[gtk+] button: Mention differentiating style classes

[Matthias Clasen <matthiasc src gnome org>]

commit 13d091f700c4bbaddc3c9cba12746a38838b6f71
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Nov 2 12:51:00 2015 -0500

    button: Mention differentiating style classes
    
    There's a lot of button variations out there, lets document
    the ones we know about.

 gtk/gtkbutton.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkbutton.c b/gtk/gtkbutton.c
index f976194..08c0dd3 100644
--- a/gtk/gtkbutton.c
+++ b/gtk/gtkbutton.c
@@ -43,6 +43,11 @@
  *
  * Other style classes that are commonly used with GtkButton include
  * .suggested-action and .destructive-action.
+ *
+ * Button-like widgets like #GtkToggleButton, #GtkMenuButton, #GtkVolumeButton,
+ * #GtkLockButton, #GtkColorButton, #GtkFontButton or #GtkFileChooserButton use
+ * style classes such as .toggle, .popup, .scale, .lock, .color, .font, .file
+ * to differentiate themselves from a plain GtkButton.
  */
 
 #include "config.h"