Fix warnings on startup about display monitor (flutter#162653)

Create the display monitor at initialization, not engine start.
Handle case where the window is not visible and the monitor can't be
determined.
Don't leak the monitor when the engine is disposed.

Author: robert-ancell

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

@@ -467,6 +467,7 @@ static void fl_engine_dispose(GObject* object) {
   fl_texture_registrar_shutdown(self->texture_registrar);
 
   g_clear_object(&self->project);
+  g_clear_object(&self->display_monitor);
   g_clear_object(&self->renderer);
   g_clear_object(&self->texture_registrar);
   g_clear_object(&self->binary_messenger);
@@ -519,27 +520,46 @@ static void fl_engine_init(FlEngine* self) {
     g_warning("Failed get get engine function pointers");
   }
 
+  self->display_monitor =
+      fl_display_monitor_new(self, gdk_display_get_default());
+  self->task_runner = fl_task_runner_new(self);
+
   // Implicit view is 0, so start at 1.
   self->next_view_id = 1;
 
   self->texture_registrar = fl_texture_registrar_new(self);
 }
 
-FlEngine* fl_engine_new_with_renderer(FlDartProject* project,
-                                      FlRenderer* renderer) {
+static FlEngine* fl_engine_new_full(FlDartProject* project,
+                                    FlRenderer* renderer,
+                                    FlBinaryMessenger* binary_messenger) {
   g_return_val_if_fail(FL_IS_DART_PROJECT(project), nullptr);
   g_return_val_if_fail(FL_IS_RENDERER(renderer), nullptr);
 
   FlEngine* self = FL_ENGINE(g_object_new(fl_engine_get_type(), nullptr));
   self->project = FL_DART_PROJECT(g_object_ref(project));
   self->renderer = FL_RENDERER(g_object_ref(renderer));
-  self->binary_messenger = fl_binary_messenger_new(self);
-
+  if (binary_messenger != nullptr) {
+    self->binary_messenger =
+        FL_BINARY_MESSENGER(g_object_ref(binary_messenger));
+  } else {
+    self->binary_messenger = fl_binary_messenger_new(self);
+  }
+  self->keyboard_manager = fl_keyboard_manager_new(self);
+  self->mouse_cursor_handler =
+      fl_mouse_cursor_handler_new(self->binary_messenger);
   fl_renderer_set_engine(self->renderer, self);
 
   return self;
 }
 
+FlEngine* fl_engine_new_with_renderer(FlDartProject* project,
+                                      FlRenderer* renderer) {
+  g_return_val_if_fail(FL_IS_DART_PROJECT(project), nullptr);
+  g_return_val_if_fail(FL_IS_RENDERER(renderer), nullptr);
+  return fl_engine_new_full(project, renderer, nullptr);
+}
+
 G_MODULE_EXPORT FlEngine* fl_engine_new(FlDartProject* project) {
   g_autoptr(FlRendererGdk) renderer = fl_renderer_gdk_new();
   return fl_engine_new_with_renderer(project, FL_RENDERER(renderer));
@@ -548,10 +568,8 @@ G_MODULE_EXPORT FlEngine* fl_engine_new(FlDartProject* project) {
 FlEngine* fl_engine_new_with_binary_messenger(
     FlBinaryMessenger* binary_messenger) {
   g_autoptr(FlDartProject) project = fl_dart_project_new();
-  FlEngine* self = fl_engine_new(project);
-  g_object_unref(self->binary_messenger);
-  self->binary_messenger = FL_BINARY_MESSENGER(g_object_ref(binary_messenger));
-  return self;
+  g_autoptr(FlRendererGdk) renderer = fl_renderer_gdk_new();
+  return fl_engine_new_full(project, FL_RENDERER(renderer), binary_messenger);
 }
 
 G_MODULE_EXPORT FlEngine* fl_engine_new_headless(FlDartProject* project) {
@@ -572,8 +590,6 @@ FlDisplayMonitor* fl_engine_get_display_monitor(FlEngine* self) {
 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);
@@ -671,8 +687,6 @@ 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->mouse_cursor_handler =
-      fl_mouse_cursor_handler_new(self->binary_messenger);
 
   setup_keyboard(self);
 
@@ -681,8 +695,6 @@ gboolean fl_engine_start(FlEngine* self, GError** error) {
     g_warning("Failed to enable accessibility features on Flutter engine");
   }
 
-  self->display_monitor =
-      fl_display_monitor_new(self, gdk_display_get_default());
   fl_display_monitor_start(self->display_monitor);
 
   return TRUE;

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

@@ -946,4 +946,17 @@ TEST(FlEngineTest, SendKeyEventError) {
   EXPECT_TRUE(called);
 }
 
+TEST(FlEngineTest, ChildObjects) {
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  g_autoptr(FlEngine) engine = fl_engine_new(project);
+
+  // Check objects exist before engine started.
+  EXPECT_NE(fl_engine_get_binary_messenger(engine), nullptr);
+  EXPECT_NE(fl_engine_get_renderer(engine), nullptr);
+  EXPECT_NE(fl_engine_get_display_monitor(engine), nullptr);
+  EXPECT_NE(fl_engine_get_task_runner(engine), nullptr);
+  EXPECT_NE(fl_engine_get_keyboard_manager(engine), nullptr);
+  EXPECT_NE(fl_engine_get_mouse_cursor_handler(engine), nullptr);
+}
+
 // NOLINTEND(clang-analyzer-core.StackAddressEscape)

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

@@ -211,13 +211,22 @@ static void handle_geometry_changed(FlView* self) {
 
   GdkWindow* window =
       gtk_widget_get_window(gtk_widget_get_toplevel(GTK_WIDGET(self)));
-  GdkMonitor* monitor = gdk_display_get_monitor_at_window(
-      gtk_widget_get_display(GTK_WIDGET(self)), window);
+  // NOTE(robert-ancell) If we haven't got a window we default to display 0.
+  // This is probably indicating a problem with this code in that we
+  // shouldn't be generating anything until the window is created.
+  // Another event with the correct display ID is generated soon after.
+  // I haven't changed this code in case there are side-effects but we
+  // probably shouldn't call handle_geometry_changed after the view is
+  // added but only when the window is realized.
+  FlutterEngineDisplayId display_id = 0;
+  if (window != nullptr) {
+    GdkMonitor* monitor = gdk_display_get_monitor_at_window(
+        gtk_widget_get_display(GTK_WIDGET(self)), window);
+    display_id = fl_display_monitor_get_display_id(
+        fl_engine_get_display_monitor(self->engine), monitor);
+  }
   fl_engine_send_window_metrics_event(
-      self->engine,
-      fl_display_monitor_get_display_id(
-          fl_engine_get_display_monitor(self->engine), monitor),
-      self->view_id, allocation.width * scale_factor,
+      self->engine, display_id, self->view_id, allocation.width * scale_factor,
       allocation.height * scale_factor, scale_factor);
 
   // Make sure the view has been realized and its size has been allocated before