bogged down in drawingarea tutorial

[Ron Lockwood-Childs <rchilds vctlabs com>]

Hello,

I'm looking through the DrawingArea tutorial, the first section that 
describes how to use GC's:

Gdk::GC some_gc;
some_gc.create(get_window());
Gdk::Color some_color;
Gdk::Colormap some_colormap(Gdk::Colormap::get_system());
some_color.set_red(65535);
some_color.set_green(0);
some_color.set_blue(0);
some_colormap.alloc(some_color);
some_gc.set_foreground(some_color);

I'm writing a sample app to draw pixels in a drawing area.  There are 
256 shades of red, which I have implemented as follows:
Gdk::Color colorList[NSHADES];
I have a for loop that calls the .set_(red)|(green)|(blue) member 
functions for each distinct shade.

However, I can't even get past the GC!  This is how I've declared it:
Gdk::GC drawGc;

GCC complains thus:
/usr/include/gdkmm-2.4/gdkmm/gc.h:389: error: `Gdk::GC::GC()' is protected

I've looked in the gc.h file, which is not at all illuminating about why 
this is protected.

The next line fails as well:
Gdk::Colormap appColormap(Gdk::Colormap::get_system());

and here's the relevant GCC complaint:
test.cc:61: error: no matching function for call to 
`Gdk::Colormap::Colormap(Glib::RefPtr<Gdk::Colormap>)'
/usr/include/gdkmm-2.4/gdkmm/colormap.h:101: note: candidates are: 
Gdk::Colormap::Colormap(const Glib::RefPtr<Gdk::Visual>&, bool)
/usr/include/gdkmm-2.4/gdkmm/colormap.h:76: note: 
Gdk::Colormap::Colormap(GdkColormap*)
/usr/include/gdkmm-2.4/gdkmm/colormap.h:75: note: 
Gdk::Colormap::Colormap(const Glib::ConstructParams&)
/usr/include/gdkmm-2.4/gdkmm/colormap.h:71: note: 
Gdk::Colormap::Colormap(const Gdk::Colormap&)

I'm completely confused.  I'm no newbie to GTK+ either, I've used the 
library in a number of applications via the ruby-gnome2 wrappers, and 
thought I understood what I was doing..  I can't even figure out from 
the gtkmm tutorial how to allocate a specific size to the DrawingArea 
(!), and there's not even an overloaded constructor for DrawingArea with 
a pair of ints to specify width/height, I tried that..

Is there a better tutorial, or do I continue to rely on the kindness of 
strangers on the gtkmm-list (which, by the way, I don't actually receive 
email from despite joining the mailing list) ??

please help ?

--
Ron Lockwood-Childs