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From c9dcd393405c1f43fb64344da08b79936d1bc417 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 24 Sep 2021 21:49:45 +0800
Subject: [PATCH 01/42] onscreen/native: Keep the onscreen alive longer than
 `MetaDrmBufferGbm`

Because `MetaDrmBufferGbm` uses `gbm_surface` in its destructor and
`gbm_surface` can't be refcounted directly. So we reference its owner
(the onscreen) instead.

This avoids a crash that might otherwise occur when hotplugging monitors as
the old onscreen might get disposed before the new onscreen has presented
a replacement frame on the same `MetaKmsCrtc`.

We could instead wrap and refcount all users of `gbm_surface`, but that
would be a lot more work for no additional benefit right now.
---
 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 2388a44a28..7c0f883d5b 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -596,6 +596,16 @@ import_shared_framebuffer (CoglOnscreen                        *onscreen,
   return imported_buffer;
 }
 
+static void
+reference_owning_gbm_surface (CoglOnscreen     *onscreen,
+                              MetaDrmBufferGbm *buffer_gbm)
+{
+  g_object_set_data_full (G_OBJECT (buffer_gbm),
+                          "gbm_surface owner",
+                          g_object_ref (onscreen),
+                          (GDestroyNotify) g_object_unref);
+}
+
 static MetaDrmBuffer *
 copy_shared_framebuffer_gpu (CoglOnscreen                        *onscreen,
                              MetaOnscreenNativeSecondaryGpuState *secondary_gpu_state,
@@ -681,6 +691,8 @@ copy_shared_framebuffer_gpu (CoglOnscreen                        *onscreen,
       return NULL;
     }
 
+  reference_owning_gbm_surface (onscreen, buffer_gbm);
+
   g_object_set_qdata_full (G_OBJECT (buffer_gbm),
                            blit_source_quark,
                            g_object_ref (primary_gpu_fb),
@@ -1113,6 +1125,7 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
           return;
         }
 
+      reference_owning_gbm_surface (onscreen, buffer_gbm);
       primary_gpu_fb = META_DRM_BUFFER (g_steal_pointer (&buffer_gbm));
       break;
     case META_RENDERER_NATIVE_MODE_SURFACELESS:
-- 
GitLab

From 91bfbf5572d0290b3c01202db1dd6c9e5aeed5fc Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Mon, 16 Aug 2021 17:06:43 +0800
Subject: [PATCH 02/42] kms/update: Hold a reference to the buffer used in a
 plane assignment

---
 src/backends/native/meta-kms-update.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/backends/native/meta-kms-update.c b/src/backends/native/meta-kms-update.c
index 5189c5ab32..bb7349ecf5 100644
--- a/src/backends/native/meta-kms-update.c
+++ b/src/backends/native/meta-kms-update.c
@@ -190,6 +190,7 @@ static void
 meta_kms_plane_assignment_free (MetaKmsPlaneAssignment *plane_assignment)
 {
   g_clear_pointer (&plane_assignment->fb_damage, meta_kms_fb_damage_free);
+  g_clear_object (&plane_assignment->buffer);
   g_free (plane_assignment);
 }
 
@@ -292,7 +293,7 @@ meta_kms_update_assign_plane (MetaKmsUpdate          *update,
     .update = update,
     .crtc = crtc,
     .plane = plane,
-    .buffer = buffer,
+    .buffer = g_object_ref (buffer),
     .src_rect = src_rect,
     .dst_rect = dst_rect,
     .flags = flags,
-- 
GitLab

From 7b8a1c624effdfe57b42972b73b720a4b87bd0ff Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Mon, 16 Aug 2021 18:04:10 +0800
Subject: [PATCH 03/42] native: Introduce MetaSwapChain to hold plane buffer
 references

---
 src/backends/native/meta-swap-chain.c | 149 ++++++++++++++++++++++++++
 src/backends/native/meta-swap-chain.h |  48 +++++++++
 src/meson.build                       |   2 +
 3 files changed, 199 insertions(+)
 create mode 100644 src/backends/native/meta-swap-chain.c
 create mode 100644 src/backends/native/meta-swap-chain.h

diff --git a/src/backends/native/meta-swap-chain.c b/src/backends/native/meta-swap-chain.c
new file mode 100644
index 0000000000..c3bed569d8
--- /dev/null
+++ b/src/backends/native/meta-swap-chain.c
@@ -0,0 +1,149 @@
+/*
+ * Copyright (C) 2022 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ * Author: Daniel van Vugt <daniel.van.vugt@canonical.com>
+ */
+
+#include "backends/native/meta-swap-chain.h"
+
+typedef struct
+{
+  GObject *front, *back;
+  gboolean back_is_set;
+} PlaneState;
+
+typedef struct _MetaSwapChainPrivate MetaSwapChainPrivate;
+struct _MetaSwapChainPrivate
+{
+  GHashTable *plane_states;
+};
+
+G_DEFINE_TYPE_WITH_PRIVATE (MetaSwapChain, meta_swap_chain, G_TYPE_OBJECT)
+
+MetaSwapChain *
+meta_swap_chain_new (void)
+{
+  return g_object_new (META_TYPE_SWAP_CHAIN, NULL);
+}
+
+void
+meta_swap_chain_push_buffer (MetaSwapChain *swap_chain,
+                             unsigned int   plane_id,
+                             GObject       *buffer)
+{
+  MetaSwapChainPrivate *priv =
+    meta_swap_chain_get_instance_private (swap_chain);
+  gpointer key = GUINT_TO_POINTER (plane_id);
+  PlaneState *plane_state;
+
+  plane_state = g_hash_table_lookup (priv->plane_states, key);
+  if (plane_state == NULL)
+    {
+      plane_state = g_new0 (PlaneState, 1);
+      g_hash_table_insert (priv->plane_states, key, plane_state);
+    }
+
+  plane_state->back_is_set = TRUE;  /* note buffer may be NULL */
+  g_set_object (&plane_state->back, buffer);
+}
+
+static void
+swap_plane_buffers (gpointer key,
+                    gpointer value,
+                    gpointer user_data)
+{
+  PlaneState *plane_state = value;
+
+  if (plane_state->back_is_set)
+    {
+      g_set_object (&plane_state->front, plane_state->back);
+      g_clear_object (&plane_state->back);
+      plane_state->back_is_set = FALSE;
+    }
+}
+
+void
+meta_swap_chain_swap_buffers (MetaSwapChain *swap_chain)
+{
+  MetaSwapChainPrivate *priv =
+    meta_swap_chain_get_instance_private (swap_chain);
+
+  g_hash_table_foreach (priv->plane_states, swap_plane_buffers, NULL);
+}
+
+void
+meta_swap_chain_release_buffers (MetaSwapChain *swap_chain)
+{
+  MetaSwapChainPrivate *priv =
+    meta_swap_chain_get_instance_private (swap_chain);
+
+  g_hash_table_remove_all (priv->plane_states);
+}
+
+static void
+meta_swap_chain_dispose (GObject *object)
+{
+  MetaSwapChain *swap_chain = META_SWAP_CHAIN (object);
+
+  meta_swap_chain_release_buffers (swap_chain);
+
+  G_OBJECT_CLASS (meta_swap_chain_parent_class)->dispose (object);
+}
+
+static void
+meta_swap_chain_finalize (GObject *object)
+{
+  MetaSwapChain *swap_chain = META_SWAP_CHAIN (object);
+  MetaSwapChainPrivate *priv =
+    meta_swap_chain_get_instance_private (swap_chain);
+
+  g_hash_table_unref (priv->plane_states);
+
+  G_OBJECT_CLASS (meta_swap_chain_parent_class)->finalize (object);
+}
+
+static void
+destroy_plane_state (gpointer data)
+{
+  PlaneState *plane_state = data;
+
+  g_clear_object (&plane_state->front);
+  g_clear_object (&plane_state->back);
+  g_free (plane_state);
+}
+
+static void
+meta_swap_chain_init (MetaSwapChain *swap_chain)
+{
+  MetaSwapChainPrivate *priv =
+    meta_swap_chain_get_instance_private (swap_chain);
+
+  priv->plane_states = g_hash_table_new_full (NULL,
+                                              NULL,
+                                              NULL,
+                                              destroy_plane_state);
+}
+
+static void
+meta_swap_chain_class_init (MetaSwapChainClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->dispose = meta_swap_chain_dispose;
+  object_class->finalize = meta_swap_chain_finalize;
+}
diff --git a/src/backends/native/meta-swap-chain.h b/src/backends/native/meta-swap-chain.h
new file mode 100644
index 0000000000..bad772b892
--- /dev/null
+++ b/src/backends/native/meta-swap-chain.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2022 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ * Author: Daniel van Vugt <daniel.van.vugt@canonical.com>
+ */
+
+#ifndef META_SWAP_CHAIN_H
+#define META_SWAP_CHAIN_H
+
+#include <glib-object.h>
+
+#define META_TYPE_SWAP_CHAIN (meta_swap_chain_get_type ())
+G_DECLARE_DERIVABLE_TYPE (MetaSwapChain,
+                          meta_swap_chain,
+                          META, SWAP_CHAIN,
+                          GObject)
+
+struct _MetaSwapChainClass
+{
+  GObjectClass parent_class;
+};
+
+MetaSwapChain * meta_swap_chain_new (void);
+
+void meta_swap_chain_push_buffer (MetaSwapChain *swap_chain,
+                                  unsigned int   plane_id,
+                                  GObject       *buffer);
+
+void meta_swap_chain_swap_buffers (MetaSwapChain *swap_chain);
+
+void meta_swap_chain_release_buffers (MetaSwapChain *swap_chain);
+
+#endif /* META_SWAP_CHAIN_H */
diff --git a/src/meson.build b/src/meson.build
index ca2ef166cf..0038988bd2 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -850,6 +850,8 @@ if have_native_backend
     'backends/native/meta-seat-native.h',
     'backends/native/meta-stage-native.c',
     'backends/native/meta-stage-native.h',
+    'backends/native/meta-swap-chain.c',
+    'backends/native/meta-swap-chain.h',
     'backends/native/meta-thread-impl.c',
     'backends/native/meta-thread-impl.h',
     'backends/native/meta-thread-private.h',
-- 
GitLab

From ff9ae92b7e1c89e1e7f65274f2b932b9467c8e98 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 18 Jan 2023 18:42:01 +0800
Subject: [PATCH 04/42] kms/crtc: Add a local swap chain

---
 src/backends/native/meta-kms-crtc.c | 21 +++++++++++++++++++++
 src/backends/native/meta-kms-crtc.h |  3 +++
 2 files changed, 24 insertions(+)

diff --git a/src/backends/native/meta-kms-crtc.c b/src/backends/native/meta-kms-crtc.c
index 707da9dc17..932e5e6a08 100644
--- a/src/backends/native/meta-kms-crtc.c
+++ b/src/backends/native/meta-kms-crtc.c
@@ -48,6 +48,8 @@ struct _MetaKmsCrtc
   MetaKmsCrtcState current_state;
 
   MetaKmsCrtcPropTable prop_table;
+
+  MetaSwapChain *swap_chain;
 };
 
 G_DEFINE_TYPE (MetaKmsCrtc, meta_kms_crtc, G_TYPE_OBJECT)
@@ -99,6 +101,12 @@ meta_kms_crtc_get_prop_drm_value (MetaKmsCrtc     *crtc,
   return meta_kms_prop_convert_value (prop, value);
 }
 
+MetaSwapChain *
+meta_kms_crtc_get_swap_chain (MetaKmsCrtc *crtc)
+{
+  return crtc->swap_chain;
+}
+
 gboolean
 meta_kms_crtc_is_active (MetaKmsCrtc *crtc)
 {
@@ -465,12 +473,23 @@ meta_kms_crtc_new (MetaKmsImplDevice  *impl_device,
   return crtc;
 }
 
+static void
+meta_kms_crtc_dispose (GObject *object)
+{
+  MetaKmsCrtc *crtc = META_KMS_CRTC (object);
+
+  meta_swap_chain_release_buffers (crtc->swap_chain);
+
+  G_OBJECT_CLASS (meta_kms_crtc_parent_class)->dispose (object);
+}
+
 static void
 meta_kms_crtc_finalize (GObject *object)
 {
   MetaKmsCrtc *crtc = META_KMS_CRTC (object);
 
   g_clear_pointer (&crtc->current_state.gamma.value, meta_gamma_lut_free);
+  g_clear_object (&crtc->swap_chain);
 
   G_OBJECT_CLASS (meta_kms_crtc_parent_class)->finalize (object);
 }
@@ -480,6 +499,7 @@ meta_kms_crtc_init (MetaKmsCrtc *crtc)
 {
   crtc->current_state.gamma.size = 0;
   crtc->current_state.gamma.value = NULL;
+  crtc->swap_chain = meta_swap_chain_new ();
 }
 
 static void
@@ -487,6 +507,7 @@ meta_kms_crtc_class_init (MetaKmsCrtcClass *klass)
 {
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
+  object_class->dispose = meta_kms_crtc_dispose;
   object_class->finalize = meta_kms_crtc_finalize;
 }
 
diff --git a/src/backends/native/meta-kms-crtc.h b/src/backends/native/meta-kms-crtc.h
index b26b682ddb..a30a6de6e7 100644
--- a/src/backends/native/meta-kms-crtc.h
+++ b/src/backends/native/meta-kms-crtc.h
@@ -22,6 +22,7 @@
 #include <xf86drmMode.h>
 
 #include "backends/native/meta-kms-types.h"
+#include "backends/native/meta-swap-chain.h"
 #include "backends/meta-backend-types.h"
 #include "core/util-private.h"
 #include "meta/boxes.h"
@@ -60,3 +61,5 @@ int meta_kms_crtc_get_idx (MetaKmsCrtc *crtc);
 
 META_EXPORT_TEST
 gboolean meta_kms_crtc_is_active (MetaKmsCrtc *crtc);
+
+MetaSwapChain * meta_kms_crtc_get_swap_chain (MetaKmsCrtc *crtc);
-- 
GitLab

From 698464ef1757482d524f2953a821ff223aae2da1 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 17 Aug 2021 16:35:18 +0800
Subject: [PATCH 05/42] onscreen/native: Pump the CRTC's buffer reference queue
 on scanout

Precise timing of this call is not important. We only need to notify
that the *previous* scanout is definitely no longer happening. So any
old buffers no longer used in the latest scanout can be released.
---
 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 7c0f883d5b..e95d01a1ea 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -229,6 +229,7 @@ notify_view_crtc_presented (MetaRendererView *view,
 
   meta_onscreen_native_notify_frame_complete (onscreen);
   meta_onscreen_native_swap_drm_fb (onscreen);
+  meta_swap_chain_swap_buffers (meta_kms_crtc_get_swap_chain (kms_crtc));
 }
 
 static void
-- 
GitLab

From 8f41552e05952cc144cc19e5e4b74f54daeceeaa Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 9 Feb 2022 16:44:09 +0800
Subject: [PATCH 06/42] kms/impl-device: Release buffers from MetaKmsCrtc in
 prepare_shutdown

This allows them to release their buffers cleanly while all the
associated resources to do the release still exist. Otherwise we
might crash later in meta_drm_buffer_finalize.
---
 src/backends/native/meta-kms-impl-device.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/backends/native/meta-kms-impl-device.c b/src/backends/native/meta-kms-impl-device.c
index da372383d9..7bc5efa654 100644
--- a/src/backends/native/meta-kms-impl-device.c
+++ b/src/backends/native/meta-kms-impl-device.c
@@ -1848,6 +1848,16 @@ meta_kms_impl_device_init_mode_setting (MetaKmsImplDevice  *impl_device,
   return TRUE;
 }
 
+static void
+release_buffers (gpointer data,
+                 gpointer user_data)
+{
+  MetaKmsCrtc *crtc = data;
+  MetaSwapChain *swap_chain = meta_kms_crtc_get_swap_chain (crtc);
+
+  meta_swap_chain_release_buffers (swap_chain);
+}
+
 void
 meta_kms_impl_device_prepare_shutdown (MetaKmsImplDevice *impl_device)
 {
@@ -1855,6 +1865,8 @@ meta_kms_impl_device_prepare_shutdown (MetaKmsImplDevice *impl_device)
     meta_kms_impl_device_get_instance_private (impl_device);
   MetaKmsImplDeviceClass *klass = META_KMS_IMPL_DEVICE_GET_CLASS (impl_device);
 
+  g_list_foreach (priv->crtcs, release_buffers, NULL);
+
   if (klass->prepare_shutdown)
     klass->prepare_shutdown (impl_device);
 
-- 
GitLab

From 1f6fc877f03a9f4aac31a97b8131ae7cafc4732d Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 7 Dec 2021 18:31:16 +0800
Subject: [PATCH 07/42] kms/impl-device/simple: Pump the CRTC's buffer
 reference queue on scanout

In this case "on scanout" means when `drmModeSetCrtc` succeeds. This is
the only case where there won't be a `meta_kms_page_flip_data_flipped` to
do it for us.
---
 src/backends/native/meta-kms-impl-device-simple.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/backends/native/meta-kms-impl-device-simple.c b/src/backends/native/meta-kms-impl-device-simple.c
index 2d68ba11f6..7196837f9c 100644
--- a/src/backends/native/meta-kms-impl-device-simple.c
+++ b/src/backends/native/meta-kms-impl-device-simple.c
@@ -485,6 +485,8 @@ process_mode_set (MetaKmsImplDevice  *impl_device,
       return FALSE;
     }
 
+  meta_swap_chain_swap_buffers (meta_kms_crtc_get_swap_chain (crtc));
+
   if (drm_mode)
     {
       g_hash_table_replace (impl_device_simple->cached_mode_sets,
@@ -877,6 +879,8 @@ mode_set_fallback (MetaKmsImplDeviceSimple  *impl_device_simple,
       return FALSE;
     }
 
+  meta_swap_chain_swap_buffers (meta_kms_crtc_get_swap_chain (crtc));
+
   if (!impl_device_simple->mode_set_fallback_feedback_source)
     {
       MetaKmsImpl *impl = meta_kms_impl_device_get_impl (impl_device);
-- 
GitLab

From 6345d86fd7d2d4b5f15ee6905ecd99bfcf043f8b Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 17 Aug 2021 17:40:57 +0800
Subject: [PATCH 08/42] kms/impl-device/simple: Keep a reference to buffers
 assigned to planes

The MetaKmsCrtc will hold these references during future scanouts until
such time as a new buffer is assigned to the plane AND another scanout
has occurred after that.
---
 src/backends/native/meta-kms-impl-device-simple.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/backends/native/meta-kms-impl-device-simple.c b/src/backends/native/meta-kms-impl-device-simple.c
index 7196837f9c..26660e5f48 100644
--- a/src/backends/native/meta-kms-impl-device-simple.c
+++ b/src/backends/native/meta-kms-impl-device-simple.c
@@ -1303,7 +1303,7 @@ process_plane_assignment (MetaKmsImplDevice       *impl_device,
     {
     case META_KMS_PLANE_TYPE_PRIMARY:
       /* Handled as part of the mode-set and page flip. */
-      return TRUE;
+      goto assigned;
     case META_KMS_PLANE_TYPE_CURSOR:
       if (!process_cursor_plane_assignment (impl_device, update,
                                             plane_assignment,
@@ -1317,7 +1317,7 @@ process_plane_assignment (MetaKmsImplDevice       *impl_device,
         }
       else
         {
-          return TRUE;
+          goto assigned;
         }
     case META_KMS_PLANE_TYPE_OVERLAY:
       error = g_error_new_literal (G_IO_ERROR, G_IO_ERROR_FAILED,
@@ -1330,6 +1330,12 @@ process_plane_assignment (MetaKmsImplDevice       *impl_device,
     }
 
   g_assert_not_reached ();
+
+assigned:
+  meta_swap_chain_push_buffer (meta_kms_crtc_get_swap_chain (plane_assignment->crtc),
+                               meta_kms_plane_get_id (plane),
+                               G_OBJECT (plane_assignment->buffer));
+  return TRUE;
 }
 
 static gboolean
-- 
GitLab

From 8024d68dc0453a1d8bbf5118c8954de6264c5847 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 7 Dec 2021 17:54:15 +0800
Subject: [PATCH 09/42] kms/impl-device/simple: Keep a reference to buffers
 needed in retries

---
 .../native/meta-kms-impl-device-simple.c      | 24 ++++++++++++-------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/backends/native/meta-kms-impl-device-simple.c b/src/backends/native/meta-kms-impl-device-simple.c
index 26660e5f48..f4e23df074 100644
--- a/src/backends/native/meta-kms-impl-device-simple.c
+++ b/src/backends/native/meta-kms-impl-device-simple.c
@@ -556,7 +556,7 @@ is_timestamp_earlier_than (uint64_t ts1,
 typedef struct _RetryPageFlipData
 {
   MetaKmsCrtc *crtc;
-  uint32_t fb_id;
+  MetaDrmBuffer *fb;
   MetaKmsPageFlipData *page_flip_data;
   float refresh_rate;
   uint64_t retry_time_us;
@@ -569,6 +569,7 @@ retry_page_flip_data_free (RetryPageFlipData *retry_page_flip_data)
   g_assert (!retry_page_flip_data->page_flip_data);
   g_clear_pointer (&retry_page_flip_data->custom_page_flip,
                    meta_kms_custom_page_flip_free);
+  g_clear_object (&retry_page_flip_data->fb);
   g_free (retry_page_flip_data);
 }
 
@@ -636,16 +637,21 @@ retry_page_flips (gpointer user_data)
         }
       else
         {
+          uint32_t fb_id =
+            retry_page_flip_data->fb ?
+            meta_drm_buffer_get_fb_id (retry_page_flip_data->fb) :
+            0;
+
           meta_topic (META_DEBUG_KMS,
                       "[simple] Retrying page flip on CRTC %u (%s) with %u",
                       meta_kms_crtc_get_id (crtc),
                       meta_kms_impl_device_get_path (impl_device),
-                      retry_page_flip_data->fb_id);
+                      fb_id);
 
           fd = meta_kms_impl_device_get_fd (impl_device);
           ret = drmModePageFlip (fd,
                                  meta_kms_crtc_get_id (crtc),
-                                 retry_page_flip_data->fb_id,
+                                 fb_id,
                                  DRM_MODE_PAGE_FLIP_EVENT,
                                  retry_page_flip_data->page_flip_data);
         }
@@ -732,7 +738,7 @@ retry_page_flips (gpointer user_data)
 static void
 schedule_retry_page_flip (MetaKmsImplDeviceSimple *impl_device_simple,
                           MetaKmsCrtc             *crtc,
-                          uint32_t                 fb_id,
+                          MetaDrmBuffer           *fb,
                           float                    refresh_rate,
                           MetaKmsPageFlipData     *page_flip_data,
                           MetaKmsCustomPageFlip   *custom_page_flip)
@@ -747,7 +753,7 @@ schedule_retry_page_flip (MetaKmsImplDeviceSimple *impl_device_simple,
   retry_page_flip_data = g_new0 (RetryPageFlipData, 1);
   *retry_page_flip_data = (RetryPageFlipData) {
     .crtc = crtc,
-    .fb_id = fb_id,
+    .fb = fb ? g_object_ref (fb) : NULL,
     .page_flip_data = page_flip_data,
     .refresh_rate = refresh_rate,
     .retry_time_us = retry_time_us,
@@ -1007,20 +1013,20 @@ dispatch_page_flip (MetaKmsImplDevice    *impl_device,
       cached_mode_set = get_cached_mode_set (impl_device_simple, crtc);
       if (cached_mode_set)
         {
-          uint32_t fb_id;
+          MetaDrmBuffer *fb;
           drmModeModeInfo *drm_mode;
           float refresh_rate;
 
           if (plane_assignment)
-            fb_id = meta_drm_buffer_get_fb_id (plane_assignment->buffer);
+            fb = plane_assignment->buffer;
           else
-            fb_id = 0;
+            fb = NULL;
           drm_mode = cached_mode_set->drm_mode;
           refresh_rate = meta_calculate_drm_mode_refresh_rate (drm_mode);
           meta_kms_impl_device_hold_fd (impl_device);
           schedule_retry_page_flip (impl_device_simple,
                                     crtc,
-                                    fb_id,
+                                    fb,
                                     refresh_rate,
                                     page_flip_data,
                                     g_steal_pointer (&custom_page_flip));
-- 
GitLab

From ff6752168208f156171aad34ce9faa1955ee1c4b Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Tue, 17 Aug 2021 16:36:25 +0800
Subject: [PATCH 10/42] kms/impl-device/atomic: Keep a reference to buffers
 assigned to planes

The MetaKmsCrtc will hold these references during future scanouts until
such time as a new buffer is assigned to the plane AND another scanout
has occurred after that.
---
 src/backends/native/meta-kms-impl-device-atomic.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/backends/native/meta-kms-impl-device-atomic.c b/src/backends/native/meta-kms-impl-device-atomic.c
index d3fd772686..e7497607b5 100644
--- a/src/backends/native/meta-kms-impl-device-atomic.c
+++ b/src/backends/native/meta-kms-impl-device-atomic.c
@@ -505,6 +505,7 @@ process_plane_assignment (MetaKmsImplDevice  *impl_device,
 {
   MetaKmsPlaneAssignment *plane_assignment = update_entry;
   MetaKmsPlane *plane = plane_assignment->plane;
+  MetaKmsUpdateFlag flags = (MetaKmsUpdateFlag) user_data;
   MetaDrmBuffer *buffer;
   MetaKmsFbDamage *fb_damage;
   uint32_t prop_id;
@@ -657,6 +658,12 @@ process_plane_assignment (MetaKmsImplDevice  *impl_device,
                                error))
         return FALSE;
     }
+
+  if (!(flags & META_KMS_UPDATE_FLAG_TEST_ONLY))
+    meta_swap_chain_push_buffer (meta_kms_crtc_get_swap_chain (plane_assignment->crtc),
+                                 meta_kms_plane_get_id (plane),
+                                 G_OBJECT (buffer));
+
   return TRUE;
 }
 
@@ -1001,7 +1008,7 @@ meta_kms_impl_device_atomic_process_update (MetaKmsImplDevice *impl_device,
                         req,
                         blob_ids,
                         meta_kms_update_get_plane_assignments (update),
-                        NULL,
+                        GUINT_TO_POINTER (flags),
                         process_plane_assignment,
                         &error))
     goto err;
-- 
GitLab

From 36c9d57f7cec8b364ba2530028a6105d4cbe9401 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Wed, 18 Aug 2021 15:04:27 +0800
Subject: [PATCH 11/42] onscreen/native: Stop holding the current onscreen
 buffer

The scanout lifetime of the buffer is now automatically managed via
meta_crtc_kms_assign_primary_plane. Se we don't need `current_fb` at
all, and `next_fb` can be unreferenced as soon as we've passed it to
meta_crtc_kms_assign_primary_plane.
---
 src/backends/native/meta-onscreen-native.c | 43 ++--------------------
 1 file changed, 4 insertions(+), 39 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index e95d01a1ea..636dff1311 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -93,7 +93,6 @@ struct _MetaOnscreenNative
 
   struct {
     struct gbm_surface *surface;
-    MetaDrmBuffer *current_fb;
     MetaDrmBuffer *next_fb;
   } gbm;
 
@@ -128,36 +127,6 @@ init_secondary_gpu_state (MetaRendererNative  *renderer_native,
                           CoglOnscreen        *onscreen,
                           GError             **error);
 
-static void
-free_current_bo (CoglOnscreen *onscreen)
-{
-  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
-
-  g_clear_object (&onscreen_native->gbm.current_fb);
-}
-
-static void
-meta_onscreen_native_swap_drm_fb (CoglOnscreen *onscreen)
-{
-  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
-
-  if (!onscreen_native->gbm.next_fb)
-    return;
-
-  free_current_bo (onscreen);
-
-  g_set_object (&onscreen_native->gbm.current_fb, onscreen_native->gbm.next_fb);
-  g_clear_object (&onscreen_native->gbm.next_fb);
-}
-
-static void
-meta_onscreen_native_clear_next_fb (CoglOnscreen *onscreen)
-{
-  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
-
-  g_clear_object (&onscreen_native->gbm.next_fb);
-}
-
 static void
 maybe_update_frame_info (MetaCrtc         *crtc,
                          CoglFrameInfo    *frame_info,
@@ -228,7 +197,6 @@ notify_view_crtc_presented (MetaRendererView *view,
   maybe_update_frame_info (crtc, frame_info, time_us, flags, sequence);
 
   meta_onscreen_native_notify_frame_complete (onscreen);
-  meta_onscreen_native_swap_drm_fb (onscreen);
   meta_swap_chain_swap_buffers (meta_kms_crtc_get_swap_chain (kms_crtc));
 }
 
@@ -337,7 +305,6 @@ 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);
 }
 
 static const MetaKmsPageFlipListenerVtable page_flip_listener_vtable = {
@@ -402,8 +369,9 @@ void
 meta_onscreen_native_dummy_power_save_page_flip (CoglOnscreen *onscreen)
 {
   CoglFrameInfo *frame_info;
+  MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
 
-  meta_onscreen_native_swap_drm_fb (onscreen);
+  g_clear_object (&onscreen_native->gbm.next_fb);
 
   frame_info = cogl_onscreen_peek_tail_frame_info (onscreen);
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
@@ -426,7 +394,7 @@ meta_onscreen_native_flip_crtc (CoglOnscreen                *onscreen,
   MetaKmsCrtc *kms_crtc = meta_crtc_kms_get_kms_crtc (crtc_kms);
   MetaRendererNativeGpuData *renderer_gpu_data;
   MetaGpuKms *gpu_kms;
-  MetaDrmBuffer *buffer;
+  g_autoptr (MetaDrmBuffer) buffer = NULL;
   MetaKmsPlaneAssignment *plane_assignment;
 
   COGL_TRACE_BEGIN_SCOPED (MetaOnscreenNativeFlipCrtcs,
@@ -441,7 +409,7 @@ meta_onscreen_native_flip_crtc (CoglOnscreen                *onscreen,
   switch (renderer_gpu_data->mode)
     {
     case META_RENDERER_NATIVE_MODE_GBM:
-      buffer = onscreen_native->gbm.next_fb;
+      buffer = g_steal_pointer (&onscreen_native->gbm.next_fb);
 
       plane_assignment = meta_crtc_kms_assign_primary_plane (crtc_kms,
                                                              buffer,
@@ -1045,7 +1013,6 @@ 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);
 }
 
 static const MetaKmsResultListenerVtable swap_buffer_result_listener_vtable = {
@@ -1333,7 +1300,6 @@ 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);
 }
 
 static const MetaKmsResultListenerVtable scanout_result_listener_vtable = {
@@ -2435,7 +2401,6 @@ meta_onscreen_native_dispose (GObject *object)
     {
     case META_RENDERER_NATIVE_MODE_GBM:
       g_clear_object (&onscreen_native->gbm.next_fb);
-      free_current_bo (onscreen);
       break;
     case META_RENDERER_NATIVE_MODE_SURFACELESS:
       g_assert_not_reached ();
-- 
GitLab

From 9f88429f51942f44b7902fe48c0e7f2a92029ff2 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 2 Mar 2023 18:01:26 +0800
Subject: [PATCH 12/42] FIXME: Temporary workaround for the scanout-failed
 signal

---
 src/backends/native/meta-onscreen-native.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 636dff1311..74a5fcec1b 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -94,6 +94,11 @@ struct _MetaOnscreenNative
   struct {
     struct gbm_surface *surface;
     MetaDrmBuffer *next_fb;
+
+    /* Temporary workaround for the scanout-failed signal wanting the buffer
+     * to live longer than it does, and then it doesn't use it anyway...
+     */
+    MetaDrmBuffer *direct_fb;
   } gbm;
 
 #ifdef HAVE_EGL_DEVICE
@@ -1277,6 +1282,7 @@ scanout_result_feedback (const MetaKmsFeedback *kms_feedback,
   CoglOnscreen *onscreen = COGL_ONSCREEN (onscreen_native);
   const GError *error;
   CoglFrameInfo *frame_info;
+  g_autoptr (MetaDrmBuffer) direct_fb = g_steal_pointer (&onscreen_native->gbm.direct_fb);
 
   error = meta_kms_feedback_get_error (kms_feedback);
   if (!error)
@@ -1290,8 +1296,7 @@ scanout_result_feedback (const MetaKmsFeedback *kms_feedback,
 
       g_warning ("Direct scanout page flip failed: %s", error->message);
 
-      cogl_scanout_notify_failed (COGL_SCANOUT (onscreen_native->gbm.next_fb),
-                                  onscreen);
+      cogl_scanout_notify_failed (COGL_SCANOUT (direct_fb), onscreen);
       clutter_stage_view_add_redraw_clip (view, NULL);
       clutter_stage_view_schedule_update_now (view);
     }
@@ -1365,6 +1370,8 @@ meta_onscreen_native_direct_scanout (CoglOnscreen   *onscreen,
   kms_device = meta_kms_crtc_get_device (kms_crtc);
   kms_update = meta_frame_native_ensure_kms_update (frame_native, kms_device);
 
+  g_set_object (&onscreen_native->gbm.direct_fb,
+                onscreen_native->gbm.next_fb);
   meta_kms_update_add_result_listener (kms_update,
                                        &scanout_result_listener_vtable,
                                        NULL,
@@ -2401,6 +2408,7 @@ meta_onscreen_native_dispose (GObject *object)
     {
     case META_RENDERER_NATIVE_MODE_GBM:
       g_clear_object (&onscreen_native->gbm.next_fb);
+      g_clear_object (&onscreen_native->gbm.direct_fb);
       break;
     case META_RENDERER_NATIVE_MODE_SURFACELESS:
       g_assert_not_reached ();
-- 
GitLab

From e3337d62869873fbb120076686941b482db9185d Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 15 Sep 2023 18:24:22 +0800
Subject: [PATCH 13/42] renderer/native: Release buffers from disabled CRTCs on
 hotplug

CRTCs tend to live for the lifetime of the device, but they also
(currently) own the swap chains. So when a monitor is unplugged we
need to tell the CRTC when it's safe to clear its swap chain and release
all buffers. This only happens after the mode set to disable the CRTC
has completed.

Without this change, CRTCs that had been used in the past would keep
their swap chains populated even after the monitor was unplugged and the
CRTC disabled. This led to a leak of the old onscreen too, because of:

onscreen/native: Keep the onscreen alive longer than `MetaDrmBufferGbm`
---
 src/backends/native/meta-renderer-native.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 57cb20b7e9..9502473d6c 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -98,6 +98,7 @@ struct _MetaRendererNative
 
   GList *detached_onscreens;
   GList *lingering_onscreens;
+  GList *disabled_crtcs;
   guint release_unused_gpus_idle_id;
 
   GList *power_save_page_flip_onscreens;
@@ -676,6 +677,9 @@ configure_disabled_crtcs (MetaKmsDevice      *kms_device,
 
       kms_update = ensure_mode_set_update (renderer_native, kms_device);
       meta_kms_update_mode_set (kms_update, kms_crtc, NULL, NULL);
+
+      renderer_native->disabled_crtcs =
+        g_list_prepend (renderer_native->disabled_crtcs, kms_crtc);
     }
 }
 
@@ -810,6 +814,22 @@ clear_detached_onscreens (MetaRendererNative *renderer_native)
                 g_object_unref);
 }
 
+static void
+clear_disabled_crtcs (MetaRendererNative *renderer_native)
+{
+  GList *l;
+
+  for (l = renderer_native->disabled_crtcs; l; l = l->next)
+    {
+      MetaKmsCrtc *kms_crtc = l->data;
+      MetaSwapChain *swap_chain = meta_kms_crtc_get_swap_chain (kms_crtc);
+
+      meta_swap_chain_release_buffers (swap_chain);
+    }
+
+  g_clear_list (&renderer_native->disabled_crtcs, NULL);
+}
+
 static void
 mode_sets_update_result_feedback (const MetaKmsFeedback *kms_feedback,
                                   gpointer               user_data)
@@ -871,6 +891,7 @@ meta_renderer_native_post_mode_set_updates (MetaRendererNative *renderer_native)
   post_mode_set_updates (renderer_native);
 
   clear_detached_onscreens (renderer_native);
+  clear_disabled_crtcs (renderer_native);
 
   meta_kms_notify_modes_set (kms);
 
@@ -2237,6 +2258,7 @@ meta_renderer_native_finalize (GObject *object)
   g_clear_handle_id (&renderer_native->release_unused_gpus_idle_id,
                      g_source_remove);
   clear_detached_onscreens (renderer_native);
+  clear_disabled_crtcs (renderer_native);
 
   g_hash_table_destroy (renderer_native->gpu_datas);
   g_clear_object (&renderer_native->gles3);
-- 
GitLab

From 1d5a301654a16b7824813cfa611f2f2a9d5c42d7 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 14/42] 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 9dbecfd0c9..681d91d2b0 100644
--- a/cogl/cogl/cogl-onscreen-private.h
+++ b/cogl/cogl/cogl-onscreen-private.h
@@ -95,3 +95,6 @@ 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 73425e4985..02c4474b2d 100644
--- a/cogl/cogl/cogl-onscreen.c
+++ b/cogl/cogl/cogl-onscreen.c
@@ -508,6 +508,14 @@ 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 5429d2dd84954d292528b34f232a73edb015e46e 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 15/42] 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 ec009ec8cd..c6708946e8 100644
--- a/src/backends/native/meta-kms.c
+++ b/src/backends/native/meta-kms.c
@@ -155,6 +155,8 @@ struct _MetaKms
   int kernel_thread_inhibit_count;
 
   MetaKmsCursorManager *cursor_manager;
+
+  gboolean shutting_down;
 };
 
 G_DEFINE_TYPE (MetaKms, meta_kms, META_TYPE_THREAD)
@@ -433,6 +435,7 @@ 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));
 
@@ -487,6 +490,12 @@ 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 7434014063..f6b19520be 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 5ab50e440426cf74e1e2c6726767dd6273e41ac8 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 16/42] 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 9502473d6c..f47db924b9 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -704,6 +704,9 @@ 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 95fbd33b03dce1dc8a946172414360998f74c50c 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 17/42] 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 f47db924b9..f50c930eea 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -687,12 +687,18 @@ 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 410ec19e45f6d370e9e260179836d87621631b62 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 18/42] 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 74a5fcec1b..5965845548 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1062,6 +1062,19 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   COGL_TRACE_BEGIN_SCOPED (MetaRendererNativeSwapBuffers,
                            "Onscreen (swap-buffers)");
 
+  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 2c7956b62632c7822756547892cfd26dbccb0fc2 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 19/42] 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 5965845548..b0e90528e8 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -167,7 +167,7 @@ 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_assert (info);
 
   _cogl_onscreen_notify_frame_sync (onscreen, info);
   _cogl_onscreen_notify_complete (onscreen, info);
-- 
GitLab

From a62bec8dc8f4bcdcb19aa9e80aac1a351230e5d7 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 20/42] 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 b0e90528e8..420c685397 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1145,6 +1145,9 @@ 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
@@ -1181,8 +1184,6 @@ 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;
     }
 
@@ -1202,8 +1203,6 @@ 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))
@@ -1217,8 +1216,6 @@ 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;
@@ -1234,8 +1231,6 @@ 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;
@@ -1250,7 +1245,6 @@ 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 04e51088cb481173054e09e5c87dc56641206a51 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 21/42] 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 | 66 +++++++++++++++++-----
 1 file changed, 53 insertions(+), 13 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 420c685397..7346c04d95 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -120,6 +120,12 @@ struct _MetaOnscreenNative
   gulong privacy_screen_changed_handler_id;
   gulong color_space_changed_handler_id;
   gulong hdr_metadata_changed_handler_id;
+
+  struct {
+    int *rectangles;  /* 4 x n_rectangles */
+    int n_rectangles;
+    ClutterFrame *frame;
+  } next_post;
 };
 
 G_DEFINE_TYPE (MetaOnscreenNative, meta_onscreen_native,
@@ -127,6 +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,
@@ -1038,26 +1047,18 @@ 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);
   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 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;
-  MetaKmsCrtc *kms_crtc;
-  MetaKmsDevice *kms_device;
+  size_t rectangles_size;
 
   COGL_TRACE_BEGIN_SCOPED (MetaRendererNativeSwapBuffers,
                            "Onscreen (swap-buffers)");
@@ -1157,12 +1158,47 @@ 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_post.rectangles =
+    g_realloc (onscreen_native->next_post.rectangles, rectangles_size);
+  memcpy (onscreen_native->next_post.rectangles, rectangles, rectangles_size);
+  onscreen_native->next_post.n_rectangles = n_rectangles;
+
+  g_clear_pointer (&onscreen_native->next_post.frame, clutter_frame_unref);
+  onscreen_native->next_post.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;
+  g_autoptr (ClutterFrame) frame =
+    g_steal_pointer (&onscreen_native->next_post.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,
@@ -1177,8 +1213,8 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
                                       onscreen_native->crtc,
                                       kms_update,
                                       META_KMS_PAGE_FLIP_LISTENER_FLAG_NONE,
-                                      rectangles,
-                                      n_rectangles);
+                                      onscreen_native->next_post.rectangles,
+                                      onscreen_native->next_post.n_rectangles);
     }
   else
     {
@@ -2449,6 +2485,10 @@ meta_onscreen_native_dispose (GObject *object)
 
   g_clear_object (&onscreen_native->output);
   g_clear_object (&onscreen_native->crtc);
+
+  g_clear_pointer (&onscreen_native->next_post.rectangles, g_free);
+  g_clear_pointer (&onscreen_native->next_post.frame, clutter_frame_unref);
+  onscreen_native->next_post.n_rectangles = 0;
 }
 
 static void
-- 
GitLab

From c8afe60de6a7d5244b6a560c555b0ed5a551b30d Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 28 Oct 2021 17:24:11 +0800
Subject: [PATCH 22/42] onscreen/native: Add a missing frame notification

In the unlikely event that swap_buffers_with_damage drops the previous swap
it was forgetting to notify about the discarded frame. That could lead to
frame clock freezes.
---
 src/backends/native/meta-onscreen-native.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 7346c04d95..ad1d4acab6 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1133,6 +1133,15 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
     {
     case META_RENDERER_NATIVE_MODE_GBM:
       g_warn_if_fail (onscreen_native->gbm.next_fb == NULL);
+      if (onscreen_native->gbm.next_fb != NULL)
+        {
+          CoglFrameInfo *frame_info;
+
+          frame_info = cogl_onscreen_peek_head_frame_info (onscreen);
+          frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
+          meta_onscreen_native_notify_frame_complete (onscreen);
+        }
+
       if (onscreen_native->secondary_gpu_state)
         g_set_object (&onscreen_native->gbm.next_fb, secondary_gpu_fb);
       else
-- 
GitLab

From a9e74e78ca6f57a1058aa13d1906fa0d552b87ab 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 23/42] 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 | 186 +++++++++++++++++----
 1 file changed, 158 insertions(+), 28 deletions(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index ad1d4acab6..8e26d54de2 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -94,6 +94,7 @@ struct _MetaOnscreenNative
   struct {
     struct gbm_surface *surface;
     MetaDrmBuffer *next_fb;
+    MetaDrmBuffer *stalled_fb;
 
     /* Temporary workaround for the scanout-failed signal wanting the buffer
      * to live longer than it does, and then it doesn't use it anyway...
@@ -121,6 +122,10 @@ struct _MetaOnscreenNative
   gulong color_space_changed_handler_id;
   gulong hdr_metadata_changed_handler_id;
 
+  gboolean needs_flush;
+
+  unsigned int swaps_pending;
+
   struct {
     int *rectangles;  /* 4 x n_rectangles */
     int n_rectangles;
@@ -134,7 +139,11 @@ 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,
@@ -212,6 +221,7 @@ notify_view_crtc_presented (MetaRendererView *view,
 
   meta_onscreen_native_notify_frame_complete (onscreen);
   meta_swap_chain_swap_buffers (meta_kms_crtc_get_swap_chain (kms_crtc));
+  try_post_latest_swap (onscreen);
 }
 
 static void
@@ -261,15 +271,13 @@ 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->gbm.next_fb);
-
   meta_onscreen_native_notify_frame_complete (onscreen);
+  try_post_latest_swap (onscreen);
 }
 
 static void
@@ -319,6 +327,7 @@ page_flip_feedback_discarded (MetaKmsCrtc  *kms_crtc,
   frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
 
   meta_onscreen_native_notify_frame_complete (onscreen);
+  try_post_latest_swap (onscreen);
 }
 
 static const MetaKmsPageFlipListenerVtable page_flip_listener_vtable = {
@@ -379,19 +388,40 @@ 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);
 
-  g_clear_object (&onscreen_native->gbm.next_fb);
+  /* Remember we can't compare stalled_fb because it's not used by
+   * META_RENDERER_NATIVE_MODE_EGL_DEVICE. So we judge stalled to be whenever
+   * swaps_pending > 1.
+   */
+  if (onscreen_native->swaps_pending <= 1)
+    return;
+
+  onscreen_native->swaps_pending--;
+
+  g_clear_object (&onscreen_native->gbm.stalled_fb);
 
   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
 meta_onscreen_native_flip_crtc (CoglOnscreen                *onscreen,
                                 MetaRendererView            *view,
@@ -1024,9 +1054,15 @@ 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);
+    }
 }
 
 static const MetaKmsResultListenerVtable swap_buffer_result_listener_vtable = {
@@ -1132,14 +1168,13 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   switch (renderer_gpu_data->mode)
     {
     case META_RENDERER_NATIVE_MODE_GBM:
-      g_warn_if_fail (onscreen_native->gbm.next_fb == NULL);
       if (onscreen_native->gbm.next_fb != NULL)
         {
-          CoglFrameInfo *frame_info;
-
-          frame_info = cogl_onscreen_peek_head_frame_info (onscreen);
-          frame_info->flags |= COGL_FRAME_INFO_FLAG_SYMBOLIC;
-          meta_onscreen_native_notify_frame_complete (onscreen);
+          g_warn_if_fail (onscreen_native->gbm.stalled_fb == NULL);
+          drop_stalled_swap (onscreen);
+          g_assert (onscreen_native->gbm.stalled_fb == NULL);
+          onscreen_native->gbm.stalled_fb =
+            g_steal_pointer (&onscreen_native->gbm.next_fb);
         }
 
       if (onscreen_native->secondary_gpu_state)
@@ -1176,11 +1211,12 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   g_clear_pointer (&onscreen_native->next_post.frame, clutter_frame_unref);
   onscreen_native->next_post.frame = clutter_frame_ref (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);
@@ -1199,15 +1235,41 @@ post_latest_swap (CoglOnscreen *onscreen)
   MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);
   MetaKmsUpdate *kms_update;
   g_autoptr (MetaKmsFeedback) kms_feedback = NULL;
-  g_autoptr (ClutterFrame) frame =
-    g_steal_pointer (&onscreen_native->next_post.frame);
+  g_autoptr (ClutterFrame) frame = NULL;
   MetaFrameNative *frame_native;
 
+  if (onscreen_native->next_post.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 = g_steal_pointer (&onscreen_native->next_post.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,
@@ -1408,6 +1470,18 @@ 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);
 
@@ -1594,22 +1668,79 @@ 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_post.frame == NULL);
+
+      g_clear_pointer (&onscreen_native->next_post.frame, clutter_frame_unref);
+      onscreen_native->next_post.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_post.frame != NULL);
+
+      older_frame_native =
+        meta_frame_native_from_frame (onscreen_native->next_post.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,
@@ -1633,7 +1764,6 @@ 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
-- 
GitLab

From 1f8d2574b19be280b0fff714f643f6c597e8f1ee 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 24/42] 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 8e26d54de2..820cb7cbe9 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -72,7 +72,7 @@ typedef struct _MetaOnscreenNativeSecondaryGpuState
 
   struct {
     MetaDrmBufferDumb *current_dumb_fb;
-    MetaDrmBufferDumb *dumb_fbs[2];
+    MetaDrmBufferDumb *dumb_fbs[3];
   } cpu;
 
   gboolean noted_primary_gpu_copy_ok;
@@ -718,12 +718,17 @@ 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 f2c3de4d7b91b5b7ba3ecffaa8c364271f4c66c3 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 25/42] 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 820cb7cbe9..80ea1da611 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1771,6 +1771,17 @@ 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_object (&onscreen_native->gbm.stalled_fb);
+  g_clear_object (&onscreen_native->gbm.next_fb);
+}
+
 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 91eb7b533e..11bb5ba561 100644
--- a/src/backends/native/meta-onscreen-native.h
+++ b/src/backends/native/meta-onscreen-native.h
@@ -45,6 +45,8 @@ void meta_onscreen_native_finish_frame (CoglOnscreen *onscreen,
 
 void meta_onscreen_native_dummy_power_save_page_flip (CoglOnscreen *onscreen);
 
+void meta_onscreen_native_discard_pending_swaps (CoglOnscreen *onscreen);
+
 gboolean meta_onscreen_native_is_buffer_scanout_compatible (CoglOnscreen  *onscreen,
                                                             MetaDrmBuffer *fb);
 
-- 
GitLab

From 249645d383acbb07e777460fec6f06f04a384dd8 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 26/42] 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

Also remember to discard_pending_swaps to break the circular reference
between MetaOnscreenNative and its next_fb caused by the association
"gbm_surface owner". Or else that would trigger another assertion failure:

meta_device_pool_finalize: runtime check failed: (!pool->files)
---
 src/backends/native/meta-onscreen-native.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 80ea1da611..914ae6f4ab 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1231,6 +1231,8 @@ 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);
@@ -1246,6 +1248,12 @@ try_post_latest_swap (CoglOnscreen *onscreen)
   if (onscreen_native->next_post.frame == NULL)
     return;
 
+  if (meta_kms_is_shutting_down (kms))
+    {
+      meta_onscreen_native_discard_pending_swaps (onscreen);
+      return;
+    }
+
   power_save_mode = meta_monitor_manager_get_power_save_mode (monitor_manager);
   if (power_save_mode == META_POWER_SAVE_ON)
     {
-- 
GitLab

From 8d1e26ecf4270576436d55c1dab4b996dfefe5aa 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 27/42] 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 f50c930eea..6acc099181 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -1523,6 +1523,26 @@ 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)
 {
@@ -1533,6 +1553,7 @@ 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 85647296275c86e7af25efcafa98f43d4c66f5e4 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 28/42] 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 30cc6fb12a..783baa8af6 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -734,7 +734,7 @@ 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 7bd6cf6964fc056f47b8a95672d8fc1f0c75dea2 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 29/42] 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 | 28 ++++++++++-----------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 783baa8af6..dcde9f260d 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -55,8 +55,7 @@ typedef enum _ClutterFrameClockState
   CLUTTER_FRAME_CLOCK_STATE_INIT,
   CLUTTER_FRAME_CLOCK_STATE_IDLE,
   CLUTTER_FRAME_CLOCK_STATE_SCHEDULED,
-  CLUTTER_FRAME_CLOCK_STATE_DISPATCHING,
-  CLUTTER_FRAME_CLOCK_STATE_PENDING_PRESENTED,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED,
 } ClutterFrameClockState;
 
 struct _ClutterFrameClock
@@ -378,8 +377,7 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       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;
@@ -398,8 +396,7 @@ clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       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;
@@ -613,8 +610,7 @@ clutter_frame_clock_inhibit (ClutterFrameClock *frame_clock)
           frame_clock->pending_reschedule = 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;
         }
 
@@ -652,8 +648,7 @@ clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       next_update_time_us = g_get_monotonic_time ();
       break;
-    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;
@@ -693,8 +688,7 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
       break;
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       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;
     }
@@ -758,7 +752,7 @@ 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++;
 
@@ -790,19 +784,19 @@ 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:
       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;
@@ -935,8 +929,6 @@ 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 393294b46e4f5b39e2e210b7df5088d2e4db6487 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 30/42] clutter/frame-clock: Don't clamp measurements

Because values over refresh_interval_us are real and valid. They
tell us when we're not keeping up.

This reverts commit 9c021b0bc2e4f0d2698f36db41224645ed31b6dc.
---
 clutter/clutter/clutter-frame-clock.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index dcde9f260d..de217313c0 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -348,10 +348,9 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
                     swap_to_flip_us);
 
       frame_clock->shortterm_max_update_duration_us =
-        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);
+        MAX (frame_clock->shortterm_max_update_duration_us,
+             frame_clock->last_dispatch_lateness_us + dispatch_to_swap_us +
+             MAX (swap_to_rendering_done_us, swap_to_flip_us));
 
       maybe_update_longterm_max_duration_us (frame_clock, frame_info);
 
@@ -434,8 +433,6 @@ 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);
-
   return max_render_time_us;
 }
 
-- 
GitLab

From cc26cfac043564590834c532c96fceb46d4421d6 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 31/42] clutter/frame-clock: Add triple buffering support

---
 clutter/clutter/clutter-frame-clock.c | 159 +++++++++++++++++++++-----
 1 file changed, 133 insertions(+), 26 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index de217313c0..3c70808184 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -55,7 +55,9 @@ typedef enum _ClutterFrameClockState
   CLUTTER_FRAME_CLOCK_STATE_INIT,
   CLUTTER_FRAME_CLOCK_STATE_IDLE,
   CLUTTER_FRAME_CLOCK_STATE_SCHEDULED,
-  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED,
+  CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO,
 } ClutterFrameClockState;
 
 struct _ClutterFrameClock
@@ -72,6 +74,7 @@ struct _ClutterFrameClock
 
   ClutterFrameClockState state;
   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;
@@ -86,6 +89,7 @@ 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;
@@ -330,14 +334,33 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
   if (frame_info->cpu_time_before_buffer_swap_us != 0)
     {
       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:
+          g_warn_if_reached ();
+          G_GNUC_FALLTHROUGH;
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+          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,
@@ -376,10 +399,18 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       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_TWO:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      maybe_reschedule_update (frame_clock);
+      break;
     }
 }
 
@@ -395,10 +426,18 @@ clutter_frame_clock_notify_ready (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       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_TWO:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      maybe_reschedule_update (frame_clock);
+      break;
     }
 }
 
@@ -413,7 +452,14 @@ 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 refresh_interval_us * SYNC_DELAY_FALLBACK_FRACTION;
+    {
+      int64_t ret = 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
@@ -447,7 +493,7 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
   int64_t refresh_interval_us;
   int64_t min_render_time_allowed_us;
   int64_t max_render_time_allowed_us;
-  int64_t next_presentation_time_us;
+  int64_t next_presentation_time_us = 0;
   int64_t next_update_time_us;
 
   now_us = g_get_monotonic_time ();
@@ -492,7 +538,24 @@ 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;
+  switch (frame_clock->state)
+    {
+    case CLUTTER_FRAME_CLOCK_STATE_INIT:
+    case CLUTTER_FRAME_CLOCK_STATE_IDLE:
+    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+      next_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:
+      next_presentation_time_us = last_presentation_time_us +
+                                  2 * refresh_interval_us;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
+      next_presentation_time_us = last_presentation_time_us +
+                                  3 * refresh_interval_us;
+      break;
+    }
 
   /*
    * However, the last presentation could have happened more than a frame ago.
@@ -607,7 +670,12 @@ clutter_frame_clock_inhibit (ClutterFrameClock *frame_clock)
           frame_clock->pending_reschedule = 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:
+        case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
           break;
         }
 
@@ -644,8 +712,15 @@ clutter_frame_clock_schedule_update_now (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_IDLE:
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
       next_update_time_us = g_get_monotonic_time ();
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
       break;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+      next_update_time_us = g_get_monotonic_time ();
+      frame_clock->state =
+        CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       frame_clock->pending_reschedule = TRUE;
       frame_clock->pending_reschedule_now = TRUE;
       return;
@@ -655,7 +730,6 @@ 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;
   frame_clock->is_next_presentation_time_valid = FALSE;
 }
 
@@ -674,6 +748,7 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
     {
     case CLUTTER_FRAME_CLOCK_STATE_INIT:
       next_update_time_us = g_get_monotonic_time ();
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
       break;
     case CLUTTER_FRAME_CLOCK_STATE_IDLE:
       calculate_next_update_time_us (frame_clock,
@@ -682,10 +757,21 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
                                      &frame_clock->min_render_time_allowed_us);
       frame_clock->is_next_presentation_time_valid =
         (frame_clock->next_presentation_time_us != 0);
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_SCHEDULED;
       break;
     case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
       return;
-    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED:
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+      calculate_next_update_time_us (frame_clock,
+                                     &next_update_time_us,
+                                     &frame_clock->next_presentation_time_us,
+                                     &frame_clock->min_render_time_allowed_us);
+      frame_clock->is_next_presentation_time_valid =
+        (frame_clock->next_presentation_time_us != 0);
+      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;
     }
@@ -694,7 +780,6 @@ 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;
 }
 
 static void
@@ -746,10 +831,25 @@ 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:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+      break;
+    case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
+      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO;
+      break;
+    }
 
   frame_count = frame_clock->frame_count++;
 
@@ -778,25 +878,31 @@ 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 ();
-      break;
-    case CLUTTER_FRAME_CLOCK_STATE_IDLE:
-      /* Presentation completed synchronously in the above listener */
-    case CLUTTER_FRAME_CLOCK_STATE_SCHEDULED:
+    case CLUTTER_FRAME_RESULT_PENDING_PRESENTED:
       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:
+          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_TWO:
+          frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE;
+          maybe_reschedule_update (frame_clock);
+          break;
         }
       break;
     }
@@ -832,6 +938,7 @@ 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 b07d2c10c779cc294eb44bbbb796512a35af33b1 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 32/42] 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 3c70808184..93d2d3a114 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -252,6 +252,12 @@ 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,
                            "Frame Clock (presented)");
 
@@ -364,7 +370,8 @@ 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,
@@ -382,7 +389,8 @@ 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 038305e8cb2dedfccb723395b621ae40e945661f 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 33/42] 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 93ebc94386..b6650a5a05 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 0a0226b0a5..55c76df72e 100644
--- a/clutter/clutter/clutter-frame-private.h
+++ b/clutter/clutter/clutter-frame-private.h
@@ -34,6 +34,7 @@ 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 85baef274e..413ce9c2b6 100644
--- a/clutter/clutter/clutter-frame.c
+++ b/clutter/clutter/clutter-frame.c
@@ -113,3 +113,16 @@ 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 1d5660d685..0e7f618a4e 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 0518dee8e72c2cf71509194cf973ef09e70d3ef3 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 34/42] 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 c35cb36e32..2130e4042d 100644
--- a/src/backends/meta-stage-impl.c
+++ b/src/backends/meta-stage-impl.c
@@ -775,6 +775,8 @@ 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 5a2892c74834706df0e1ad0948b3352569f6558a 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 35/42] 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 93d2d3a114..80f256726c 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -91,6 +91,8 @@ 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 */
@@ -943,11 +945,13 @@ 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 b6650a5a05..e1fd6b9861 100644
--- a/clutter/clutter/clutter-frame-clock.h
+++ b/clutter/clutter/clutter-frame-clock.h
@@ -97,7 +97,8 @@ 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 168746dd4a..f0e36619e8 100644
--- a/clutter/clutter/clutter-stage-view.c
+++ b/clutter/clutter/clutter-stage-view.c
@@ -1264,14 +1264,21 @@ 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 b7f877643cb291788bf371265b3087e45f7ddb74 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 36/42] clutter/frame-clock: Throttle back to double buffering
 for direct scanout

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.
---
 clutter/clutter/clutter-frame-clock.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 80f256726c..bd69623f7d 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -773,6 +773,13 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
       return;
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
+      if (frame_clock->last_flip_hints & CLUTTER_FRAME_HINT_DIRECT_SCANOUT_ATTEMPTED)
+        {
+          /* Force double buffering, disable triple buffering */
+          frame_clock->pending_reschedule = TRUE;
+          return;
+        }
+
       calculate_next_update_time_us (frame_clock,
                                      &next_update_time_us,
                                      &frame_clock->next_presentation_time_us,
-- 
GitLab

From 8d2b52858a40aa416ba6b1a1539e923282cd83cc Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 10 Mar 2022 16:44:14 +0800
Subject: [PATCH 37/42] clutter/frame-clock: Add environment variable
 MUTTER_DEBUG_TRIPLE_BUFFERING

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

This also allows some unification with automatic throttling for
direct scanout.
---
 clutter/clutter/clutter-frame-clock.c | 53 ++++++++++++++++++++++-----
 1 file changed, 43 insertions(+), 10 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index bd69623f7d..692056b380 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -35,6 +35,15 @@ 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 0.875
 
 typedef struct _ClutterFrameListener
@@ -747,6 +756,12 @@ 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 &&
+      (frame_clock->last_flip_hints &
+       CLUTTER_FRAME_HINT_DIRECT_SCANOUT_ATTEMPTED))
+    current_mode = TRIPLE_BUFFERING_MODE_NEVER;
 
   if (frame_clock->inhibit_count > 0)
     {
@@ -773,20 +788,29 @@ clutter_frame_clock_schedule_update (ClutterFrameClock *frame_clock)
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED:
       return;
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE:
-      if (frame_clock->last_flip_hints & CLUTTER_FRAME_HINT_DIRECT_SCANOUT_ATTEMPTED)
+      switch (current_mode)
         {
-          /* Force double buffering, disable triple buffering */
+        case TRIPLE_BUFFERING_MODE_NEVER:
           frame_clock->pending_reschedule = TRUE;
           return;
+        case TRIPLE_BUFFERING_MODE_AUTO:
+          calculate_next_update_time_us (frame_clock,
+                                         &next_update_time_us,
+                                         &frame_clock->next_presentation_time_us,
+                                         &frame_clock->min_render_time_allowed_us);
+          frame_clock->is_next_presentation_time_valid =
+            (frame_clock->next_presentation_time_us != 0);
+          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;
+          break;
         }
-
-      calculate_next_update_time_us (frame_clock,
-                                     &next_update_time_us,
-                                     &frame_clock->next_presentation_time_us,
-                                     &frame_clock->min_render_time_allowed_us);
-      frame_clock->is_next_presentation_time_valid =
-        (frame_clock->next_presentation_time_us != 0);
-      frame_clock->state = CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_ONE_AND_SCHEDULED;
       break;
     case CLUTTER_FRAME_CLOCK_STATE_DISPATCHED_TWO:
       frame_clock->pending_reschedule = TRUE;
@@ -1072,6 +1096,15 @@ 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 46a7c555a973701fa6a2db1d0e8ba49f6bdd1f3e 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 38/42] 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 | 107 ++++++++++++++++++++++++++++------
 1 file changed, 88 insertions(+), 19 deletions(-)

diff --git a/src/tests/native-kms-render.c b/src/tests/native-kms-render.c
index 31e74a9a42..259d315dce 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
@@ -134,6 +138,7 @@ on_scanout_before_paint (ClutterStage     *stage,
 {
   CoglScanout *scanout;
   MetaDrmBuffer *buffer;
+  uint32_t fb_id;
 
   scanout = clutter_stage_view_peek_scanout (stage_view);
   if (!scanout)
@@ -141,8 +146,14 @@ on_scanout_before_paint (ClutterStage     *stage,
 
   g_assert_true (META_IS_DRM_BUFFER (scanout));
   buffer = META_DRM_BUFFER (scanout);
-  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
@@ -171,12 +182,12 @@ 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);
 
@@ -195,15 +206,41 @@ 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
@@ -242,7 +279,9 @@ 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,
   };
 
@@ -268,7 +307,8 @@ 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");
@@ -290,10 +330,15 @@ 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);
@@ -305,10 +350,15 @@ 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);
@@ -362,6 +412,15 @@ 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))
@@ -399,6 +458,15 @@ 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));
     }
 }
 
@@ -408,11 +476,11 @@ 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
@@ -441,6 +509,7 @@ 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 dac1e526c714f3b6692db529ba9b0ad23cf7d94a Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Fri, 19 May 2023 14:31:07 +0800
Subject: [PATCH 39/42] tests/clutter/event-delivery: Add a wait for
 clutter_actor_destroy

Because the destroy meant we were producing more frames/updates than
were waited on. This becomes a problem when triple buffering is enabled
because stage changes are then delayed by one update, causing spurious
test failures unless we wait on every change to keep it synchronous like
in double buffering.
---
 src/tests/clutter/conform/event-delivery.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/tests/clutter/conform/event-delivery.c b/src/tests/clutter/conform/event-delivery.c
index 383ad0bae0..3b259139a9 100644
--- a/src/tests/clutter/conform/event-delivery.c
+++ b/src/tests/clutter/conform/event-delivery.c
@@ -329,6 +329,7 @@ event_delivery_implicit_grab_cancelled (void)
   n_child_1_leave_events = n_child_2_leave_events = n_stage_leave_events = 0;
   n_action_sequences_cancelled = 0;
   clutter_actor_destroy (child_1);
+  wait_stage_updated (&was_updated);
   g_assert_cmpint (n_child_1_enter_events, ==, 0);
   g_assert_cmpint (n_child_1_leave_events, ==, 0);
   g_assert_cmpint (n_action_sequences_cancelled, ==, 1);
-- 
GitLab

From 9f3459991092d8174ca80628c551649794abc663 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 40/42] 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.

Fixes: https://launchpad.net/bugs/2020049
---
 src/backends/native/meta-onscreen-native.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index 914ae6f4ab..6f74011d11 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1245,7 +1245,8 @@ try_post_latest_swap (CoglOnscreen *onscreen)
   g_autoptr (ClutterFrame) frame = NULL;
   MetaFrameNative *frame_native;
 
-  if (onscreen_native->next_post.frame == NULL)
+  if (onscreen_native->next_post.frame == NULL ||
+      onscreen_native->view == NULL)
     return;
 
   if (meta_kms_is_shutting_down (kms))
-- 
GitLab

From 49eb4964826943f9d1c5897a1c23bdfebd54e00c 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 41/42] 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.

Fixes: https://launchpad.net/bugs/2023363
---
 clutter/clutter/clutter-frame-clock.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index 692056b380..d652a6e5fb 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -233,10 +233,6 @@ 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;
@@ -348,7 +344,8 @@ 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)
+  if (frame_info->cpu_time_before_buffer_swap_us != 0 ||
+      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;
@@ -371,14 +368,21 @@ 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 04094e9ff9b97019a1547f386cbf5d6fc258841e 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 42/42] 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 | 6 ------
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/src/backends/native/meta-kms-impl-device.c b/src/backends/native/meta-kms-impl-device.c
index 7bc5efa654..972873ac48 100644
--- a/src/backends/native/meta-kms-impl-device.c
+++ b/src/backends/native/meta-kms-impl-device.c
@@ -1483,9 +1483,11 @@ 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 6f74011d11..14d727c557 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -1557,12 +1557,6 @@ void
 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);
 }
 
 void
-- 
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File _service:download_url:1441.patch of Package mutter (Revision 043199d37a6cfdc85189512c5500f5a9)

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