gdkdisplay: Document get_monitor_at_surface can return NULL

Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/5075

diff --git a/gdk/gdkdisplay.c b/gdk/gdkdisplay.c
index be5e2f5ff13dc6576384c14d2b99fa8f0a00e27a..ad5d6772b7e340f00a99e34a8358a1f7c27ae6e0 100644 (file)
--- a/gdk/gdkdisplay.c
+++ b/gdk/gdkdisplay.c
@@ -2013,7 +2013,7 @@ gdk_display_get_monitors (GdkDisplay *self)
  * Returns a monitor close to @surface if it is outside
  * of all monitors.
  *
- * Returns: (transfer none): the monitor with the largest
+ * Returns: (transfer none) (nullable): the monitor with the largest
  *   overlap with @surface
  */
 GdkMonitor *