panel: Add the sidebar-activated signal

This is necessary for the application panel to warn that an element of
its sidebar has been activated so the window can focus on it when the
window will use a leaflet.

shell/cc-panel.c

@@ -53,6 +53,12 @@ typedef struct
 
 G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (CcPanel, cc_panel, GTK_TYPE_BIN)
 
+enum
+{
+  SIDEBAR_ACTIVATED,
+  LAST_SIGNAL
+};
+
 enum
 {
   PROP_0,
@@ -63,6 +69,8 @@ enum
 
 static GParamSpec *properties [N_PROPS];
 
+static guint signals [LAST_SIGNAL] = { 0 };
+
 static void
 cc_panel_set_property (GObject      *object,
                        guint         prop_id,
@@ -152,6 +160,13 @@ cc_panel_class_init (CcPanelClass *klass)
   object_class->set_property = cc_panel_set_property;
   object_class->finalize = cc_panel_finalize;
 
+  signals[SIDEBAR_ACTIVATED] = g_signal_new ("sidebar-activated",
+                                             G_TYPE_FROM_CLASS (object_class),
+                                             G_SIGNAL_RUN_LAST,
+                                             0, NULL, NULL,
+                                             g_cclosure_marshal_VOID__VOID,
+                                             G_TYPE_NONE, 0);
+
   properties[PROP_SHELL] = g_param_spec_object ("shell",
                                                 "Shell",
                                                 "Shell the Panel resides in",