[mutter] clutter-main: Add hooks to plug kbd accessibility

[Olivier Fourdan <ofourdan src gnome org>]

commit 7d5e08c8438f486b522219a7b11baa063a4bf5db
Author: Olivier Fourdan <ofourdan redhat com>
Date:   Thu Oct 12 15:14:51 2017 +0200

    clutter-main: Add hooks to plug kbd accessibility
    
    On X11, when AccessX is enabled, all X11 clients benefit from the
    AccessX features, including gnome-shell/mutter, meaning that special
    keys like the overview or other shortcuts are also affected.
    
    To achieve the same in Wayland, we need to implement the same features
    in clutter main rather than the Wayland backend, so that all depending
    code within the compositor but also Wayland clients (which rely on the
    compositor to get keyboard events) similarly benefit from the
    accessibility features.
    
    Add hooks to the clutter main loop to be able to implement such
    features.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=788564

 clutter/clutter/clutter-device-manager-private.h |    8 ++++++++
 clutter/clutter/clutter-main.c                   |   17 ++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletions(-)
---
diff --git a/clutter/clutter/clutter-device-manager-private.h 
b/clutter/clutter/clutter-device-manager-private.h
index 57423c4..2364fd2 100644
--- a/clutter/clutter/clutter-device-manager-private.h
+++ b/clutter/clutter/clutter-device-manager-private.h
@@ -145,6 +145,9 @@ struct _ClutterInputDevice
   guint is_enabled : 1;
 };
 
+typedef void (*ClutterEmitInputDeviceEvent) (ClutterEvent       *event,
+                                             ClutterInputDevice *device);
+
 struct _ClutterInputDeviceClass
 {
   GObjectClass parent_class;
@@ -163,6 +166,11 @@ struct _ClutterInputDeviceClass
 
   gboolean (* is_grouped) (ClutterInputDevice *device,
                            ClutterInputDevice *other_device);
+
+  /* Keyboard accessbility */
+  void (* process_kbd_a11y_event) (ClutterEvent               *event,
+                                   ClutterInputDevice         *device,
+                                   ClutterEmitInputDeviceEvent emit_event_func);
 };
 
 /* Platform-dependent interface */
diff --git a/clutter/clutter/clutter-main.c b/clutter/clutter/clutter-main.c
index 0f85db6..46537f3 100644
--- a/clutter/clutter/clutter-main.c
+++ b/clutter/clutter/clutter-main.c
@@ -2089,6 +2089,21 @@ emit_keyboard_event (ClutterEvent       *event,
     }
 }
 
+static inline void
+process_key_event (ClutterEvent       *event,
+                   ClutterInputDevice *device)
+{
+  ClutterInputDeviceClass *device_class = CLUTTER_INPUT_DEVICE_GET_CLASS (device);
+
+  if (device_class->process_kbd_a11y_event)
+    {
+      device_class->process_kbd_a11y_event (event, device, emit_keyboard_event);
+      return;
+    }
+
+  emit_keyboard_event (event, device);
+}
+
 static gboolean
 is_off_stage (ClutterActor *stage,
               gfloat        x,
@@ -2176,7 +2191,7 @@ _clutter_process_event_details (ClutterActor        *stage,
                 }
             }
 
-          emit_keyboard_event (event, device);
+          process_key_event (event, device);
         }
         break;