list widgets: Document css structure

We didn't fill in this expected part of the widget
documentation yet.

gtk/gtkcolumnview.c

@@ -55,6 +55,31 @@
  * must be attached to a sort model for the data that the view is showing, and the
  * columns must have sorters attached to them by calling gtk_column_view_column_set_sorter().
  * The initial sort order can be set with gtk_column_view_sort_by_column().
+ *
+ * # CSS nodes
+ *
+ * |[<!-- language="plain" -->
+ * columnview[.column-separators]
+ * ├── header
+ * │   ├── <column header>
+ * ┊   ┊
+ * │   ╰── <column header>
+ * │
+ * ├── listview
+ * │
+ * ┊
+ * ╰── [rubberband]
+
+ * ]|
+ *
+ * GtkColumnView uses a single CSS node named columnview. It may carry the
+ * .column-separators style class, when #GtkColumnView:show-column-separators
+ * property is set. Header widets appear below a node with name header.
+ * The rows are contained in a GtkListView widget, so there is a listview
+ * node with the same structure as for a standalone GtkListView widget. If
+ * #GtkColumnView:show-row-separators is set, it will be passed on to the
+ * list view, causing its CSS node to carry the .separators style class.
+ * For rubberband selection, a node with name rubberband is used.
  */
 
 struct _GtkColumnView

gtk/gtkgridview.c

@@ -48,6 +48,22 @@
  * @see_also: #GListModel
  *
  * GtkGridView is a widget to present a view into a large dynamic grid of items.
+ *
+ * # CSS nodes
+ *
+ * |[<!-- language="plain" -->
+ * gridview
+ * ├── child
+ * │
+ * ├── child
+ * │
+ * ┊
+ * ╰── [rubberband]
+ * ]|
+ *
+ * GtkGridView uses a single CSS node with name gridview. Each child
+ * uses a single CSS node with name child. For rubberband selection,
+ * a subnode with name rubberband is used.
  */
 
 typedef struct _Cell Cell;

gtk/gtklistview.c

@@ -46,6 +46,24 @@
  * @see_also: #GListModel
  *
  * GtkListView is a widget to present a view into a large dynamic list of items.
+ *
+ * # CSS nodes
+ *
+ * |[<!-- language="plain" -->
+ * listview[.separators]
+ * ├── row
+ * │
+ * ├── row
+ * │
+ * ┊
+ * ╰── [rubberband]
+
+ * ]|
+ *
+ * GtkListView uses a single CSS node named listview. It may carry the
+ * .separators style class, when #GtkListView:show-separators property
+ * is set. Each child widget uses a single CSS node named row. For
+ * rubberband selection, a node with name rubberband is used.
  */
 
 typedef struct _ListRow ListRow;