keybindings: Add a switch-monitor builtin keybinding

Moved from g-s-d's media keys plugin, where it was called "video-out",
since it requires changing the current monitor configuration and we
want to remove the old DBus API.

This implementation is intentionally simple and not really meant for
more than debugging and validating the various configurations. A
better user experience will be introduced in gnome-shell with a custom
keybinding handler.

The default value includes <Super>P in addition to the standard keysym
for historical reasons.

https://bugzilla.gnome.org/show_bug.cgi?id=781906

src/core/keybindings.c

@@ -3328,6 +3328,27 @@ handle_switch_vt (MetaDisplay     *display,
 }
 #endif /* HAVE_NATIVE_BACKEND */
 
+static void
+handle_switch_monitor (MetaDisplay    *display,
+                       MetaScreen     *screen,
+                       MetaWindow     *window,
+                       ClutterKeyEvent *event,
+                       MetaKeyBinding *binding,
+                       gpointer        dummy)
+{
+  MetaBackend *backend = meta_get_backend ();
+  MetaMonitorManager *monitor_manager =
+    meta_backend_get_monitor_manager (backend);
+  MetaMonitorSwitchConfigType config_type =
+    meta_monitor_manager_get_switch_config (monitor_manager);
+
+  if (!meta_monitor_manager_can_switch_config (monitor_manager))
+    return;
+
+  config_type = (config_type + 1) % (META_MONITOR_SWITCH_CONFIG_UNKNOWN);
+  meta_monitor_manager_switch_config (monitor_manager, config_type);
+}
+
 static void
 handle_rotate_monitor (MetaDisplay    *display,
                        MetaScreen     *screen,
@@ -3632,6 +3653,13 @@ init_builtin_key_bindings (MetaDisplay *display)
                           META_KEYBINDING_ACTION_SET_SPEW_MARK,
                           handle_set_spew_mark, 0);
 
+  add_builtin_keybinding (display,
+                          "switch-monitor",
+                          mutter_keybindings,
+                          META_KEY_BINDING_NONE,
+                          META_KEYBINDING_ACTION_SWITCH_MONITOR,
+                          handle_switch_monitor, 0);
+
   add_builtin_keybinding (display,
                           "rotate-monitor",
                           mutter_keybindings,

src/meta/prefs.h

@@ -357,6 +357,7 @@ typedef enum _MetaKeyBindingAction
   META_KEYBINDING_ACTION_OVERLAY_KEY,
   META_KEYBINDING_ACTION_ISO_NEXT_GROUP,
   META_KEYBINDING_ACTION_ALWAYS_ON_TOP,
+  META_KEYBINDING_ACTION_SWITCH_MONITOR,
   META_KEYBINDING_ACTION_ROTATE_MONITOR,
 
   META_KEYBINDING_ACTION_LAST