Add windowing channel support to Linux embedder (#163180)

Implement flutter/windowing for the Linux embedder.

Author: robert-ancell

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -43869,6 +43869,11 @@ ORIGIN: ../../../flutter/shell/platform/linux/fl_view_test.cc + ../../../flutter
 ORIGIN: ../../../flutter/shell/platform/linux/fl_window_state_monitor.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/linux/fl_window_state_monitor.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/linux/fl_window_state_monitor_test.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/linux/fl_windowing_channel.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/linux/fl_windowing_channel.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/linux/fl_windowing_handler.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/linux/fl_windowing_handler.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/linux/fl_windowing_handler_test.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/linux/key_mapping.g.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/linux/key_mapping.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/linux/key_mapping_test.cc + ../../../flutter/LICENSE
@@ -46813,6 +46818,11 @@ FILE: ../../../flutter/shell/platform/linux/fl_view_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_window_state_monitor.cc
 FILE: ../../../flutter/shell/platform/linux/fl_window_state_monitor.h
 FILE: ../../../flutter/shell/platform/linux/fl_window_state_monitor_test.cc
+FILE: ../../../flutter/shell/platform/linux/fl_windowing_channel.cc
+FILE: ../../../flutter/shell/platform/linux/fl_windowing_channel.h
+FILE: ../../../flutter/shell/platform/linux/fl_windowing_handler.cc
+FILE: ../../../flutter/shell/platform/linux/fl_windowing_handler.h
+FILE: ../../../flutter/shell/platform/linux/fl_windowing_handler_test.cc
 FILE: ../../../flutter/shell/platform/linux/key_mapping.g.cc
 FILE: ../../../flutter/shell/platform/linux/key_mapping.h
 FILE: ../../../flutter/shell/platform/linux/key_mapping_test.cc

engine/src/flutter/shell/platform/linux/.clang-tidy

@@ -1,8 +1,10 @@
 InheritParentConfig: true
 
 # EnumCastOutOfRange warns about some common usages of GTK macros
+# Malloc generates false positives with g_autofree usage.
 Checks: >-
-  -clang-analyzer-optin.core.EnumCastOutOfRange
+  -clang-analyzer-optin.core.EnumCastOutOfRange,
+  -clang-analyzer-unix.Malloc
 
 CheckOptions:
   - key: readability-identifier-naming.EnumConstantCase

engine/src/flutter/shell/platform/linux/BUILD.gn

@@ -158,6 +158,8 @@ source_set("flutter_linux_sources") {
     "fl_view.cc",
     "fl_view_accessible.cc",
     "fl_window_state_monitor.cc",
+    "fl_windowing_channel.cc",
+    "fl_windowing_handler.cc",
     "key_mapping.g.cc",
   ]
 
@@ -248,6 +250,7 @@ executable("flutter_linux_unittests") {
     "fl_view_accessible_test.cc",
     "fl_view_test.cc",
     "fl_window_state_monitor_test.cc",
+    "fl_windowing_handler_test.cc",
     "key_mapping_test.cc",
     "testing/fl_mock_binary_messenger.cc",
     "testing/fl_test.cc",

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

@@ -9,6 +9,7 @@
 #include <gdk/gdkx.h>
 #endif
 
+#include "flutter/shell/platform/linux/fl_engine_private.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_dart_project.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_plugin_registry.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_view.h"
@@ -31,6 +32,15 @@ G_DEFINE_TYPE_WITH_CODE(FlApplication,
                         GTK_TYPE_APPLICATION,
                         G_ADD_PRIVATE(FlApplication))
 
+// Called when the platform creates a window.
+static GtkWindow* create_window_cb(FlApplication* self, FlView* view) {
+  GtkWindow* window;
+  g_signal_emit(self, fl_application_signals[SIGNAL_CREATE_WINDOW], 0, view,
+                &window);
+
+  return window;
+}
+
 // Called when the first frame is received.
 static void first_frame_cb(FlApplication* self, FlView* view) {
   GtkWidget* window = gtk_widget_get_toplevel(GTK_WIDGET(view));
@@ -94,6 +104,11 @@ static void fl_application_activate(GApplication* application) {
                            self);
   gtk_widget_show(GTK_WIDGET(view));
 
+  FlWindowingHandler* windowing_handler =
+      fl_engine_get_windowing_handler(fl_view_get_engine(view));
+  g_signal_connect_swapped(windowing_handler, "create_window",
+                           G_CALLBACK(create_window_cb), self);
+
   GtkWindow* window;
   g_signal_emit(self, fl_application_signals[SIGNAL_CREATE_WINDOW], 0, view,
                 &window);

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

@@ -24,6 +24,7 @@
 #include "flutter/shell/platform/linux/fl_settings_handler.h"
 #include "flutter/shell/platform/linux/fl_texture_gl_private.h"
 #include "flutter/shell/platform/linux/fl_texture_registrar_private.h"
+#include "flutter/shell/platform/linux/fl_windowing_handler.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_plugin_registry.h"
 
 // Unique number associated with platform tasks.
@@ -58,6 +59,9 @@ struct _FlEngine {
   // Implements the flutter/platform channel.
   FlPlatformHandler* platform_handler;
 
+  // Implements the flutter/windowing channel.
+  FlWindowingHandler* windowing_handler;
+
   // Process keyboard events.
   FlKeyboardManager* keyboard_manager;
 
@@ -487,6 +491,7 @@ static void fl_engine_dispose(GObject* object) {
   g_clear_object(&self->binary_messenger);
   g_clear_object(&self->settings_handler);
   g_clear_object(&self->platform_handler);
+  g_clear_object(&self->windowing_handler);
   g_clear_object(&self->keyboard_manager);
   g_clear_object(&self->text_input_handler);
   g_clear_object(&self->keyboard_handler);
@@ -702,6 +707,7 @@ gboolean fl_engine_start(FlEngine* self, GError** error) {
   fl_settings_handler_start(self->settings_handler, settings);
 
   self->platform_handler = fl_platform_handler_new(self->binary_messenger);
+  self->windowing_handler = fl_windowing_handler_new(self);
 
   setup_keyboard(self);
 
@@ -1295,6 +1301,11 @@ void fl_engine_request_app_exit(FlEngine* self) {
   fl_platform_handler_request_app_exit(self->platform_handler);
 }
 
+FlWindowingHandler* fl_engine_get_windowing_handler(FlEngine* self) {
+  g_return_val_if_fail(FL_IS_ENGINE(self), nullptr);
+  return self->windowing_handler;
+}
+
 FlKeyboardManager* fl_engine_get_keyboard_manager(FlEngine* self) {
   g_return_val_if_fail(FL_IS_ENGINE(self), nullptr);
   return self->keyboard_manager;

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

@@ -14,6 +14,7 @@
 #include "flutter/shell/platform/linux/fl_renderer.h"
 #include "flutter/shell/platform/linux/fl_task_runner.h"
 #include "flutter/shell/platform/linux/fl_text_input_handler.h"
+#include "flutter/shell/platform/linux/fl_windowing_handler.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_dart_project.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_engine.h"
 
@@ -576,13 +577,23 @@ void fl_engine_update_accessibility_features(FlEngine* engine, int32_t flags);
  */
 void fl_engine_request_app_exit(FlEngine* engine);
 
+/**
+ * fl_engine_get_windowing_handler:
+ * @engine: an #FlEngine.
+ *
+ * Gets the windowing handler used by this engine.
+ *
+ * Returns: an #FlWindowingHandler.
+ */
+FlWindowingHandler* fl_engine_get_windowing_handler(FlEngine* engine);
+
 /**
  * fl_engine_get_keyboard_manager:
  * @engine: an #FlEngine.
  *
  * Gets the keyboard manager used by this engine.
  *
- * Returns: a #FlKeyboardManager.
+ * Returns: an #FlKeyboardManager.
  */
 FlKeyboardManager* fl_engine_get_keyboard_manager(FlEngine* engine);
 
@@ -592,7 +603,7 @@ FlKeyboardManager* fl_engine_get_keyboard_manager(FlEngine* engine);
  *
  * Gets the text input handler used by this engine.
  *
- * Returns: a #FlTextInputHandler.
+ * Returns: an #FlTextInputHandler.
  */
 FlTextInputHandler* fl_engine_get_text_input_handler(FlEngine* engine);
 
@@ -602,7 +613,7 @@ FlTextInputHandler* fl_engine_get_text_input_handler(FlEngine* engine);
  *
  * Gets the mouse cursor handler used by this engine.
  *
- * Returns: a #FlMouseCursorHandler.
+ * Returns: an #FlMouseCursorHandler.
  */
 FlMouseCursorHandler* fl_engine_get_mouse_cursor_handler(FlEngine* engine);
 

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

@@ -765,7 +765,7 @@ G_MODULE_EXPORT FlView* fl_view_new(FlDartProject* project) {
   fl_engine_set_update_semantics_handler(self->engine, update_semantics_cb,
                                          self, nullptr);
   self->on_pre_engine_restart_cb_id =
-      g_signal_connect_swapped(engine, "on-pre-engine-restart",
+      g_signal_connect_swapped(self->engine, "on-pre-engine-restart",
                                G_CALLBACK(on_pre_engine_restart_cb), self);
 
   g_signal_connect_swapped(self->gl_area, "create-context",
@@ -790,7 +790,7 @@ G_MODULE_EXPORT FlView* fl_view_new_for_engine(FlEngine* engine) {
       g_signal_connect_swapped(engine, "on-pre-engine-restart",
                                G_CALLBACK(on_pre_engine_restart_cb), self);
 
-  self->view_id = fl_engine_add_view(self->engine, 1, 1, 1.0, self->cancellable,
+  self->view_id = fl_engine_add_view(engine, 1, 1, 1.0, self->cancellable,
                                      view_added_cb, self);
   fl_renderer_add_renderable(FL_RENDERER(self->renderer), self->view_id,
                              FL_RENDERABLE(self));

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

@@ -7,6 +7,7 @@
 #include "flutter/shell/platform/linux/fl_engine_private.h"
 #include "flutter/shell/platform/linux/testing/fl_test.h"
 #include "flutter/shell/platform/linux/testing/fl_test_gtk_logs.h"
+#include "flutter/shell/platform/linux/testing/mock_window.h"
 
 #include "gtest/gtest.h"
 
@@ -136,8 +137,8 @@ TEST(FlViewTest, ViewDestroy) {
   int64_t implicit_view_id = fl_view_get_id(implicit_view);
   int64_t secondary_view_id = fl_view_get_id(secondary_view);
 
-  gtk_widget_destroy(GTK_WIDGET(secondary_view));
-  gtk_widget_destroy(GTK_WIDGET(implicit_view));
+  fl_gtk_widget_destroy(GTK_WIDGET(secondary_view));
+  fl_gtk_widget_destroy(GTK_WIDGET(implicit_view));
 
   EXPECT_EQ(removed_views->len, 2u);
   EXPECT_EQ(GPOINTER_TO_INT(g_ptr_array_index(removed_views, 0)),
@@ -165,6 +166,6 @@ TEST(FlViewTest, ViewDestroyError) {
 
   FlView* secondary_view = fl_view_new_for_engine(engine);
 
-  gtk_widget_destroy(GTK_WIDGET(secondary_view));
-  gtk_widget_destroy(GTK_WIDGET(implicit_view));
+  fl_gtk_widget_destroy(GTK_WIDGET(secondary_view));
+  fl_gtk_widget_destroy(GTK_WIDGET(implicit_view));
 }