docs: Add a diagram for GtkListBox nodes

GtkListBox's API reference for CSS nodes should follow the template of
other widget classes.

diff --git a/gtk/gtklistbox.c b/gtk/gtklistbox.c
index 3adb904b539172518e142ab2000e295e239ed369..026911509e167a27a45bd831843413a5645c48c3 100644 (file)
--- a/gtk/gtklistbox.c
+++ b/gtk/gtklistbox.c
@@ -65,8 +65,13 @@
  *
  * # CSS nodes
  *
- * GtkListBox uses a single CSS node with name list. GtkListBoxRow uses
- * a single CSS node with name row. The row nodes get the .activatable
+ * |[<!-- language="plain" -->
+ * list
+ * ╰── row[.activatable]
+ * ]|
+ *
+ * GtkListBox uses a single CSS node named list. Each GtkListBoxRow uses
+ * a single CSS node named row. The row nodes get the .activatable
  * style class added when appropriate.
  */