seat/native/impl: Start reading input device events when starting

This opens up for a possibility to handle initial events (devices
discovered on startup) during initialization, meaning we can figure out
a more correct initial state that depends on available input devices.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3070>

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

@@ -756,6 +756,17 @@ init_gpus (MetaBackendNative  *native,
   return TRUE;
 }
 
+static void
+on_started (MetaContext *context,
+            MetaBackend *backend)
+{
+  ClutterBackend *clutter_backend = meta_backend_get_clutter_backend (backend);
+  ClutterSeat *seat;
+
+  seat = clutter_backend_get_default_seat (clutter_backend);
+  meta_seat_native_start (META_SEAT_NATIVE (seat));
+}
+
 static gboolean
 meta_backend_native_initable_init (GInitable     *initable,
                                    GCancellable  *cancellable,
@@ -804,6 +815,11 @@ meta_backend_native_initable_init (GInitable     *initable,
   if (!init_gpus (native, error))
     return FALSE;
 
+  g_signal_connect (meta_backend_get_context (backend),
+                    "started",
+                    G_CALLBACK (on_started),
+                    backend);
+
   return initable_parent_iface->init (initable, cancellable, error);
 }
 

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

@@ -2809,7 +2809,6 @@ static gboolean
 init_libinput (MetaSeatImpl  *seat_impl,
                GError       **error)
 {
-  MetaEventSource *source;
   struct udev *udev;
   struct libinput *libinput;
 
@@ -2841,12 +2840,19 @@ init_libinput (MetaSeatImpl  *seat_impl,
     }
 
   seat_impl->libinput = libinput;
-  source = meta_event_source_new (seat_impl);
-  seat_impl->event_source = source;
 
   return TRUE;
 }
 
+static void
+init_libinput_source (MetaSeatImpl *seat_impl)
+{
+  MetaEventSource *source;
+
+  source = meta_event_source_new (seat_impl);
+  seat_impl->event_source = source;
+}
+
 static gpointer
 input_thread (MetaSeatImpl *seat_impl)
 {
@@ -3773,6 +3779,32 @@ meta_seat_impl_new (MetaSeatNative     *seat_native,
                          NULL);
 }
 
+static gboolean
+start_in_impl (GTask *task)
+{
+  MetaSeatImpl *seat_impl = g_task_get_source_object (task);
+
+  if (seat_impl->libinput)
+    init_libinput_source (seat_impl);
+
+  g_task_return_boolean (task, TRUE);
+
+  return G_SOURCE_REMOVE;
+}
+
+void
+meta_seat_impl_start (MetaSeatImpl *seat_impl)
+{
+  GTask *task;
+
+  g_return_if_fail (META_IS_SEAT_IMPL (seat_impl));
+
+  task = g_task_new (seat_impl, NULL, NULL, NULL);
+  meta_seat_impl_run_input_task (seat_impl, task,
+                                 (GSourceFunc) start_in_impl);
+  g_object_unref (task);
+}
+
 void
 meta_seat_impl_notify_kbd_a11y_flags_changed_in_impl (MetaSeatImpl          *seat_impl,
                                                       MetaKeyboardA11yFlags  new_flags,

src/backends/native/meta-seat-impl.h

@@ -131,6 +131,8 @@ MetaSeatImpl * meta_seat_impl_new (MetaSeatNative     *seat_native,
                                    const char         *seat_id,
                                    MetaSeatNativeFlag  flags);
 
+void meta_seat_impl_start (MetaSeatImpl *seat_impl);
+
 void meta_seat_impl_destroy (MetaSeatImpl *seat_impl);
 
 META_EXPORT_TEST

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

@@ -425,6 +425,12 @@ meta_seat_native_init (MetaSeatNative *seat)
   seat->reserved_virtual_slots = g_hash_table_new (NULL, NULL);
 }
 
+void
+meta_seat_native_start (MetaSeatNative *seat_native)
+{
+  meta_seat_impl_start (seat_native->impl);
+}
+
 /**
  * meta_seat_native_release_devices:
  *

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

@@ -71,6 +71,8 @@ META_EXPORT_TEST
 G_DECLARE_FINAL_TYPE (MetaSeatNative, meta_seat_native,
                       META, SEAT_NATIVE, ClutterSeat)
 
+void meta_seat_native_start (MetaSeatNative *seat_native);
+
 void meta_seat_native_set_libinput_seat (MetaSeatNative       *seat,
                                          struct libinput_seat *libinput_seat);