From b2014c71942cf2f9e12ef933693e22491ac3d83a Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 4 Feb 2025 13:19:07 +0100
Subject: [PATCH 01/11] [Linux] Move rendering to raster thread

---
 .../flutter/shell/platform/linux/fl_engine.cc |   3 +-
 .../shell/platform/linux/fl_renderer.cc       | 120 +++++++++++++++++-
 .../shell/platform/linux/fl_renderer.h        |   8 ++
 .../shell/platform/linux/fl_task_runner.cc    |  35 ++++-
 .../shell/platform/linux/fl_task_runner.h     |  20 ++-
 .../flutter/shell/platform/linux/fl_view.cc   |   4 +
 .../platform/linux/testing/mock_renderer.cc   |  11 ++
 7 files changed, 186 insertions(+), 15 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_engine.cc b/engine/src/flutter/shell/platform/linux/fl_engine.cc
index 38edff1af9a44..108539afd9629 100644
--- a/engine/src/flutter/shell/platform/linux/fl_engine.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_engine.cc
@@ -356,7 +356,7 @@ static void fl_engine_post_task(FlutterTask task,
                                 void* user_data) {
   FlEngine* self = static_cast<FlEngine*>(user_data);
 
-  fl_task_runner_post_task(self->task_runner, task, target_time_nanos);
+  fl_task_runner_post_flutter_task(self->task_runner, task, target_time_nanos);
 }
 
 // Called when a platform message is received from the engine.
@@ -630,7 +630,6 @@ gboolean fl_engine_start(FlEngine* self, GError** error) {
   FlutterCustomTaskRunners custom_task_runners = {};
   custom_task_runners.struct_size = sizeof(FlutterCustomTaskRunners);
   custom_task_runners.platform_task_runner = &platform_task_runner;
-  custom_task_runners.render_task_runner = &platform_task_runner;
 
   g_autoptr(GPtrArray) command_line_args =
       g_ptr_array_new_with_free_func(g_free);
diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index 2d5d918d0d293..9d508b9addee1 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -73,6 +73,11 @@ typedef struct {
 
   // Framebuffers to render keyed by view ID.
   GHashTable* framebuffers_by_view_id;
+
+  // Mutex and condition used when block the raster thread until a task
+  // is completed on platform thread.
+  GMutex mutex;
+  GCond cond;
 } FlRendererPrivate;
 
 G_DEFINE_TYPE_WITH_PRIVATE(FlRenderer, fl_renderer, G_TYPE_OBJECT)
@@ -313,10 +318,32 @@ static void fl_renderer_dispose(GObject* object) {
   g_clear_pointer(&priv->framebuffers_by_view_id, g_hash_table_unref);
 
   G_OBJECT_CLASS(fl_renderer_parent_class)->dispose(object);
+
+  g_mutex_clear(&priv->mutex);
+  g_cond_clear(&priv->cond);
+}
+
+static gboolean fl_renderer_schedule_on_main_thread(
+    FlRenderer* self,
+    void (*callback)(gpointer data),
+    gpointer callback_data) {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+  g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
+
+  if (engine == nullptr) {
+    return FALSE;
+  }
+
+  FlTaskRunner* task_runner = fl_engine_get_task_runner(engine);
+  fl_task_runner_post_callback(task_runner, callback, callback_data);
+  return TRUE;
 }
 
 static void fl_renderer_class_init(FlRendererClass* klass) {
   G_OBJECT_CLASS(klass)->dispose = fl_renderer_dispose;
+  FL_RENDERER_CLASS(klass)->schedule_on_main_thread =
+      fl_renderer_schedule_on_main_thread;
 }
 
 static void fl_renderer_init(FlRenderer* self) {
@@ -327,6 +354,8 @@ static void fl_renderer_init(FlRenderer* self) {
   priv->framebuffers_by_view_id = g_hash_table_new_full(
       g_direct_hash, g_direct_equal, nullptr,
       reinterpret_cast<GDestroyNotify>(g_ptr_array_unref));
+  g_mutex_init(&priv->mutex);
+  g_cond_init(&priv->cond);
 }
 
 void fl_renderer_set_engine(FlRenderer* self, FlEngine* engine) {
@@ -388,6 +417,53 @@ guint32 fl_renderer_get_fbo(FlRenderer* self) {
   return 0;
 }
 
+struct _FlRendererCallBlockingTrampolineData {
+  FlRenderer* renderer;
+  gboolean* finished;
+  void (*callback)(gpointer data);
+  gpointer data;
+};
+
+static void fl_renderer_call_blocking_trampoline(gpointer user_data) {
+  auto* data = static_cast<_FlRendererCallBlockingTrampolineData*>(user_data);
+  data->callback(data->data);
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(data->renderer));
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
+  *data->finished = TRUE;
+  g_cond_signal(&priv->cond);
+}
+
+// Executes the given function on the main thread and blocks until it completes.
+static void fl_renderer_call_blocking(FlRenderer* self,
+                                      void (*callback)(gpointer data),
+                                      gpointer callback_data) {
+  gboolean finished = FALSE;
+  _FlRendererCallBlockingTrampolineData trampoline_data = {
+      self,
+      &finished,
+      callback,
+      callback_data,
+  };
+
+  gboolean scheduled = FL_RENDERER_GET_CLASS(self)->schedule_on_main_thread(
+      self, fl_renderer_call_blocking_trampoline, &trampoline_data);
+
+  // Don't block if the task was not sucessfully scheduled.
+  if (!scheduled) {
+    return;
+  }
+
+  // Wait for the task to complete.
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
+  while (!finished) {
+    g_cond_wait(&priv->cond, &priv->mutex);
+  }
+}
+
 gboolean fl_renderer_create_backing_store(
     FlRenderer* self,
     const FlutterBackingStoreConfig* config,
@@ -450,10 +526,11 @@ void fl_renderer_wait_for_frame(FlRenderer* self,
   }
 }
 
-gboolean fl_renderer_present_layers(FlRenderer* self,
-                                    FlutterViewId view_id,
-                                    const FlutterLayer** layers,
-                                    size_t layers_count) {
+static gboolean fl_renderer_present_layers_on_main_thread(
+    FlRenderer* self,
+    FlutterViewId view_id,
+    const FlutterLayer** layers,
+    size_t layers_count) {
   FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
       fl_renderer_get_instance_private(self));
 
@@ -564,6 +641,41 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
   return TRUE;
 }
 
+struct _FlRendererPresentLayersData {
+  FlRenderer* self;
+  FlutterViewId view_id;
+  const FlutterLayer** layers;
+  size_t layers_count;
+  gboolean* res;
+};
+
+static void fl_renderer_present_layers_trampoline(gpointer trampoline_data) {
+  _FlRendererPresentLayersData* data =
+      reinterpret_cast<_FlRendererPresentLayersData*>(trampoline_data);
+  fl_renderer_make_current(data->self);
+  *data->res = fl_renderer_present_layers_on_main_thread(
+      data->self, data->view_id, data->layers, data->layers_count);
+  fl_renderer_clear_current(data->self);
+}
+
+gboolean fl_renderer_present_layers(FlRenderer* self,
+                                    FlutterViewId view_id,
+                                    const FlutterLayer** layers,
+                                    size_t layers_count) {
+  gboolean res = FALSE;
+  _FlRendererPresentLayersData data = {
+      .self = self,
+      .view_id = view_id,
+      .layers = layers,
+      .layers_count = layers_count,
+      .res = &res,
+  };
+  fl_renderer_clear_current(self);
+  fl_renderer_call_blocking(self, fl_renderer_present_layers_trampoline, &data);
+  fl_renderer_make_current(self);
+  return res;
+}
+
 void fl_renderer_setup(FlRenderer* self) {
   FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
       fl_renderer_get_instance_private(self));
diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.h b/engine/src/flutter/shell/platform/linux/fl_renderer.h
index b4b5216c70f80..ca31785feca79 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.h
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.h
@@ -55,6 +55,14 @@ struct _FlRendererClass {
    * @renderer: an #FlRenderer.
    */
   void (*clear_current)(FlRenderer* renderer);
+
+  /**
+   * Virtual method responsible for scheduling the callback on the main thread.
+   * Overriden in the mock renderer.
+   */
+  gboolean (*schedule_on_main_thread)(FlRenderer* renderer,
+                                      void (*callback)(gpointer data),
+                                      gpointer data);
 };
 
 /**
diff --git a/engine/src/flutter/shell/platform/linux/fl_task_runner.cc b/engine/src/flutter/shell/platform/linux/fl_task_runner.cc
index 147550c504d3f..d09b96ca9b7ae 100644
--- a/engine/src/flutter/shell/platform/linux/fl_task_runner.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_task_runner.cc
@@ -22,9 +22,16 @@ struct _FlTaskRunner {
 };
 
 typedef struct _FlTaskRunnerTask {
-  // absolute time of task (based on g_get_monotonic_time)
+  // absolute time of task (based on g_get_monotonic_time).
   gint64 task_time_micros;
+
+  // flutter task to execute if schedule through
+  // fl_task_runner_post_flutter_task.
   FlutterTask task;
+
+  // callback to execute if scheduled through fl_task_runner_post_callback.
+  void (*callback)(gpointer data);
+  gpointer callback_data;
 } FlTaskRunnerTask;
 
 G_DEFINE_TYPE(FlTaskRunner, fl_task_runner, G_TYPE_OBJECT)
@@ -56,7 +63,11 @@ static void fl_task_runner_process_expired_tasks_locked(FlTaskRunner* self) {
     l = expired_tasks;
     while (l != nullptr) {
       FlTaskRunnerTask* task = static_cast<FlTaskRunnerTask*>(l->data);
-      fl_engine_execute_task(engine, &task->task);
+      if (task->callback != nullptr) {
+        task->callback(task->callback_data);
+      } else {
+        fl_engine_execute_task(engine, &task->task);
+      }
       l = l->next;
     }
   }
@@ -158,9 +169,9 @@ FlTaskRunner* fl_task_runner_new(FlEngine* engine) {
   return self;
 }
 
-void fl_task_runner_post_task(FlTaskRunner* self,
-                              FlutterTask task,
-                              uint64_t target_time_nanos) {
+void fl_task_runner_post_flutter_task(FlTaskRunner* self,
+                                      FlutterTask task,
+                                      uint64_t target_time_nanos) {
   g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&self->mutex);
   (void)locker;  // unused variable
 
@@ -173,6 +184,20 @@ void fl_task_runner_post_task(FlTaskRunner* self,
   fl_task_runner_tasks_did_change_locked(self);
 }
 
+void fl_task_runner_post_callback(FlTaskRunner* self,
+                                  void (*callback)(gpointer data),
+                                  gpointer data) {
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&self->mutex);
+  (void)locker;  // unused variable
+
+  FlTaskRunnerTask* runner_task = g_new0(FlTaskRunnerTask, 1);
+  runner_task->callback = callback;
+  runner_task->callback_data = data;
+
+  self->pending_tasks = g_list_append(self->pending_tasks, runner_task);
+  fl_task_runner_tasks_did_change_locked(self);
+}
+
 void fl_task_runner_block_main_thread(FlTaskRunner* self) {
   g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&self->mutex);
   (void)locker;  // unused variable
diff --git a/engine/src/flutter/shell/platform/linux/fl_task_runner.h b/engine/src/flutter/shell/platform/linux/fl_task_runner.h
index ca4f84b3ee521..7e1383ce8d605 100644
--- a/engine/src/flutter/shell/platform/linux/fl_task_runner.h
+++ b/engine/src/flutter/shell/platform/linux/fl_task_runner.h
@@ -25,7 +25,7 @@ G_DECLARE_FINAL_TYPE(FlTaskRunner, fl_task_runner, FL, TASK_RUNNER, GObject);
 FlTaskRunner* fl_task_runner_new(FlEngine* engine);
 
 /**
- * fl_task_runner_post_task:
+ * fl_task_runner_post_flutter_task:
  * @task_runner: an #FlTaskRunner.
  * @task: Flutter task being scheduled
  * @target_time_nanos: absolute time in nanoseconds
@@ -33,9 +33,21 @@ FlTaskRunner* fl_task_runner_new(FlEngine* engine);
  * Posts a Flutter task to be executed on main thread. This function is thread
  * safe and may be called from any thread.
  */
-void fl_task_runner_post_task(FlTaskRunner* task_runner,
-                              FlutterTask task,
-                              uint64_t target_time_nanos);
+void fl_task_runner_post_flutter_task(FlTaskRunner* task_runner,
+                                      FlutterTask task,
+                                      uint64_t target_time_nanos);
+
+/**
+ * fl_task_runner_post_callback:
+ * @task_runner: an #FlTaskRunner.
+ * @callback: callback to be scheduled
+ * @data: data to be passed to the callback
+ *
+ * Schedules arbitrary callback to be executed on main thread.
+ */
+void fl_task_runner_post_callback(FlTaskRunner* task_runner,
+                                  void (*callback)(gpointer data),
+                                  gpointer data);
 
 /**
  * fl_task_runner_block_main_thread:
diff --git a/engine/src/flutter/shell/platform/linux/fl_view.cc b/engine/src/flutter/shell/platform/linux/fl_view.cc
index 1299a086f6ce6..964e2aeb41728 100644
--- a/engine/src/flutter/shell/platform/linux/fl_view.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_view.cc
@@ -476,6 +476,10 @@ static void realize_cb(FlView* self) {
   fl_renderer_add_renderable(FL_RENDERER(self->renderer), self->view_id,
                              FL_RENDERABLE(self));
 
+  // Flutter engine will need to make the context current from raster thread
+  // during initialization.
+  fl_renderer_clear_current(FL_RENDERER(self->renderer));
+
   if (!fl_engine_start(self->engine, &error)) {
     g_warning("Failed to start Flutter engine: %s", error->message);
     return;
diff --git a/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc b/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
index 5ae2926efa53d..f40a94b58e76e 100644
--- a/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
@@ -29,6 +29,15 @@ static void fl_mock_renderer_make_current(FlRenderer* renderer) {}
 // Implements FlRenderer::make_resource_current.
 static void fl_mock_renderer_make_resource_current(FlRenderer* renderer) {}
 
+// Implements FlRenderer::schedule_on_main_thread.
+static gboolean fl_mock_renderer_schedule_on_main_thread(
+    FlRenderer* renderer,
+    void (*callback)(gpointer data),
+    gpointer data) {
+  callback(data);
+  return TRUE;
+}
+
 // Implements FlRenderer::clear_current.
 static void fl_mock_renderer_clear_current(FlRenderer* renderer) {}
 
@@ -37,6 +46,8 @@ static void fl_mock_renderer_class_init(FlMockRendererClass* klass) {
   FL_RENDERER_CLASS(klass)->make_resource_current =
       fl_mock_renderer_make_resource_current;
   FL_RENDERER_CLASS(klass)->clear_current = fl_mock_renderer_clear_current;
+  FL_RENDERER_CLASS(klass)->schedule_on_main_thread =
+      fl_mock_renderer_schedule_on_main_thread;
 }
 
 static void fl_mock_renderer_init(FlMockRenderer* self) {}

From 5394d0025d1d55af7dbc2d447ff10690a5a96a2a Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:24:06 +0100
Subject: [PATCH 02/11] simplify

---
 .../shell/platform/linux/fl_renderer.cc       | 115 +++++++-----------
 .../shell/platform/linux/fl_renderer.h        |   8 --
 .../platform/linux/testing/mock_renderer.cc   |   9 --
 3 files changed, 41 insertions(+), 91 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index 9d508b9addee1..1d8e0b3b4b0a1 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -323,27 +323,8 @@ static void fl_renderer_dispose(GObject* object) {
   g_cond_clear(&priv->cond);
 }
 
-static gboolean fl_renderer_schedule_on_main_thread(
-    FlRenderer* self,
-    void (*callback)(gpointer data),
-    gpointer callback_data) {
-  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
-      fl_renderer_get_instance_private(self));
-  g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
-
-  if (engine == nullptr) {
-    return FALSE;
-  }
-
-  FlTaskRunner* task_runner = fl_engine_get_task_runner(engine);
-  fl_task_runner_post_callback(task_runner, callback, callback_data);
-  return TRUE;
-}
-
 static void fl_renderer_class_init(FlRendererClass* klass) {
   G_OBJECT_CLASS(klass)->dispose = fl_renderer_dispose;
-  FL_RENDERER_CLASS(klass)->schedule_on_main_thread =
-      fl_renderer_schedule_on_main_thread;
 }
 
 static void fl_renderer_init(FlRenderer* self) {
@@ -417,53 +398,6 @@ guint32 fl_renderer_get_fbo(FlRenderer* self) {
   return 0;
 }
 
-struct _FlRendererCallBlockingTrampolineData {
-  FlRenderer* renderer;
-  gboolean* finished;
-  void (*callback)(gpointer data);
-  gpointer data;
-};
-
-static void fl_renderer_call_blocking_trampoline(gpointer user_data) {
-  auto* data = static_cast<_FlRendererCallBlockingTrampolineData*>(user_data);
-  data->callback(data->data);
-  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
-      fl_renderer_get_instance_private(data->renderer));
-  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
-  *data->finished = TRUE;
-  g_cond_signal(&priv->cond);
-}
-
-// Executes the given function on the main thread and blocks until it completes.
-static void fl_renderer_call_blocking(FlRenderer* self,
-                                      void (*callback)(gpointer data),
-                                      gpointer callback_data) {
-  gboolean finished = FALSE;
-  _FlRendererCallBlockingTrampolineData trampoline_data = {
-      self,
-      &finished,
-      callback,
-      callback_data,
-  };
-
-  gboolean scheduled = FL_RENDERER_GET_CLASS(self)->schedule_on_main_thread(
-      self, fl_renderer_call_blocking_trampoline, &trampoline_data);
-
-  // Don't block if the task was not sucessfully scheduled.
-  if (!scheduled) {
-    return;
-  }
-
-  // Wait for the task to complete.
-  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
-      fl_renderer_get_instance_private(self));
-
-  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
-  while (!finished) {
-    g_cond_wait(&priv->cond, &priv->mutex);
-  }
-}
-
 gboolean fl_renderer_create_backing_store(
     FlRenderer* self,
     const FlutterBackingStoreConfig* config,
@@ -646,34 +580,67 @@ struct _FlRendererPresentLayersData {
   FlutterViewId view_id;
   const FlutterLayer** layers;
   size_t layers_count;
-  gboolean* res;
+  gboolean res;
+  gboolean finished;
 };
 
-static void fl_renderer_present_layers_trampoline(gpointer trampoline_data) {
+// Scheduled from the raster thread to run on main thread and forward
+// the arguments to fl_renderer_present_layers_on_main_thread.
+static void fl_renderer_present_layers_trampoline(gpointer user_data) {
   _FlRendererPresentLayersData* data =
-      reinterpret_cast<_FlRendererPresentLayersData*>(trampoline_data);
+      static_cast<_FlRendererPresentLayersData*>(user_data);
+
   fl_renderer_make_current(data->self);
-  *data->res = fl_renderer_present_layers_on_main_thread(
+  data->res = fl_renderer_present_layers_on_main_thread(
       data->self, data->view_id, data->layers, data->layers_count);
   fl_renderer_clear_current(data->self);
+
+  // Unblock the raster thread.
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(data->self));
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
+  data->finished = TRUE;
+  g_cond_signal(&priv->cond);
 }
 
+// Called by the engine on the raster thread. Will reschedule
+// the call to fl_renderer_present_layers_on_main_thread
+// and block until it completes.
 gboolean fl_renderer_present_layers(FlRenderer* self,
                                     FlutterViewId view_id,
                                     const FlutterLayer** layers,
                                     size_t layers_count) {
-  gboolean res = FALSE;
   _FlRendererPresentLayersData data = {
       .self = self,
       .view_id = view_id,
       .layers = layers,
       .layers_count = layers_count,
-      .res = &res,
+      .res = FALSE,
+      .finished = FALSE,
   };
   fl_renderer_clear_current(self);
-  fl_renderer_call_blocking(self, fl_renderer_present_layers_trampoline, &data);
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+  g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
+
+  if (engine == nullptr) {
+    // Task runner not available (i.e. test environment), run the callback
+    // synchronously.
+    fl_renderer_present_layers_trampoline(&data);
+    return data.res;
+  }
+
+  FlTaskRunner* task_runner = fl_engine_get_task_runner(engine);
+  fl_task_runner_post_callback(task_runner,
+                               fl_renderer_present_layers_trampoline, &data);
+
+  // Wait for the task to complete.
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
+  while (!data.finished) {
+    g_cond_wait(&priv->cond, &priv->mutex);
+  }
   fl_renderer_make_current(self);
-  return res;
+  return data.res;
 }
 
 void fl_renderer_setup(FlRenderer* self) {
diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.h b/engine/src/flutter/shell/platform/linux/fl_renderer.h
index ca31785feca79..b4b5216c70f80 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.h
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.h
@@ -55,14 +55,6 @@ struct _FlRendererClass {
    * @renderer: an #FlRenderer.
    */
   void (*clear_current)(FlRenderer* renderer);
-
-  /**
-   * Virtual method responsible for scheduling the callback on the main thread.
-   * Overriden in the mock renderer.
-   */
-  gboolean (*schedule_on_main_thread)(FlRenderer* renderer,
-                                      void (*callback)(gpointer data),
-                                      gpointer data);
 };
 
 /**
diff --git a/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc b/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
index f40a94b58e76e..e40a558d61c1c 100644
--- a/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
@@ -30,13 +30,6 @@ static void fl_mock_renderer_make_current(FlRenderer* renderer) {}
 static void fl_mock_renderer_make_resource_current(FlRenderer* renderer) {}
 
 // Implements FlRenderer::schedule_on_main_thread.
-static gboolean fl_mock_renderer_schedule_on_main_thread(
-    FlRenderer* renderer,
-    void (*callback)(gpointer data),
-    gpointer data) {
-  callback(data);
-  return TRUE;
-}
 
 // Implements FlRenderer::clear_current.
 static void fl_mock_renderer_clear_current(FlRenderer* renderer) {}
@@ -46,8 +39,6 @@ static void fl_mock_renderer_class_init(FlMockRendererClass* klass) {
   FL_RENDERER_CLASS(klass)->make_resource_current =
       fl_mock_renderer_make_resource_current;
   FL_RENDERER_CLASS(klass)->clear_current = fl_mock_renderer_clear_current;
-  FL_RENDERER_CLASS(klass)->schedule_on_main_thread =
-      fl_mock_renderer_schedule_on_main_thread;
 }
 
 static void fl_mock_renderer_init(FlMockRenderer* self) {}

From b5d8acbd98282868b46e497b043caa145a5461f7 Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:31:42 +0100
Subject: [PATCH 03/11] Add documentation

---
 engine/src/flutter/shell/platform/linux/fl_task_runner.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_task_runner.h b/engine/src/flutter/shell/platform/linux/fl_task_runner.h
index 7e1383ce8d605..953583090caae 100644
--- a/engine/src/flutter/shell/platform/linux/fl_task_runner.h
+++ b/engine/src/flutter/shell/platform/linux/fl_task_runner.h
@@ -43,7 +43,9 @@ void fl_task_runner_post_flutter_task(FlTaskRunner* task_runner,
  * @callback: callback to be scheduled
  * @data: data to be passed to the callback
  *
- * Schedules arbitrary callback to be executed on main thread.
+ * Schedules arbitrary callback to be executed on main thread. The callback
+ * will be executed in next run loop turn.This function is thread
+ * safe and may be called from any thread.
  */
 void fl_task_runner_post_callback(FlTaskRunner* task_runner,
                                   void (*callback)(gpointer data),

From ab6e170ecbd3ca8c3743f6180d527e8fe099bdfb Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:32:28 +0100
Subject: [PATCH 04/11] reorder

---
 engine/src/flutter/shell/platform/linux/fl_renderer.cc | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index 1d8e0b3b4b0a1..e5848e3c6e93b 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -316,11 +316,10 @@ static void fl_renderer_dispose(GObject* object) {
   g_weak_ref_clear(&priv->engine);
   g_clear_pointer(&priv->views, g_hash_table_unref);
   g_clear_pointer(&priv->framebuffers_by_view_id, g_hash_table_unref);
-
-  G_OBJECT_CLASS(fl_renderer_parent_class)->dispose(object);
-
   g_mutex_clear(&priv->mutex);
   g_cond_clear(&priv->cond);
+
+  G_OBJECT_CLASS(fl_renderer_parent_class)->dispose(object);
 }
 
 static void fl_renderer_class_init(FlRendererClass* klass) {

From e799ce9a0aa37ca4f884c28c6a43093d63436275 Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:36:25 +0100
Subject: [PATCH 05/11] document every field

---
 engine/src/flutter/shell/platform/linux/fl_renderer.cc    | 7 +++++--
 engine/src/flutter/shell/platform/linux/fl_task_runner.cc | 2 ++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index e5848e3c6e93b..fc3c3d8c30b84 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -74,9 +74,12 @@ typedef struct {
   // Framebuffers to render keyed by view ID.
   GHashTable* framebuffers_by_view_id;
 
-  // Mutex and condition used when block the raster thread until a task
-  // is completed on platform thread.
+  // Mutex used when blocking the raster thread until a task is completed on
+  // platform thread.
   GMutex mutex;
+
+  // Condition to unblock the raster thread after task is completed on platform
+  // thread.
   GCond cond;
 } FlRendererPrivate;
 
diff --git a/engine/src/flutter/shell/platform/linux/fl_task_runner.cc b/engine/src/flutter/shell/platform/linux/fl_task_runner.cc
index d09b96ca9b7ae..5a225da1ed692 100644
--- a/engine/src/flutter/shell/platform/linux/fl_task_runner.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_task_runner.cc
@@ -31,6 +31,8 @@ typedef struct _FlTaskRunnerTask {
 
   // callback to execute if scheduled through fl_task_runner_post_callback.
   void (*callback)(gpointer data);
+
+  // data for the callback.
   gpointer callback_data;
 } FlTaskRunnerTask;
 

From 58a23785a4ebeef4c5429fb15fd2e10fa91e4c78 Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:38:00 +0100
Subject: [PATCH 06/11] missing space

---
 engine/src/flutter/shell/platform/linux/fl_task_runner.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_task_runner.h b/engine/src/flutter/shell/platform/linux/fl_task_runner.h
index 953583090caae..0c7c7effc2ac7 100644
--- a/engine/src/flutter/shell/platform/linux/fl_task_runner.h
+++ b/engine/src/flutter/shell/platform/linux/fl_task_runner.h
@@ -44,7 +44,7 @@ void fl_task_runner_post_flutter_task(FlTaskRunner* task_runner,
  * @data: data to be passed to the callback
  *
  * Schedules arbitrary callback to be executed on main thread. The callback
- * will be executed in next run loop turn.This function is thread
+ * will be executed in next run loop turn. This function is thread
  * safe and may be called from any thread.
  */
 void fl_task_runner_post_callback(FlTaskRunner* task_runner,

From de3fc9184e8cb312ec2c267d96dfc4096616280b Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:44:34 +0100
Subject: [PATCH 07/11] restore context

---
 engine/src/flutter/shell/platform/linux/fl_renderer.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index fc3c3d8c30b84..54c4ab3be1d6f 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -612,6 +612,8 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
                                     FlutterViewId view_id,
                                     const FlutterLayer** layers,
                                     size_t layers_count) {
+  fl_renderer_clear_current(self);
+
   _FlRendererPresentLayersData data = {
       .self = self,
       .view_id = view_id,
@@ -620,7 +622,6 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
       .res = FALSE,
       .finished = FALSE,
   };
-  fl_renderer_clear_current(self);
   FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
       fl_renderer_get_instance_private(self));
   g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
@@ -629,6 +630,7 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
     // Task runner not available (i.e. test environment), run the callback
     // synchronously.
     fl_renderer_present_layers_trampoline(&data);
+    fl_renderer_make_current(self);
     return data.res;
   }
 
@@ -641,6 +643,7 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
   while (!data.finished) {
     g_cond_wait(&priv->cond, &priv->mutex);
   }
+
   fl_renderer_make_current(self);
   return data.res;
 }

From 81c68d32649807f2f2532faafedcb132d2fd8e4f Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 11 Feb 2025 23:47:37 +0100
Subject: [PATCH 08/11] remove obsolete comment

---
 .../src/flutter/shell/platform/linux/testing/mock_renderer.cc   | 2 --
 1 file changed, 2 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc b/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
index e40a558d61c1c..5ae2926efa53d 100644
--- a/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/testing/mock_renderer.cc
@@ -29,8 +29,6 @@ static void fl_mock_renderer_make_current(FlRenderer* renderer) {}
 // Implements FlRenderer::make_resource_current.
 static void fl_mock_renderer_make_resource_current(FlRenderer* renderer) {}
 
-// Implements FlRenderer::schedule_on_main_thread.
-
 // Implements FlRenderer::clear_current.
 static void fl_mock_renderer_clear_current(FlRenderer* renderer) {}
 

From e40a802fcde917f94c371847f4fa7e8cd17db745 Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Thu, 13 Feb 2025 10:41:13 +0100
Subject: [PATCH 09/11] Fix tests instead of having special codepath in
 fl_renderer

---
 .../shell/platform/linux/fl_renderer.cc       |   8 -
 .../shell/platform/linux/fl_renderer_test.cc  | 218 ++++++++++++++----
 2 files changed, 174 insertions(+), 52 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index 54c4ab3be1d6f..363da64854b3f 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -626,14 +626,6 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
       fl_renderer_get_instance_private(self));
   g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
 
-  if (engine == nullptr) {
-    // Task runner not available (i.e. test environment), run the callback
-    // synchronously.
-    fl_renderer_present_layers_trampoline(&data);
-    fl_renderer_make_current(self);
-    return data.res;
-  }
-
   FlTaskRunner* task_runner = fl_engine_get_task_runner(engine);
   fl_task_runner_post_callback(task_runner,
                                fl_renderer_present_layers_trampoline, &data);
diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer_test.cc b/engine/src/flutter/shell/platform/linux/fl_renderer_test.cc
index 0c808fb2f1707..ab300fad0dff7 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer_test.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer_test.cc
@@ -2,10 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <thread>
 #include "gtest/gtest.h"
 
 #include "flutter/common/constants.h"
 #include "flutter/fml/logging.h"
+#include "flutter/fml/synchronization/waitable_event.h"
 #include "flutter/shell/platform/linux/fl_framebuffer.h"
 #include "flutter/shell/platform/linux/testing/mock_epoxy.h"
 #include "flutter/shell/platform/linux/testing/mock_renderer.h"
@@ -14,6 +16,8 @@
 
 TEST(FlRendererTest, BackgroundColor) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   ON_CALL(epoxy, epoxy_is_desktop_gl).WillByDefault(::testing::Return(true));
   EXPECT_CALL(epoxy, epoxy_gl_version).WillRepeatedly(::testing::Return(30));
@@ -25,6 +29,7 @@ TEST(FlRendererTest, BackgroundColor) {
   g_autoptr(FlMockRenderable) renderable = fl_mock_renderable_new();
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
   fl_renderer_setup(FL_RENDERER(renderer));
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   fl_renderer_add_renderable(FL_RENDERER(renderer),
                              flutter::kFlutterImplicitViewId,
                              FL_RENDERABLE(renderable));
@@ -35,27 +40,47 @@ TEST(FlRendererTest, BackgroundColor) {
   FlutterBackingStore backing_store;
   fl_renderer_create_backing_store(FL_RENDERER(renderer), &config,
                                    &backing_store);
-  const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
-                               .type = kFlutterLayerContentTypeBackingStore,
-                               .backing_store = &backing_store,
-                               .size = {.width = 1024, .height = 1024}};
-  const FlutterLayer* layers[] = {&layer0};
-  fl_renderer_present_layers(FL_RENDERER(renderer),
-                             flutter::kFlutterImplicitViewId, layers, 1);
+
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
+                                 .type = kFlutterLayerContentTypeBackingStore,
+                                 .backing_store = &backing_store,
+                                 .size = {.width = 1024, .height = 1024}};
+    const FlutterLayer* layers[] = {&layer0};
+
+    fl_renderer_present_layers(FL_RENDERER(renderer),
+                               flutter::kFlutterImplicitViewId, layers, 1);
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
+
   GdkRGBA background_color = {
       .red = 0.2, .green = 0.3, .blue = 0.4, .alpha = 0.5};
   fl_renderer_render(FL_RENDERER(renderer), flutter::kFlutterImplicitViewId,
                      1024, 1024, &background_color);
+
+  // Wait until the raster thread has finished before letting
+  // the engine go out of scope.
+  latch.Wait();
 }
 
 TEST(FlRendererTest, RestoresGLState) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   constexpr int kWidth = 100;
   constexpr int kHeight = 100;
 
   g_autoptr(FlMockRenderable) renderable = fl_mock_renderable_new();
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   g_autoptr(FlFramebuffer) framebuffer =
       fl_framebuffer_new(GL_RGB, kWidth, kHeight);
 
@@ -79,9 +104,20 @@ TEST(FlRendererTest, RestoresGLState) {
   constexpr GLuint kFakeTextureName = 123;
   glBindTexture(GL_TEXTURE_2D, kFakeTextureName);
 
-  fl_renderer_present_layers(FL_RENDERER(renderer),
-                             flutter::kFlutterImplicitViewId, layers.data(),
-                             layers.size());
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    fl_renderer_present_layers(FL_RENDERER(renderer),
+                               flutter::kFlutterImplicitViewId, layers.data(),
+                               layers.size());
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
+
   GdkRGBA background_color = {
       .red = 0.0, .green = 0.0, .blue = 0.0, .alpha = 1.0};
   fl_renderer_render(FL_RENDERER(renderer), flutter::kFlutterImplicitViewId,
@@ -91,10 +127,16 @@ TEST(FlRendererTest, RestoresGLState) {
   glGetIntegerv(GL_TEXTURE_BINDING_2D,
                 reinterpret_cast<GLint*>(&texture_2d_binding));
   EXPECT_EQ(texture_2d_binding, kFakeTextureName);
+
+  // Wait until the raster thread has finished before letting
+  // the engine go out of scope.
+  latch.Wait();
 }
 
 TEST(FlRendererTest, BlitFramebuffer) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   // OpenGL 3.0
   ON_CALL(epoxy, glGetString(GL_VENDOR))
@@ -108,6 +150,7 @@ TEST(FlRendererTest, BlitFramebuffer) {
   g_autoptr(FlMockRenderable) renderable = fl_mock_renderable_new();
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
   fl_renderer_setup(FL_RENDERER(renderer));
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   fl_renderer_add_renderable(FL_RENDERER(renderer),
                              flutter::kFlutterImplicitViewId,
                              FL_RENDERABLE(renderable));
@@ -118,21 +161,37 @@ TEST(FlRendererTest, BlitFramebuffer) {
   FlutterBackingStore backing_store;
   fl_renderer_create_backing_store(FL_RENDERER(renderer), &config,
                                    &backing_store);
-  const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
-                               .type = kFlutterLayerContentTypeBackingStore,
-                               .backing_store = &backing_store,
-                               .size = {.width = 1024, .height = 1024}};
-  const FlutterLayer* layers[] = {&layer0};
-  fl_renderer_present_layers(FL_RENDERER(renderer),
-                             flutter::kFlutterImplicitViewId, layers, 1);
+
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
+                                 .type = kFlutterLayerContentTypeBackingStore,
+                                 .backing_store = &backing_store,
+                                 .size = {.width = 1024, .height = 1024}};
+    const FlutterLayer* layers[] = {&layer0};
+    fl_renderer_present_layers(FL_RENDERER(renderer),
+                               flutter::kFlutterImplicitViewId, layers, 1);
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
+
   GdkRGBA background_color = {
       .red = 0.0, .green = 0.0, .blue = 0.0, .alpha = 1.0};
   fl_renderer_render(FL_RENDERER(renderer), flutter::kFlutterImplicitViewId,
                      1024, 1024, &background_color);
+
+  latch.Wait();
 }
 
 TEST(FlRendererTest, BlitFramebufferExtension) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   // OpenGL 2.0 with GL_EXT_framebuffer_blit extension
   ON_CALL(epoxy, glGetString(GL_VENDOR))
@@ -151,6 +210,7 @@ TEST(FlRendererTest, BlitFramebufferExtension) {
   g_autoptr(FlMockRenderable) renderable = fl_mock_renderable_new();
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
   fl_renderer_setup(FL_RENDERER(renderer));
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   fl_renderer_add_renderable(FL_RENDERER(renderer),
                              flutter::kFlutterImplicitViewId,
                              FL_RENDERABLE(renderable));
@@ -161,21 +221,37 @@ TEST(FlRendererTest, BlitFramebufferExtension) {
   FlutterBackingStore backing_store;
   fl_renderer_create_backing_store(FL_RENDERER(renderer), &config,
                                    &backing_store);
-  const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
-                               .type = kFlutterLayerContentTypeBackingStore,
-                               .backing_store = &backing_store,
-                               .size = {.width = 1024, .height = 1024}};
-  const FlutterLayer* layers[] = {&layer0};
-  fl_renderer_present_layers(FL_RENDERER(renderer),
-                             flutter::kFlutterImplicitViewId, layers, 1);
+
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
+                                 .type = kFlutterLayerContentTypeBackingStore,
+                                 .backing_store = &backing_store,
+                                 .size = {.width = 1024, .height = 1024}};
+    const FlutterLayer* layers[] = {&layer0};
+    fl_renderer_present_layers(FL_RENDERER(renderer),
+                               flutter::kFlutterImplicitViewId, layers, 1);
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
   GdkRGBA background_color = {
       .red = 0.0, .green = 0.0, .blue = 0.0, .alpha = 1.0};
   fl_renderer_render(FL_RENDERER(renderer), flutter::kFlutterImplicitViewId,
                      1024, 1024, &background_color);
+  // Wait until the raster thread has finished before letting
+  // the engine go out of scope.
+  latch.Wait();
 }
 
 TEST(FlRendererTest, NoBlitFramebuffer) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   // OpenGL 2.0
   ON_CALL(epoxy, glGetString(GL_VENDOR))
@@ -187,6 +263,7 @@ TEST(FlRendererTest, NoBlitFramebuffer) {
   g_autoptr(FlMockRenderable) renderable = fl_mock_renderable_new();
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
   fl_renderer_setup(FL_RENDERER(renderer));
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   fl_renderer_add_renderable(FL_RENDERER(renderer),
                              flutter::kFlutterImplicitViewId,
                              FL_RENDERABLE(renderable));
@@ -197,21 +274,39 @@ TEST(FlRendererTest, NoBlitFramebuffer) {
   FlutterBackingStore backing_store;
   fl_renderer_create_backing_store(FL_RENDERER(renderer), &config,
                                    &backing_store);
-  const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
-                               .type = kFlutterLayerContentTypeBackingStore,
-                               .backing_store = &backing_store,
-                               .size = {.width = 1024, .height = 1024}};
-  const FlutterLayer* layers[] = {&layer0};
-  fl_renderer_present_layers(FL_RENDERER(renderer),
-                             flutter::kFlutterImplicitViewId, layers, 1);
+
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
+                                 .type = kFlutterLayerContentTypeBackingStore,
+                                 .backing_store = &backing_store,
+                                 .size = {.width = 1024, .height = 1024}};
+    const FlutterLayer* layers[] = {&layer0};
+    fl_renderer_present_layers(FL_RENDERER(renderer),
+                               flutter::kFlutterImplicitViewId, layers, 1);
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
+
   GdkRGBA background_color = {
       .red = 0.0, .green = 0.0, .blue = 0.0, .alpha = 1.0};
   fl_renderer_render(FL_RENDERER(renderer), flutter::kFlutterImplicitViewId,
                      1024, 1024, &background_color);
+
+  // Wait until the raster thread has finished before letting
+  // the engine go out of scope.
+  latch.Wait();
 }
 
 TEST(FlRendererTest, BlitFramebufferNvidia) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   // OpenGL 3.0, but on NVIDIA driver so temporarily disabled due to
   // https://github.com/flutter/flutter/issues/152099
@@ -224,6 +319,7 @@ TEST(FlRendererTest, BlitFramebufferNvidia) {
   g_autoptr(FlMockRenderable) renderable = fl_mock_renderable_new();
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
   fl_renderer_setup(FL_RENDERER(renderer));
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   fl_renderer_add_renderable(FL_RENDERER(renderer),
                              flutter::kFlutterImplicitViewId,
                              FL_RENDERABLE(renderable));
@@ -234,21 +330,39 @@ TEST(FlRendererTest, BlitFramebufferNvidia) {
   FlutterBackingStore backing_store;
   fl_renderer_create_backing_store(FL_RENDERER(renderer), &config,
                                    &backing_store);
-  const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
-                               .type = kFlutterLayerContentTypeBackingStore,
-                               .backing_store = &backing_store,
-                               .size = {.width = 1024, .height = 1024}};
-  const FlutterLayer* layers[] = {&layer0};
-  fl_renderer_present_layers(FL_RENDERER(renderer),
-                             flutter::kFlutterImplicitViewId, layers, 1);
+
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
+                                 .type = kFlutterLayerContentTypeBackingStore,
+                                 .backing_store = &backing_store,
+                                 .size = {.width = 1024, .height = 1024}};
+    const FlutterLayer* layers[] = {&layer0};
+    fl_renderer_present_layers(FL_RENDERER(renderer),
+                               flutter::kFlutterImplicitViewId, layers, 1);
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
+
   GdkRGBA background_color = {
       .red = 0.0, .green = 0.0, .blue = 0.0, .alpha = 1.0};
   fl_renderer_render(FL_RENDERER(renderer), flutter::kFlutterImplicitViewId,
                      1024, 1024, &background_color);
+
+  // Wait until the raster thread has finished before letting
+  // the engine go out of scope.
+  latch.Wait();
 }
 
 TEST(FlRendererTest, MultiView) {
   ::testing::NiceMock<flutter::testing::MockEpoxy> epoxy;
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
 
   // OpenGL 3.0
   ON_CALL(epoxy, glGetString(GL_VENDOR))
@@ -262,6 +376,7 @@ TEST(FlRendererTest, MultiView) {
 
   g_autoptr(FlMockRenderer) renderer = fl_mock_renderer_new();
   fl_renderer_setup(FL_RENDERER(renderer));
+  fl_renderer_set_engine(FL_RENDERER(renderer), engine);
   fl_renderer_add_renderable(FL_RENDERER(renderer),
                              flutter::kFlutterImplicitViewId,
                              FL_RENDERABLE(renderable));
@@ -280,15 +395,30 @@ TEST(FlRendererTest, MultiView) {
   FlutterBackingStore backing_store;
   fl_renderer_create_backing_store(FL_RENDERER(renderer), &config,
                                    &backing_store);
-  const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
-                               .type = kFlutterLayerContentTypeBackingStore,
-                               .backing_store = &backing_store,
-                               .size = {.width = 1024, .height = 1024}};
-  const FlutterLayer* layers[] = {&layer0};
-  fl_renderer_present_layers(FL_RENDERER(renderer), 1, layers, 1);
+
+  fml::AutoResetWaitableEvent latch;
+
+  // Simulate raster thread.
+  std::thread([&]() {
+    const FlutterLayer layer0 = {.struct_size = sizeof(FlutterLayer),
+                                 .type = kFlutterLayerContentTypeBackingStore,
+                                 .backing_store = &backing_store,
+                                 .size = {.width = 1024, .height = 1024}};
+    const FlutterLayer* layers[] = {&layer0};
+    fl_renderer_present_layers(FL_RENDERER(renderer), 1, layers, 1);
+    latch.Signal();
+  }).detach();
+
+  while (fl_mock_renderable_get_redraw_count(secondary_renderable) == 0) {
+    g_main_context_iteration(nullptr, true);
+  }
 
   EXPECT_EQ(fl_mock_renderable_get_redraw_count(renderable),
             static_cast<size_t>(0));
   EXPECT_EQ(fl_mock_renderable_get_redraw_count(secondary_renderable),
             static_cast<size_t>(1));
+
+  // Wait until the raster thread has finished before letting
+  // the engine go out of scope.
+  latch.Wait();
 }

From e1f68676c293162a1872a6078d9bb8beb3ee6145 Mon Sep 17 00:00:00 2001
From: Robert Ancell <robert.ancell@canonical.com>
Date: Tue, 4 Mar 2025 12:50:54 +1300
Subject: [PATCH 10/11] Improvements to naming, structure and comments

---
 .../shell/platform/linux/fl_renderer.cc       | 330 +++++++++---------
 1 file changed, 165 insertions(+), 165 deletions(-)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index 363da64854b3f..e720f87dbcc47 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -76,11 +76,11 @@ typedef struct {
 
   // Mutex used when blocking the raster thread until a task is completed on
   // platform thread.
-  GMutex mutex;
+  GMutex present_mutex;
 
   // Condition to unblock the raster thread after task is completed on platform
   // thread.
-  GCond cond;
+  GCond present_condition;
 } FlRendererPrivate;
 
 G_DEFINE_TYPE_WITH_PRIVATE(FlRenderer, fl_renderer, G_TYPE_OBJECT)
@@ -309,6 +309,151 @@ static void render(FlRenderer* self,
   }
 }
 
+static gboolean present_layers(FlRenderer* self,
+                               FlutterViewId view_id,
+                               const FlutterLayer** layers,
+                               size_t layers_count) {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+
+  g_return_val_if_fail(FL_IS_RENDERER(self), FALSE);
+
+  // ignore incoming frame with wrong dimensions in trivial case with just one
+  // layer
+  if (priv->blocking_main_thread && layers_count == 1 &&
+      layers[0]->offset.x == 0 && layers[0]->offset.y == 0 &&
+      (layers[0]->size.width != priv->target_width ||
+       layers[0]->size.height != priv->target_height)) {
+    return TRUE;
+  }
+
+  priv->had_first_frame = true;
+
+  fl_renderer_unblock_main_thread(self);
+
+  g_autoptr(GPtrArray) framebuffers =
+      g_ptr_array_new_with_free_func(g_object_unref);
+  for (size_t i = 0; i < layers_count; ++i) {
+    const FlutterLayer* layer = layers[i];
+    switch (layer->type) {
+      case kFlutterLayerContentTypeBackingStore: {
+        const FlutterBackingStore* backing_store = layer->backing_store;
+        FlFramebuffer* framebuffer =
+            FL_FRAMEBUFFER(backing_store->open_gl.framebuffer.user_data);
+        g_ptr_array_add(framebuffers, g_object_ref(framebuffer));
+      } break;
+      case kFlutterLayerContentTypePlatformView: {
+        // TODO(robert-ancell) Not implemented -
+        // https://github.com/flutter/flutter/issues/41724
+      } break;
+    }
+  }
+
+  GWeakRef* ref = static_cast<GWeakRef*>(
+      g_hash_table_lookup(priv->views, GINT_TO_POINTER(view_id)));
+  g_autoptr(FlRenderable) renderable =
+      ref != nullptr ? FL_RENDERABLE(g_weak_ref_get(ref)) : nullptr;
+  if (renderable == nullptr) {
+    return TRUE;
+  }
+
+  if (view_id == flutter::kFlutterImplicitViewId) {
+    // Store for rendering later
+    g_hash_table_insert(priv->framebuffers_by_view_id, GINT_TO_POINTER(view_id),
+                        g_ptr_array_ref(framebuffers));
+  } else {
+    // Composite into a single framebuffer.
+    if (framebuffers->len > 1) {
+      size_t width = 0, height = 0;
+
+      for (guint i = 0; i < framebuffers->len; i++) {
+        FlFramebuffer* framebuffer =
+            FL_FRAMEBUFFER(g_ptr_array_index(framebuffers, i));
+
+        size_t w = fl_framebuffer_get_width(framebuffer);
+        size_t h = fl_framebuffer_get_height(framebuffer);
+        if (w > width) {
+          width = w;
+        }
+        if (h > height) {
+          height = h;
+        }
+      }
+
+      FlFramebuffer* view_framebuffer =
+          fl_framebuffer_new(priv->general_format, width, height);
+      glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
+                        fl_framebuffer_get_id(view_framebuffer));
+      render(self, framebuffers, width, height);
+      g_ptr_array_set_size(framebuffers, 0);
+      g_ptr_array_add(framebuffers, view_framebuffer);
+    }
+
+    // Read back pixel values.
+    FlFramebuffer* framebuffer =
+        FL_FRAMEBUFFER(g_ptr_array_index(framebuffers, 0));
+    size_t width = fl_framebuffer_get_width(framebuffer);
+    size_t height = fl_framebuffer_get_height(framebuffer);
+    size_t data_length = width * height * 4;
+    g_autofree uint8_t* data = static_cast<uint8_t*>(malloc(data_length));
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, fl_framebuffer_get_id(framebuffer));
+    glReadPixels(0, 0, width, height, priv->general_format, GL_UNSIGNED_BYTE,
+                 data);
+
+    // Write into a texture in the views context.
+    fl_renderable_make_current(renderable);
+    FlFramebuffer* view_framebuffer =
+        fl_framebuffer_new(priv->general_format, width, height);
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
+                      fl_framebuffer_get_id(view_framebuffer));
+    glBindTexture(GL_TEXTURE_2D,
+                  fl_framebuffer_get_texture_id(view_framebuffer));
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA,
+                 GL_UNSIGNED_BYTE, data);
+
+    g_autoptr(GPtrArray) secondary_framebuffers =
+        g_ptr_array_new_with_free_func(g_object_unref);
+    g_ptr_array_add(secondary_framebuffers, g_object_ref(view_framebuffer));
+    g_hash_table_insert(priv->framebuffers_by_view_id, GINT_TO_POINTER(view_id),
+                        g_ptr_array_ref(secondary_framebuffers));
+  }
+
+  fl_renderable_redraw(renderable);
+
+  return TRUE;
+}
+
+typedef struct {
+  FlRenderer* self;
+
+  FlutterViewId view_id;
+
+  const FlutterLayer** layers;
+  size_t layers_count;
+
+  gboolean result;
+
+  gboolean finished;
+} PresentLayersData;
+
+// Perform the present on the main thread.
+static void present_layers_task_cb(gpointer user_data) {
+  PresentLayersData* data = static_cast<PresentLayersData*>(user_data);
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(data->self));
+
+  // Perform the present.
+  fl_renderer_make_current(data->self);
+  data->result = present_layers(data->self, data->view_id, data->layers,
+                                data->layers_count);
+  fl_renderer_clear_current(data->self);
+
+  // Complete fl_renderer_present_layers().
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->present_mutex);
+  data->finished = TRUE;
+  g_cond_signal(&priv->present_condition);
+}
+
 static void fl_renderer_dispose(GObject* object) {
   FlRenderer* self = FL_RENDERER(object);
   FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
@@ -319,8 +464,8 @@ static void fl_renderer_dispose(GObject* object) {
   g_weak_ref_clear(&priv->engine);
   g_clear_pointer(&priv->views, g_hash_table_unref);
   g_clear_pointer(&priv->framebuffers_by_view_id, g_hash_table_unref);
-  g_mutex_clear(&priv->mutex);
-  g_cond_clear(&priv->cond);
+  g_mutex_clear(&priv->present_mutex);
+  g_cond_clear(&priv->present_condition);
 
   G_OBJECT_CLASS(fl_renderer_parent_class)->dispose(object);
 }
@@ -337,8 +482,8 @@ static void fl_renderer_init(FlRenderer* self) {
   priv->framebuffers_by_view_id = g_hash_table_new_full(
       g_direct_hash, g_direct_equal, nullptr,
       reinterpret_cast<GDestroyNotify>(g_ptr_array_unref));
-  g_mutex_init(&priv->mutex);
-  g_cond_init(&priv->cond);
+  g_mutex_init(&priv->present_mutex);
+  g_cond_init(&priv->present_condition);
 }
 
 void fl_renderer_set_engine(FlRenderer* self, FlEngine* engine) {
@@ -462,182 +607,37 @@ void fl_renderer_wait_for_frame(FlRenderer* self,
   }
 }
 
-static gboolean fl_renderer_present_layers_on_main_thread(
-    FlRenderer* self,
-    FlutterViewId view_id,
-    const FlutterLayer** layers,
-    size_t layers_count) {
-  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
-      fl_renderer_get_instance_private(self));
-
-  g_return_val_if_fail(FL_IS_RENDERER(self), FALSE);
-
-  // ignore incoming frame with wrong dimensions in trivial case with just one
-  // layer
-  if (priv->blocking_main_thread && layers_count == 1 &&
-      layers[0]->offset.x == 0 && layers[0]->offset.y == 0 &&
-      (layers[0]->size.width != priv->target_width ||
-       layers[0]->size.height != priv->target_height)) {
-    return TRUE;
-  }
-
-  priv->had_first_frame = true;
-
-  fl_renderer_unblock_main_thread(self);
-
-  g_autoptr(GPtrArray) framebuffers =
-      g_ptr_array_new_with_free_func(g_object_unref);
-  for (size_t i = 0; i < layers_count; ++i) {
-    const FlutterLayer* layer = layers[i];
-    switch (layer->type) {
-      case kFlutterLayerContentTypeBackingStore: {
-        const FlutterBackingStore* backing_store = layer->backing_store;
-        FlFramebuffer* framebuffer =
-            FL_FRAMEBUFFER(backing_store->open_gl.framebuffer.user_data);
-        g_ptr_array_add(framebuffers, g_object_ref(framebuffer));
-      } break;
-      case kFlutterLayerContentTypePlatformView: {
-        // TODO(robert-ancell) Not implemented -
-        // https://github.com/flutter/flutter/issues/41724
-      } break;
-    }
-  }
-
-  GWeakRef* ref = static_cast<GWeakRef*>(
-      g_hash_table_lookup(priv->views, GINT_TO_POINTER(view_id)));
-  g_autoptr(FlRenderable) renderable =
-      ref != nullptr ? FL_RENDERABLE(g_weak_ref_get(ref)) : nullptr;
-  if (renderable == nullptr) {
-    return TRUE;
-  }
-
-  if (view_id == flutter::kFlutterImplicitViewId) {
-    // Store for rendering later
-    g_hash_table_insert(priv->framebuffers_by_view_id, GINT_TO_POINTER(view_id),
-                        g_ptr_array_ref(framebuffers));
-  } else {
-    // Composite into a single framebuffer.
-    if (framebuffers->len > 1) {
-      size_t width = 0, height = 0;
-
-      for (guint i = 0; i < framebuffers->len; i++) {
-        FlFramebuffer* framebuffer =
-            FL_FRAMEBUFFER(g_ptr_array_index(framebuffers, i));
-
-        size_t w = fl_framebuffer_get_width(framebuffer);
-        size_t h = fl_framebuffer_get_height(framebuffer);
-        if (w > width) {
-          width = w;
-        }
-        if (h > height) {
-          height = h;
-        }
-      }
-
-      FlFramebuffer* view_framebuffer =
-          fl_framebuffer_new(priv->general_format, width, height);
-      glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
-                        fl_framebuffer_get_id(view_framebuffer));
-      render(self, framebuffers, width, height);
-      g_ptr_array_set_size(framebuffers, 0);
-      g_ptr_array_add(framebuffers, view_framebuffer);
-    }
-
-    // Read back pixel values.
-    FlFramebuffer* framebuffer =
-        FL_FRAMEBUFFER(g_ptr_array_index(framebuffers, 0));
-    size_t width = fl_framebuffer_get_width(framebuffer);
-    size_t height = fl_framebuffer_get_height(framebuffer);
-    size_t data_length = width * height * 4;
-    g_autofree uint8_t* data = static_cast<uint8_t*>(malloc(data_length));
-    glBindFramebuffer(GL_READ_FRAMEBUFFER, fl_framebuffer_get_id(framebuffer));
-    glReadPixels(0, 0, width, height, priv->general_format, GL_UNSIGNED_BYTE,
-                 data);
-
-    // Write into a texture in the views context.
-    fl_renderable_make_current(renderable);
-    FlFramebuffer* view_framebuffer =
-        fl_framebuffer_new(priv->general_format, width, height);
-    glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
-                      fl_framebuffer_get_id(view_framebuffer));
-    glBindTexture(GL_TEXTURE_2D,
-                  fl_framebuffer_get_texture_id(view_framebuffer));
-    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA,
-                 GL_UNSIGNED_BYTE, data);
-
-    g_autoptr(GPtrArray) secondary_framebuffers =
-        g_ptr_array_new_with_free_func(g_object_unref);
-    g_ptr_array_add(secondary_framebuffers, g_object_ref(view_framebuffer));
-    g_hash_table_insert(priv->framebuffers_by_view_id, GINT_TO_POINTER(view_id),
-                        g_ptr_array_ref(secondary_framebuffers));
-  }
-
-  fl_renderable_redraw(renderable);
-
-  return TRUE;
-}
-
-struct _FlRendererPresentLayersData {
-  FlRenderer* self;
-  FlutterViewId view_id;
-  const FlutterLayer** layers;
-  size_t layers_count;
-  gboolean res;
-  gboolean finished;
-};
-
-// Scheduled from the raster thread to run on main thread and forward
-// the arguments to fl_renderer_present_layers_on_main_thread.
-static void fl_renderer_present_layers_trampoline(gpointer user_data) {
-  _FlRendererPresentLayersData* data =
-      static_cast<_FlRendererPresentLayersData*>(user_data);
-
-  fl_renderer_make_current(data->self);
-  data->res = fl_renderer_present_layers_on_main_thread(
-      data->self, data->view_id, data->layers, data->layers_count);
-  fl_renderer_clear_current(data->self);
-
-  // Unblock the raster thread.
-  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
-      fl_renderer_get_instance_private(data->self));
-  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
-  data->finished = TRUE;
-  g_cond_signal(&priv->cond);
-}
-
-// Called by the engine on the raster thread. Will reschedule
-// the call to fl_renderer_present_layers_on_main_thread
-// and block until it completes.
 gboolean fl_renderer_present_layers(FlRenderer* self,
                                     FlutterViewId view_id,
                                     const FlutterLayer** layers,
                                     size_t layers_count) {
   fl_renderer_clear_current(self);
 
-  _FlRendererPresentLayersData data = {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+  g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
+
+  // Schedule the present to run on the main thread.
+  FlTaskRunner* task_runner = fl_engine_get_task_runner(engine);
+  PresentLayersData data = {
       .self = self,
       .view_id = view_id,
       .layers = layers,
       .layers_count = layers_count,
-      .res = FALSE,
+      .result = FALSE,
       .finished = FALSE,
   };
-  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
-      fl_renderer_get_instance_private(self));
-  g_autoptr(FlEngine) engine = FL_ENGINE(g_weak_ref_get(&priv->engine));
-
-  FlTaskRunner* task_runner = fl_engine_get_task_runner(engine);
-  fl_task_runner_post_callback(task_runner,
-                               fl_renderer_present_layers_trampoline, &data);
+  fl_task_runner_post_callback(task_runner, present_layers_task_cb, &data);
 
-  // Wait for the task to complete.
-  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->mutex);
+  // Block until present completes.
+  g_autoptr(GMutexLocker) locker = g_mutex_locker_new(&priv->present_mutex);
   while (!data.finished) {
-    g_cond_wait(&priv->cond, &priv->mutex);
+    g_cond_wait(&priv->present_condition, &priv->present_mutex);
   }
 
   fl_renderer_make_current(self);
-  return data.res;
+
+  return data.result;
 }
 
 void fl_renderer_setup(FlRenderer* self) {

From 432b8bd33bbbb3bd00ed6a5ce1c8791d8ecb1798 Mon Sep 17 00:00:00 2001
From: Matej <matej.knopp@gmail.com>
Date: Tue, 4 Mar 2025 11:47:48 +0100
Subject: [PATCH 11/11] Comments

---
 engine/src/flutter/shell/platform/linux/fl_renderer.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/engine/src/flutter/shell/platform/linux/fl_renderer.cc b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
index e720f87dbcc47..518b0b2904302 100644
--- a/engine/src/flutter/shell/platform/linux/fl_renderer.cc
+++ b/engine/src/flutter/shell/platform/linux/fl_renderer.cc
@@ -611,6 +611,8 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
                                     FlutterViewId view_id,
                                     const FlutterLayer** layers,
                                     size_t layers_count) {
+  // Detach the context from raster thread. Needed because blitting
+  // will be done on the main thread, which will make the context current.
   fl_renderer_clear_current(self);
 
   FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
@@ -635,6 +637,8 @@ gboolean fl_renderer_present_layers(FlRenderer* self,
     g_cond_wait(&priv->present_condition, &priv->present_mutex);
   }
 
+  // Restore the context to the raster thread in case the engine needs it
+  // to do some cleanup.
   fl_renderer_make_current(self);
 
   return data.result;

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Transitional//EN' 'http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd'>
<html xmlns='http://www.w3.org/1999/xhtml'>
<head>
<title>pFad - Phonifier reborn</title>
<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />
</head>
<body>
<h1>Pfad - The Proxy pFad of &#169; 2024 Garber Painting. All rights reserved.</h1>


<!-- Disclaimer -->
<p>Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.</p>
<br>
<p>Alternative Proxies:</p><p><a href="http://clevelandohioweatherforecast.com/php-proxy/index.php?q=https://patch-diff.githubusercontent.com/raw/flutter/flutter/pull/161879.patch" target="_blank">Alternative Proxy</a></p><p><a href="http://clevelandohioweatherforecast.com/pFad/index.php?u=https://patch-diff.githubusercontent.com/raw/flutter/flutter/pull/161879.patch" target="_blank">pFad Proxy</a></p><p><a href="http://clevelandohioweatherforecast.com/pFad/v3index.php?u=https://patch-diff.githubusercontent.com/raw/flutter/flutter/pull/161879.patch" target="_blank">pFad v3 Proxy</a></p><p><a href="http://clevelandohioweatherforecast.com/pFad/v4index.php?u=https://patch-diff.githubusercontent.com/raw/flutter/flutter/pull/161879.patch" target="_blank">pFad v4 Proxy</a></p></body>
</html>