Add a confirmation dialog for display changes

Unfortunately, display configuration can and does fail, due
to unspecified HW constraints, drivers bugs, unsupported exotic
configurations or just bad luck.
So when the user makes a change in the control center, show
a dialog asking him if it looks OK, and revert back after 20 seconds
otherwise.

https://bugzilla.gnome.org/show_bug.cgi?id=706208

src/gnome-shell-plugin.c

@@ -75,6 +75,9 @@ static gboolean              gnome_shell_plugin_xevent_filter (MetaPlugin *plugi
 
 static gboolean              gnome_shell_plugin_keybinding_filter (MetaPlugin *plugin,
                                                                    MetaKeyBinding *binding);
+
+static void gnome_shell_plugin_confirm_display_change (MetaPlugin *plugin);
+
 static const MetaPluginInfo *gnome_shell_plugin_plugin_info   (MetaPlugin *plugin);
 
 
@@ -132,6 +135,9 @@ gnome_shell_plugin_class_init (GnomeShellPluginClass *klass)
 
   plugin_class->xevent_filter     = gnome_shell_plugin_xevent_filter;
   plugin_class->keybinding_filter = gnome_shell_plugin_keybinding_filter;
+
+  plugin_class->confirm_display_change = gnome_shell_plugin_confirm_display_change;
+
   plugin_class->plugin_info       = gnome_shell_plugin_plugin_info;
 }
 
@@ -399,6 +405,12 @@ gnome_shell_plugin_keybinding_filter (MetaPlugin     *plugin,
   return _shell_wm_filter_keybinding (get_shell_wm (), binding);
 }
 
+static void
+gnome_shell_plugin_confirm_display_change (MetaPlugin *plugin)
+{
+  _shell_wm_confirm_display_change (get_shell_wm ());
+}
+
 static const
 MetaPluginInfo *gnome_shell_plugin_plugin_info (MetaPlugin *plugin)
 {

src/shell-wm-private.h

@@ -38,6 +38,8 @@ void _shell_wm_kill_switch_workspace (ShellWM             *wm);
 gboolean _shell_wm_filter_keybinding (ShellWM             *wm,
                                       MetaKeyBinding      *binding);
 
+void _shell_wm_confirm_display_change (ShellWM            *wm);
+
 G_END_DECLS
 
 #endif /* __SHELL_WM_PRIVATE_H__ */

src/shell-wm.c

@@ -27,6 +27,7 @@ enum
   KILL_SWITCH_WORKSPACE,
   KILL_WINDOW_EFFECTS,
   FILTER_KEYBINDING,
+  CONFIRM_DISPLAY_CHANGE,
 
   LAST_SIGNAL
 };
@@ -124,6 +125,13 @@ shell_wm_class_init (ShellWMClass *klass)
                   g_signal_accumulator_true_handled, NULL, NULL,
                   G_TYPE_BOOLEAN, 1,
                   META_TYPE_KEY_BINDING);
+  shell_wm_signals[CONFIRM_DISPLAY_CHANGE] =
+    g_signal_new ("confirm-display-change",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
 }
 
 void
@@ -219,6 +227,20 @@ shell_wm_completed_destroy (ShellWM         *wm,
   meta_plugin_destroy_completed (wm->plugin, actor);
 }
 
+/**
+ * shell_wm_complete_display_change:
+ * @wm: the ShellWM
+ * @ok: if the new configuration was OK
+ *
+ * The plugin must call this after the user responded to the confirmation dialog.
+ */
+void
+shell_wm_complete_display_change (ShellWM  *wm,
+                                  gboolean  ok)
+{
+  meta_plugin_complete_display_change (wm->plugin, ok);
+}
+
 void
 _shell_wm_kill_switch_workspace (ShellWM      *wm)
 {
@@ -287,6 +309,12 @@ _shell_wm_filter_keybinding (ShellWM             *wm,
   return rv;
 }
 
+void
+_shell_wm_confirm_display_change (ShellWM *wm)
+{
+  g_signal_emit (wm, shell_wm_signals[CONFIRM_DISPLAY_CHANGE], 0);
+}
+
 /**
  * shell_wm_new:
  * @plugin: the #MetaPlugin

src/shell-wm.h

@@ -39,6 +39,9 @@ void     shell_wm_completed_destroy          (ShellWM         *wm,
                                               MetaWindowActor *actor);
 void     shell_wm_completed_switch_workspace (ShellWM         *wm);
 
+void     shell_wm_complete_display_change    (ShellWM         *wm,
+                                              gboolean         ok);
+
 G_END_DECLS
 
 #endif /* __SHELL_WM_H__ */