
   meta_onscreen_native_clear_posted_fb (onscreen);
 }
 
+static void
+assign_next_frame (MetaOnscreenNative *onscreen_native,
+                   ClutterFrame       *frame)
+{
+  CoglOnscreen *onscreen = COGL_ONSCREEN (onscreen_native);
+
+  if (onscreen_native->next_frame != NULL)
+    {
+      g_warn_if_fail (onscreen_native->stalled_frame == NULL);
+      drop_stalled_swap (onscreen);
+      g_warn_if_fail (onscreen_native->stalled_frame == NULL);
+      g_clear_pointer (&onscreen_native->stalled_frame, clutter_frame_unref);
+      onscreen_native->stalled_frame =
+        g_steal_pointer (&onscreen_native->next_frame);
+    }
+
+  onscreen_native->next_frame = clutter_frame_ref (frame);
+}
+
 static const MetaKmsResultListenerVtable swap_buffer_result_listener_vtable = {
   .feedback = swap_buffer_result_feedback,
 };
@@ -1424,15 +1477,14 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   memcpy (onscreen_native->next_rectangles, rectangles, rectangles_size);
   onscreen_native->next_n_rectangles = n_rectangles;
 
-  g_warn_if_fail (!onscreen_native->next_frame);
-  g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
-  onscreen_native->next_frame = clutter_frame_ref (frame);
+  assign_next_frame (onscreen_native, frame);
 
-  post_latest_swap (onscreen);
+  onscreen_native->swaps_pending++;
+  try_post_latest_swap (onscreen);
 }
 
 static void
-post_latest_swap (CoglOnscreen *onscreen)
+try_post_latest_swap (CoglOnscreen *onscreen)
 {
   CoglFramebuffer *framebuffer = COGL_FRAMEBUFFER (onscreen);
   CoglContext *cogl_context = cogl_framebuffer_get_context (framebuffer);
@@ -1454,12 +1506,38 @@ post_latest_swap (CoglOnscreen *onscreen)
   g_autoptr (ClutterFrame) frame = NULL;
   MetaFrameNative *frame_native;
 
+  if (onscreen_native->next_frame == NULL)
+    return;
+
   power_save_mode = meta_monitor_manager_get_power_save_mode (monitor_manager);
   if (power_save_mode == META_POWER_SAVE_ON)
     {
+      unsigned int frames_pending =
+        cogl_onscreen_count_pending_frames (onscreen);
+      unsigned int posts_pending;
+
+      g_assert (frames_pending >= onscreen_native->swaps_pending);
+      posts_pending = frames_pending - onscreen_native->swaps_pending;
+      if (posts_pending > 0)
+        return;  /* wait for the next frame notification and then try again */
+
       frame = clutter_frame_ref (onscreen_native->next_frame);
       frame_native = meta_frame_native_from_frame (frame);
 
+      if (onscreen_native->swaps_pending == 0)
+        {
+          if (frame_native)
+            {
+              kms_update = meta_frame_native_steal_kms_update (frame_native);
+              if (kms_update)
+                post_finish_frame (onscreen_native, kms_update);
+            }
+          return;
+        }
+
+      drop_stalled_swap (onscreen);
+      onscreen_native->swaps_pending--;
+
       kms_update = meta_frame_native_ensure_kms_update (frame_native,
                                                         kms_device);
       meta_kms_update_add_result_listener (kms_update,
@@ -1485,7 +1563,7 @@ post_latest_swap (CoglOnscreen *onscreen)
     }
 
   COGL_TRACE_BEGIN_SCOPED (MetaRendererNativePostKmsUpdate,
-                           "Meta::OnscreenNative::post_latest_swap#post_pending_update()");
+                           "Meta::OnscreenNative::try_post_latest_swap#post_pending_update()");
 
   switch (renderer_gpu_data->mode)
     {
@@ -1678,13 +1756,24 @@ meta_onscreen_native_direct_scanout (CoglOnscreen   *onscreen,
       return FALSE;
     }
 
+  /* Our direct scanout frame counts as 1, so more than that means we would
+   * be jumping the queue (and post would fail).
+   */
+  if (cogl_onscreen_count_pending_frames (onscreen) > 1)
+    {
+      g_set_error_literal (error,
+                           COGL_SCANOUT_ERROR,
+                           COGL_SCANOUT_ERROR_INHIBITED,
+                           "Direct scanout is inhibited during triple buffering");
+      return FALSE;
+    }
+
   renderer_gpu_data = meta_renderer_native_get_gpu_data (renderer_native,
                                                          render_gpu);
 
   g_warn_if_fail (renderer_gpu_data->mode == META_RENDERER_NATIVE_MODE_GBM);
 
-  g_warn_if_fail (!onscreen_native->next_frame);
-  onscreen_native->next_frame = clutter_frame_ref (frame);
+  assign_next_frame (onscreen_native, frame);
 
   meta_frame_native_set_scanout (frame_native, scanout);
   meta_frame_native_set_buffer (frame_native,
@@ -1914,22 +2003,79 @@ meta_onscreen_native_finish_frame (CoglOnscreen *onscreen,
   MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);
   MetaFrameNative *frame_native = meta_frame_native_from_frame (frame);
   MetaKmsUpdate *kms_update;
+  unsigned int frames_pending = cogl_onscreen_count_pending_frames (onscreen);
+  unsigned int swaps_pending = onscreen_native->swaps_pending;
+  unsigned int posts_pending = frames_pending - swaps_pending;
 
-  kms_update = meta_frame_native_steal_kms_update (frame_native);
-  if (!kms_update)
+  onscreen_native->needs_flush |= meta_kms_device_handle_flush (kms_device,
+                                                                kms_crtc);
+
+  if (!meta_frame_native_has_kms_update (frame_native))
     {
-      if (meta_kms_device_handle_flush (kms_device, kms_crtc))
-        {
-          kms_update = meta_kms_update_new (kms_device);
-          meta_kms_update_set_flushing (kms_update, kms_crtc);
-        }
-      else
+      if (!onscreen_native->needs_flush || posts_pending)
         {
           clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_IDLE);
           return;
         }
     }
 
+  if (posts_pending && !swaps_pending)
+    {
+      g_return_if_fail (meta_frame_native_has_kms_update (frame_native));
+      g_warn_if_fail (onscreen_native->next_frame == NULL);
+
+      g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
+      onscreen_native->next_frame = clutter_frame_ref (frame);
+      clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
+      return;
+    }
+
+  kms_update = meta_frame_native_steal_kms_update (frame_native);
+
+  if (posts_pending && swaps_pending)
+    {
+      MetaFrameNative *older_frame_native;
+      MetaKmsUpdate *older_kms_update;
+
+      g_return_if_fail (kms_update);
+      g_return_if_fail (onscreen_native->next_frame != NULL);
+
+      older_frame_native =
+        meta_frame_native_from_frame (onscreen_native->next_frame);
+      older_kms_update =
+        meta_frame_native_ensure_kms_update (older_frame_native, kms_device);
+      meta_kms_update_merge_from (older_kms_update, kms_update);
+      meta_kms_update_free (kms_update);
+      clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_IDLE);
+      return;
+    }
+
+  if (!kms_update)
+    {
+      kms_update = meta_kms_update_new (kms_device);
+      g_warn_if_fail (onscreen_native->needs_flush);
+    }
+
+  if (onscreen_native->needs_flush)
+    {
+      meta_kms_update_set_flushing (kms_update, kms_crtc);
+      onscreen_native->needs_flush = FALSE;
+    }
+
+  post_finish_frame (onscreen_native, kms_update);
+
+  clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
+}
+
+static void
+post_finish_frame (MetaOnscreenNative *onscreen_native,
+                   MetaKmsUpdate      *kms_update)
+{
+  MetaCrtc *crtc = onscreen_native->crtc;
+  MetaKmsCrtc *kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
+  MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);
+  g_autoptr (MetaKmsFeedback) kms_feedback = NULL;
+
   meta_kms_update_add_result_listener (kms_update,
                                        &finish_frame_result_listener_vtable,
                                        NULL,
@@ -1952,7 +2098,6 @@ meta_onscreen_native_finish_frame (CoglOnscreen *onscreen,
   meta_kms_update_set_flushing (kms_update, kms_crtc);
   meta_kms_device_post_update (kms_device, kms_update,
                                META_KMS_UPDATE_FLAG_NONE);
-  clutter_frame_set_result (frame, CLUTTER_FRAME_RESULT_PENDING_PRESENTED);
 }
 
 static gboolean
@@ -2860,6 +3005,7 @@ meta_onscreen_native_dispose (GObject *object)
   meta_onscreen_native_detach (onscreen_native);
 
   g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
+  g_clear_pointer (&onscreen_native->stalled_frame, clutter_frame_unref);
   g_clear_pointer (&onscreen_native->posted_frame, clutter_frame_unref);
   g_clear_pointer (&onscreen_native->presented_frame, clutter_frame_unref);
 
-- 
GitLab

From 07ea4a2f06628fd57e2a319d4d569c48e52b4be5 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 9 Dec 2022 14:22:31 +0800
Subject: [PATCH 12/30] onscreen/native: Increase secondary GPU dumb_fbs from 2
 to 3

So that they don't get overwritten prematurely during triple buffering
causing tearing.

https://launchpad.net/bugs/1999216
---
 src/backends/native/meta-onscreen-native.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 93451ff2c3b..9bff9fe3842 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -76,7 +76,7 @@ typedef struct _MetaOnscreenNativeSecondaryGpuState
 
   struct {
     MetaDrmBufferDumb *current_dumb_fb;
-    MetaDrmBufferDumb *dumb_fbs[2];
+    MetaDrmBufferDumb *dumb_fbs[3];
   } cpu;
 
   gboolean noted_primary_gpu_copy_ok;
@@ -946,12 +946,17 @@ static MetaDrmBufferDumb *
 secondary_gpu_get_next_dumb_buffer (MetaOnscreenNativeSecondaryGpuState *secondary_gpu_state)
 {
   MetaDrmBufferDumb *current_dumb_fb;
+  const int n_dumb_fbs = G_N_ELEMENTS (secondary_gpu_state->cpu.dumb_fbs);
+  int i;
 
   current_dumb_fb = secondary_gpu_state->cpu.current_dumb_fb;
-  if (current_dumb_fb == secondary_gpu_state->cpu.dumb_fbs[0])
-    return secondary_gpu_state->cpu.dumb_fbs[1];
-  else
-    return secondary_gpu_state->cpu.dumb_fbs[0];
+  for (i = 0; i < n_dumb_fbs; i++)
+    {
+      if (current_dumb_fb == secondary_gpu_state->cpu.dumb_fbs[i])
+        return secondary_gpu_state->cpu.dumb_fbs[(i + 1) % n_dumb_fbs];
+    }
+
+  return secondary_gpu_state->cpu.dumb_fbs[0];
 }
 
 static MetaDrmBuffer *
-- 
GitLab

From 652cf8d804073fa0e44f9a9f716201bf34ff1c4a Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 4 Nov 2021 16:09:26 +0800
Subject: [PATCH 13/30] onscreen/native: Add function
 meta_onscreen_native_discard_pending_swaps

---
 src/backends/native/meta-onscreen-native.c | 11 +++++++++++
 src/backends/native/meta-onscreen-native.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 9bff9fe3842..a88a34decce 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -2105,6 +2105,17 @@ post_finish_frame (MetaOnscreenNative *onscreen_native,
                                META_KMS_UPDATE_FLAG_NONE);
 }
 
+void
+meta_onscreen_native_discard_pending_swaps (CoglOnscreen *onscreen)
+{
+  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
+
+  onscreen_native->swaps_pending = 0;
+
+  g_clear_pointer (&onscreen_native->stalled_frame, clutter_frame_unref);
+  g_clear_pointer (&onscreen_native->next_frame, clutter_frame_unref);
+}
+
 static gboolean
 should_surface_be_sharable (CoglOnscreen *onscreen)
 {
diff --git a/src/backends/native/meta-onscreen-native.h b/src/backends/native/meta-onscreen-native.h
index 0e1193325a9..e30357d19d1 100644
--- a/src/backends/native/meta-onscreen-native.h
+++ b/src/backends/native/meta-onscreen-native.h
@@ -48,6 +48,8 @@ void meta_onscreen_native_dummy_power_save_page_flip (CoglOnscreen *onscreen);
 gboolean meta_onscreen_native_is_buffer_scanout_compatible (CoglOnscreen *onscreen,
                                                             CoglScanout  *scanout);
 
+void meta_onscreen_native_discard_pending_swaps (CoglOnscreen *onscreen);
+
 void meta_onscreen_native_set_view (CoglOnscreen     *onscreen,
                                     MetaRendererView *view);
 
-- 
GitLab

From bc03998d074642b4fb1050c2b58f459560a32a52 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 11 May 2022 16:00:32 +0800
Subject: [PATCH 14/30] onscreen/native: Skip try_post_latest_swap if shutting
 down

Otherwise we could get:

meta_kms_prepare_shutdown ->
  flush_callbacks ->
  ... ->
  try_post_latest_swap ->
  post and queue more callbacks

So later in shutdown those callbacks would trigger an assertion failure
in meta_kms_impl_device_atomic_finalize:

g_hash_table_size (impl_device_atomic->page_flip_datas) == 0
---
 src/backends/native/meta-onscreen-native.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index a88a34decce..665b24c05e2 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1499,6 +1499,8 @@ try_post_latest_swap (CoglOnscreen *onscreen)
   MetaRendererNative *renderer_native = renderer_gpu_data->renderer_native;
   MetaRenderer *renderer = META_RENDERER (renderer_native);
   MetaBackend *backend = meta_renderer_get_backend (renderer);
+  MetaBackendNative *backend_native = META_BACKEND_NATIVE (backend);
+  MetaKms *kms = meta_backend_native_get_kms (backend_native);
   MetaMonitorManager *monitor_manager =
     meta_backend_get_monitor_manager (backend);
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
@@ -1511,7 +1513,8 @@ try_post_latest_swap (CoglOnscreen *onscreen)
   g_autoptr (ClutterFrame) frame = NULL;
   MetaFrameNative *frame_native;
 
-  if (onscreen_native->next_frame == NULL)
+  if (onscreen_native->next_frame == NULL ||
+      meta_kms_is_shutting_down (kms))
     return;
 
   power_save_mode = meta_monitor_manager_get_power_save_mode (monitor_manager);
-- 
GitLab

From bf2b9b937ee98921d6fad02572f9fc2038d32cb1 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 4 Nov 2021 16:09:52 +0800
Subject: [PATCH 15/30] renderer/native: Discard pending swaps when rebuilding
 views

It's analogous to discard_pending_page_flips but represents swaps that
might become flips after the next frame notification callbacks, thanks
to triple buffering. Since the views are being rebuilt and their onscreens
are about to be destroyed, turning those swaps into more flips/posts would
just lead to unexpected behaviour (like trying to flip on a half-destroyed
inactive CRTC).
---
 src/backends/native/meta-renderer-native.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 02d1e3e0c06..120ac4a9be7 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -1511,6 +1511,26 @@ detach_onscreens (MetaRenderer *renderer)
     }
 }
 
+static void
+discard_pending_swaps (MetaRenderer *renderer)
+{
+  GList *views = meta_renderer_get_views (renderer);;
+  GList *l;
+
+  for (l = views; l; l = l->next)
+    {
+      ClutterStageView *stage_view = l->data;
+      CoglFramebuffer *fb = clutter_stage_view_get_onscreen (stage_view);
+      CoglOnscreen *onscreen;
+
+      if (!COGL_IS_ONSCREEN (fb))
+        continue;
+
+      onscreen = COGL_ONSCREEN (fb);
+      meta_onscreen_native_discard_pending_swaps (onscreen);
+    }
+}
+
 static void
 meta_renderer_native_rebuild_views (MetaRenderer *renderer)
 {
@@ -1521,6 +1541,7 @@ meta_renderer_native_rebuild_views (MetaRenderer *renderer)
   MetaRendererClass *parent_renderer_class =
     META_RENDERER_CLASS (meta_renderer_native_parent_class);
 
+  discard_pending_swaps (renderer);
   meta_kms_discard_pending_page_flips (kms);
   g_hash_table_remove_all (renderer_native->mode_set_updates);
 
-- 
GitLab

From 8a0f463adf11b0d3d30c96e29db8e3d5a75eea6f Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 7 Dec 2023 16:28:20 +0800
Subject: [PATCH 16/30] clutter/frame-clock: Reuse existing idle period
 detection

While it was correct for double buffering, the test was wrong for
triple buffering and would lead to accidentally staying in triple
buffering for too long.

Fixes: 8f27ebf87eee6057992a90560d4118ab7bdf138d
---
 clutter/clutter/clutter-frame-clock.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 75563161f28..30f4938ffe5 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -496,6 +496,7 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
   int64_t min_render_time_allowed_us;
   int64_t max_render_time_allowed_us;
   int64_t next_presentation_time_us;
+  int64_t next_smooth_presentation_time_us;
   int64_t next_update_time_us;
 
   now_us = g_get_monotonic_time ();
@@ -540,7 +541,8 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
    *
    */
   last_presentation_time_us = frame_clock->last_presentation_time_us;
-  next_presentation_time_us = last_presentation_time_us + refresh_interval_us;
+  next_smooth_presentation_time_us = last_presentation_time_us + refresh_interval_us;
+  next_presentation_time_us = next_smooth_presentation_time_us;
 
   /*
    * However, the last presentation could have happened more than a frame ago.
@@ -607,7 +609,7 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
     }
 
   if (frame_clock->last_presentation_flags & CLUTTER_FRAME_INFO_FLAG_VSYNC &&
-      next_presentation_time_us != last_presentation_time_us + refresh_interval_us)
+      next_presentation_time_us != next_smooth_presentation_time_us)
     {
       /* There was an idle period since the last presentation, so there seems
        * be no constantly updating actor. In this case it's best to start
-- 
GitLab

From 54fbca291553733932dc8ca6b09e9285210eb835 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 10 Aug 2021 17:46:49 +0800
Subject: [PATCH 17/30] clutter/frame-clock: Lower the threshold for disabling
 error diffusion

Error diffusion was introduced in 0555a5bbc15 for Nvidia where last
presentation time is always unknown (zero). Dispatch times would drift
apart always being a fraction of a frame late, and accumulated to cause
periodic frame skips. So error diffusion corrected that precisely and
avoided the skips.

That works great with double buffering but less great with triple
buffering. It's certainly still needed with triple buffering but
correcting for a lateness of many milliseconds isn't a good idea. That's
because a dispatch being that late is not due to main loop jitter but due
to Nvidia's swap buffers blocking when the queue is full. So scheduling
the next frame even earlier using last_dispatch_lateness_us would just
perpetuate the problem of swap buffers blocking for too long.

So now we lower the threshold of when error diffusion gets disabled. It's
still high enough to fix the original smoothness problem it was for, but
now low enough to detect Nvidia's occasionally blocking swaps and backs
off in that case.

Since the average duration of a blocking swap is half a frame interval
and we want to distinguish between that and sub-millisecond jitter, the
logical threshold is halfway again: refresh_interval_us/4.
---
 clutter/clutter/clutter-frame-clock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 30f4938ffe5..f5abde28944 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -930,7 +930,7 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
                              frame_clock->refresh_interval_us;
 
   lateness_us = time_us - ideal_dispatch_time_us;
-  if (lateness_us < 0 || lateness_us >= frame_clock->refresh_interval_us)
+  if (lateness_us < 0 || lateness_us >= frame_clock->refresh_interval_us / 4)
     frame_clock->last_dispatch_lateness_us = 0;
   else
     frame_clock->last_dispatch_lateness_us = lateness_us;
-- 
GitLab

From ff96012c63b4d8244c605709151d6ae9fe57669a Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 24 Jul 2020 14:13:11 +0800
Subject: [PATCH 18/30] clutter/frame-clock: Merge states DISPATCHING and
 PENDING_PRESENTED

Chronologically they already overlap in time as presentation may
complete in the middle of the dispatch function, otherwise they are
contiguous in time. And most switch statements treated the two states
the same already so they're easy to merge into a single `DISPATCHED`
state.

Having fewer states now will make life easier when we add more states
later.
---
 clutter/clutter/clutter-frame-clock.c | 31 ++++++++++-----------------
 1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index f5abde28944..ec96f9e351f 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -70,8 +70,7 @@ typedef enum _ClutterFrameClockState
   CLUTTER_FRAME_CLOCK_STATE_IDLE,
   CLUTTER_FRAME_CLOCK_STATE_SCHEDULED,
   CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW,
-  CLUTTER_FRAME_CLOCK_STATE_DISPATCHING,
-  CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED,
 } ClutterFrameClockState;
 
 struct _ClutterFrameClock
@@ -418,8 +417,7 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       g_warn_if_reached ();
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
-    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
       maybe_reschedule_update (frame_clock);
       break;
@@ -440,8 +438,7 @@ clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       g_warn_if_reached ();
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
-    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
       maybe_reschedule_update (frame_clock);
       break;
@@ -741,8 +738,7 @@ clutter_frame_clock_inhibit (ClutterFrameClock *frame_clock)
           frame_clock->pending_reschedule_now = TRUE;
           frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
           break;
-        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
-        case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
           break;
         }
 
@@ -781,8 +777,7 @@ clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
       break;
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       return;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
-    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
       frame_clock->pending_reschedule = TRUE;
       frame_clock->pending_reschedule_now = TRUE;
       return;
@@ -837,8 +832,7 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       return;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
-    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
       frame_clock->pending_reschedule = TRUE;
       return;
     }
@@ -893,8 +887,7 @@ clutter_frame_clock_set_mode (ClutterFrameClock     *frame_clock,
       frame_clock->pending_reschedule_now = TRUE;
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
-    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
       break;
     }
 
@@ -954,7 +947,7 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
   frame_clock->last_dispatch_time_us = time_us;
   g_source_set_ready_time (frame_clock->source, -1);
 
-  frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHING;
+  frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED;
 
   frame_count = frame_clock->frame_count++;
 
@@ -988,20 +981,20 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
   switch (frame_clock->state)
     {
     case CLUTTER_FRAME_CLOCK_STATE_INIT:
-    case CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED:
       g_warn_if_reached ();
       break;
     case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+      /* Presentation completed synchronously in the above listener */
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHING:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
       switch (result)
         {
         case CLUTTER_FRAME_RESULT_PENDING_PRESENTED:
-          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED;
           break;
         case CLUTTER_FRAME_RESULT_IDLE:
+          /* The frame was aborted; nothing to paint/present */
           frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
           maybe_reschedule_update (frame_clock);
           break;
@@ -1218,8 +1211,6 @@ clutter_frame_clock_dispose (GObject *object)
 {
   ClutterFrameClock *frame_clock = CLUTTER_FRAME_CLOCK (object);
 
-  g_warn_if_fail (frame_clock->state != CLUTTER_FRAME_CLOCK_STATE_DISPATCHING);
-
   if (frame_clock->source)
     {
       g_signal_emit (frame_clock, signals[DESTROY], 0);
-- 
GitLab

From 2d0a338ea9a21be8c6f147d6d017a2066ed3d9b6 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Mon, 13 Dec 2021 17:03:44 +0800
Subject: [PATCH 19/30] clutter/frame-clock: Clamp render times to two frames,
 not one

Because the buffer queue may grow by an extra frame in triple buffering,
we need measurements exceeding one frame to indicate when and by how much
the scaling is necessary.
---
 clutter/clutter/clutter-frame-clock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index ec96f9e351f..bb6d7ab333f 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -390,7 +390,7 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
         CLAMP (frame_clock->last_dispatch_lateness_us + dispatch_to_swap_us +
                MAX (swap_to_rendering_done_us, swap_to_flip_us),
                frame_clock->shortterm_max_update_duration_us,
-               frame_clock->refresh_interval_us);
+               2 * frame_clock->refresh_interval_us);
 
       maybe_update_longterm_max_duration_us (frame_clock, frame_info);
 
@@ -476,7 +476,7 @@ clutter_frame_clock_compute_max_render_time_us (ClutterFrameClock *frame_clock)
     frame_clock->vblank_duration_us +
     clutter_max_render_time_constant_us;
 
-  max_render_time_us = CLAMP (max_render_time_us, 0, refresh_interval_us);
+  max_render_time_us = CLAMP (max_render_time_us, 0, 2 * refresh_interval_us);
 
   return max_render_time_us;
 }
-- 
GitLab

From 3ab1eaf7df7ac9cc68f7419f2c3c2510c7bdcfde Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 10 Sep 2020 16:34:53 +0800
Subject: [PATCH 20/30] clutter/frame-clock: Add triple buffering support

---
 clutter/clutter/clutter-frame-clock.c | 191 ++++++++++++++++++++++----
 1 file changed, 163 insertions(+), 28 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index bb6d7ab333f..7f39d3fbb98 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -70,7 +70,10 @@ typedef enum _ClutterFrameClockState
   CLUTTER_FRAME_CLOCK_STATE_IDLE,
   CLUTTER_FRAME_CLOCK_STATE_SCHEDULED,
   CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW,
-  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO,
 } ClutterFrameClockState;
 
 struct _ClutterFrameClock
@@ -91,6 +94,7 @@ struct _ClutterFrameClock
   ClutterFrameClockMode mode;
 
   int64_t last_dispatch_time_us;
+  int64_t prev_last_dispatch_time_us;
   int64_t last_dispatch_lateness_us;
   int64_t last_presentation_time_us;
   int64_t next_update_time_us;
@@ -112,6 +116,7 @@ struct _ClutterFrameClock
   int64_t vblank_duration_us;
   /* Last KMS buffer submission time. */
   int64_t last_flip_time_us;
+  int64_t prev_last_flip_time_us;
 
   /* Last time we promoted short-term maximum to long-term one */
   int64_t longterm_promotion_us;
@@ -369,14 +374,35 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
       frame_info->has_valid_gpu_rendering_duration)
     {
       int64_t dispatch_to_swap_us, swap_to_rendering_done_us, swap_to_flip_us;
+      int64_t dispatch_time_us = 0, flip_time_us = 0;
+
+      switch (frame_clock->state)
+        {
+        case CLUTTER_FRAME_CLOCK_STATE_INIT:
+        case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+        case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+        case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
+          g_warn_if_reached ();
+          G_GNUC_FALLTHROUGH;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+          dispatch_time_us = frame_clock->last_dispatch_time_us;
+          flip_time_us = frame_clock->last_flip_time_us;
+          break;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+          dispatch_time_us = frame_clock->prev_last_dispatch_time_us;
+          flip_time_us = frame_clock->prev_last_flip_time_us;
+          break;
+        }
 
       dispatch_to_swap_us =
         frame_info->cpu_time_before_buffer_swap_us -
-        frame_clock->last_dispatch_time_us;
+        dispatch_time_us;
       swap_to_rendering_done_us =
         frame_info->gpu_rendering_duration_ns / 1000;
       swap_to_flip_us =
-        frame_clock->last_flip_time_us -
+        flip_time_us -
         frame_info->cpu_time_before_buffer_swap_us;
 
       CLUTTER_NOTE (FRAME_TIMINGS,
@@ -417,10 +443,22 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       g_warn_if_reached ();
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
       maybe_reschedule_update (frame_clock);
       break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
+      maybe_reschedule_update (frame_clock);
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW;
+      maybe_reschedule_update (frame_clock);
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      maybe_reschedule_update (frame_clock);
+      break;
     }
 }
 
@@ -438,10 +476,22 @@ clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
       g_warn_if_reached ();
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
       maybe_reschedule_update (frame_clock);
       break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
+      maybe_reschedule_update (frame_clock);
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW;
+      maybe_reschedule_update (frame_clock);
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      maybe_reschedule_update (frame_clock);
+      break;
     }
 }
 
@@ -456,7 +506,14 @@ clutter_frame_clock_compute_max_render_time_us (ClutterFrameClock *frame_clock)
   if (!frame_clock->ever_got_measurements ||
       G_UNLIKELY (clutter_paint_debug_flags &
                   CLUTTER_DEBUG_DISABLE_DYNAMIC_MAX_RENDER_TIME))
-    return (int64_t) (refresh_interval_us * SYNC_DELAY_FALLBACK_FRACTION);
+    {
+      int64_t ret = (int64_t) (refresh_interval_us * SYNC_DELAY_FALLBACK_FRACTION);
+
+      if (frame_clock->state == CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE)
+        ret += refresh_interval_us;
+
+      return ret;
+    }
 
   /* Max render time shows how early the frame clock needs to be dispatched
    * to make it to the predicted next presentation time. It is an estimate of
@@ -493,7 +550,7 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
   int64_t min_render_time_allowed_us;
   int64_t max_render_time_allowed_us;
   int64_t next_presentation_time_us;
-  int64_t next_smooth_presentation_time_us;
+  int64_t next_smooth_presentation_time_us = 0;
   int64_t next_update_time_us;
 
   now_us = g_get_monotonic_time ();
@@ -538,7 +595,27 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
    *
    */
   last_presentation_time_us = frame_clock->last_presentation_time_us;
-  next_smooth_presentation_time_us = last_presentation_time_us + refresh_interval_us;
+  switch (frame_clock->state)
+    {
+    case CLUTTER_FRAME_CLOCK_STATE_INIT:
+    case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
+      next_smooth_presentation_time_us = last_presentation_time_us +
+                                         refresh_interval_us;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+      next_smooth_presentation_time_us = last_presentation_time_us +
+                                         2 * refresh_interval_us;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+      next_smooth_presentation_time_us = last_presentation_time_us +
+                                         3 * refresh_interval_us;
+      break;
+    }
+
   next_presentation_time_us = next_smooth_presentation_time_us;
 
   /*
@@ -738,7 +815,17 @@ clutter_frame_clock_inhibit (ClutterFrameClock *frame_clock)
           frame_clock->pending_reschedule_now = TRUE;
           frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
           break;
-        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+          frame_clock->pending_reschedule = TRUE;
+          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+          break;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+          frame_clock->pending_reschedule = TRUE;
+          frame_clock->pending_reschedule_now = TRUE;
+          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+          break;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
           break;
         }
 
@@ -774,10 +861,17 @@ clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_INIT:
     case CLUTTER_FRAME_CLOCK_STATE_IDLE:
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW;
       break;
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
       return;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+      frame_clock->state =
+        CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       frame_clock->pending_reschedule = TRUE;
       frame_clock->pending_reschedule_now = TRUE;
       return;
@@ -806,7 +900,6 @@ clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
 
   frame_clock->next_update_time_us = next_update_time_us;
   g_source_set_ready_time (frame_clock->source, next_update_time_us);
-  frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW;
 }
 
 void
@@ -828,11 +921,17 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
       return;
     case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
       break;
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
       return;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       frame_clock->pending_reschedule = TRUE;
       return;
     }
@@ -861,7 +960,6 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
 
   frame_clock->next_update_time_us = next_update_time_us;
   g_source_set_ready_time (frame_clock->source, next_update_time_us);
-  frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
 }
 
 void
@@ -877,6 +975,8 @@ clutter_frame_clock_set_mode (ClutterFrameClock     *frame_clock,
     {
     case CLUTTER_FRAME_CLOCK_STATE_INIT:
     case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       break;
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       frame_clock->pending_reschedule = TRUE;
@@ -887,7 +987,14 @@ clutter_frame_clock_set_mode (ClutterFrameClock     *frame_clock,
       frame_clock->pending_reschedule_now = TRUE;
       frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+      frame_clock->pending_reschedule = TRUE;
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+      frame_clock->pending_reschedule = TRUE;
+      frame_clock->pending_reschedule_now = TRUE;
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
       break;
     }
 
@@ -944,10 +1051,27 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
     }
 #endif
 
+  frame_clock->prev_last_dispatch_time_us = frame_clock->last_dispatch_time_us;
   frame_clock->last_dispatch_time_us = time_us;
   g_source_set_ready_time (frame_clock->source, -1);
 
-  frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED;
+  switch (frame_clock->state)
+    {
+    case CLUTTER_FRAME_CLOCK_STATE_INIT:
+    case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+      g_warn_if_reached ();
+      return;
+    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO;
+      break;
+    }
 
   frame_count = frame_clock->frame_count++;
 
@@ -978,26 +1102,36 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
   result = iface->frame (frame_clock, frame, frame_clock->listener.user_data);
   COGL_TRACE_END (ClutterFrameClockFrame);
 
-  switch (frame_clock->state)
+  switch (result)
     {
-    case CLUTTER_FRAME_CLOCK_STATE_INIT:
-      g_warn_if_reached ();
+    case CLUTTER_FRAME_RESULT_PENDING_PRESENTED:
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_IDLE:
-      /* Presentation completed synchronously in the above listener */
-    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
-    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
-      break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
-      switch (result)
+    case CLUTTER_FRAME_RESULT_IDLE:
+      /* The frame was aborted; nothing to paint/present */
+      switch (frame_clock->state)
         {
-        case CLUTTER_FRAME_RESULT_PENDING_PRESENTED:
+        case CLUTTER_FRAME_CLOCK_STATE_INIT:
+        case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+        case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+        case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
+          g_warn_if_reached ();
           break;
-        case CLUTTER_FRAME_RESULT_IDLE:
-          /* The frame was aborted; nothing to paint/present */
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
           frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_IDLE;
           maybe_reschedule_update (frame_clock);
           break;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
+          maybe_reschedule_update (frame_clock);
+          break;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
+          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW;
+          maybe_reschedule_update (frame_clock);
+          break;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+          maybe_reschedule_update (frame_clock);
+          break;
         }
       break;
     }
@@ -1033,6 +1167,7 @@ void
 clutter_frame_clock_record_flip_time (ClutterFrameClock *frame_clock,
                                       int64_t            flip_time_us)
 {
+  frame_clock->prev_last_flip_time_us = frame_clock->last_flip_time_us;
   frame_clock->last_flip_time_us = flip_time_us;
 }
 
-- 
GitLab

From 22af8f6060bff60d687bee79e837e49e2fd50c15 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 10 Dec 2021 16:28:04 +0800
Subject: [PATCH 21/30] clutter/frame-clock: Log N-buffers in
 CLUTTTER_DEBUG=frame-timings

---
 clutter/clutter/clutter-frame-clock.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 7f39d3fbb98..03ebca88023 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -281,6 +281,12 @@ void
 clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
                                       ClutterFrameInfo  *frame_info)
 {
+#ifdef CLUTTER_ENABLE_DEBUG
+  const char *debug_state =
+    frame_clock->state == CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO ?
+    "Triple buffering" : "Double buffering";
+#endif
+
   COGL_TRACE_BEGIN_SCOPED (ClutterFrameClockNotifyPresented,
                            "Clutter::FrameClock::presented()");
   COGL_TRACE_DESCRIBE (ClutterFrameClockNotifyPresented,
@@ -406,7 +412,8 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
         frame_info->cpu_time_before_buffer_swap_us;
 
       CLUTTER_NOTE (FRAME_TIMINGS,
-                    "update2dispatch %ld µs, dispatch2swap %ld µs, swap2render %ld µs, swap2flip %ld µs",
+                    "%s: update2dispatch %ld µs, dispatch2swap %ld µs, swap2render %ld µs, swap2flip %ld µs",
+                    debug_state,
                     frame_clock->last_dispatch_lateness_us,
                     dispatch_to_swap_us,
                     swap_to_rendering_done_us,
@@ -425,7 +432,8 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     }
   else
     {
-      CLUTTER_NOTE (FRAME_TIMINGS, "update2dispatch %ld µs",
+      CLUTTER_NOTE (FRAME_TIMINGS, "%s: update2dispatch %ld µs",
+                    debug_state,
                     frame_clock->last_dispatch_lateness_us);
     }
 
-- 
GitLab

From b1d977dc8372ea59dd99d8e1a0b0a20b82de4342 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 7 Sep 2021 19:08:15 +0800
Subject: [PATCH 22/30] clutter/frame: Add ClutterFrameHint to ClutterFrame

This will allow the backend to provide performance hints to the frame
clock in future.
---
 clutter/clutter/clutter-frame-clock.h   |  6 ++++++
 clutter/clutter/clutter-frame-private.h |  1 +
 clutter/clutter/clutter-frame.c         | 13 +++++++++++++
 clutter/clutter/clutter-frame.h         |  7 +++++++
 4 files changed, 27 insertions(+)

diff --git a/clutter/clutter/clutter-frame-clock.h b/clutter/clutter/clutter-frame-clock.h
index a7be5ef3167..5adf995098b 100644
--- a/clutter/clutter/clutter-frame-clock.h
+++ b/clutter/clutter/clutter-frame-clock.h
@@ -33,6 +33,12 @@ typedef enum _ClutterFrameResult
   CLUTTER_FRAME_RESULT_IDLE,
 } ClutterFrameResult;
 
+typedef enum _ClutterFrameHint
+{
+  CLUTTER_FRAME_HINT_NONE                     = 0,
+  CLUTTER_FRAME_HINT_DIRECT_SCANOUT_ATTEMPTED = 1 << 0,
+} ClutterFrameHint;
+
 #define CLUTTER_TYPE_FRAME_CLOCK (clutter_frame_clock_get_type ())
 CLUTTER_EXPORT
 G_DECLARE_FINAL_TYPE (ClutterFrameClock, clutter_frame_clock,
diff --git a/clutter/clutter/clutter-frame-private.h b/clutter/clutter/clutter-frame-private.h
index ef66b874edf..ce140560a89 100644
--- a/clutter/clutter/clutter-frame-private.h
+++ b/clutter/clutter/clutter-frame-private.h
@@ -36,6 +36,7 @@ struct _ClutterFrame
 
   gboolean has_result;
   ClutterFrameResult result;
+  ClutterFrameHint hints;
 };
 
 CLUTTER_EXPORT
diff --git a/clutter/clutter/clutter-frame.c b/clutter/clutter/clutter-frame.c
index 7436f9f182d..53c289b2c5a 100644
--- a/clutter/clutter/clutter-frame.c
+++ b/clutter/clutter/clutter-frame.c
@@ -115,3 +115,16 @@ clutter_frame_set_result (ClutterFrame       *frame,
   frame->result = result;
   frame->has_result = TRUE;
 }
+
+void
+clutter_frame_set_hint (ClutterFrame     *frame,
+                        ClutterFrameHint  hint)
+{
+  frame->hints |= hint;
+}
+
+ClutterFrameHint
+clutter_frame_get_hints (ClutterFrame *frame)
+{
+  return frame->hints;
+}
diff --git a/clutter/clutter/clutter-frame.h b/clutter/clutter/clutter-frame.h
index 34f0770bd7d..c7b3d02acb9 100644
--- a/clutter/clutter/clutter-frame.h
+++ b/clutter/clutter/clutter-frame.h
@@ -54,4 +54,11 @@ void clutter_frame_set_result (ClutterFrame       *frame,
 CLUTTER_EXPORT
 gboolean clutter_frame_has_result (ClutterFrame *frame);
 
+CLUTTER_EXPORT
+void clutter_frame_set_hint (ClutterFrame     *frame,
+                             ClutterFrameHint  hint);
+
+CLUTTER_EXPORT
+ClutterFrameHint clutter_frame_get_hints (ClutterFrame *frame);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC (ClutterFrame, clutter_frame_unref)
-- 
GitLab

From 00e171cf0ada96d360cb5a7e457a589712e359f8 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 7 Sep 2021 19:10:26 +0800
Subject: [PATCH 23/30] backends: Flag that the frame attempted direct scanout

We need this hint whether direct scanout succeeds or fails because it's
the mechanism by which we will tell the clock to enforce double buffering,
thus making direct scanout possible on future frames. Triple buffering
will be disabled until such time that direct scanout is not being attempted.
---
 src/backends/meta-stage-impl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/backends/meta-stage-impl.c b/src/backends/meta-stage-impl.c
index 552cc1637cb..c4bed1a83dd 100644
--- a/src/backends/meta-stage-impl.c
+++ b/src/backends/meta-stage-impl.c
@@ -774,6 +774,8 @@ meta_stage_impl_redraw_view (ClutterStageWindow *stage_window,
     {
       g_autoptr (GError) error = NULL;
 
+      clutter_frame_set_hint (frame, CLUTTER_FRAME_HINT_DIRECT_SCANOUT_ATTEMPTED);
+
       if (meta_stage_impl_scanout_view (stage_impl,
                                         stage_view,
                                         scanout,
-- 
GitLab

From 5a804a67aba159a95e589d3ac04b0592dccd4c19 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 7 Sep 2021 19:15:18 +0800
Subject: [PATCH 24/30] clutter: Pass ClutterFrameHint(s) to the frame clock

---
 clutter/clutter/clutter-frame-clock.c |  8 ++++++--
 clutter/clutter/clutter-frame-clock.h |  5 +++--
 clutter/clutter/clutter-stage-view.c  | 11 +++++++++--
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 03ebca88023..cc4242abfe3 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -118,6 +118,8 @@ struct _ClutterFrameClock
   int64_t last_flip_time_us;
   int64_t prev_last_flip_time_us;
 
+  ClutterFrameHint last_flip_hints;
+
   /* Last time we promoted short-term maximum to long-term one */
   int64_t longterm_promotion_us;
   /* Long-term maximum update duration */
@@ -1172,11 +1174,13 @@ frame_clock_source_dispatch (GSource     *source,
 }
 
 void
-clutter_frame_clock_record_flip_time (ClutterFrameClock *frame_clock,
-                                      int64_t            flip_time_us)
+clutter_frame_clock_record_flip (ClutterFrameClock *frame_clock,
+                                 int64_t            flip_time_us,
+                                 ClutterFrameHint   hints)
 {
   frame_clock->prev_last_flip_time_us = frame_clock->last_flip_time_us;
   frame_clock->last_flip_time_us = flip_time_us;
+  frame_clock->last_flip_hints = hints;
 }
 
 GString *
diff --git a/clutter/clutter/clutter-frame-clock.h b/clutter/clutter/clutter-frame-clock.h
index 5adf995098b..bfc89bde091 100644
--- a/clutter/clutter/clutter-frame-clock.h
+++ b/clutter/clutter/clutter-frame-clock.h
@@ -108,7 +108,8 @@ void clutter_frame_clock_remove_timeline (ClutterFrameClock *frame_clock,
 CLUTTER_EXPORT
 float clutter_frame_clock_get_refresh_rate (ClutterFrameClock *frame_clock);
 
-void clutter_frame_clock_record_flip_time (ClutterFrameClock *frame_clock,
-                                           int64_t            flip_time_us);
+void clutter_frame_clock_record_flip (ClutterFrameClock *frame_clock,
+                                      int64_t            flip_time_us,
+                                      ClutterFrameHint   hints);
 
 GString * clutter_frame_clock_get_max_render_time_debug_info (ClutterFrameClock *frame_clock);
diff --git a/clutter/clutter/clutter-stage-view.c b/clutter/clutter/clutter-stage-view.c
index 1e9f98cfc9f..3686c25e065 100644
--- a/clutter/clutter/clutter-stage-view.c
+++ b/clutter/clutter/clutter-stage-view.c
@@ -898,14 +898,21 @@ handle_frame_clock_frame (ClutterFrameClock *frame_clock,
 
       _clutter_stage_window_redraw_view (stage_window, view, frame);
 
-      clutter_frame_clock_record_flip_time (frame_clock,
-                                            g_get_monotonic_time ());
+      clutter_frame_clock_record_flip (frame_clock,
+                                       g_get_monotonic_time (),
+                                       clutter_frame_get_hints (frame));
 
       clutter_stage_emit_after_paint (stage, view, frame);
 
       if (_clutter_context_get_show_fps ())
         end_frame_timing_measurement (view);
     }
+  else
+    {
+      clutter_frame_clock_record_flip (frame_clock,
+                                       g_get_monotonic_time (),
+                                       clutter_frame_get_hints (frame));
+    }
 
   _clutter_stage_window_finish_frame (stage_window, view, frame);
 
-- 
GitLab

From 6816a22d4bbe01c8cdfbbebc4e7d812faff5c963 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 7 Sep 2021 19:15:55 +0800
Subject: [PATCH 25/30] clutter/frame-clock: Conditionally disable triple
 buffering

1. When direct scanout is attempted

There's no compositing during direct scanout so the "render" time is zero.
Thus there is no need to implement triple buffering for direct scanouts.
Stick to double buffering and enjoy the lower latency.

2. If disabled by environment variable MUTTER_DEBUG_TRIPLE_BUFFERING

With possible values {never, auto, always} where auto is the default.

3. When VRR is in use

VRR calls `clutter_frame_clock_schedule_update_now` which would keep
the buffer queue full, which in turn prevented direct scanout mode.
Because OnscreenNative currently only supports direct scanout with
double buffering.

We now break that feedback loop by preventing triple buffering from
being scheduled when the frame clock mode becomes variable. Long term
this could also be solved by supporting triple buffering in direct
scanout mode. But whether or not that would be desirable given the
latency penalty remains to be seen.
---
 clutter/clutter/clutter-frame-clock.c | 70 ++++++++++++++++++++++++++-
 1 file changed, 68 insertions(+), 2 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index cc4242abfe3..4b83501b43e 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -42,6 +42,15 @@ enum
 
 static guint signals[N_SIGNALS];
 
+typedef enum
+{
+  TRIPLE_BUFFERING_MODE_NEVER,
+  TRIPLE_BUFFERING_MODE_AUTO,
+  TRIPLE_BUFFERING_MODE_ALWAYS,
+} TripleBufferingMode;
+
+static TripleBufferingMode triple_buffering_mode = TRIPLE_BUFFERING_MODE_AUTO;
+
 #define SYNC_DELAY_FALLBACK_FRACTION 0.875f
 
 #define MINIMUM_REFRESH_RATE 30.f
@@ -854,6 +863,25 @@ clutter_frame_clock_uninhibit (ClutterFrameClock *frame_clock)
     maybe_reschedule_update (frame_clock);
 }
 
+static gboolean
+want_triple_buffering (ClutterFrameClock *frame_clock)
+{
+  switch (triple_buffering_mode)
+    {
+    case TRIPLE_BUFFERING_MODE_NEVER:
+      return FALSE;
+    case TRIPLE_BUFFERING_MODE_AUTO:
+      return frame_clock->mode == CLUTTER_FRAME_CLOCK_MODE_FIXED &&
+             !(frame_clock->last_flip_hints &
+               CLUTTER_FRAME_HINT_DIRECT_SCANOUT_ATTEMPTED);
+    case TRIPLE_BUFFERING_MODE_ALWAYS:
+      return TRUE;
+    }
+
+  g_assert_not_reached ();
+  return FALSE;
+}
+
 void
 clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
 {
@@ -876,11 +904,18 @@ clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW:
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
       return;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
       frame_clock->state =
         CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW;
       break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+      if (want_triple_buffering (frame_clock))
+        {
+          frame_clock->state =
+            CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW;
+          break;
+        }
+      G_GNUC_FALLTHROUGH;
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       frame_clock->pending_reschedule = TRUE;
       frame_clock->pending_reschedule_now = TRUE;
@@ -916,6 +951,11 @@ void
 clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
 {
   int64_t next_update_time_us = -1;
+  TripleBufferingMode current_mode = triple_buffering_mode;
+
+  if (current_mode == TRIPLE_BUFFERING_MODE_AUTO &&
+      !want_triple_buffering (frame_clock))
+    current_mode = TRIPLE_BUFFERING_MODE_NEVER;
 
   if (frame_clock->inhibit_count > 0)
     {
@@ -939,7 +979,23 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED_NOW:
       return;
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
-      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED;
+      switch (current_mode)
+        {
+        case TRIPLE_BUFFERING_MODE_NEVER:
+          frame_clock->pending_reschedule = TRUE;
+          return;
+        case TRIPLE_BUFFERING_MODE_AUTO:
+          frame_clock->state =
+            CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED;
+          break;
+        case TRIPLE_BUFFERING_MODE_ALWAYS:
+          next_update_time_us = g_get_monotonic_time ();
+          frame_clock->next_presentation_time_us = 0;
+          frame_clock->is_next_presentation_time_valid = FALSE;
+          frame_clock->state =
+            CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED;
+          goto got_update_time;
+        }
       break;
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       frame_clock->pending_reschedule = TRUE;
@@ -966,6 +1022,7 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
       break;
     }
 
+got_update_time:
   g_warn_if_fail (next_update_time_us != -1);
 
   frame_clock->next_update_time_us = next_update_time_us;
@@ -1381,6 +1438,15 @@ static void
 clutter_frame_clock_class_init (ClutterFrameClockClass *klass)
 {
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  const char *mode_str;
+
+  mode_str = g_getenv ("MUTTER_DEBUG_TRIPLE_BUFFERING");
+  if (!g_strcmp0 (mode_str, "never"))
+    triple_buffering_mode = TRIPLE_BUFFERING_MODE_NEVER;
+  else if (!g_strcmp0 (mode_str, "auto"))
+    triple_buffering_mode = TRIPLE_BUFFERING_MODE_AUTO;
+  else if (!g_strcmp0 (mode_str, "always"))
+    triple_buffering_mode = TRIPLE_BUFFERING_MODE_ALWAYS;
 
   object_class->dispose = clutter_frame_clock_dispose;
 
-- 
GitLab

From 1a305603803767d0896dc089419438861ebdafbb Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 30 Jun 2022 18:56:06 +0800
Subject: [PATCH 26/30] tests/native-kms-render: Fix failing client-scanout
 test

It was assuming an immediate transition from compositing (triple
buffering) to direct scanout (double buffering), whereas there is
a one frame delay in that transition as the buffer queue shrinks.
We don't lose any frames in the transition.
---
 src/tests/native-kms-render.c | 106 ++++++++++++++++++++++++++++------
 1 file changed, 87 insertions(+), 19 deletions(-)

diff --git a/src/tests/native-kms-render.c b/src/tests/native-kms-render.c
index f5ebc23fec7..2f870fdc331 100644
--- a/src/tests/native-kms-render.c
+++ b/src/tests/native-kms-render.c
@@ -39,6 +39,8 @@
 #include "tests/meta-wayland-test-driver.h"
 #include "tests/meta-wayland-test-utils.h"
 
+#define N_FRAMES_PER_TEST 30
+
 typedef struct
 {
   int number_of_frames_left;
@@ -46,12 +48,15 @@ typedef struct
 
   struct {
     int n_paints;
-    uint32_t fb_id;
+    int n_presentations;
+    int n_direct_scanouts;
+    GList *fb_ids;
   } scanout;
 
   gboolean wait_for_scanout;
 
   struct {
+    int scanouts_attempted;
     gboolean scanout_sabotaged;
     gboolean fallback_painted;
     guint repaint_guard_id;
@@ -101,7 +106,7 @@ meta_test_kms_render_basic (void)
   gulong handler_id;
 
   test = (KmsRenderingTest) {
-    .number_of_frames_left = 10,
+    .number_of_frames_left = N_FRAMES_PER_TEST,
     .loop = g_main_loop_new (NULL, FALSE),
   };
   handler_id = g_signal_connect (stage, "after-update",
@@ -123,7 +128,6 @@ on_scanout_before_update (ClutterStage     *stage,
                           KmsRenderingTest *test)
 {
   test->scanout.n_paints = 0;
-  test->scanout.fb_id = 0;
 }
 
 static void
@@ -135,6 +139,7 @@ on_scanout_before_paint (ClutterStage     *stage,
   CoglScanout *scanout;
   CoglScanoutBuffer *scanout_buffer;
   MetaDrmBuffer *buffer;
+  uint32_t fb_id;
 
   scanout = clutter_stage_view_peek_scanout (stage_view);
   if (!scanout)
@@ -143,8 +148,13 @@ on_scanout_before_paint (ClutterStage     *stage,
   scanout_buffer = cogl_scanout_get_buffer (scanout);
   g_assert_true (META_IS_DRM_BUFFER (scanout_buffer));
   buffer = META_DRM_BUFFER (scanout_buffer);
-  test->scanout.fb_id = meta_drm_buffer_get_fb_id (buffer);
-  g_assert_cmpuint (test->scanout.fb_id, >, 0);
+  fb_id = meta_drm_buffer_get_fb_id (buffer);
+  g_assert_cmpuint (fb_id, >, 0);
+  test->scanout.fb_ids = g_list_append (test->scanout.fb_ids,
+                                        GUINT_TO_POINTER (fb_id));
+
+  /* Triple buffering, but no higher */
+  g_assert_cmpuint (g_list_length (test->scanout.fb_ids), <=, 2);
 }
 
 static void
@@ -173,12 +183,12 @@ on_scanout_presented (ClutterStage     *stage,
   MetaDeviceFile *device_file;
   GError *error = NULL;
   drmModeCrtc *drm_crtc;
+  uint32_t first_fb_id_expected;
 
-  if (test->wait_for_scanout && test->scanout.n_paints > 0)
+  if (test->wait_for_scanout && test->scanout.fb_ids == NULL)
     return;
 
-  if (test->wait_for_scanout && test->scanout.fb_id == 0)
-    return;
+  test->scanout.n_presentations++;
 
   device_pool = meta_backend_native_get_device_pool (backend_native);
 
@@ -197,15 +207,41 @@ on_scanout_presented (ClutterStage     *stage,
   drm_crtc = drmModeGetCrtc (meta_device_file_get_fd (device_file),
                              meta_kms_crtc_get_id (kms_crtc));
   g_assert_nonnull (drm_crtc);
-  if (test->scanout.fb_id == 0)
-    g_assert_cmpuint (drm_crtc->buffer_id, !=, test->scanout.fb_id);
+
+  if (test->scanout.fb_ids)
+    {
+      test->scanout.n_direct_scanouts++;
+      first_fb_id_expected = GPOINTER_TO_UINT (test->scanout.fb_ids->data);
+      test->scanout.fb_ids = g_list_delete_link (test->scanout.fb_ids,
+                                                 test->scanout.fb_ids);
+    }
   else
-    g_assert_cmpuint (drm_crtc->buffer_id, ==, test->scanout.fb_id);
+    {
+      first_fb_id_expected = 0;
+    }
+
+  /* The buffer ID won't match on the first frame because switching from
+   * triple buffered compositing to double buffered direct scanout takes
+   * an extra frame to drain the queue. Thereafter we are in direct scanout
+   * mode and expect the buffer IDs to match.
+   */
+  if (test->scanout.n_presentations > 1)
+    {
+      if (first_fb_id_expected == 0)
+        g_assert_cmpuint (drm_crtc->buffer_id, !=, first_fb_id_expected);
+      else
+        g_assert_cmpuint (drm_crtc->buffer_id, ==, first_fb_id_expected);
+    }
+
   drmModeFreeCrtc (drm_crtc);
 
   meta_device_file_release (device_file);
 
-  g_main_loop_quit (test->loop);
+  test->number_of_frames_left--;
+  if (test->number_of_frames_left <= 0)
+    g_main_loop_quit (test->loop);
+  else
+    clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
 }
 
 typedef enum
@@ -244,7 +280,9 @@ meta_test_kms_render_client_scanout (void)
   g_assert_nonnull (wayland_test_client);
 
   test = (KmsRenderingTest) {
+    .number_of_frames_left = N_FRAMES_PER_TEST,
     .loop = g_main_loop_new (NULL, FALSE),
+    .scanout = {0},
     .wait_for_scanout = TRUE,
   };
 
@@ -270,7 +308,8 @@ meta_test_kms_render_client_scanout (void)
   clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
   g_main_loop_run (test.loop);
 
-  g_assert_cmpuint (test.scanout.fb_id, >, 0);
+  g_assert_cmpint (test.scanout.n_presentations, ==, N_FRAMES_PER_TEST);
+  g_assert_cmpint (test.scanout.n_direct_scanouts, ==, N_FRAMES_PER_TEST);
 
   g_debug ("Unmake fullscreen");
   window = meta_find_window_from_title (test_context, "dma-buf-scanout-test");
@@ -292,10 +331,15 @@ meta_test_kms_render_client_scanout (void)
   g_assert_cmpint (buffer_rect.y, ==, 10);
 
   test.wait_for_scanout = FALSE;
+  test.number_of_frames_left = N_FRAMES_PER_TEST;
+  test.scanout.n_presentations = 0;
+  test.scanout.n_direct_scanouts = 0;
+
   clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
   g_main_loop_run (test.loop);
 
-  g_assert_cmpuint (test.scanout.fb_id, ==, 0);
+  g_assert_cmpint (test.scanout.n_presentations, ==, N_FRAMES_PER_TEST);
+  g_assert_cmpint (test.scanout.n_direct_scanouts, ==, 0);
 
   g_debug ("Moving back to 0, 0");
   meta_window_move_frame (window, TRUE, 0, 0);
@@ -307,10 +351,15 @@ meta_test_kms_render_client_scanout (void)
   g_assert_cmpint (buffer_rect.y, ==, 0);
 
   test.wait_for_scanout = TRUE;
+  test.number_of_frames_left = N_FRAMES_PER_TEST;
+  test.scanout.n_presentations = 0;
+  test.scanout.n_direct_scanouts = 0;
+
   clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
   g_main_loop_run (test.loop);
 
-  g_assert_cmpuint (test.scanout.fb_id, >, 0);
+  g_assert_cmpint (test.scanout.n_presentations, ==, N_FRAMES_PER_TEST);
+  g_assert_cmpint (test.scanout.n_direct_scanouts, ==, N_FRAMES_PER_TEST);
 
   g_signal_handler_disconnect (stage, before_update_handler_id);
   g_signal_handler_disconnect (stage, before_paint_handler_id);
@@ -364,6 +413,15 @@ on_scanout_fallback_before_paint (ClutterStage     *stage,
   if (!scanout)
     return;
 
+  test->scanout_fallback.scanouts_attempted++;
+
+  /* The first scanout candidate frame will get composited due to triple
+   * buffering draining the queue to drop to double buffering. So don't
+   * sabotage that first frame.
+   */
+  if (test->scanout_fallback.scanouts_attempted < 2)
+    return;
+
   g_assert_false (test->scanout_fallback.scanout_sabotaged);
 
   if (is_atomic_mode_setting (kms_device))
@@ -401,6 +459,15 @@ on_scanout_fallback_paint_view (ClutterStage     *stage,
       g_clear_handle_id (&test->scanout_fallback.repaint_guard_id,
                          g_source_remove);
       test->scanout_fallback.fallback_painted = TRUE;
+      test->scanout_fallback.scanout_sabotaged = FALSE;
+    }
+  else if (test->scanout_fallback.scanouts_attempted == 1)
+    {
+      /* Now that we've seen the first scanout attempt that was inhibited by
+       * triple buffering, try a second frame. The second one should scanout
+       * and will be sabotaged.
+       */
+      clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
     }
 }
 
@@ -410,11 +477,11 @@ on_scanout_fallback_presented (ClutterStage     *stage,
                                ClutterFrameInfo *frame_info,
                                KmsRenderingTest *test)
 {
-  if (!test->scanout_fallback.scanout_sabotaged)
-    return;
+  if (test->scanout_fallback.fallback_painted)
+    g_main_loop_quit (test->loop);
 
-  g_assert_true (test->scanout_fallback.fallback_painted);
-  g_main_loop_quit (test->loop);
+  test->number_of_frames_left--;
+  g_assert_cmpint (test->number_of_frames_left, >, 0);
 }
 
 static void
@@ -443,6 +510,7 @@ meta_test_kms_render_client_scanout_fallback (void)
   g_assert_nonnull (wayland_test_client);
 
   test = (KmsRenderingTest) {
+    .number_of_frames_left = N_FRAMES_PER_TEST,
     .loop = g_main_loop_new (NULL, FALSE),
   };
 
-- 
GitLab

From 3eaf8770a708b3e2a113f9b708ca5dcf61c15cf7 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 22 Jun 2023 15:19:53 +0800
Subject: [PATCH 27/30] onscreen/native: Avoid callbacks on "detached"
 onscreens

Detached onscreens have no valid view so avoid servicing callbacks on
them during/after sleep mode. As previously mentioned in 45bda2d969f.

Closes: https://launchpad.net/bugs/2020049
---
 src/backends/native/meta-onscreen-native.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 665b24c05e2..5cd61fe1f8b 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1514,6 +1514,7 @@ try_post_latest_swap (CoglOnscreen *onscreen)
   MetaFrameNative *frame_native;
 
   if (onscreen_native->next_frame == NULL ||
+      onscreen_native->view == NULL ||
       meta_kms_is_shutting_down (kms))
     return;
 
-- 
GitLab

From 10fbd49e8bcef1dafb9c7aa1eaf4feaa2394b796 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 18 Jul 2023 16:08:25 +0800
Subject: [PATCH 28/30] clutter/frame-clock: Record measurements of zero for
 cursor-only updates

But only if we've ever got actual swap measurements
(COGL_FEATURE_ID_TIMESTAMP_QUERY). If it's supported then we now drop to
double buffering and get optimal latency on a burst of cursor-only
updates.

Closes: https://launchpad.net/bugs/2023363
---
 clutter/clutter/clutter-frame-clock.c | 28 +++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 4b83501b43e..87928771300 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -262,10 +262,6 @@ static void
 maybe_update_longterm_max_duration_us (ClutterFrameClock *frame_clock,
                                        ClutterFrameInfo  *frame_info)
 {
-  /* Do not update long-term max if there has been no measurement */
-  if (!frame_clock->shortterm_max_update_duration_us)
-    return;
-
   if ((frame_info->presentation_time - frame_clock->longterm_promotion_us) <
       G_USEC_PER_SEC)
     return;
@@ -387,8 +383,9 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
 
   frame_clock->got_measurements_last_frame = FALSE;
 
-  if (frame_info->cpu_time_before_buffer_swap_us != 0 &&
-      frame_info->has_valid_gpu_rendering_duration)
+  if ((frame_info->cpu_time_before_buffer_swap_us != 0 &&
+       frame_info->has_valid_gpu_rendering_duration) ||
+      frame_clock->ever_got_measurements)
     {
       int64_t dispatch_to_swap_us, swap_to_rendering_done_us, swap_to_flip_us;
       int64_t dispatch_time_us = 0, flip_time_us = 0;
@@ -413,14 +410,21 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
           break;
         }
 
-      dispatch_to_swap_us =
-        frame_info->cpu_time_before_buffer_swap_us -
-        dispatch_time_us;
+      if (frame_info->cpu_time_before_buffer_swap_us == 0)
+        {
+          /* Cursor-only updates with no "swap" or "flip" */
+          dispatch_to_swap_us = 0;
+          swap_to_flip_us = 0;
+        }
+      else
+        {
+          dispatch_to_swap_us = frame_info->cpu_time_before_buffer_swap_us -
+                                dispatch_time_us;
+          swap_to_flip_us = flip_time_us -
+                            frame_info->cpu_time_before_buffer_swap_us;
+        }
       swap_to_rendering_done_us =
         frame_info->gpu_rendering_duration_ns / 1000;
-      swap_to_flip_us =
-        flip_time_us -
-        frame_info->cpu_time_before_buffer_swap_us;
 
       CLUTTER_NOTE (FRAME_TIMINGS,
                     "%s: update2dispatch %ld µs, dispatch2swap %ld µs, swap2render %ld µs, swap2flip %ld µs",
-- 
GitLab

From adf059e91be30c1a2e88c1b5056ba24d33d40672 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 26 Jul 2023 17:27:10 +0800
Subject: [PATCH 29/30] backends/native: Make await_flush later and inlined

"Later" as in after GL is finished rendering so as to not block the deadline
timer from updating the cursor smoothly during long GL renders. Indeed this
could make a primary plane frame late in some cases but that's only when
going from idle to active, so there is no previous frame to observe stutter
within the primary plane. It does however fix observable stutter in the
cursor plane by not dropping/stalling an otherwise good cursor update in a
continuous stream of cursor updates.

"Inlined" as in we don't need most of `meta_kms_device_await_flush`. The
important part is that it calls `disarm_crtc_frame_deadline_timer` to avoid
attempting two posts at once. So that's all that is kept.

This also fixes a deadlock in triple buffering. By not cancelling the
cursor update during a GL render we're also not cancelling a primary plane
update that might have already been piggybacked onto it by `queue_update`.

Cherry picked from !3149
---
 src/backends/native/meta-kms-impl-device.c | 4 +++-
 src/backends/native/meta-onscreen-native.c | 4 ----
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/backends/native/meta-kms-impl-device.c b/src/backends/native/meta-kms-impl-device.c
index 946af626f4a..65857c51a79 100644
--- a/src/backends/native/meta-kms-impl-device.c
+++ b/src/backends/native/meta-kms-impl-device.c
@@ -1779,9 +1779,11 @@ meta_kms_impl_device_handle_update (MetaKmsImplDevice *impl_device,
       meta_kms_update_merge_from (crtc_frame->pending_update, update);
       meta_kms_update_free (update);
       update = g_steal_pointer (&crtc_frame->pending_update);
-      disarm_crtc_frame_deadline_timer (crtc_frame);
     }
 
+  if (crtc_frame->deadline.armed)
+    disarm_crtc_frame_deadline_timer (crtc_frame);
+
   meta_kms_device_handle_flush (priv->device, latch_crtc);
 
   feedback = do_process (impl_device, latch_crtc, update, flags);
diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 5cd61fe1f8b..7f3d67e4dff 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1892,11 +1892,7 @@ meta_onscreen_native_before_redraw (CoglOnscreen *onscreen,
                                     ClutterFrame *frame)
 {
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
-  MetaCrtcKms *crtc_kms = META_CRTC_KMS (onscreen_native->crtc);
-  MetaKmsCrtc *kms_crtc = meta_crtc_kms_get_kms_crtc (crtc_kms);
 
-  meta_kms_device_await_flush (meta_kms_crtc_get_device (kms_crtc),
-                               kms_crtc);
   maybe_update_frame_sync (onscreen_native, frame);
 }
 
-- 
GitLab

From 3752b8f2ce3da1977d92049797870c44c9cb17a6 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 17 Jan 2024 17:21:03 +0800
Subject: [PATCH 30/30] clutter/frame-clock: Optimize latency for platforms
 missing TIMESTAMP_QUERY

Previously if we had no measurements then `compute_max_render_time_us`
would pessimise its answer to ensure triple buffering could be reached:
```
if (frame_clock->state == CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE)
  ret += refresh_interval_us;
```
But that also meant entering triple buffering even when not required.

Now we make `compute_max_render_time_us` more honest and return failure
if the answer isn't known (or is disabled). This in turn allows us to
optimize `calculate_next_update_time_us` for this special case, ensuring
triple buffering can be used, but isn't blindly always used.

This makes a visible difference to the latency when dragging windows in
Xorg, but will also help Wayland sessions on platforms lacking
TIMESTAMP_QUERY such as Raspberry Pi.
---
 clutter/clutter/clutter-frame-clock.c | 69 +++++++++++++++++----------
 1 file changed, 45 insertions(+), 24 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 87928771300..72f1dd3a394 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -518,25 +518,18 @@ clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock)
     }
 }
 
-static int64_t
-clutter_frame_clock_compute_max_render_time_us (ClutterFrameClock *frame_clock)
+static gboolean
+clutter_frame_clock_compute_max_render_time_us (ClutterFrameClock *frame_clock,
+                                                int64_t           *max_render_time_us)
 {
   int64_t refresh_interval_us;
-  int64_t max_render_time_us;
 
   refresh_interval_us = frame_clock->refresh_interval_us;
 
   if (!frame_clock->ever_got_measurements ||
       G_UNLIKELY (clutter_paint_debug_flags &
                   CLUTTER_DEBUG_DISABLE_DYNAMIC_MAX_RENDER_TIME))
-    {
-      int64_t ret = (int64_t) (refresh_interval_us * SYNC_DELAY_FALLBACK_FRACTION);
-
-      if (frame_clock->state == CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE)
-        ret += refresh_interval_us;
-
-      return ret;
-    }
+    return FALSE;
 
   /* Max render time shows how early the frame clock needs to be dispatched
    * to make it to the predicted next presentation time. It is an estimate of
@@ -550,15 +543,15 @@ clutter_frame_clock_compute_max_render_time_us (ClutterFrameClock *frame_clock)
    * - The duration of vertical blank.
    * - A constant to account for variations in the above estimates.
    */
-  max_render_time_us =
+  *max_render_time_us =
     MAX (frame_clock->longterm_max_update_duration_us,
          frame_clock->shortterm_max_update_duration_us) +
     frame_clock->vblank_duration_us +
     clutter_max_render_time_constant_us;
 
-  max_render_time_us = CLAMP (max_render_time_us, 0, 2 * refresh_interval_us);
+  *max_render_time_us = CLAMP (*max_render_time_us, 0, 2 * refresh_interval_us);
 
-  return max_render_time_us;
+  return TRUE;
 }
 
 static void
@@ -575,6 +568,7 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
   int64_t next_presentation_time_us;
   int64_t next_smooth_presentation_time_us = 0;
   int64_t next_update_time_us;
+  gboolean max_render_time_is_known;
 
   now_us = g_get_monotonic_time ();
 
@@ -594,10 +588,13 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
     }
 
   min_render_time_allowed_us = refresh_interval_us / 2;
-  max_render_time_allowed_us =
-    clutter_frame_clock_compute_max_render_time_us (frame_clock);
 
-  if (min_render_time_allowed_us > max_render_time_allowed_us)
+  max_render_time_is_known =
+    clutter_frame_clock_compute_max_render_time_us (frame_clock,
+                                                    &max_render_time_allowed_us);
+
+  if (max_render_time_is_known &&
+      min_render_time_allowed_us > max_render_time_allowed_us)
     min_render_time_allowed_us = max_render_time_allowed_us;
 
   /*
@@ -718,6 +715,24 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
     }
   else
     {
+      /* If the max render time isn't known then using the current value of
+       * next_presentation_time_us is suboptimal. Targeting always one frame
+       * prior to that we'd lose the ability to scale up to triple buffering
+       * on late presentation. But targeting two frames prior we would be
+       * always triple buffering even when not required.
+       *   So the algorithm for deciding when to scale up to triple buffering
+       * in the absence of render time measurements is to simply target full
+       * frame rate. If we're keeping up then we'll stay double buffering. If
+       * we're not keeping up then this will switch us to triple buffering.
+       */
+      if (!max_render_time_is_known)
+        {
+          max_render_time_allowed_us =
+            (int64_t) (refresh_interval_us * SYNC_DELAY_FALLBACK_FRACTION);
+          next_presentation_time_us =
+            last_presentation_time_us + refresh_interval_us;
+        }
+
       while (next_presentation_time_us - min_render_time_allowed_us < now_us)
         next_presentation_time_us += refresh_interval_us;
 
@@ -749,7 +764,9 @@ calculate_next_variable_update_time_us (ClutterFrameClock *frame_clock,
 
   refresh_interval_us = frame_clock->refresh_interval_us;
 
-  if (frame_clock->last_presentation_time_us == 0)
+  if (frame_clock->last_presentation_time_us == 0 ||
+      !clutter_frame_clock_compute_max_render_time_us (frame_clock,
+                                                       &max_render_time_allowed_us))
     {
       *out_next_update_time_us =
         frame_clock->last_dispatch_time_us ?
@@ -762,9 +779,6 @@ calculate_next_variable_update_time_us (ClutterFrameClock *frame_clock,
       return;
     }
 
-  max_render_time_allowed_us =
-    clutter_frame_clock_compute_max_render_time_us (frame_clock);
-
   last_presentation_time_us = frame_clock->last_presentation_time_us;
   next_presentation_time_us = last_presentation_time_us + refresh_interval_us;
 
@@ -1247,12 +1261,19 @@ clutter_frame_clock_record_flip (ClutterFrameClock *frame_clock,
 GString *
 clutter_frame_clock_get_max_render_time_debug_info (ClutterFrameClock *frame_clock)
 {
+  int64_t max_render_time_us;
   int64_t max_update_duration_us;
   GString *string;
 
-  string = g_string_new (NULL);
-  g_string_append_printf (string, "Max render time: %ld µs",
-                          clutter_frame_clock_compute_max_render_time_us (frame_clock));
+  string = g_string_new ("Max render time: ");
+  if (!clutter_frame_clock_compute_max_render_time_us (frame_clock,
+                                                       &max_render_time_us))
+    {
+      g_string_append (string, "unknown");
+      return string;
+    }
+
+  g_string_append_printf (string, "%ld µs", max_render_time_us);
 
   if (frame_clock->got_measurements_last_frame)
     g_string_append_printf (string, " =");
-- 
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File _service:download_url:1441.patch of Package mutter (Revision fe666f4b081f3a009fd6da0a71057b0f)

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