Allow Qt graphics callbacks to work again (bug #56857) * Object.h, Object.cc (Object::do_connections): New virtual method. Do connections that were previously done in qt_graphics_toolkit::create_object * qt_graphics_toolkit.cc (qt_graphics_toolkit::create_object): Let Object::do_connections do the signal/slot connections. * Figure.h, Figure.cc (Figure::do_connection): Overload Object::do_connections to also make connections on peer Canvas object. * Panel.h, Panel.cc (Panel::do_connection): Overload Object::do_connections to also make connections on peer Canvas object.

--- a/libgui/graphics/Object.h	Thu Sep 05 17:42:07 2019 -0400
+++ b/libgui/graphics/Object.h	Thu Sep 05 10:13:39 2019 +0200
@@ -78,6 +78,9 @@
 
     static Object * fromQObject (QObject *obj);
 
+    virtual void do_connections (const QObject *receiver,
+                                 const QObject *emitter = nullptr);
+
   signals:
 
     void interpreter_event (const octave::fcn_callback& fcn);