DisplayConfig: Add API to get and set output luminance

This will in turn change the GSetting, where the setting is actually
stored.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4271>

data/dbus-interfaces/org.gnome.Mutter.DisplayConfig.xml

@@ -246,6 +246,47 @@
     -->
     <property name="Backlight" type="(uaa{sv})" access="read" />
 
+    <!--
+        SetOutputLuminance:
+
+        Sets the luminance of a monitor when in the specified color mode (see
+        GetCurrentState() for available color modes). The luminance is a
+        floating point value representing the luminance in percent (%).
+    -->
+    <method name="SetLuminance">
+      <arg name="connector" direction="in" type="s" />
+      <arg name="color_mode" direction="in" type="u" />
+      <arg name="luminance" direction="in" type="d" />
+    </method>
+
+    <!--
+        ResetOutputLuminance:
+
+        Resets the luminance of a monitor to its default when in the specified
+        color mode (see GetCurrentState() for available color modes).
+    -->
+    <method name="ResetLuminance">
+      <arg name="connector" direction="in" type="s" />
+      <arg name="color_mode" direction="in" type="u" />
+    </method>
+
+    <!--
+        Luminance:
+
+        Luminance settings. The property is a list of dictionaries of luminance
+        settings entries.
+
+        The luminance setting is per color mode and monitor.
+
+        Each dictionary consists of the following entries:
+	  * 'connector' (s) - The associated connector.
+	  * 'color-mode' (u) - The associated color mode.
+	  * 'luminance' (d) - The current luminance.
+	  * 'is-unset' (b) - True if the luminance is not explicitly set.
+	  * 'default' (d) - The default luminance.
+    -->
+    <property name="Luminance" type="aa{sv}" access="read" />
+
     <!--
         GetCrtcGamma:
 	@serial: configuration serial

src/backends/meta-monitor-manager.c

@@ -1109,6 +1109,71 @@ apply_privacy_screen_settings (MetaMonitorManager *manager)
     }
 }
 
+static void
+update_output_luminance (MetaMonitorManager *monitor_manager)
+{
+  MetaSettings *settings = meta_backend_get_settings (monitor_manager->backend);
+  GVariantBuilder builder;
+  GList *l;
+
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("aa{sv}"));
+
+  for (l = meta_monitor_manager_get_monitors (monitor_manager); l; l = l->next)
+    {
+      MetaMonitor *monitor = META_MONITOR (l->data);
+      MetaMonitorSpec *monitor_spec = meta_monitor_get_spec (monitor);
+      GVariantBuilder luminance_dic_builder;
+      const char *connector;
+      GList *l_color_mode;
+
+      for (l_color_mode = meta_monitor_get_supported_color_modes (monitor);
+           l_color_mode;
+           l_color_mode = l_color_mode->next)
+        {
+          MetaColorMode color_mode = GPOINTER_TO_INT (l_color_mode->data);
+          double luminance;
+          double default_luminance;
+          gboolean is_unset;
+
+          connector = meta_monitor_get_connector (monitor);
+          luminance = meta_settings_get_output_luminance (settings,
+                                                          monitor_spec,
+                                                          color_mode);
+          default_luminance =
+            meta_settings_get_default_output_luminance (settings,
+                                                        monitor_spec,
+                                                        color_mode);
+          is_unset = !meta_settings_has_output_luminance (settings,
+                                                          monitor_spec,
+                                                          color_mode);
+
+          g_variant_builder_init (&luminance_dic_builder,
+                                  G_VARIANT_TYPE ("a{sv}"));
+          g_variant_builder_add (&luminance_dic_builder, "{sv}",
+                                 "connector",
+                                 g_variant_new_string (connector));
+          g_variant_builder_add (&luminance_dic_builder, "{sv}",
+                                 "color-mode",
+                                 g_variant_new_uint32 (color_mode));
+          g_variant_builder_add (&luminance_dic_builder, "{sv}",
+                                 "luminance",
+                                 g_variant_new_double (luminance));
+          g_variant_builder_add (&luminance_dic_builder, "{sv}",
+                                 "default",
+                                 g_variant_new_double (default_luminance));
+          g_variant_builder_add (&luminance_dic_builder, "{sv}",
+                                 "is-unset",
+                                 g_variant_new_boolean (is_unset));
+
+          g_variant_builder_add (&builder, "a{sv}",
+                                 &luminance_dic_builder);
+        }
+    }
+
+  meta_dbus_display_config_set_luminance (monitor_manager->display_config,
+                                          g_variant_builder_end (&builder));
+}
+
 static void
 update_panel_orientation_managed (MetaMonitorManager *manager)
 {
@@ -1318,6 +1383,11 @@ meta_monitor_manager_constructed (GObject *object)
                            G_CALLBACK (apply_privacy_screen_settings),
                            manager, G_CONNECT_SWAPPED);
 
+  g_signal_connect_object (settings,
+                           "output-luminance-changed",
+                           G_CALLBACK (update_output_luminance),
+                           manager, G_CONNECT_SWAPPED);
+
   monitor_manager_setup_dbus_config_handlers (manager);
 
   g_signal_connect_object (manager->display_config, "notify::power-save-mode",
@@ -3134,6 +3204,103 @@ meta_monitor_manager_handle_set_backlight (MetaDBusDisplayConfig *skeleton,
   return G_DBUS_METHOD_INVOCATION_HANDLED;
 }
 
+static gboolean
+validate_color_mode_value (uint32_t       color_mode_value,
+                           MetaColorMode *color_mode)
+{
+  switch (color_mode_value)
+    {
+    case META_COLOR_MODE_DEFAULT:
+    case META_COLOR_MODE_BT2100:
+      *color_mode = (MetaColorMode) color_mode_value;
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+static gboolean
+meta_monitor_manager_handle_set_luminance (MetaDBusDisplayConfig *skeleton,
+                                           GDBusMethodInvocation *invocation,
+                                           const char *           connector,
+                                           uint32_t               color_mode_value,
+                                           double                 value,
+                                           MetaMonitorManager    *monitor_manager)
+{
+  MetaSettings *settings = meta_backend_get_settings (monitor_manager->backend);
+  MetaMonitor *monitor;
+  MetaColorMode color_mode;
+
+  monitor = meta_monitor_manager_get_monitor_from_connector (monitor_manager,
+                                                             connector);
+  if (!monitor)
+    {
+      g_dbus_method_invocation_return_error (invocation,
+                                             G_DBUS_ERROR,
+                                             G_DBUS_ERROR_FAILED,
+                                             "The connector doesn't have a connected monitor");
+      return G_DBUS_METHOD_INVOCATION_HANDLED;
+    }
+
+  if (!validate_color_mode_value (color_mode_value, &color_mode))
+    {
+      g_dbus_method_invocation_return_error (invocation,
+                                             G_DBUS_ERROR,
+                                             G_DBUS_ERROR_FAILED,
+                                             "Invalid color mode");
+      return G_DBUS_METHOD_INVOCATION_HANDLED;
+    }
+
+  meta_settings_set_output_luminance (settings,
+                                      meta_monitor_get_spec (monitor),
+                                      color_mode,
+                                      value);
+
+  meta_dbus_display_config_complete_set_luminance (monitor_manager->display_config,
+                                                   invocation);
+  return G_DBUS_METHOD_INVOCATION_HANDLED;
+}
+
+static gboolean
+meta_monitor_manager_handle_reset_luminance (MetaDBusDisplayConfig *skeleton,
+                                             GDBusMethodInvocation *invocation,
+                                             const char *           connector,
+                                             uint32_t               color_mode_value,
+                                             MetaMonitorManager    *monitor_manager)
+{
+  MetaSettings *settings = meta_backend_get_settings (monitor_manager->backend);
+  MetaMonitor *monitor;
+  MetaColorMode color_mode;
+
+  monitor = meta_monitor_manager_get_monitor_from_connector (monitor_manager,
+                                                             connector);
+  if (!monitor)
+    {
+      g_dbus_method_invocation_return_error (invocation,
+                                             G_DBUS_ERROR,
+                                             G_DBUS_ERROR_FAILED,
+                                             "The connector doesn't have a connected monitor");
+      return G_DBUS_METHOD_INVOCATION_HANDLED;
+    }
+
+  if (!validate_color_mode_value (color_mode_value, &color_mode))
+    {
+      g_dbus_method_invocation_return_error (invocation,
+                                             G_DBUS_ERROR,
+                                             G_DBUS_ERROR_FAILED,
+                                             "Invalid color mode");
+      return G_DBUS_METHOD_INVOCATION_HANDLED;
+    }
+
+  meta_settings_reset_output_luminance (settings,
+                                        meta_monitor_get_spec (monitor),
+                                        color_mode);
+
+  meta_dbus_display_config_complete_reset_luminance (monitor_manager->display_config,
+                                                     invocation);
+  return G_DBUS_METHOD_INVOCATION_HANDLED;
+}
+
 static gboolean
 meta_monitor_manager_handle_get_crtc_gamma  (MetaDBusDisplayConfig *skeleton,
                                              GDBusMethodInvocation *invocation,
@@ -3319,6 +3486,12 @@ monitor_manager_setup_dbus_config_handlers (MetaMonitorManager *manager)
   g_signal_connect_object (manager->display_config, "handle-set-backlight",
                            G_CALLBACK (meta_monitor_manager_handle_set_backlight),
                            manager, G_CONNECT_DEFAULT);
+  g_signal_connect_object (manager->display_config, "handle-set-luminance",
+                           G_CALLBACK (meta_monitor_manager_handle_set_luminance),
+                           manager, G_CONNECT_DEFAULT);
+  g_signal_connect_object (manager->display_config, "handle-reset-luminance",
+                           G_CALLBACK (meta_monitor_manager_handle_reset_luminance),
+                           manager, G_CONNECT_DEFAULT);
   g_signal_connect_object (manager->display_config, "handle-get-crtc-gamma",
                            G_CALLBACK (meta_monitor_manager_handle_get_crtc_gamma),
                            manager, G_CONNECT_DEFAULT);
@@ -3938,6 +4111,7 @@ meta_monitor_manager_update_logical_state (MetaMonitorManager *manager,
       manager->current_switch_config = META_MONITOR_SWITCH_CONFIG_UNKNOWN;
     }
 
+  update_output_luminance (manager);
   meta_monitor_manager_rebuild_logical_monitors (manager, config);
 }