Gtk::Builder::get_widget_derived() Issue on Fedora 33

[ahmet öztürk via gtkmm-list]

Hi all,

On Fedora 33, derived widgets does not seem to be constructed properly by
Gtk::Builder::get_widget_derived(). The reason I think so is that the
overridden methods are not called for these widgets. Apart from that
everything seems normal. No error message or anything.

I attached a sample code with a very simple case to replicate this problem.
on_button_press_event() is never called for the derived widget.

I have also noticed that if a dummy instance of the derived widget is
created separately (using another constructor) before calling
Gkt::Builder::add_from_string(), then the widget created by Builder also
works normally.

Please note that this may not occur on all distributions. e.g. I know that
it does not occur on Arch Linux.

Does anybody know if this a Fedora 33 specific issue or is it due to a
recent update in Gtkmm that is only affecting Fedora for now?

#include <iostream>
#include <gtkmm.h>

class TVDerived : public Gtk::TextView
{
    public:
        TVDerived() {}
        
        TVDerived( BaseObjectType* obj, const Glib::RefPtr< Gtk::Builder >& )
        : Gtk::TextView( obj ) {}
        
        ~TVDerived() {}

    protected:
        bool on_button_press_event( GdkEventButton* event ) override
        {
            std::cout << "on button press event" << std::endl;
            return Gtk::TextView::on_button_press_event( event );
        }
};


class ExampleWindow : public Gtk::Window
{
    public:
        ExampleWindow()  
        {
            set_title( "get_widget_derived() Issue" );
            set_default_size( 400, 200 );
            
            const Glib::ustring ui_def = 
            "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\
            <interface>\
                <object class=\"GtkTextView\" id=\"tvd\">\
                    <property name=\"visible\">True</property>\
                    <property name=\"can-focus\">True</property>\
                    <property name=\"monospace\">True</property>\
                </object>\
            </interface>";

            //TVDerived dummy; // solves the problem when uncommented

            auto refBuilder = Gtk::Builder::create();
            try
            {
                refBuilder->add_from_string( ui_def );
            }
            catch( ... )
            {
                std::cout << "Glade Error! " << std::endl;
                return;
            }

            refBuilder->get_widget_derived( "tvd", m_TextView );

            add( *m_TextView );
            
            show_all_children();
        }
        virtual ~ExampleWindow() {}

    protected:
        TVDerived* m_TextView;
};


int main( int argc, char *argv[] )
{
    auto app = Gtk::Application::create( argc, argv, "org.gtkmm.example" );
    ExampleWindow window;
    return app->run(window);
}


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