I have trouble to convert a Glib::RefPtr into a GtkWidget, with T derived from Widget:
#include <gtkmm/drawingarea.h>
#include <gtkmm/application.h>
#include <gtkmm/window.h>
#include <gtkmm/fixed.h>
class MyPic : public Gtk::DrawingArea {
public:
};
int main(int argc, char* argv[]) {
Gtk::Fixed f;
Gtk::DrawingArea da; // this works.
Gtk::DrawingArea mp; // this works.
Glib::RefPtr<MyPic> rp_mp; // this not.
f.put(da, 10, 20);
f.put(mp, 10, 30);
f.put(rp_mp, 10, 40); // Line # 19
}
This does not compile:
joerg> g++ x.cpp `pkg-config --cflags --libs gtkmm-3.0`
x.cpp: In function ‘int main(int, char**)’:
x.cpp:19:24: error: no matching function for call to ‘Gtk::Fixed::put(Glib::RefPtr<MyPic>&, int, int)’
x.cpp:19:24: note: candidate is:
/usr/include/gtkmm-3.0/gtkmm/fixed.h:123:8: note: void Gtk::Fixed::put(Gtk::Widget&, int, int)
/usr/include/gtkmm-3.0/gtkmm/fixed.h:123:8: note: no known conversion for argument 1 from ‘Glib::RefPtr<MyPic>’ to ‘Gtk::Widget&’
joerg> g++ --version
g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3 Copyright (C) 2011 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Glib::RefPtr is a smart pointer, and DrawingArea is derived from Widget, so this should work.
Dereferencing (like f.put(*rp_mp,...)
) is intentionally not working. The documentation states: "*Unlike most other smart pointers, RefPtr doesn't support dereferencing through * object_ptr.*"
How do I get a Widget& from the SmartPtr?
Although I suspect you can design around the need, you can dereference e.g. Glib::RefPtr foo
as follows:
some_method_needing_a_reference(*foo.operator->())