How are drag images implemented?

[Jacques Du Toit <Jacques Du-toit postgrad manchester ac uk>]

Hi all

I'm a bit new to X programming, and I'm trying to write some code to
create a ghosted drag image that looks (and behaves) the same as the
picture that Nautilus displays when, for example, you drag an image
and drop it onto the desktop.  Particularly, I need to figure out how
to create a window which is alpha blended (this is relatively easy)
and input transparent (all mouse events on the window are passed
through to whatever lies underneath the window).

I've downloaded the Nautilus 2.22.3 source code, but I'm having some
difficulty finding the section of code which is responsible for creating
the drag image.  Could someone perhaps point me in the right direction?

Thanks a lot
Jacques