clutter/evdev: Dispatch libinput before generating key repeat events

Since both the libinput event source and the key repeat timer have the
same priority, the order in which both handlers are called is
arbitrary if both sources are ready on the same poll return. This
means that sometimes we generate key repeats when there's already a
real key event queued on libinput that would cancel the repeat timer
if only it was processed before.

One solution would be lowering the repeat timer source priority a
notch lower than the libinput source but that would mean that a steady
stream of events from libinput (e.g. pointer device motion) would
prevent any key repeats to happen.

Instead, we can fix this problem by trying to dispatch libinput from
the key repeat timer and checking if the timer source has been
destroyed before generating more key repeats.

https://bugzilla.gnome.org/show_bug.cgi?id=774989

3 files changed, 14 insertions, 0 deletions

diff --git a/clutter/clutter/evdev/clutter-device-manager-evdev.c b/clutter/clutter/evdev/clutter-device-manager-evdev.c
index c03c68cec..04dcb2eb7 100644
--- a/clutter/clutter/evdev/clutter-device-manager-evdev.c
+++ b/clutter/clutter/evdev/clutter-device-manager-evdev.c
@@ -2261,6 +2261,12 @@ _clutter_device_manager_evdev_acquire_device_id (ClutterDeviceManagerEvdev *mana
   return next_id;
 }
 
+void
+_clutter_device_manager_evdev_dispatch (ClutterDeviceManagerEvdev *manager_evdev)
+{
+  dispatch_libinput (manager_evdev);
+}
+
 static int
 compare_ids (gconstpointer a,
              gconstpointer b)
diff --git a/clutter/clutter/evdev/clutter-device-manager-evdev.h b/clutter/clutter/evdev/clutter-device-manager-evdev.h
index 1b01b8d06..c2dbe3198 100644
--- a/clutter/clutter/evdev/clutter-device-manager-evdev.h
+++ b/clutter/clutter/evdev/clutter-device-manager-evdev.h
@@ -76,6 +76,8 @@ void _clutter_device_manager_evdev_constrain_pointer (ClutterDeviceManagerEvdev
                                                       float                     *new_x,
                                                       float                     *new_y);
 
+void _clutter_device_manager_evdev_dispatch (ClutterDeviceManagerEvdev *manager_evdev);
+
 static inline guint64
 us (guint64 us)
 {
diff --git a/clutter/clutter/evdev/clutter-seat-evdev.c b/clutter/clutter/evdev/clutter-seat-evdev.c
index 2fc040bb6..17464cf75 100644
--- a/clutter/clutter/evdev/clutter-seat-evdev.c
+++ b/clutter/clutter/evdev/clutter-seat-evdev.c
@@ -186,6 +186,12 @@ keyboard_repeat (gpointer data)
   ClutterSeatEvdev *seat = data;
   GSource *source;
 
+  /* There might be events queued in libinput that could cancel the
+     repeat timer. */
+  _clutter_device_manager_evdev_dispatch (seat->manager_evdev);
+  if (!seat->repeat_timer)
+    return G_SOURCE_REMOVE;
+
   g_return_val_if_fail (seat->repeat_device != NULL, G_SOURCE_REMOVE);
   source = g_main_context_find_source_by_id (NULL, seat->repeat_timer);