backends/native: Release virtual buttons on dispose instead of finalize

GObject recommends to break references to other objects on dispose
instead of finalize, also we want to release the pressed virtual buttons
as early as possible if we know the object is getting destroyed.

So release the pressed buttons and unref our virtual
MetaInputDeviceNative when the dispose vfunc is called, which also
allows us to release the buttons immediately from javascript instead of
waiting for the garbage collector by calling run_dispose() on the
object.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1157

src/backends/native/meta-virtual-input-device-native.c

@@ -155,6 +155,8 @@ meta_virtual_input_device_native_notify_relative_motion (ClutterVirtualInputDevi
   MetaVirtualInputDeviceNative *virtual_evdev =
     META_VIRTUAL_INPUT_DEVICE_NATIVE (virtual_device);
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -174,6 +176,8 @@ meta_virtual_input_device_native_notify_absolute_motion (ClutterVirtualInputDevi
   MetaVirtualInputDeviceNative *virtual_evdev =
     META_VIRTUAL_INPUT_DEVICE_NATIVE (virtual_device);
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -215,6 +219,8 @@ meta_virtual_input_device_native_notify_button (ClutterVirtualInputDevice *virtu
   int button_count;
   int evdev_button;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -258,6 +264,8 @@ meta_virtual_input_device_native_notify_key (ClutterVirtualInputDevice *virtual_
     META_VIRTUAL_INPUT_DEVICE_NATIVE (virtual_device);
   int key_count;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -395,6 +403,8 @@ meta_virtual_input_device_native_notify_keyval (ClutterVirtualInputDevice *virtu
   int key_count;
   guint keycode = 0, level = 0, evcode = 0;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -482,6 +492,8 @@ meta_virtual_input_device_native_notify_discrete_scroll (ClutterVirtualInputDevi
     META_VIRTUAL_INPUT_DEVICE_NATIVE (virtual_device);
   double discrete_dx = 0.0, discrete_dy = 0.0;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -505,6 +517,8 @@ meta_virtual_input_device_native_notify_scroll_continuous (ClutterVirtualInputDe
   MetaVirtualInputDeviceNative *virtual_evdev =
     META_VIRTUAL_INPUT_DEVICE_NATIVE (virtual_device);
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -529,6 +543,8 @@ meta_virtual_input_device_native_notify_touch_down (ClutterVirtualInputDevice *v
     META_INPUT_DEVICE_NATIVE (virtual_evdev->device);
   MetaTouchState *touch_state;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -562,6 +578,8 @@ meta_virtual_input_device_native_notify_touch_motion (ClutterVirtualInputDevice
     META_INPUT_DEVICE_NATIVE (virtual_evdev->device);
   MetaTouchState *touch_state;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -593,6 +611,8 @@ meta_virtual_input_device_native_notify_touch_up (ClutterVirtualInputDevice *vir
     META_INPUT_DEVICE_NATIVE (virtual_evdev->device);
   MetaTouchState *touch_state;
 
+  g_return_if_fail (virtual_evdev->device != NULL);
+
   if (time_us == CLUTTER_CURRENT_TIME)
     time_us = g_get_monotonic_time ();
 
@@ -682,24 +702,26 @@ meta_virtual_input_device_native_constructed (GObject *object)
 }
 
 static void
-meta_virtual_input_device_native_finalize (GObject *object)
+meta_virtual_input_device_native_dispose (GObject *object)
 {
   ClutterVirtualInputDevice *virtual_device =
     CLUTTER_VIRTUAL_INPUT_DEVICE (object);
   MetaVirtualInputDeviceNative *virtual_evdev =
     META_VIRTUAL_INPUT_DEVICE_NATIVE (object);
-  GObjectClass *object_class;
+  GObjectClass *object_class =
+    G_OBJECT_CLASS (meta_virtual_input_device_native_parent_class);
 
+  if (virtual_evdev->device)
+    {
       release_pressed_buttons (virtual_device);
       g_signal_emit_by_name (virtual_evdev->seat,
                              "device-removed",
                              virtual_evdev->device);
 
       g_clear_object (&virtual_evdev->device);
+    }
 
-  object_class =
+  object_class->dispose (object);
-    G_OBJECT_CLASS (meta_virtual_input_device_native_parent_class);
-  object_class->finalize (object);
 }
 
 static void
@@ -717,7 +739,7 @@ meta_virtual_input_device_native_class_init (MetaVirtualInputDeviceNativeClass *
   object_class->get_property = meta_virtual_input_device_native_get_property;
   object_class->set_property = meta_virtual_input_device_native_set_property;
   object_class->constructed = meta_virtual_input_device_native_constructed;
-  object_class->finalize = meta_virtual_input_device_native_finalize;
+  object_class->dispose = meta_virtual_input_device_native_dispose;
 
   virtual_input_device_class->notify_relative_motion = meta_virtual_input_device_native_notify_relative_motion;
   virtual_input_device_class->notify_absolute_motion = meta_virtual_input_device_native_notify_absolute_motion;