main2.cpp

#include <gtkmm.h>
#define TITLE "Test"

enum Size : unsigned int { WIDTH = 640, HEIGHT = 480 };

class DrawingArea : public Gtk::DrawingArea
{
    public:
        DrawingArea()
        {
            _dimensions.set_x(0);
            _dimensions.set_y(0);
            _dimensions.set_width(Size::WIDTH);
            _dimensions.set_height(Size::HEIGHT);
            set_size_request(_dimensions.get_width(), _dimensions.get_height());
            signal_draw().connect(sigc::mem_fun(*this, &DrawingArea::draw_draw));
        }

        void set_mouse()
        {
            get_window()->set_events(Gdk::EventMask::BUTTON1_MOTION_MASK);
            signal_button_press_event().connect(sigc::mem_fun(*this, &DrawingArea::draw_get_mouse), false);
        }

    private:
        bool draw_draw(const Cairo::RefPtr<Cairo::Context>& cr)
        {
            cr->set_source_rgb(0.0, 0.0, 0.0);
            cr->rectangle(_dimensions.get_x(), _dimensions.get_y(), _dimensions.get_width(), _dimensions.get_height());
            cr->fill();

            return true;
        }

        // this doesn't work
        bool draw_get_mouse(const GdkEventButton *button)
        {
            g_print("%0.0f\t%0.0f\n", button->x, button->y);
            return true;
        }

        Gdk::Rectangle _dimensions;
};

class Window : public Gtk::Window
{
    public:
        Window()
        {
            set_default_size(Size::WIDTH, Size::HEIGHT);
            set_title(TITLE);

            _scrolled_window.set_overlay_scrolling(true);
            _scrolled_window.set_policy(Gtk::PolicyType::POLICY_AUTOMATIC, Gtk::PolicyType::POLICY_AUTOMATIC);

            _scrolled_window.add(_drawing_area);
            add(_scrolled_window);

            _drawing_area.queue_draw();
        }

        void set_mouse()
        {
            _drawing_area.set_mouse();
        }
    private:
        Gtk::ScrolledWindow _scrolled_window;
        DrawingArea _drawing_area;
};

int main(int argc, char **argv)
{
    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create();
    Window win;
    win.show_all();
    win.set_mouse();
    return app->run(win);
}