[mutter/gnome-3-36] seat-native: Process device added/removed events as ClutterEvents

[Marco Trevisan <marcotrevi src gnome org>]

commit f5e4abd48e7ed2274a1e1ec60088a887d2078f95
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Fri Jul 17 17:50:17 2020 +0200

    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
    
    (cherry picked from commit e44c42f254a068147c87985d93b12a68f130b1b3)

 src/backends/native/meta-seat-native.c | 108 +++++++++++++++++----------------
 1 file changed, 57 insertions(+), 51 deletions(-)
---
diff --git a/src/backends/native/meta-seat-native.c b/src/backends/native/meta-seat-native.c
index ecff929bd8..128d7c8aff 100644
--- a/src/backends/native/meta-seat-native.c
+++ b/src/backends/native/meta-seat-native.c
@@ -1404,14 +1404,13 @@ 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));
@@ -1434,25 +1433,7 @@ evdev_add_device (MetaSeatNative         *seat,
       _clutter_input_device_add_slave (master, device);
     }
 
-  g_signal_emit_by_name (seat, "device-added", 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);
+  return device;
 }
 
 static void
@@ -1460,74 +1441,98 @@ 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);
+  g_object_unref (device);
+}
+
+static gboolean
+meta_seat_native_handle_device_event (ClutterSeat  *seat,
+                                      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;
 
-  device_type = clutter_input_device_get_device_type (device);
+  check_touch_mode =
+    clutter_input_device_get_device_type (device) == CLUTTER_TOUCHSCREEN_DEVICE;
 
-  if (device_type == CLUTTER_TOUCHSCREEN_DEVICE)
+  switch (event->type)
     {
-      seat->has_touchscreen = has_touchscreen (seat);
-      update_touch_mode (seat);
-    }
+      case CLUTTER_DEVICE_ADDED:
+        seat_native->has_touchscreen = check_touch_mode;
 
-  if (seat->repeat_timer && seat->repeat_device == device)
-    meta_seat_native_clear_repeat_timer (seat);
+        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;
 
-  g_object_run_dispose (G_OBJECT (device));
-  g_object_unref (device);
-}
+      case CLUTTER_DEVICE_REMOVED:
+        if (check_touch_mode)
+          seat_native->has_touchscreen = has_touchscreen (seat_native);
 
-static void
-flush_event_queue (void)
-{
-  ClutterEvent *event;
+        if (seat_native->repeat_timer && seat_native->repeat_device == device)
+          meta_seat_native_clear_repeat_timer (seat_native);
+        break;
 
-  while ((event = clutter_event_get ()) != NULL)
-    {
-      _clutter_process_event (event);
-      clutter_event_free (event);
+      default:
+        break;
     }
+
+  if (check_touch_mode)
+    update_touch_mode (seat_native);
+
+  return TRUE;
 }
 
 static gboolean
 process_base_event (MetaSeatNative        *seat,
                     struct libinput_event *event)
 {
-  ClutterInputDevice *device;
+  ClutterInputDevice *device = NULL;
+  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)
+    {
+      device_event->device.stage = _clutter_input_device_get_stage (device);
+      queue_event (device_event);
+      return TRUE;
+    }
+
+  return FALSE;
 }
 
 static ClutterScrollSource
@@ -2781,6 +2786,7 @@ 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",