[gtk+] Expand window style class documentation a bit

[Matthias Clasen <matthiasc src gnome org>]

commit 00aca5d689db1eed73f485e217a395300635f177
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jan 17 12:13:59 2016 -0500

    Expand window style class documentation a bit

 gtk/gtkwindow.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index 8b4e86a..008a2d9 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -136,9 +136,15 @@
  * ]|
  *
  * GtkWindow has a main CSS node with name window and style class .background,
- * and a subnode with name decoration. Style classes that are typically used
- * with the main CSS node are .csd, .solid-csd, .ssd, .tiled, .maximized,
- * .fullscreen, .popup, .tooltip.
+ * and a subnode with name decoration.
+ *
+ * Style classes that are typically used with the main CSS node are .csd (when
+ * client-side decorations are in use), .solid-csd (for client-side decorations
+ * without invisible borders), .ssd (used by mutter when rendering server-side
+ * decorations). GtkWindow also represents window states with the following
+ * style classes on the main node: .tiled, .maximized, .fullscreen. Specialized
+ * types of window often add their own discriminating style classes, such as
+ * .popup or .tooltip.
  *
  * GtkWindow adds the .titlebar and .default-decoration style classes to the
  * widget that is added as a titlebar child.