evdev: sync the keyboard state when releasing and reclaiming devices

When we release a device, we lose all the events after that point,
so our state can become stale. Similarly, we need to sync the
state with the effectively pressed keys when we reclaim.
This ensures that modifier keys don't get stuck when switching
VTs using a keybinding.

https://bugzilla.gnome.org/show_bug.cgi?id=706494

clutter/evdev/clutter-device-manager-evdev.c

@@ -188,12 +188,12 @@ remove_key (GArray  *keys,
 }
 
 static void
-notify_key (ClutterEventSource *source,
+notify_key_device (ClutterInputDevice *input_device,
-            guint32             time_,
+		   guint32             time_,
-            guint32             key,
+		   guint32             key,
-            guint32             state)
+		   guint32             state,
+		   gboolean            update_keys)
 {
-  ClutterInputDevice *input_device = (ClutterInputDevice *) source->device;
   ClutterDeviceManagerEvdev *manager_evdev;
   ClutterStage *stage;
   ClutterEvent *event = NULL;
@@ -223,16 +223,29 @@ notify_key (ClutterEventSource *source,
 	{
 	  xkb_state_update_key (manager_evdev->priv->xkb, event->key.hardware_keycode, state ? XKB_KEY_DOWN : XKB_KEY_UP);
 
-	  if (state)
+	  if (update_keys)
-	    add_key (manager_evdev->priv->keys, event->key.hardware_keycode);
+	    {
-	  else
+	      if (state)
-	    remove_key (manager_evdev->priv->keys, event->key.hardware_keycode);
+		add_key (manager_evdev->priv->keys, event->key.hardware_keycode);
+	      else
+		remove_key (manager_evdev->priv->keys, event->key.hardware_keycode);
+	    }
 	}
 
       queue_event (event);
     }
 }
 
+static void
+notify_key (ClutterEventSource *source,
+            guint32             time_,
+            guint32             key,
+            guint32             state)
+{
+  ClutterInputDevice *input_device = (ClutterInputDevice *) source->device;
+
+  notify_key_device (input_device, time_, key, state, TRUE);
+}
 
 static void
 notify_relative_motion (ClutterEventSource *source,
@@ -1197,6 +1210,8 @@ clutter_evdev_release_devices (void)
   ClutterDeviceManagerEvdev *evdev_manager;
   ClutterDeviceManagerEvdevPrivate *priv;
   GSList *l, *next;
+  uint32_t time_;
+  unsigned i;
 
   if (!manager)
     {
@@ -1218,6 +1233,13 @@ clutter_evdev_release_devices (void)
       return;
     }
 
+  /* Fake release events for all currently pressed keys */
+  time_ = g_get_monotonic_time () / 1000;
+  for (i = 0; i < priv->keys->len; i++)
+    notify_key_device (priv->core_keyboard, time_,
+		       g_array_index (priv->keys, uint32_t, i) - 8, 0, FALSE);
+  g_array_set_size (priv->keys, 0);
+
   for (l = priv->devices; l; l = next)
     {
       ClutterInputDevice *device = l->data;
@@ -1251,6 +1273,13 @@ clutter_evdev_reclaim_devices (void)
   ClutterDeviceManager *manager = clutter_device_manager_get_default ();
   ClutterDeviceManagerEvdev *evdev_manager;
   ClutterDeviceManagerEvdevPrivate *priv;
+#define LONG_BITS (sizeof(long) * 8)
+#define NLONGS(x) (((x) + LONG_BITS - 1) / LONG_BITS)
+  unsigned long key_bits[NLONGS(KEY_CNT)];
+  unsigned long source_key_bits[NLONGS(KEY_CNT)];
+  GSList *iter;
+  int i, j, rc;
+  guint32 time_;
 
   if (!manager)
     {
@@ -1273,6 +1302,37 @@ clutter_evdev_reclaim_devices (void)
 
   priv->released = FALSE;
   clutter_device_manager_evdev_probe_devices (evdev_manager);
+
+  memset (key_bits, 0, sizeof (key_bits));
+  for (iter = priv->event_sources; iter; iter++)
+    {
+      ClutterEventSource *source = iter->data;
+      ClutterInputDevice *slave = CLUTTER_INPUT_DEVICE (source->device);
+
+      if (clutter_input_device_get_device_type (slave) == CLUTTER_KEYBOARD_DEVICE)
+	{
+	  rc = ioctl (source->event_poll_fd.fd, EVIOCGBIT(EV_KEY, sizeof (source_key_bits)), source_key_bits);
+	  if (rc < 0)
+	    continue;
+
+	  for (i = 0; i < NLONGS(KEY_CNT); i++)
+	    key_bits[i] |= source_key_bits[i];
+	}
+    }
+
+  /* Fake press events for all currently pressed keys */
+  time_ = g_get_monotonic_time () / 1000;
+  for (i = 0; i < NLONGS(KEY_CNT); i++)
+    {
+      for (j = 0; j < 8; j++)
+	{
+	  if (key_bits[i] & (1 << j))
+	    notify_key_device (priv->core_keyboard, time_, i * 8 + j, 1, TRUE);
+	}
+    }
+
+#undef LONG_BITS
+#undef NLONGS
 }
 
 /**