Why my app uses a different theme than the desktop?

[Georgios Petasis <petasisg yahoo gr>]

Hi all,

I am a newbie with GTK+, and my first application is a "strange" one :-)
I am trying to write a theme for the Tcl/Tk theme engine, and I have 
made some steps.
See for example:

http://www.ellogon.org/~petasis/tcl/tile-gtk-dev-0.2.png
http://www.ellogon.org/~petasis/tcl/tile-gtk-dev-0.2-win.png

My code initialises gtk through gtk_init_check(&argc, &argv);
However, my app uses a different style (named Nodoka), while my gnome 
desktop seems to use a style named Clearlooks.
Why is that? What is the "official" way to see what style I am using?
Also, is it possible to change the style used by the application into a 
different one?

George