Get position of cursor in widget?

["charlesvpacker" <charlesvpacker cpacker org>]

I'm a GTK newbie who has successfully taken the very first
steps toward building a custom image processing application.
I've figured out how to read and display an image using
a GtkImage and GtkPixbuf. I've also modified a block of pixels
in the existing pixbuf and updated the displayed image
via gtk_image_set_from_pixbuf. Now I want to get the pixel
position of the mouse cursor resting on the image. I don't recall
seeing a GTK tutorial on capturing pointer position or motion. 
Could somebody, um, point me to one?