Add fl_engine_add/remove_view (flutter/engine#54018)

This is API that will be required when we get multi-view support on
Linux. While this internal API is not currently used, I've made a PR so
it can be more easily reviewed.

engine/src/flutter/shell/platform/linux/fl_engine.cc

@@ -49,6 +49,9 @@ struct _FlEngine {
   FLUTTER_API_SYMBOL(FlutterEngine) engine;
   FlutterEngineProcTable embedder_api;
 
+  // Next ID to use for a view.
+  FlutterViewId next_view_id;
+
   // Function to call when a platform message is received.
   FlEnginePlatformMessageHandler platform_message_handler;
   gpointer platform_message_handler_data;
@@ -123,6 +126,29 @@ static void parse_locale(const gchar* locale,
   }
 }
 
+static void view_added_cb(const FlutterAddViewResult* result) {
+  g_autoptr(GTask) task = G_TASK(result->user_data);
+
+  FlutterViewId view_id = GPOINTER_TO_INT(g_task_get_task_data(task));
+  if (result->added) {
+    g_task_return_pointer(task, GINT_TO_POINTER(view_id), nullptr);
+  } else {
+    g_task_return_new_error(task, fl_engine_error_quark(),
+                            FL_ENGINE_ERROR_FAILED, "Failed to add view");
+  }
+}
+
+static void view_removed_cb(const FlutterRemoveViewResult* result) {
+  g_autoptr(GTask) task = G_TASK(result->user_data);
+
+  if (result->removed) {
+    g_task_return_boolean(task, TRUE);
+  } else {
+    g_task_return_new_error(task, fl_engine_error_quark(),
+                            FL_ENGINE_ERROR_FAILED, "Failed to remove view");
+  }
+}
+
 // Passes locale information to the Flutter engine.
 static void setup_locales(FlEngine* self) {
   const gchar* const* languages = g_get_language_names();
@@ -177,12 +203,11 @@ static bool compositor_collect_backing_store_callback(
 }
 
 // Called when embedder should composite contents of each layer onto the screen.
-static bool compositor_present_layers_callback(const FlutterLayer** layers,
-                                               size_t layers_count,
-                                               void* user_data) {
-  g_return_val_if_fail(FL_IS_RENDERER(user_data), false);
-  return fl_renderer_present_layers(FL_RENDERER(user_data), layers,
-                                    layers_count);
+static bool compositor_present_view_callback(
+    const FlutterPresentViewInfo* info) {
+  g_return_val_if_fail(FL_IS_RENDERER(info->user_data), false);
+  return fl_renderer_present_layers(FL_RENDERER(info->user_data), info->layers,
+                                    info->layers_count);
 }
 
 // Flutter engine rendering callbacks.
@@ -211,7 +236,7 @@ static uint32_t fl_engine_gl_get_fbo(void* user_data) {
 
 static bool fl_engine_gl_present(void* user_data) {
   // No action required, as this is handled in
-  // compositor_present_layers_callback.
+  // compositor_present_view_callback.
   return true;
 }
 
@@ -429,6 +454,9 @@ static void fl_engine_init(FlEngine* self) {
   self->embedder_api.struct_size = sizeof(FlutterEngineProcTable);
   FlutterEngineGetProcAddresses(&self->embedder_api);
 
+  // Implicit view is 0, so start at 1.
+  self->next_view_id = 1;
+
   self->texture_registrar = fl_texture_registrar_new(self);
 }
 
@@ -511,7 +539,7 @@ gboolean fl_engine_start(FlEngine* self, GError** error) {
       compositor_create_backing_store_callback;
   compositor.collect_backing_store_callback =
       compositor_collect_backing_store_callback;
-  compositor.present_layers_callback = compositor_present_layers_callback;
+  compositor.present_view_callback = compositor_present_view_callback;
   args.compositor = &compositor;
 
   if (self->embedder_api.RunsAOTCompiledDartCode()) {
@@ -580,6 +608,82 @@ FlutterEngineProcTable* fl_engine_get_embedder_api(FlEngine* self) {
   return &(self->embedder_api);
 }
 
+void fl_engine_add_view(FlEngine* self,
+                        size_t width,
+                        size_t height,
+                        double pixel_ratio,
+                        GCancellable* cancellable,
+                        GAsyncReadyCallback callback,
+                        gpointer user_data) {
+  g_return_if_fail(FL_IS_ENGINE(self));
+
+  g_autoptr(GTask) task = g_task_new(self, cancellable, callback, user_data);
+
+  FlutterViewId view_id = self->next_view_id;
+  self->next_view_id++;
+  g_task_set_task_data(task, GINT_TO_POINTER(view_id), nullptr);
+
+  FlutterWindowMetricsEvent metrics;
+  metrics.struct_size = sizeof(FlutterWindowMetricsEvent);
+  metrics.width = width;
+  metrics.height = height;
+  metrics.pixel_ratio = pixel_ratio;
+  metrics.view_id = view_id;
+  FlutterAddViewInfo info;
+  info.struct_size = sizeof(FlutterAddViewInfo);
+  info.view_id = view_id;
+  info.view_metrics = &metrics;
+  info.user_data = g_object_ref(task);
+  info.add_view_callback = view_added_cb;
+  FlutterEngineResult result = self->embedder_api.AddView(self->engine, &info);
+  if (result != kSuccess) {
+    g_task_return_new_error(task, fl_engine_error_quark(),
+                            FL_ENGINE_ERROR_FAILED, "AddView returned %d",
+                            result);
+    // This would have been done in the callback, but that won't occur now.
+    g_object_unref(task);
+  }
+}
+
+FlutterViewId fl_engine_add_view_finish(FlEngine* self,
+                                        GAsyncResult* result,
+                                        GError** error) {
+  g_return_val_if_fail(FL_IS_ENGINE(self), FALSE);
+  return GPOINTER_TO_INT(g_task_propagate_pointer(G_TASK(result), error));
+}
+
+void fl_engine_remove_view(FlEngine* self,
+                           FlutterViewId view_id,
+                           GCancellable* cancellable,
+                           GAsyncReadyCallback callback,
+                           gpointer user_data) {
+  g_return_if_fail(FL_IS_ENGINE(self));
+
+  g_autoptr(GTask) task = g_task_new(self, cancellable, callback, user_data);
+
+  FlutterRemoveViewInfo info;
+  info.struct_size = sizeof(FlutterRemoveViewInfo);
+  info.view_id = view_id;
+  info.user_data = g_object_ref(task);
+  info.remove_view_callback = view_removed_cb;
+  FlutterEngineResult result =
+      self->embedder_api.RemoveView(self->engine, &info);
+  if (result != kSuccess) {
+    g_task_return_new_error(task, fl_engine_error_quark(),
+                            FL_ENGINE_ERROR_FAILED, "RemoveView returned %d",
+                            result);
+    // This would have been done in the callback, but that won't occur now.
+    g_object_unref(task);
+  }
+}
+
+gboolean fl_engine_remove_view_finish(FlEngine* self,
+                                      GAsyncResult* result,
+                                      GError** error) {
+  g_return_val_if_fail(FL_IS_ENGINE(self), FALSE);
+  return g_task_propagate_boolean(G_TASK(result), error);
+}
+
 void fl_engine_set_platform_message_handler(
     FlEngine* self,
     FlEnginePlatformMessageHandler handler,

engine/src/flutter/shell/platform/linux/fl_engine_private.h

@@ -81,6 +81,18 @@ typedef void (*FlEngineOnPreEngineRestartHandler)(FlEngine* engine,
  */
 FlEngine* fl_engine_new(FlDartProject* project, FlRenderer* renderer);
 
+/**
+ * fl_engine_start:
+ * @engine: an #FlEngine.
+ * @error: (allow-none): #GError location to store the error occurring, or %NULL
+ * to ignore.
+ *
+ * Starts the Flutter engine.
+ *
+ * Returns: %TRUE on success.
+ */
+gboolean fl_engine_start(FlEngine* engine, GError** error);
+
 /**
  * fl_engine_get_embedder_api:
  * @engine: an #FlEngine.
@@ -91,6 +103,74 @@ FlEngine* fl_engine_new(FlDartProject* project, FlRenderer* renderer);
  */
 FlutterEngineProcTable* fl_engine_get_embedder_api(FlEngine* engine);
 
+/**
+ * fl_engine_add_view:
+ * @engine: an #FlEngine.
+ * @width: width of view in pixels.
+ * @height: height of view in pixels.
+ * @pixel_ratio: scale factor for view.
+ * @cancellable: (allow-none): a #GCancellable or %NULL.
+ * @callback: (scope async): a #GAsyncReadyCallback to call when the view is
+ * added.
+ * @user_data: (closure): user data to pass to @callback.
+ *
+ * Asynchronously add a new view.
+ */
+void fl_engine_add_view(FlEngine* engine,
+                        size_t width,
+                        size_t height,
+                        double pixel_ratio,
+                        GCancellable* cancellable,
+                        GAsyncReadyCallback callback,
+                        gpointer user_data);
+
+/**
+ * fl_engine_add_view_finish:
+ * @engine: an #FlEngine.
+ * @result: a #GAsyncResult.
+ * @error: (allow-none): #GError location to store the error occurring, or %NULL
+ * to ignore.
+ *
+ * Completes request started with fl_engine_add_view().
+ *
+ * Returns: the newly added view ID or 0 on error.
+ */
+FlutterViewId fl_engine_add_view_finish(FlEngine* engine,
+                                        GAsyncResult* result,
+                                        GError** error);
+
+/**
+ * fl_engine_remove_view:
+ * @engine: an #FlEngine.
+ * @view_id: ID to remove.
+ * @cancellable: (allow-none): a #GCancellable or %NULL.
+ * @callback: (scope async): a #GAsyncReadyCallback to call when the view is
+ * added.
+ * @user_data: (closure): user data to pass to @callback.
+ *
+ * Removes a view previously added with fl_engine_add_view().
+ */
+void fl_engine_remove_view(FlEngine* engine,
+                           FlutterViewId view_id,
+                           GCancellable* cancellable,
+                           GAsyncReadyCallback callback,
+                           gpointer user_data);
+
+/**
+ * fl_engine_remove_view_finish:
+ * @engine: an #FlEngine.
+ * @result: a #GAsyncResult.
+ * @error: (allow-none): #GError location to store the error occurring, or %NULL
+ * to ignore.
+ *
+ * Completes request started with fl_engine_remove_view().
+ *
+ * Returns: TRUE on succcess.
+ */
+gboolean fl_engine_remove_view_finish(FlEngine* engine,
+                                      GAsyncResult* result,
+                                      GError** error);
+
 /**
  * fl_engine_set_platform_message_handler:
  * @engine: an #FlEngine.
@@ -143,18 +223,6 @@ void fl_engine_set_on_pre_engine_restart_handler(
     gpointer user_data,
     GDestroyNotify destroy_notify);
 
-/**
- * fl_engine_start:
- * @engine: an #FlEngine.
- * @error: (allow-none): #GError location to store the error occurring, or %NULL
- * to ignore.
- *
- * Starts the Flutter engine.
- *
- * Returns: %TRUE on success.
- */
-gboolean fl_engine_start(FlEngine* engine, GError** error);
-
 /**
  * fl_engine_send_window_metrics_event:
  * @engine: an #FlEngine.

engine/src/flutter/shell/platform/linux/fl_engine_test.cc

@@ -425,6 +425,215 @@ TEST(FlEngineTest, SwitchesEmpty) {
   EXPECT_EQ(switches->len, 0U);
 }
 
+static void add_view_cb(GObject* object,
+                        GAsyncResult* result,
+                        gpointer user_data) {
+  g_autoptr(GError) error = nullptr;
+  FlutterViewId view_id =
+      fl_engine_add_view_finish(FL_ENGINE(object), result, &error);
+  EXPECT_GT(view_id, 0);
+  EXPECT_EQ(error, nullptr);
+
+  g_main_loop_quit(static_cast<GMainLoop*>(user_data));
+}
+
+TEST(FlEngineTest, AddView) {
+  g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, 0);
+
+  g_autoptr(FlEngine) engine = make_mock_engine();
+  FlutterEngineProcTable* embedder_api = fl_engine_get_embedder_api(engine);
+
+  bool called = false;
+  embedder_api->AddView = MOCK_ENGINE_PROC(
+      AddView, ([&called](auto engine, const FlutterAddViewInfo* info) {
+        called = true;
+        EXPECT_EQ(info->view_metrics->width, 123u);
+        EXPECT_EQ(info->view_metrics->height, 456u);
+        EXPECT_EQ(info->view_metrics->pixel_ratio, 2.0);
+
+        FlutterAddViewResult result;
+        result.struct_size = sizeof(FlutterAddViewResult);
+        result.added = true;
+        result.user_data = info->user_data;
+        info->add_view_callback(&result);
+
+        return kSuccess;
+      }));
+
+  fl_engine_add_view(engine, 123, 456, 2.0, nullptr, add_view_cb, loop);
+  EXPECT_TRUE(called);
+
+  // Blocks here until add_view_cb is called.
+  g_main_loop_run(loop);
+}
+
+static void add_view_error_cb(GObject* object,
+                              GAsyncResult* result,
+                              gpointer user_data) {
+  g_autoptr(GError) error = nullptr;
+  FlutterViewId view_id =
+      fl_engine_add_view_finish(FL_ENGINE(object), result, &error);
+  EXPECT_EQ(view_id, 0);
+  EXPECT_NE(error, nullptr);
+
+  g_main_loop_quit(static_cast<GMainLoop*>(user_data));
+}
+
+TEST(FlEngineTest, AddViewError) {
+  g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, 0);
+
+  g_autoptr(FlEngine) engine = make_mock_engine();
+  FlutterEngineProcTable* embedder_api = fl_engine_get_embedder_api(engine);
+
+  embedder_api->AddView = MOCK_ENGINE_PROC(
+      AddView, ([](auto engine, const FlutterAddViewInfo* info) {
+        FlutterAddViewResult result;
+        result.struct_size = sizeof(FlutterAddViewResult);
+        result.added = false;
+        result.user_data = info->user_data;
+        info->add_view_callback(&result);
+
+        return kSuccess;
+      }));
+
+  fl_engine_add_view(engine, 123, 456, 2.0, nullptr, add_view_error_cb, loop);
+
+  // Blocks here until add_view_error_cb is called.
+  g_main_loop_run(loop);
+}
+
+static void add_view_engine_error_cb(GObject* object,
+                                     GAsyncResult* result,
+                                     gpointer user_data) {
+  g_autoptr(GError) error = nullptr;
+  FlutterViewId view_id =
+      fl_engine_add_view_finish(FL_ENGINE(object), result, &error);
+  EXPECT_EQ(view_id, 0);
+  EXPECT_NE(error, nullptr);
+
+  g_main_loop_quit(static_cast<GMainLoop*>(user_data));
+}
+
+TEST(FlEngineTest, AddViewEngineError) {
+  g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, 0);
+
+  g_autoptr(FlEngine) engine = make_mock_engine();
+  FlutterEngineProcTable* embedder_api = fl_engine_get_embedder_api(engine);
+
+  embedder_api->AddView = MOCK_ENGINE_PROC(
+      AddView, ([](auto engine, const FlutterAddViewInfo* info) {
+        return kInvalidArguments;
+      }));
+
+  fl_engine_add_view(engine, 123, 456, 2.0, nullptr, add_view_engine_error_cb,
+                     loop);
+
+  // Blocks here until remove_view_engine_error_cb is called.
+  g_main_loop_run(loop);
+}
+
+static void remove_view_cb(GObject* object,
+                           GAsyncResult* result,
+                           gpointer user_data) {
+  g_autoptr(GError) error = nullptr;
+  gboolean r = fl_engine_remove_view_finish(FL_ENGINE(object), result, &error);
+  EXPECT_TRUE(r);
+  EXPECT_EQ(error, nullptr);
+
+  g_main_loop_quit(static_cast<GMainLoop*>(user_data));
+}
+
+TEST(FlEngineTest, RemoveView) {
+  g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, 0);
+
+  g_autoptr(FlEngine) engine = make_mock_engine();
+  FlutterEngineProcTable* embedder_api = fl_engine_get_embedder_api(engine);
+
+  bool called = false;
+  embedder_api->RemoveView = MOCK_ENGINE_PROC(
+      RemoveView, ([&called](auto engine, const FlutterRemoveViewInfo* info) {
+        called = true;
+        EXPECT_EQ(info->view_id, 123);
+
+        FlutterRemoveViewResult result;
+        result.struct_size = sizeof(FlutterRemoveViewResult);
+        result.removed = true;
+        result.user_data = info->user_data;
+        info->remove_view_callback(&result);
+
+        return kSuccess;
+      }));
+
+  fl_engine_remove_view(engine, 123, nullptr, remove_view_cb, loop);
+  EXPECT_TRUE(called);
+
+  // Blocks here until remove_view_cb is called.
+  g_main_loop_run(loop);
+}
+
+static void remove_view_error_cb(GObject* object,
+                                 GAsyncResult* result,
+                                 gpointer user_data) {
+  g_autoptr(GError) error = nullptr;
+  gboolean r = fl_engine_remove_view_finish(FL_ENGINE(object), result, &error);
+  EXPECT_FALSE(r);
+  EXPECT_NE(error, nullptr);
+
+  g_main_loop_quit(static_cast<GMainLoop*>(user_data));
+}
+
+TEST(FlEngineTest, RemoveViewError) {
+  g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, 0);
+
+  g_autoptr(FlEngine) engine = make_mock_engine();
+  FlutterEngineProcTable* embedder_api = fl_engine_get_embedder_api(engine);
+
+  embedder_api->RemoveView = MOCK_ENGINE_PROC(
+      RemoveView, ([](auto engine, const FlutterRemoveViewInfo* info) {
+        FlutterRemoveViewResult result;
+        result.struct_size = sizeof(FlutterRemoveViewResult);
+        result.removed = false;
+        result.user_data = info->user_data;
+        info->remove_view_callback(&result);
+
+        return kSuccess;
+      }));
+
+  fl_engine_remove_view(engine, 123, nullptr, remove_view_error_cb, loop);
+
+  // Blocks here until remove_view_error_cb is called.
+  g_main_loop_run(loop);
+}
+
+static void remove_view_engine_error_cb(GObject* object,
+                                        GAsyncResult* result,
+                                        gpointer user_data) {
+  g_autoptr(GError) error = nullptr;
+  gboolean r = fl_engine_remove_view_finish(FL_ENGINE(object), result, &error);
+  EXPECT_FALSE(r);
+  EXPECT_NE(error, nullptr);
+
+  g_main_loop_quit(static_cast<GMainLoop*>(user_data));
+}
+
+TEST(FlEngineTest, RemoveViewEngineError) {
+  g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, 0);
+
+  g_autoptr(FlEngine) engine = make_mock_engine();
+  FlutterEngineProcTable* embedder_api = fl_engine_get_embedder_api(engine);
+
+  embedder_api->RemoveView = MOCK_ENGINE_PROC(
+      RemoveView, ([](auto engine, const FlutterRemoveViewInfo* info) {
+        return kInvalidArguments;
+      }));
+
+  fl_engine_remove_view(engine, 123, nullptr, remove_view_engine_error_cb,
+                        loop);
+
+  // Blocks here until remove_view_engine_error_cb is called.
+  g_main_loop_run(loop);
+}
+
 #ifndef FLUTTER_RELEASE
 TEST(FlEngineTest, Switches) {
   g_autoptr(FlEngine) engine = make_mock_engine();