gtk-callbacks and viewport doubts using pixmaps

[Luis Velez <luis hpcf upr edu>]

Hello,
I just have a few questions. I have been working with gtk for not so
long. I have some mayor doubts about signal handling and callbacks. I
would just like some help either directly or by pointing me in the right

direction towards finding some information to guide me. First of all how

can I redisplay my pixmaps after a callback has been done. I am trying
to do some buttons which I can click and my image turns grayscale, I
already have the functions to get the pointer from a pixbuf and can do
the grayscale algorithm yet I cannot redisplay the new image where the
old one is, the only thing I can do is create another window with the
grayscale image but the old window still stays in the screen. Second, I
have been trying to get the coordenates for x and y inside a pixmap
rendered from a pixbuf using a button_press_event but I have the pixmap
inside a viewport(because I need it scrollable) so I get the viewport
coordenates. Any help would be greatly appreciated.
Thanks,
Luis Velez