[gtkmm] GdkDrawable Newbie Question

[Kent Moya <fliegen bellsouth net>]

Hello,

I am new to gtkmm (I'm using 2.2.5 on RedHat 9), and I am trying to 
write a program in which I would like to manipulate individual bits in a 
window.  I am trying to use the gdk_draw_rgb_image() function to do 
this, but I can't seem to get it to compile, I keep getting the 
following error:

cannot convert `Glib::RefPtr<Gdk::Window>' to `GdkDrawable*' for 
argument `1' to `void gdk_draw_rgb_image(GdkDrawable*, GdkGC*, int, int, 
int, int, GdkRgbDither, guchar*, int)'

I have attached some sample code below that produces this compiler error 
for me.  I hacked this code together from some of the examples in the 
documentation, but I think it should work.

class rgb_draw_area: public Gtk::DrawingArea
{
    guchar *rgbbuff;
    public:
        rgb_draw_area(int x_size = 0, int y_size = 0);
        virtual bool on_expose_event(GdkEventExpose *event);
        guchar *get_buffer() const;
};

virtual bool rgb_draw_area::on_expose_event(GdkEventExpose *event)
{
    gdk_draw_rgb_image(this->get_window(),
                       this->get_style()->get_fg_gc(GTK_STATE_NORMAL),
                       0,
                       0,
                       400,
                       200,
                       GDK_RGB_DITHER_MAX,
                       this->rgbbuff,
                       (this->width)*3);
}

int main(int argc, char* argv[])
{
   Gtk::Main kit(argc, argv);

   Gtk::Window win;
   win.set_default_size(400, 200);

   rgb_draw_area area;
   win.add(area);
   area.show();

   Gtk::Main::run(win);

   return 0;
}


I was under the impression that a Gdk::Window was a child of 
Gdk::Drawable - is that not tue?  Every code snippet I've seen that uses 
the gdk_draw_rgb_image (or similar) function simply passes in a call to 
get_window() (as is done above), but I can't seem to get that to work. 
Does anyone have any pointers, or any idea what I'm doing wrong?

Thanks!

Kent