shell: Remember the last used panel

And restore it if the application is launched without any panels
requested.

https://bugzilla.gnome.org/show_bug.cgi?id=786607

meson.build

@@ -16,6 +16,7 @@ control_center_sysconfdir = join_paths(control_center_prefix, get_option('syscon
 control_center_pkgdatadir = join_paths(control_center_datadir, meson.project_name())
 control_center_desktopdir = join_paths(control_center_datadir, 'applications')
 control_center_icondir = join_paths(control_center_datadir, 'icons')
+control_center_schemadir = join_paths (control_center_datadir, 'glib-2.0', 'schemas')
 
 control_center_gettext = meson.project_name() + '-2.0'
 

shell/cc-window.c

@@ -74,6 +74,7 @@ struct _CcWindow
   GtkListStore *store;
 
   CcPanel *active_panel;
+  GSettings *settings;
 };
 
 static void     cc_shell_iface_init         (CcShellInterface      *iface);
@@ -123,6 +124,8 @@ activate_panel (CcWindow    *self,
   if (!id)
     return FALSE;
 
+  g_settings_set_string (self->settings, "last-panel", id);
+
   self->current_panel = GTK_WIDGET (cc_panel_loader_load_by_name (CC_SHELL (self), id, parameters));
   cc_shell_set_active_panel (CC_SHELL (self), CC_PANEL (self->current_panel));
   gtk_widget_show (self->current_panel);
@@ -664,6 +667,8 @@ cc_window_finalize (GObject *object)
       self->previous_panels = NULL;
     }
 
+  g_clear_object (&self->settings);
+
   G_OBJECT_CLASS (cc_window_parent_class)->finalize (object);
 }
 
@@ -713,11 +718,14 @@ static void
 cc_window_init (CcWindow *self)
 {
   GtkSettings *settings;
+  g_autofree char *id = NULL;
 
   gtk_widget_init_template (GTK_WIDGET (self));
 
   gtk_widget_add_events (GTK_WIDGET (self), GDK_BUTTON_RELEASE_MASK);
 
+  self->settings = g_settings_new ("org.gnome.ControlCenter");
+
   /* Handle decorations for the split headers. */
   settings = gtk_settings_get_default ();
   g_signal_connect (settings,
@@ -733,7 +741,12 @@ cc_window_init (CcWindow *self)
 
   setup_model (self);
 
-  /* After everything is loaded, select the first visible panel */
+  /* After everything is loaded, select the last used panel, if any,
+   * or the first visible panel */
+  id = g_settings_get_string (self->settings, "last-panel");
+  if (id != NULL && *id != '\0')
+    cc_panel_list_set_active_panel (CC_PANEL_LIST (self->panel_list), id);
+  else
     cc_panel_list_activate (CC_PANEL_LIST (self->panel_list));
 }
 

shell/meson.build

@@ -133,3 +133,6 @@ exe = executable(
 )
 
 test(test_unit, exe)
+
+install_data ('org.gnome.ControlCenter.gschema.xml',
+              install_dir: control_center_schemadir)

shell/org.gnome.ControlCenter.gschema.xml

@@ -0,0 +1,12 @@
+<schemalist>
+  <schema id="org.gnome.ControlCenter" path="/org/gnome/control-center/">
+    <key name="last-panel" type="s">
+      <default>''</default>
+      <summary>The identifier for the last Settings panel to be opened</summary>
+      <description>
+        The identifier for the last Settings panel to be opened. Unrecognised values
+        will be ignored and the first panel in the list selected.
+      </description>
+    </key>
+  </schema>
+</schemalist>