I have a glade file from which I load a derived widget that has a
Glib::Property. When I load the main window, I get the following error:
```
GLib-GObject-CRITICAL **: validate_and_install_class_property: assertion
'class->set_property != NULL' failed
```
I have created a simplified example, as per this page:
https://developer-old.gnome.org/gtkmm-tutorial/stable/sec-builder-using-derived-widgets.html.en,
using a derived Gtk::Button and still see the error.
I have included Glib::ObjectBase() in the initializer list of the
derived widget and called the default constructor which also has a the
Glib::ObjectBase() to initialize the Gtype (), but I still see the error.
Additionally, the property appears to work, in that I can connect to the
signal_changed and set/get the property value as expected, but still
receive the error at runtime.
Simplified example:
```
#include #include Glib::ustring glade_str =
"\n" "\n" "\n" " lib=\"gtk+\"version=\"3.24\"/>\n" " class=\"GtkWindow\"id=\"mainwindow\">\n" " name=\"can-focus\">False\n" " \n" " class=\"GtkButton\"id=\"btn\">\n" " name=\"label\"translatable=\"yes\">button\n" " name=\"visible\">True\n" " name=\"can-focus\">True\n" " name=\"receives-default\">True\n" " \n" "
\n" " \n" ""; class DerivedButtonProp :public Gtk::Button {
public:
static void ensure_type()
{
std::cout<< __PRETTY_FUNCTION__ << std::endl;
static_cast(DerivedButtonProp()); }
DerivedButtonProp(BaseObjectType *obj, Glib::RefPtr const
)
:Glib::ObjectBase(s_type_name), Gtk::Button(obj), prop_mynum(*this,
"mynumprop")
{
std::cout<< __PRETTY_FUNCTION__ << std::endl; }
virtual ~DerivedButtonProp() =default; Glib::PropertyProxy mynum()
{return prop_mynum.get_proxy(); }; private:
DerivedButtonProp()
:Glib::ObjectBase(s_type_name), prop_mynum(*this, "mynumprop")
{
std::cout<< __PRETTY_FUNCTION__ << std::endl; }; static constexpr auto s_type_name
="DerivedButtonProp"; Glib::Property prop_mynum; }; class App :public Gtk::Window {
public:
App()
{
}
App(BaseObjectType *obj, Glib::RefPtr const & builder)
:Gtk::Window(obj)
{
builder->get_widget_derived("btn", btn_derprop); }
virtual ~App() =default; protected:
DerivedButtonProp *btn_derprop =nullptr; }; App* pWindow =nullptr;
Glib::RefPtr app; int main(int argc, char *argv[])
{
Glib::RefPtr app = Gtk::Application::create(); DerivedButtonProp::ensure_type();
Glib::RefPtr builder = Gtk::Builder::create_from_string(glade_str); App *pWindow
=nullptr; builder->get_widget_derived("mainwindow", pWindow); app->run(*pWindow); }
```
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