Support headless mode

plugins/color_panel/gtk/color_panel_plugin.cc

@@ -18,6 +18,7 @@
 
 // See color_panel.dart for documentation.
 const char kChannelName[] = "flutter/colorpanel";
+const char kNoScreenError[] = "No Screen";
 const char kShowColorPanelMethod[] = "ColorPanel.Show";
 const char kColorPanelShowAlpha[] = "ColorPanel.ShowAlpha";
 const char kHideColorPanelMethod[] = "ColorPanel.Hide";
@@ -92,9 +93,14 @@ static FlMethodResponse* show_color_panel(FlColorPanelPlugin* self,
   gboolean use_alpha =
       use_alpha_value != nullptr ? fl_value_get_bool(use_alpha_value) : FALSE;
 
+  FlView* view = fl_plugin_registrar_get_view(self->registrar);
+  if (view == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   self->color_chooser_dialog = GTK_COLOR_CHOOSER_DIALOG(
       gtk_color_chooser_dialog_new(kWindowTitle, nullptr));
-  FlView* view = fl_plugin_registrar_get_view(self->registrar);
   GtkWindow* window = GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(view)));
   gtk_window_set_transient_for(GTK_WINDOW(self->color_chooser_dialog), window);
   gtk_color_chooser_set_use_alpha(GTK_COLOR_CHOOSER(self->color_chooser_dialog),

plugins/file_chooser/gtk/file_chooser_plugin.cc

@@ -19,6 +19,7 @@
 // See channel_controller.dart for documentation.
 const char kChannelName[] = "flutter/filechooser";
 const char kBadArgumentsError[] = "Bad Arguments";
+const char kNoScreenError[] = "No Screen";
 const char kShowOpenPanelMethod[] = "FileChooser.Show.Open";
 const char kShowSavePanelMethod[] = "FileChooser.Show.Save";
 const char kInitialDirectoryKey[] = "initialDirectory";
@@ -84,6 +85,11 @@ static FlMethodResponse* show_dialog(FlFileChooserPlugin* self,
     confirm_button_text = fl_value_get_string(value);
 
   FlView* view = fl_plugin_registrar_get_view(self->registrar);
+  if (view == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   GtkWindow* window = GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(view)));
   g_autoptr(GtkFileChooserNative) dialog =
       GTK_FILE_CHOOSER_NATIVE(gtk_file_chooser_native_new(

plugins/menubar/gtk/menubar_plugin.cc

@@ -20,6 +20,7 @@
 // See menu_channel.dart for documentation.
 const char kChannelName[] = "flutter/menubar";
 const char kBadArgumentsError[] = "Bad Arguments";
+const char kNoScreenError[] = "No Screen";
 const char kFailureError[] = "Failure";
 const char kMenuSetMethod[] = "Menubar.SetMenu";
 const char kMenuItemSelectedCallbackMethod[] = "Menubar.SelectedCallback";
@@ -145,6 +146,11 @@ static FlMethodResponse* menu_set(FlMenubarPlugin* self, FlValue* args) {
   }
 
   FlView* view = fl_plugin_registrar_get_view(self->registrar);
+  if (view == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   GtkApplication* app = gtk_window_get_application(
       GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(view))));
   if (app == nullptr) {
@@ -213,8 +219,10 @@ FlMenubarPlugin* fl_menubar_plugin_new(FlPluginRegistrar* registrar) {
 
   // Add a GAction for the menubar to trigger.
   FlView* view = fl_plugin_registrar_get_view(self->registrar);
-  GtkApplication* app = gtk_window_get_application(
-      GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(view))));
+  GtkApplication* app = nullptr;
+  if (view != nullptr)
+    app = gtk_window_get_application(
+        GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(view))));
   if (app != nullptr) {
     g_autoptr(GSimpleAction) inactive_action =
         g_simple_action_new("flutter-menu-inactive", nullptr);

plugins/window_size/gtk/window_size_plugin.cc

@@ -19,6 +19,7 @@
 // See window_size_channel.dart for documentation.
 const char kChannelName[] = "flutter/windowsize";
 const char kBadArgumentsError[] = "Bad Arguments";
+const char kNoScreenError[] = "No Screen";
 const char kGetScreenListMethod[] = "getScreenList";
 const char kGetWindowInfoMethod[] = "getWindowInfo";
 const char kSetWindowFrameMethod[] = "setWindowFrame";
@@ -49,12 +50,16 @@ G_DEFINE_TYPE(FlWindowSizePlugin, fl_window_size_plugin, g_object_get_type())
 // Gets the window being controlled.
 GtkWindow* get_window(FlWindowSizePlugin* self) {
   FlView* view = fl_plugin_registrar_get_view(self->registrar);
+  if (view == nullptr) return nullptr;
+
   return GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(view)));
 }
 
 // Gets the display connection.
 GdkDisplay* get_display(FlWindowSizePlugin* self) {
   FlView* view = fl_plugin_registrar_get_view(self->registrar);
+  if (view == nullptr) return nullptr;
+
   return gtk_widget_get_display(GTK_WIDGET(view));
 }
 
@@ -97,6 +102,11 @@ static FlMethodResponse* get_screen_list(FlWindowSizePlugin* self) {
   g_autoptr(FlValue) screens = fl_value_new_list();
 
   GdkDisplay* display = get_display(self);
+  if (display == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   gint n_monitors = gdk_display_get_n_monitors(display);
   for (gint i = 0; i < n_monitors; i++) {
     GdkMonitor* monitor = gdk_display_get_monitor(display, i);
@@ -109,6 +119,10 @@ static FlMethodResponse* get_screen_list(FlWindowSizePlugin* self) {
 // Gets information about the Flutter window.
 static FlMethodResponse* get_window_info(FlWindowSizePlugin* self) {
   GtkWindow* window = get_window(self);
+  if (window == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
 
   g_autoptr(FlValue) window_info = fl_value_new_map();
 
@@ -158,6 +172,11 @@ static FlMethodResponse* set_window_frame(FlWindowSizePlugin* self,
   double height = fl_value_get_float(fl_value_get_list_value(args, 3));
 
   GtkWindow* window = get_window(self);
+  if (window == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   gtk_window_move(window, static_cast<gint>(x), static_cast<gint>(y));
   gtk_window_resize(window, static_cast<gint>(width),
                     static_cast<gint>(height));
@@ -183,6 +202,11 @@ static FlMethodResponse* set_window_minimum_size(FlWindowSizePlugin* self,
   double width = fl_value_get_float(fl_value_get_list_value(args, 0));
   double height = fl_value_get_float(fl_value_get_list_value(args, 1));
 
+  if (get_window() == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   if (width >= 0 && height >= 0) {
     self->window_geometry.min_width = static_cast<gint>(width);
     self->window_geometry.min_height = static_cast<gint>(height);
@@ -204,6 +228,11 @@ static FlMethodResponse* set_window_maximum_size(FlWindowSizePlugin* self,
   double width = fl_value_get_float(fl_value_get_list_value(args, 0));
   double height = fl_value_get_float(fl_value_get_list_value(args, 1));
 
+  if (get_window() == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
+
   self->window_geometry.max_width = static_cast<gint>(width);
   self->window_geometry.max_height = static_cast<gint>(height);
 
@@ -221,6 +250,10 @@ static FlMethodResponse* set_window_title(FlWindowSizePlugin* self,
   }
 
   GtkWindow* window = get_window(self);
+  if (window == nullptr) {
+    return FL_METHOD_RESPONSE(
+        fl_method_error_response_new(kNoScreenError, nullptr, nullptr));
+  }
   gtk_window_set_title(window, fl_value_get_string(args));
 
   return FL_METHOD_RESPONSE(fl_method_success_response_new(nullptr));

testbed/gtk/CMakeLists.txt

@@ -34,6 +34,7 @@ pkg_check_modules(GTK REQUIRED IMPORTED_TARGET gtk+-3.0)
 add_executable(${BINARY_NAME}
   "main.cc"
   "fl_application.cc"
+  "fl_headless_application.cc"
   "window_configuration.cc"
   "${FLUTTER_MANAGED_DIR}/gtk_plugin_registrant.cc"
 )

testbed/gtk/fl_headless_application.cc

@@ -0,0 +1,49 @@
+#include "fl_headless_application.h"
+
+#include <flutter_linux/flutter_linux.h>
+#include <flutter_linux/fl_engine_extra.h>
+
+#include "flutter/gtk_plugin_registrant.h"
+
+struct _FlHeadlessApplication {
+  GApplication parent_instance;
+
+  FlEngine* engine;
+};
+
+G_DEFINE_TYPE(FlHeadlessApplication, fl_headless_application,
+              G_TYPE_APPLICATION)
+
+// Implements GApplication::activate.
+static void fl_headless_application_activate(GApplication* application) {
+  FlHeadlessApplication* self = FL_HEADLESS_APPLICATION(application);
+
+  g_autoptr(FlDartProject) project = fl_dart_project_new();
+  self->engine = fl_engine_new_headless(project);
+
+  g_application_hold(application);
+
+  fl_register_plugins(FL_PLUGIN_REGISTRY(self->engine));
+}
+
+// Implements GObject::dispose.
+static void fl_headless_application_dispose(GObject* object) {
+  FlHeadlessApplication* self = FL_HEADLESS_APPLICATION(object);
+
+  g_clear_object(&self->engine);
+
+  G_OBJECT_CLASS(fl_headless_application_parent_class)->dispose(object);
+}
+
+static void fl_headless_application_class_init(
+    FlHeadlessApplicationClass* klass) {
+  G_APPLICATION_CLASS(klass)->activate = fl_headless_application_activate;
+  G_OBJECT_CLASS(klass)->dispose = fl_headless_application_dispose;
+}
+
+static void fl_headless_application_init(FlHeadlessApplication* self) {}
+
+FlHeadlessApplication* fl_headless_application_new() {
+  return FL_HEADLESS_APPLICATION(
+      g_object_new(fl_headless_application_get_type(), nullptr));
+}

testbed/gtk/fl_headless_application.h

@@ -0,0 +1,19 @@
+#ifndef FLUTTER_FL_HEADLESS_APPLICATION_H_
+#define FLUTTER_FL_HEADLESS_APPLICATION_H_
+
+#include <gio/gio.h>
+
+G_DECLARE_FINAL_TYPE(FlHeadlessApplication, fl_headless_application, FL,
+                     HEADLESS_APPLICATION, GApplication)
+
+/**
+ * fl_headless_application_new:
+ *
+ * Creates a new Flutter headless application.
+ *
+ * Returns: a new #FlHeadlessApplication.
+ */
+FlHeadlessApplication* fl_headless_application_new();
+
+#endif  // FLUTTER_FL_HEADLESS_APPLICATION_H_
+

testbed/gtk/main.cc

@@ -1,6 +1,13 @@
 #include "fl_application.h"
+#include "fl_headless_application.h"
 
 int main(int argc, char** argv) {
-  g_autoptr(FlApplication) app = fl_application_new();
-  return g_application_run(G_APPLICATION(app), argc, argv);
+  g_autoptr(GApplication) app = nullptr;
+
+  if (gdk_init_check(&argc, &argv))
+    app = G_APPLICATION(fl_application_new());
+  else
+    app = G_APPLICATION(fl_headless_application_new());
+
+  return g_application_run(app, argc, argv);
 }