Implement smooth resizing for Linux (flutter#25884)

Author: knopp

ci/licenses_golden/licenses_flutter

@@ -1480,6 +1480,8 @@ FILE: ../../../flutter/shell/platform/linux/fl_standard_method_codec.cc
 FILE: ../../../flutter/shell/platform/linux/fl_standard_method_codec_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_string_codec.cc
 FILE: ../../../flutter/shell/platform/linux/fl_string_codec_test.cc
+FILE: ../../../flutter/shell/platform/linux/fl_task_runner.cc
+FILE: ../../../flutter/shell/platform/linux/fl_task_runner.h
 FILE: ../../../flutter/shell/platform/linux/fl_text_input_plugin.cc
 FILE: ../../../flutter/shell/platform/linux/fl_text_input_plugin.h
 FILE: ../../../flutter/shell/platform/linux/fl_value.cc

shell/platform/linux/BUILD.gn

@@ -114,6 +114,8 @@ source_set("flutter_linux_sources") {
     "fl_standard_message_codec.cc",
     "fl_standard_method_codec.cc",
     "fl_string_codec.cc",
+    "fl_task_runner.cc",
+    "fl_task_runner.h",
     "fl_text_input_plugin.cc",
     "fl_value.cc",
     "fl_view.cc",

shell/platform/linux/fl_engine.cc

@@ -17,8 +17,6 @@
 #include "flutter/shell/platform/linux/fl_settings_plugin.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_plugin_registry.h"
 
-static constexpr int kMicrosecondsPerNanosecond = 1000;
-
 // Unique number associated with platform tasks.
 static constexpr size_t kPlatformTaskRunnerIdentifier = 1;
 
@@ -32,6 +30,7 @@ struct _FlEngine {
   FlRenderer* renderer;
   FlBinaryMessenger* binary_messenger;
   FlSettingsPlugin* settings_plugin;
+  FlTaskRunner* task_runner;
   FlutterEngineAOTData aot_data;
   FLUTTER_API_SYMBOL(FlutterEngine) engine;
   FlutterEngineProcTable embedder_api;
@@ -59,13 +58,6 @@ G_DEFINE_TYPE_WITH_CODE(
     G_IMPLEMENT_INTERFACE(fl_plugin_registry_get_type(),
                           fl_engine_plugin_registry_iface_init))
 
-// Subclass of GSource that integrates Flutter tasks into the GLib main loop.
-typedef struct {
-  GSource parent;
-  FlEngine* engine;
-  FlutterTask task;
-} FlutterSource;
-
 // Parse a locale into its components.
 static void parse_locale(const gchar* locale,
                          gchar** language,
@@ -143,40 +135,6 @@ static void setup_locales(FlEngine* self) {
   }
 }
 
-// Callback to run a Flutter task in the GLib main loop.
-static gboolean flutter_source_dispatch(GSource* source,
-                                        GSourceFunc callback,
-                                        gpointer user_data) {
-  FlutterSource* fl_source = reinterpret_cast<FlutterSource*>(source);
-  FlEngine* self = fl_source->engine;
-
-  FlutterEngineResult result =
-      self->embedder_api.RunTask(self->engine, &fl_source->task);
-  if (result != kSuccess) {
-    g_warning("Failed to run Flutter task\n");
-  }
-
-  return G_SOURCE_REMOVE;
-}
-
-// Called when the engine is disposed.
-static void engine_weak_notify_cb(gpointer user_data,
-                                  GObject* where_the_object_was) {
-  FlutterSource* source = reinterpret_cast<FlutterSource*>(user_data);
-  source->engine = nullptr;
-  g_source_destroy(reinterpret_cast<GSource*>(source));
-}
-
-// Called when a flutter source completes.
-static void flutter_source_finalize(GSource* source) {
-  FlutterSource* fl_source = reinterpret_cast<FlutterSource*>(source);
-  if (fl_source->engine != nullptr) {
-    g_object_weak_unref(G_OBJECT(fl_source->engine), engine_weak_notify_cb,
-                        fl_source);
-    fl_source->engine = nullptr;
-  }
-}
-
 // Called when engine needs a backing store for a specific #FlutterLayer.
 static bool compositor_create_backing_store_callback(
     const FlutterBackingStoreConfig* config,
@@ -204,16 +162,6 @@ static bool compositor_present_layers_callback(const FlutterLayer** layers,
                                     layers_count);
 }
 
-// Table of functions for Flutter GLib main loop integration.
-static GSourceFuncs flutter_source_funcs = {
-    nullptr,                  // prepare
-    nullptr,                  // check
-    flutter_source_dispatch,  // dispatch
-    flutter_source_finalize,  // finalize
-    nullptr,
-    nullptr  // Internal usage
-};
-
 // Flutter engine rendering callbacks.
 
 static void* fl_engine_gl_proc_resolver(void* user_data, const char* name) {
@@ -278,15 +226,7 @@ static void fl_engine_post_task(FlutterTask task,
                                 void* user_data) {
   FlEngine* self = static_cast<FlEngine*>(user_data);
 
-  g_autoptr(GSource) source =
-      g_source_new(&flutter_source_funcs, sizeof(FlutterSource));
-  FlutterSource* fl_source = reinterpret_cast<FlutterSource*>(source);
-  fl_source->engine = self;
-  g_object_weak_ref(G_OBJECT(self), engine_weak_notify_cb, fl_source);
-  fl_source->task = task;
-  g_source_set_ready_time(source,
-                          target_time_nanos / kMicrosecondsPerNanosecond);
-  g_source_attach(source, nullptr);
+  fl_task_runner_post_task(self->task_runner, task, target_time_nanos);
 }
 
 // Called when a platform message is received from the engine.
@@ -361,6 +301,7 @@ static void fl_engine_dispose(GObject* object) {
   g_clear_object(&self->renderer);
   g_clear_object(&self->binary_messenger);
   g_clear_object(&self->settings_plugin);
+  g_clear_object(&self->task_runner);
 
   if (self->platform_message_handler_destroy_notify) {
     self->platform_message_handler_destroy_notify(
@@ -410,6 +351,8 @@ G_MODULE_EXPORT FlEngine* fl_engine_new_headless(FlDartProject* project) {
 gboolean fl_engine_start(FlEngine* self, GError** error) {
   g_return_val_if_fail(FL_IS_ENGINE(self), FALSE);
 
+  self->task_runner = fl_task_runner_new(self);
+
   FlutterRendererConfig config = {};
   config.type = kOpenGL;
   config.open_gl.struct_size = sizeof(FlutterOpenGLRendererConfig);
@@ -722,3 +665,13 @@ G_MODULE_EXPORT FlBinaryMessenger* fl_engine_get_binary_messenger(
   g_return_val_if_fail(FL_IS_ENGINE(self), nullptr);
   return self->binary_messenger;
 }
+
+FlTaskRunner* fl_engine_get_task_runner(FlEngine* self) {
+  g_return_val_if_fail(FL_IS_ENGINE(self), nullptr);
+  return self->task_runner;
+}
+
+void fl_engine_execute_task(FlEngine* self, FlutterTask* task) {
+  g_return_if_fail(FL_IS_ENGINE(self));
+  self->embedder_api.RunTask(self->engine, task);
+}

shell/platform/linux/fl_engine_private.h

@@ -9,6 +9,7 @@
 
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/linux/fl_renderer.h"
+#include "flutter/shell/platform/linux/fl_task_runner.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_dart_project.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_engine.h"
 
@@ -226,6 +227,24 @@ GBytes* fl_engine_send_platform_message_finish(FlEngine* engine,
                                                GAsyncResult* result,
                                                GError** error);
 
+/**
+ * fl_engine_get_task_runner:
+ * @engine: an #FlEngine.
+ * @result: a #FlTaskRunner.
+ *
+ * Returns: task runner responsible for scheduling Flutter tasks.
+ */
+FlTaskRunner* fl_engine_get_task_runner(FlEngine* engine);
+
+/**
+ * fl_engine_execute_task:
+ * @engine: an #FlEngine.
+ * @task: a #FlutterTask to execute.
+ *
+ * Executes given Flutter task.
+ */
+void fl_engine_execute_task(FlEngine* engine, FlutterTask* task);
+
 G_END_DECLS
 
 #endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_ENGINE_PRIVATE_H_

shell/platform/linux/fl_renderer.cc

@@ -9,19 +9,50 @@
 
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/linux/fl_backing_store_provider.h"
+#include "flutter/shell/platform/linux/fl_engine_private.h"
 
 G_DEFINE_QUARK(fl_renderer_error_quark, fl_renderer_error)
 
 typedef struct {
   FlView* view;
 
+  // target dimension for resizing
+  int target_width;
+  int target_height;
+
+  // whether the renderer waits for frame render
+  bool blocking_main_thread;
+
+  // true if frame was completed; resizing is not synchronized until first frame
+  // was rendered
+  bool had_first_frame;
+
   GdkGLContext* main_context;
   GdkGLContext* resource_context;
 } FlRendererPrivate;
 
 G_DEFINE_TYPE_WITH_PRIVATE(FlRenderer, fl_renderer, G_TYPE_OBJECT)
 
-static void fl_renderer_class_init(FlRendererClass* klass) {}
+static void fl_renderer_unblock_main_thread(FlRenderer* self) {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+  if (priv->blocking_main_thread) {
+    priv->blocking_main_thread = false;
+
+    FlTaskRunner* runner =
+        fl_engine_get_task_runner(fl_view_get_engine(priv->view));
+    fl_task_runner_release_main_thread(runner);
+  }
+}
+
+static void fl_renderer_dispose(GObject* self) {
+  fl_renderer_unblock_main_thread(FL_RENDERER(self));
+  G_OBJECT_CLASS(fl_renderer_parent_class)->dispose(self);
+}
+
+static void fl_renderer_class_init(FlRendererClass* klass) {
+  G_OBJECT_CLASS(klass)->dispose = fl_renderer_dispose;
+}
 
 static void fl_renderer_init(FlRenderer* self) {}
 
@@ -109,9 +140,42 @@ gboolean fl_renderer_collect_backing_store(
                                                             backing_store);
 }
 
+void fl_renderer_wait_for_frame(FlRenderer* self,
+                                int target_width,
+                                int target_height) {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+
+  priv->target_width = target_width;
+  priv->target_height = target_height;
+
+  if (priv->had_first_frame && !priv->blocking_main_thread) {
+    priv->blocking_main_thread = true;
+    FlTaskRunner* runner =
+        fl_engine_get_task_runner(fl_view_get_engine(priv->view));
+    fl_task_runner_block_main_thread(runner);
+  }
+}
+
 gboolean fl_renderer_present_layers(FlRenderer* self,
                                     const FlutterLayer** layers,
                                     size_t layers_count) {
+  FlRendererPrivate* priv = reinterpret_cast<FlRendererPrivate*>(
+      fl_renderer_get_instance_private(self));
+
+  // 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);
+
   return FL_RENDERER_GET_CLASS(self)->present_layers(self, layers,
                                                      layers_count);
 }

shell/platform/linux/fl_renderer.h

@@ -242,6 +242,20 @@ gboolean fl_renderer_present_layers(FlRenderer* renderer,
                                     const FlutterLayer** layers,
                                     size_t layers_count);
 
+/**
+ * fl_renderer_wait_for_frame:
+ * @renderer: an #FlRenderer.
+ * @target_width: width of frame being waited for
+ * @target_height: height of frame being waited for
+ *
+ * Holds the thread until frame with requested dimensions is presented.
+ * While waiting for frame Flutter platform and raster tasks are being
+ * processed.
+ */
+void fl_renderer_wait_for_frame(FlRenderer* renderer,
+                                int target_width,
+                                int target_height);
+
 G_END_DECLS
 
 #endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_RENDERER_H_