shell: Expose panel launching with DBus-activation

Turn Control Center in a DBus-activable service and export a
'launch-panel' GAction which accepts a tuple containing the id of the
desired panel and its parameters as a GVariant array.

The snippet below show how the custom shortcuts section of the keyboard
panel can be invoked by a external programs through DBus:

GVariantBuilder *flags = g_variant_builder_new (G_VARIANT_TYPE_VARDICT);
GVariantBuilder *params = g_variant_builder_new (G_VARIANT_TYPE ("av"));
g_variant_builder_add (params, "v", g_variant_builder_end (flags));
g_variant_builder_add (params, "v", g_variant_new_string ("shortcuts"));
g_variant_builder_add (params, "v", g_variant_new_string ("custom"));
GVariant *v = g_variant_new ("(s@av)", "keyboard", g_variant_builder_end (params));

GApplication *gnomecc = g_application_new (id, G_APPLICATION_IS_LAUNCHER);
if (!g_application_register (gnomecc, NULL, &error))
  g_error ("Failed to register launcher for %s: %s", id, error->message);
g_action_group_activate_action (G_ACTION_GROUP (gnomecc), "launch-panel", v);

https://bugzilla.gnome.org/show_bug.cgi?id=696054

shell/Makefile.am

@@ -86,6 +86,13 @@ endif
 
 AM_CPPFLAGS = -DGNOMELOCALEDIR="\"$(datadir)/locale\""
 
+# Dbus service file
+servicefiledir = $(datadir)/dbus-1/services
+servicefile_in_files = org.gnome.ControlCenter.service.in
+servicefile_DATA = $(servicefile_in_files:.service.in=.service)
+$(servicefile_DATA): $(servicefile_in_files) Makefile
+	$(AM_V_GEN) sed -e 's|[@]bindir[@]|$(bindir)|' $< > $@
+
 sysdir = $(datadir)/applications
 sys_in_files = gnome-control-center.desktop.in
 sys_DATA = $(sys_in_files:.desktop.in=.desktop)
@@ -99,10 +106,11 @@ completions/gnome-control-center: completions/gnome-control-center.in list-panel
 
 EXTRA_DIST =					\
 	gnome-control-center.desktop.in.in	\
+	$(servicefile_in_files)                 \
 	$(completion_in_files)			\
 	list-panel.sh
 
-CLEANFILES = $(BUILT_SOURCES) $(completion_DATA)
+CLEANFILES = $(BUILT_SOURCES) $(completion_DATA) $(servicefile_DATA)
 DISTCLEANFILES = gnome-control-center.desktop gnome-control-center.desktop.in
 
 noinst_PROGRAMS = test-hostname

shell/cc-application.c

@@ -95,6 +95,27 @@ help_activated (GSimpleAction *action,
                 GDK_CURRENT_TIME, NULL);
 }
 
+static void
+launch_panel_activated (GSimpleAction *action,
+                        GVariant      *parameter,
+                        gpointer       user_data)
+{
+  CcApplication *self = CC_APPLICATION (user_data);
+  GError *error = NULL;
+  gchar *panel_id;
+  GVariant *parameters;
+
+  g_variant_get (parameter, "(&s@av)", &panel_id, &parameters);
+  g_debug ("gnome-control-center: 'launch-panel' activated for panel '%s' with %"G_GSIZE_FORMAT" arguments",
+      panel_id, g_variant_n_children (parameters));
+  if (!cc_shell_set_active_panel_from_id (CC_SHELL (self->priv->window), panel_id, parameters, &error))
+    {
+      g_warning ("Failed to activate the '%s' panel: %s", panel_id, error->message);
+      g_error_free (error);
+    }
+  g_variant_unref (parameters);
+}
+
 static int
 cc_application_command_line (GApplication *application,
                              GApplicationCommandLine *command_line)
@@ -280,6 +301,15 @@ cc_application_startup (GApplication *application)
   g_signal_connect (action, "activate", G_CALLBACK (cc_application_quit), self);
   g_object_unref (action);
 
+  /* Launch panel by id. The parameter is a (panel_id, array_of_panel_parameters)
+   * tuple. The GVariant-containing array usually is just the same array of
+   * strings that would be generated by passing panel-specific arguments on
+   * the command line. */
+  action = g_simple_action_new ("launch-panel", G_VARIANT_TYPE ("(sav)"));
+  g_action_map_add_action (G_ACTION_MAP (application), G_ACTION (action));
+  g_signal_connect (action, "activate", G_CALLBACK (launch_panel_activated), self);
+  g_object_unref (action);
+
   menu = g_menu_new ();
 
   section = g_menu_new ();

shell/org.gnome.ControlCenter.service.in

@@ -0,0 +1,3 @@
+[D-BUS Service]
+Name=org.gnome.ControlCenter
+Exec=@bindir@/gnome-control-center