[mutter] core: Add MetaDisplay::pad-mode-switch signal

[Carlos Garnacho <carlosg src gnome org>]

commit 9950b4de755d7b42c0454445f247f8995e2d7fbe
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Dec 28 13:00:18 2016 +0100

    core: Add MetaDisplay::pad-mode-switch signal
    
    This signal provides the necessary information to let gnome-shell trigger
    updates of pad leds/oleds whenever a pad group switches mode, and the
    actions associated to buttons do too.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=776543

 src/core/display.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/src/core/display.c b/src/core/display.c
index 080c328..79cd358 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -132,6 +132,7 @@ enum
   GL_VIDEO_MEMORY_PURGED,
   SHOW_PAD_OSD,
   SHOW_OSD,
+  PAD_MODE_SWITCH,
   LAST_SIGNAL
 };
 
@@ -385,6 +386,14 @@ meta_display_class_init (MetaDisplayClass *klass)
                   0, NULL, NULL, NULL,
                   G_TYPE_NONE, 3, G_TYPE_INT, G_TYPE_STRING, G_TYPE_STRING);
 
+  display_signals[PAD_MODE_SWITCH] =
+    g_signal_new ("pad-mode-switch",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  0, NULL, NULL, NULL,
+                  G_TYPE_NONE, 3, CLUTTER_TYPE_INPUT_DEVICE,
+                  G_TYPE_UINT, G_TYPE_UINT);
+
   g_object_class_install_property (object_class,
                                    PROP_FOCUS_WINDOW,
                                    g_param_spec_object ("focus-window",
@@ -3256,5 +3265,8 @@ meta_display_notify_pad_group_switch (MetaDisplay        *display,
   meta_display_show_osd (display, lookup_tablet_monitor (display, pad),
                          "input-tablet-symbolic", message->str);
 
+  g_signal_emit (display, display_signals[PAD_MODE_SWITCH], 0, pad,
+                 n_group, n_mode);
+
   g_string_free (message, TRUE);
 }