[mutter/wip/wayland-input] wayland: Use a signal emission hook to catch grabbed events

[Neil Roberts <nroberts src gnome org>]

commit 8cf1c4ad0f5b7c8c9b104945ae4a3b4b4ed516dc
Author: Neil Roberts <neil linux intel com>
Date:   Thu Apr 26 11:39:17 2012 +0100

    wayland: Use a signal emission hook to catch grabbed events
    
    The wayland input device needs to see all pointer events in order to
    update the cursor position. Previously it would do this just by
    listening for the captured event signal on the stage. Gnome Shell sets
    a pointer grab on some actors while dragging and this causes the
    captured event signal not to be emitted so the cursor position does
    not get updated. To workaround that this patch adds a signal emission
    hook on the event signal. When a pointer or keyboard event is seen and
    there is a pointer or keyboard grab in place then it will forward the
    event on to the captured event handler.

 src/wayland/meta-wayland.c |   65 +++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 64 insertions(+), 1 deletions(-)
---
diff --git a/src/wayland/meta-wayland.c b/src/wayland/meta-wayland.c
index a61e7ad..c957ca1 100644
--- a/src/wayland/meta-wayland.c
+++ b/src/wayland/meta-wayland.c
@@ -1405,10 +1405,63 @@ event_cb (ClutterActor *stage,
   return FALSE;
 }
 
+static gboolean
+event_emission_hook_cb (GSignalInvocationHint *ihint,
+                        guint n_param_values,
+                        const GValue *param_values,
+                        gpointer data)
+{
+  MetaWaylandCompositor *compositor = data;
+  ClutterActor *actor;
+  ClutterEvent *event;
+
+  g_return_val_if_fail (n_param_values == 2, FALSE);
+
+  actor = g_value_get_object (param_values + 0);
+  event = g_value_get_boxed (param_values + 1);
+
+  if (actor == NULL)
+    return TRUE /* stay connected */;
+
+  /* If this event belongs to the corresponding grab for this event
+   * type then the captured-event signal won't be emitted so we have
+   * to manually forward it on */
+
+  switch (event->type)
+    {
+      /* Pointer events */
+    case CLUTTER_MOTION:
+    case CLUTTER_ENTER:
+    case CLUTTER_LEAVE:
+    case CLUTTER_BUTTON_PRESS:
+    case CLUTTER_BUTTON_RELEASE:
+    case CLUTTER_SCROLL:
+      if (actor == clutter_get_pointer_grab ())
+        event_cb (clutter_actor_get_stage (actor),
+                  event,
+                  compositor);
+      break;
+
+      /* Keyboard events */
+    case CLUTTER_KEY_PRESS:
+    case CLUTTER_KEY_RELEASE:
+      if (actor == clutter_get_keyboard_grab ())
+        event_cb (clutter_actor_get_stage (actor),
+                  event,
+                  compositor);
+
+    default:
+      break;
+    }
+
+  return TRUE /* stay connected */;
+}
+
 void
 meta_wayland_init (void)
 {
   MetaWaylandCompositor *compositor = &_meta_wayland_compositor;
+  guint event_signal;
 
   memset (compositor, 0, sizeof (MetaWaylandCompositor));
 
@@ -1458,8 +1511,18 @@ meta_wayland_init (void)
                           G_CALLBACK (paint_finished_cb), compositor);
   g_signal_connect (compositor->stage, "destroy",
                     G_CALLBACK (stage_destroy_cb), NULL);
-  g_signal_connect (compositor->stage, "event",
+  g_signal_connect (compositor->stage, "captured-event",
                     G_CALLBACK (event_cb), compositor);
+  /* If something sets a grab on an actor then the captured event
+   * signal won't get emitted but we still want to see these events so
+   * we can update the cursor position. To make sure we see all events
+   * we also install an emission hook on the event signal */
+  event_signal = g_signal_lookup ("event", CLUTTER_TYPE_STAGE);
+  g_signal_add_emission_hook (event_signal,
+                              0 /* detail */,
+                              event_emission_hook_cb,
+                              compositor, /* hook_data */
+                              NULL /* data_destroy */);
 
   wl_data_device_manager_init (compositor->wayland_display);