[Linux] make desktop settings testable

FlSettings is an interface that provides desktop settings and notifies
changes, whereas FlSettingsPlugin merely communicates the settings to
the framework. This makes it straightforward to test both separately.
As a bonus, it will be easy to add FlSettings implementations for other
DEs too.

Author: jpnurmi

ci/licenses_golden/licenses_flutter

@@ -2027,6 +2027,9 @@ FILE: ../../../flutter/shell/platform/linux/fl_event_channel.cc
 FILE: ../../../flutter/shell/platform/linux/fl_event_channel_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_gl_area.cc
 FILE: ../../../flutter/shell/platform/linux/fl_gl_area.h
+FILE: ../../../flutter/shell/platform/linux/fl_gnome_settings.cc
+FILE: ../../../flutter/shell/platform/linux/fl_gnome_settings.h
+FILE: ../../../flutter/shell/platform/linux/fl_gnome_settings_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_json_message_codec.cc
 FILE: ../../../flutter/shell/platform/linux/fl_json_message_codec_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_json_method_codec.cc
@@ -2076,8 +2079,11 @@ FILE: ../../../flutter/shell/platform/linux/fl_renderer_gl.cc
 FILE: ../../../flutter/shell/platform/linux/fl_renderer_gl.h
 FILE: ../../../flutter/shell/platform/linux/fl_renderer_headless.cc
 FILE: ../../../flutter/shell/platform/linux/fl_renderer_headless.h
+FILE: ../../../flutter/shell/platform/linux/fl_settings.cc
+FILE: ../../../flutter/shell/platform/linux/fl_settings.h
 FILE: ../../../flutter/shell/platform/linux/fl_settings_plugin.cc
 FILE: ../../../flutter/shell/platform/linux/fl_settings_plugin.h
+FILE: ../../../flutter/shell/platform/linux/fl_settings_plugin_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_standard_message_codec.cc
 FILE: ../../../flutter/shell/platform/linux/fl_standard_message_codec_private.h
 FILE: ../../../flutter/shell/platform/linux/fl_standard_message_codec_test.cc

shell/platform/linux/BUILD.gn

@@ -107,6 +107,7 @@ source_set("flutter_linux_sources") {
     "fl_engine.cc",
     "fl_event_channel.cc",
     "fl_gl_area.cc",
+    "fl_gnome_settings.cc",
     "fl_json_message_codec.cc",
     "fl_json_method_codec.cc",
     "fl_key_channel_responder.cc",
@@ -128,6 +129,7 @@ source_set("flutter_linux_sources") {
     "fl_renderer.cc",
     "fl_renderer_gl.cc",
     "fl_renderer_headless.cc",
+    "fl_settings.cc",
     "fl_settings_plugin.cc",
     "fl_standard_message_codec.cc",
     "fl_standard_method_codec.cc",
@@ -175,6 +177,13 @@ test_fixtures("flutter_linux_fixtures") {
   fixtures = []
 }
 
+copy("flutter_linux_gschemas") {
+  testonly = true
+
+  sources = [ "testing/gschemas/ubuntu-20.04.compiled" ]
+  outputs = [ "$target_gen_dir/assets/{{source_name_part}}/gschemas.compiled" ]
+}
+
 executable("flutter_linux_unittests") {
   testonly = true
 
@@ -186,6 +195,7 @@ executable("flutter_linux_unittests") {
     "fl_dart_project_test.cc",
     "fl_engine_test.cc",
     "fl_event_channel_test.cc",
+    "fl_gnome_settings_test.cc",
     "fl_json_message_codec_test.cc",
     "fl_json_method_codec_test.cc",
     "fl_key_channel_responder_test.cc",
@@ -197,6 +207,7 @@ executable("flutter_linux_unittests") {
     "fl_method_response_test.cc",
     "fl_pixel_buffer_texture_test.cc",
     "fl_plugin_registrar_test.cc",
+    "fl_settings_plugin_test.cc",
     "fl_standard_message_codec_test.cc",
     "fl_standard_method_codec_test.cc",
     "fl_string_codec_test.cc",
@@ -210,6 +221,7 @@ executable("flutter_linux_unittests") {
     "testing/mock_epoxy.cc",
     "testing/mock_plugin_registrar.cc",
     "testing/mock_renderer.cc",
+    "testing/mock_settings.cc",
     "testing/mock_signal_handler.cc",
     "testing/mock_text_input_plugin.cc",
     "testing/mock_texture_registrar.cc",
@@ -229,6 +241,7 @@ executable("flutter_linux_unittests") {
 
   deps = [
     ":flutter_linux_fixtures",
+    ":flutter_linux_gschemas",
     ":flutter_linux_sources",
     "//flutter/runtime:libdart",
     "//flutter/shell/platform/embedder:embedder_headers",

shell/platform/linux/fl_engine.cc

@@ -516,8 +516,9 @@ gboolean fl_engine_start(FlEngine* self, GError** error) {
 
   setup_locales(self);
 
+  g_autoptr(FlSettings) settings = fl_settings_new();
   self->settings_plugin = fl_settings_plugin_new(self->binary_messenger);
-  fl_settings_plugin_start(self->settings_plugin);
+  fl_settings_plugin_start(self->settings_plugin, settings);
 
   result = self->embedder_api.UpdateSemanticsEnabled(self->engine, TRUE);
   if (result != kSuccess) {

shell/platform/linux/fl_gnome_settings.cc

@@ -0,0 +1,139 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/linux/fl_gnome_settings.h"
+
+#include <glib.h>
+
+static constexpr char kDesktopInterfaceSchema[] = "org.gnome.desktop.interface";
+static constexpr char kDesktopTextScalingFactorKey[] = "text-scaling-factor";
+static constexpr char kDesktopClockFormatKey[] = "clock-format";
+static constexpr char kDesktopGtkThemeKey[] = "gtk-theme";
+
+static constexpr char kClockFormat12Hour[] = "12h";
+static constexpr char kGtkThemeDarkSuffix[] = "-dark";
+
+G_DECLARE_FINAL_TYPE(FlGnomeSettings,
+                     fl_gnome_settings,
+                     FL,
+                     GNOME_SETTINGS,
+                     GObject);
+
+struct _FlGnomeSettings {
+  GObject parent_instance;
+
+  GSettings* interface_settings;
+};
+
+static void fl_gnome_settings_iface_init(FlSettingsInterface* iface);
+
+#define FL_UNUSED(x) (void)x;
+
+G_DEFINE_TYPE_WITH_CODE(FlGnomeSettings,
+                        fl_gnome_settings,
+                        G_TYPE_OBJECT,
+                        G_IMPLEMENT_INTERFACE(fl_settings_get_type(),
+                                              fl_gnome_settings_iface_init)
+                            FL_UNUSED(FL_IS_GNOME_SETTINGS))
+
+static FlClockFormat fl_gnome_settings_get_clock_format(FlSettings* settings) {
+  FlGnomeSettings* self = FL_GNOME_SETTINGS(settings);
+
+  FlClockFormat clock_format = FL_CLOCK_FORMAT_24H;
+
+  if (self->interface_settings != nullptr) {
+    g_autofree gchar* value =
+        g_settings_get_string(self->interface_settings, kDesktopClockFormatKey);
+    if (g_strcmp0(value, kClockFormat12Hour) == 0) {
+      clock_format = FL_CLOCK_FORMAT_12H;
+    }
+  }
+  return clock_format;
+}
+
+static FlColorScheme fl_gnome_settings_get_color_scheme(FlSettings* settings) {
+  FlGnomeSettings* self = FL_GNOME_SETTINGS(settings);
+
+  FlColorScheme color_scheme = FL_COLOR_SCHEME_LIGHT;
+
+  if (self->interface_settings != nullptr) {
+    // check whether org.gnome.desktop.interface.gtk-theme ends with "-dark"
+    g_autofree gchar* value =
+        g_settings_get_string(self->interface_settings, kDesktopGtkThemeKey);
+    if (g_str_has_suffix(value, kGtkThemeDarkSuffix)) {
+      color_scheme = FL_COLOR_SCHEME_DARK;
+    }
+  }
+  return color_scheme;
+}
+
+static gdouble fl_gnome_settings_get_text_scaling_factor(FlSettings* settings) {
+  FlGnomeSettings* self = FL_GNOME_SETTINGS(settings);
+
+  gdouble scaling_factor = 1.0;
+
+  if (self->interface_settings != nullptr) {
+    scaling_factor = g_settings_get_double(self->interface_settings,
+                                           kDesktopTextScalingFactorKey);
+  }
+  return scaling_factor;
+}
+
+static void fl_gnome_settings_dispose(GObject* object) {
+  FlGnomeSettings* self = FL_GNOME_SETTINGS(object);
+
+  g_clear_object(&self->interface_settings);
+
+  G_OBJECT_CLASS(fl_gnome_settings_parent_class)->dispose(object);
+}
+
+static void fl_gnome_settings_class_init(FlGnomeSettingsClass* klass) {
+  G_OBJECT_CLASS(klass)->dispose = fl_gnome_settings_dispose;
+}
+
+static void fl_gnome_settings_iface_init(FlSettingsInterface* iface) {
+  iface->get_clock_format = fl_gnome_settings_get_clock_format;
+  iface->get_color_scheme = fl_gnome_settings_get_color_scheme;
+  iface->get_text_scaling_factor = fl_gnome_settings_get_text_scaling_factor;
+}
+
+static void fl_gnome_settings_init(FlGnomeSettings* self) {}
+
+static GSettings* default_interface_settings() {
+  GSettings* interface_settings = nullptr;
+  GSettingsSchemaSource* source = g_settings_schema_source_get_default();
+  if (source != nullptr) {
+    g_autoptr(GSettingsSchema) schema =
+        g_settings_schema_source_lookup(source, kDesktopInterfaceSchema, TRUE);
+    if (schema != nullptr) {
+      interface_settings = g_settings_new_full(schema, nullptr, nullptr);
+    }
+  }
+  return interface_settings;
+}
+
+FlSettings* fl_gnome_settings_new(GSettings* interface_settings) {
+  FlGnomeSettings* self =
+      FL_GNOME_SETTINGS(g_object_new(fl_gnome_settings_get_type(), nullptr));
+
+  if (interface_settings != nullptr) {
+    self->interface_settings = G_SETTINGS(g_object_ref(interface_settings));
+  } else {
+    self->interface_settings = default_interface_settings();
+  }
+
+  if (self->interface_settings != nullptr) {
+    g_signal_connect_object(self->interface_settings, "changed::clock-format",
+                            G_CALLBACK(fl_settings_emit_changed), self,
+                            G_CONNECT_SWAPPED);
+    g_signal_connect_object(self->interface_settings, "changed::gtk-theme",
+                            G_CALLBACK(fl_settings_emit_changed), self,
+                            G_CONNECT_SWAPPED);
+    g_signal_connect_object(
+        self->interface_settings, "changed::text-scaling-factor",
+        G_CALLBACK(fl_settings_emit_changed), self, G_CONNECT_SWAPPED);
+  }
+
+  return FL_SETTINGS(self);
+}

shell/platform/linux/fl_gnome_settings.h

@@ -0,0 +1,26 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_LINUX_FL_GNOME_SETTINGS_H_
+#define FLUTTER_SHELL_PLATFORM_LINUX_FL_GNOME_SETTINGS_H_
+
+#include "flutter/shell/platform/linux/fl_settings.h"
+
+#include <gio/gio.h>
+
+G_BEGIN_DECLS
+
+/**
+ * fl_gnome_settings_new:
+ * @interface_settings: (allow-none): #GSettings for testing purposes, or %NULL.
+ *
+ * Creates a new settings instance for GNOME.
+ *
+ * Returns: a new #FlSettings.
+ */
+FlSettings* fl_gnome_settings_new(GSettings* interface_settings);
+
+G_END_DECLS
+
+#endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_GNOME_SETTINGS_H_

shell/platform/linux/fl_gnome_settings_test.cc

@@ -0,0 +1,104 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/linux/fl_gnome_settings.h"
+#include "flutter/shell/platform/linux/testing/fl_test.h"
+#include "flutter/shell/platform/linux/testing/mock_settings.h"
+#include "flutter/shell/platform/linux/testing/mock_signal_handler.h"
+#include "flutter/testing/testing.h"
+
+#include <gio/gio.h>
+#define G_SETTINGS_ENABLE_BACKEND
+#include <gio/gsettingsbackend.h>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+class FlGnomeSettingsTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    // force _g_io_modules_ensure_extension_points_registered() to get called
+    g_settings_backend_get_default();
+  }
+};
+
+static GSettings* create_interface_settings(const gchar* name) {
+  g_autofree gchar* path =
+      g_build_filename(flutter::testing::GetFixturesPath(), name, nullptr);
+  g_autoptr(GSettingsSchemaSource) source =
+      g_settings_schema_source_new_from_directory(path, nullptr, false,
+                                                  nullptr);
+  g_autoptr(GSettingsSchema) schema = g_settings_schema_source_lookup(
+      source, "org.gnome.desktop.interface", false);
+  g_autoptr(GSettingsBackend) backend = g_memory_settings_backend_new();
+  return g_settings_new_full(schema, backend, nullptr);
+}
+
+TEST_F(FlGnomeSettingsTest, ClockFormat) {
+  g_autoptr(GSettings) interface_settings =
+      create_interface_settings("ubuntu-20.04");
+  g_settings_set_string(interface_settings, "clock-format", "24h");
+
+  g_autoptr(FlSettings) settings = fl_gnome_settings_new(interface_settings);
+  EXPECT_EQ(fl_settings_get_clock_format(settings), FL_CLOCK_FORMAT_24H);
+
+  flutter::testing::MockSignalHandler settings_changed(settings, "changed");
+  EXPECT_SIGNAL(settings_changed).Times(1);
+
+  g_settings_set_string(interface_settings, "clock-format", "12h");
+  EXPECT_EQ(fl_settings_get_clock_format(settings), FL_CLOCK_FORMAT_12H);
+}
+
+TEST_F(FlGnomeSettingsTest, GtkTheme) {
+  g_autoptr(GSettings) interface_settings =
+      create_interface_settings("ubuntu-20.04");
+  g_settings_set_string(interface_settings, "gtk-theme", "Yaru");
+
+  g_autoptr(FlSettings) settings = fl_gnome_settings_new(interface_settings);
+  EXPECT_EQ(fl_settings_get_color_scheme(settings), FL_COLOR_SCHEME_LIGHT);
+
+  flutter::testing::MockSignalHandler settings_changed(settings, "changed");
+  EXPECT_SIGNAL(settings_changed).Times(1);
+
+  g_settings_set_string(interface_settings, "gtk-theme", "Yaru-dark");
+  EXPECT_EQ(fl_settings_get_color_scheme(settings), FL_COLOR_SCHEME_DARK);
+}
+
+TEST_F(FlGnomeSettingsTest, TextScalingFactor) {
+  g_autoptr(GSettings) interface_settings =
+      create_interface_settings("ubuntu-20.04");
+  g_settings_set_double(interface_settings, "text-scaling-factor", 1.0);
+
+  g_autoptr(FlSettings) settings = fl_gnome_settings_new(interface_settings);
+  EXPECT_EQ(fl_settings_get_text_scaling_factor(settings), 1.0);
+
+  flutter::testing::MockSignalHandler settings_changed(settings, "changed");
+  EXPECT_SIGNAL(settings_changed).Times(1);
+
+  g_settings_set_double(interface_settings, "text-scaling-factor", 1.5);
+  EXPECT_EQ(fl_settings_get_text_scaling_factor(settings), 1.5);
+}
+
+TEST_F(FlGnomeSettingsTest, SignalHandlers) {
+  g_autoptr(GSettings) interface_settings =
+      create_interface_settings("ubuntu-20.04");
+
+  FlSettings* settings = fl_gnome_settings_new(interface_settings);
+  flutter::testing::MockSignalHandler settings_changed(settings, "changed");
+
+  EXPECT_SIGNAL(settings_changed).Times(3);
+
+  g_settings_set_string(interface_settings, "clock-format", "12h");
+  g_settings_set_string(interface_settings, "gtk-theme", "Yaru-dark");
+  g_settings_set_double(interface_settings, "text-scaling-factor", 1.5);
+
+  EXPECT_SIGNAL(settings_changed).Times(0);
+
+  g_clear_object(&settings);
+
+  // destroyed FlSettings object must have disconnected its signal handlers
+  g_settings_set_string(interface_settings, "clock-format", "24h");
+  g_settings_set_string(interface_settings, "gtk-theme", "Yaru");
+  g_settings_set_double(interface_settings, "text-scaling-factor", 2.0);
+}