Make View3D trackable since it connects to a signal

diff --git a/source/3d/view.h b/source/3d/view.h
index 225e3937297a36c33202acee728fe890d58462eb..5be2d8c0adf383bf56714e113845b96006270de9 100644 (file)
--- a/source/3d/view.h
+++ b/source/3d/view.h
@@ -12,7 +12,7 @@ namespace R2C2 {
 
 class Layout3D;
 
-class View3D
+class View3D: public sigc::trackable
 {
 protected:
        Layout3D &layout;