[gtk: 1/2] properly set ScaleButton's parent_class

[Timm Bäder <baedert src gnome org>]

commit 46601325f16abda5fee4f3eba890d65a0ef2c388
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Mon Nov 23 02:47:03 2020 +0100

    properly set ScaleButton's parent_class
    
    GtkScaleButton doesn't subclass GtkButton anymore
    Fixes #3381

 gtk/gtkscalebutton.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkscalebutton.h b/gtk/gtkscalebutton.h
index 309e75eb65..67a479baac 100644
--- a/gtk/gtkscalebutton.h
+++ b/gtk/gtkscalebutton.h
@@ -38,7 +38,7 @@
 #error "Only <gtk/gtk.h> can be included directly."
 #endif
 
-#include <gtk/gtkbutton.h>
+#include <gtk/gtkwidget.h>
 
 G_BEGIN_DECLS
 
@@ -54,12 +54,12 @@ typedef struct _GtkScaleButtonClass   GtkScaleButtonClass;
 
 struct _GtkScaleButton
 {
-  GtkButton parent_instance;
+  GtkWidget parent_instance;
 };
 
 struct _GtkScaleButtonClass
 {
-  GtkButtonClass parent_class;
+  GtkWidgetClass parent_class;
 
   /* signals */
   void (* value_changed) (GtkScaleButton *button,