Add note about widgets implementing the interface adding the `horizontal`/`vertical...

diff --git a/gtk/gtkorientable.c b/gtk/gtkorientable.c
index 034cb18ffea9d44f43d152dadb42450ee6859f4e..b86071d1d4b7a7a88dae761abe396909fa25e379 100644 (file)
--- a/gtk/gtkorientable.c
+++ b/gtk/gtkorientable.c
@@ -36,6 +36,13 @@
  *
  * `GtkOrientable` is more flexible in that it allows the orientation to be
  * changed at runtime, allowing the widgets to “flip”.
+ *
+ * ## CSS nodes
+ *
+ * `GtkWidget` types implementing the `GtkOrientable` interface will
+ * automatically acquire the `horizontal` or `vertical` CSS class depending on
+ * the value of the [property@Gtk.Orientable:orientation] property.
+
  */