gtk: add missing class padding

Sorry for this late ABI break, but the newly added style classes
definitely need padding, so I can just as well add missing padding
globally.

1 files changed, 6 insertions, 0 deletions

diff --git a/gtk/gtkbbox.h b/gtk/gtkbbox.h
index df842f7fe6..a46ba4d5b5 100644
--- a/gtk/gtkbbox.h
+++ b/gtk/gtkbbox.h
@@ -59,6 +59,12 @@ struct _GtkButtonBox
 struct _GtkButtonBoxClass
 {
   GtkBoxClass parent_class;
+
+  /* Padding for future expansion */
+  void (*_gtk_reserved1) (void);
+  void (*_gtk_reserved2) (void);
+  void (*_gtk_reserved3) (void);
+  void (*_gtk_reserved4) (void);
 };