[gtk+] notebook: Document css nodes and style class

[Matthias Clasen <matthiasc src gnome org>]

commit f1b756093887b534e3a8260a10b0454d64ab4ff5
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Oct 24 10:54:56 2015 -0400

    notebook: Document css nodes and style class
    
    This will have to be updates as we do further changes to the
    way GtkNotebook does its rendering.

 gtk/gtknotebook.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtknotebook.c b/gtk/gtknotebook.c
index 84fdcfd..6452977 100644
--- a/gtk/gtknotebook.c
+++ b/gtk/gtknotebook.c
@@ -94,6 +94,20 @@
  *   </child>
  * </object>
  * ]|
+ *
+ * # CSS nodes
+ *
+ * GtkNotebook has a main CSS node with name notebook, a subnode
+ * with name tabs, and below that one subnode per tab with name
+ * tab.
+ *
+ * The main node gets the .frame style class when rendering the
+ * background of a notebook with border. It gets the .header
+ * style class for rendering the tab area background.
+ *
+ * The per-tab nodes get one of the style class .top, .bottom,
+ * .left or .right, depending on where the tabs are placed. For
+ * reorderable pages, the tab also gets the .reorderable-page class.
  */