seat-native: Process device added/removed events as ClutterEvents

Delay the addition and removal of devices using ClutterDeviceEvent's so that
they are processed following the libinput event order, and that we don't
have to flush the events on removal.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1371

src/backends/native/meta-seat-native.c

@@ -1391,14 +1391,13 @@ update_touch_mode (MetaSeatNative *seat)
     }
 }
 
-static void
+static ClutterInputDevice *
 evdev_add_device (MetaSeatNative         *seat,
                   struct libinput_device *libinput_device)
 {
   ClutterInputDeviceType type;
   ClutterInputDevice *device, *master = NULL;
   ClutterActor *stage;
-  gboolean check_touch_mode = FALSE;
 
   device = meta_input_device_native_new (seat, libinput_device);
   stage = CLUTTER_ACTOR (meta_seat_native_get_stage (seat));
@@ -1421,25 +1420,7 @@ evdev_add_device (MetaSeatNative         *seat,
       _clutter_input_device_add_slave (master, device);
     }
 
-  g_signal_emit_by_name (seat, "device-added", device);
+  return device;
-
-  if (type == CLUTTER_TOUCHSCREEN_DEVICE)
-    {
-      seat->has_touchscreen = TRUE;
-      check_touch_mode = TRUE;
-    }
-
-  if (libinput_device_has_capability (libinput_device,
-                                      LIBINPUT_DEVICE_CAP_SWITCH) &&
-      libinput_device_switch_has_switch (libinput_device,
-                                         LIBINPUT_SWITCH_TABLET_MODE))
-    {
-      seat->has_tablet_switch = TRUE;
-      check_touch_mode = TRUE;
-    }
-
-  if (check_touch_mode)
-    update_touch_mode (seat);
 }
 
 static void
@@ -1447,38 +1428,56 @@ evdev_remove_device (MetaSeatNative        *seat,
                      MetaInputDeviceNative *device_evdev)
 {
   ClutterInputDevice *device;
-  ClutterInputDeviceType device_type;
 
   device = CLUTTER_INPUT_DEVICE (device_evdev);
   seat->devices = g_slist_remove (seat->devices, device);
 
-  g_signal_emit_by_name (seat, "device-removed", device);
-
-  device_type = clutter_input_device_get_device_type (device);
-
-  if (device_type == CLUTTER_TOUCHSCREEN_DEVICE)
-    {
-      seat->has_touchscreen = has_touchscreen (seat);
-      update_touch_mode (seat);
-    }
-
-  if (seat->repeat_timer && seat->repeat_device == device)
-    meta_seat_native_clear_repeat_timer (seat);
-
-  g_object_run_dispose (G_OBJECT (device));
   g_object_unref (device);
 }
 
-static void
+static gboolean
-flush_event_queue (void)
+meta_seat_native_handle_device_event (ClutterSeat  *seat,
+                                      ClutterEvent *event)
 {
-  ClutterEvent *event;
+  MetaSeatNative *seat_native = META_SEAT_NATIVE (seat);
+  ClutterInputDevice *device = event->device.device;
+  MetaInputDeviceNative *device_native = META_INPUT_DEVICE_NATIVE (device);
+  gboolean check_touch_mode;
 
-  while ((event = clutter_event_get ()) != NULL)
+  check_touch_mode =
+    clutter_input_device_get_device_type (device) == CLUTTER_TOUCHSCREEN_DEVICE;
+
+  switch (event->type)
     {
-      _clutter_process_event (event);
+      case CLUTTER_DEVICE_ADDED:
-      clutter_event_free (event);
+        seat_native->has_touchscreen = check_touch_mode;
+
+        if (libinput_device_has_capability (device_native->libinput_device,
+                                            LIBINPUT_DEVICE_CAP_SWITCH) &&
+            libinput_device_switch_has_switch (device_native->libinput_device,
+                                               LIBINPUT_SWITCH_TABLET_MODE))
+          {
+            seat_native->has_tablet_switch = TRUE;
+            check_touch_mode = TRUE;
+          }
+        break;
+
+      case CLUTTER_DEVICE_REMOVED:
+        if (check_touch_mode)
+          seat_native->has_touchscreen = has_touchscreen (seat_native);
+
+        if (seat_native->repeat_timer && seat_native->repeat_device == device)
+          meta_seat_native_clear_repeat_timer (seat_native);
+        break;
+
+      default:
+        break;
     }
+
+  if (check_touch_mode)
+    update_touch_mode (seat_native);
+
+  return TRUE;
 }
 
 static gboolean
@@ -1486,35 +1485,40 @@ process_base_event (MetaSeatNative        *seat,
                     struct libinput_event *event)
 {
   ClutterInputDevice *device;
+  ClutterEvent *device_event;
   struct libinput_device *libinput_device;
-  gboolean handled = TRUE;
 
   switch (libinput_event_get_type (event))
     {
     case LIBINPUT_EVENT_DEVICE_ADDED:
       libinput_device = libinput_event_get_device (event);
 
-      evdev_add_device (seat, libinput_device);
+      device = evdev_add_device (seat, libinput_device);
+      device_event = clutter_event_new (CLUTTER_DEVICE_ADDED);
+      clutter_event_set_device (device_event, device);
       break;
 
     case LIBINPUT_EVENT_DEVICE_REMOVED:
-      /* Flush all queued events, there
-       * might be some from this device.
-       */
-      flush_event_queue ();
-
       libinput_device = libinput_event_get_device (event);
 
       device = libinput_device_get_user_data (libinput_device);
+      device_event = clutter_event_new (CLUTTER_DEVICE_REMOVED);
+      clutter_event_set_device (device_event, device);
       evdev_remove_device (seat,
                            META_INPUT_DEVICE_NATIVE (device));
       break;
 
     default:
-      handled = FALSE;
+      device_event = NULL;
     }
 
-  return handled;
+  if (device_event)
+    {
+      queue_event (device_event);
+      return TRUE;
+    }
+
+  return FALSE;
 }
 
 static ClutterScrollSource
@@ -2763,6 +2767,7 @@ meta_seat_native_class_init (MetaSeatNativeClass *klass)
   seat_class->get_supported_virtual_device_types = meta_seat_native_get_supported_virtual_device_types;
   seat_class->compress_motion = meta_seat_native_compress_motion;
   seat_class->warp_pointer = meta_seat_native_warp_pointer;
+  seat_class->handle_device_event = meta_seat_native_handle_device_event;
 
   props[PROP_SEAT_ID] =
     g_param_spec_string ("seat-id",