🚀 go-pugleaf

I'm working on some drag 'n' drop stuff where I intend to use ghosting,
a la File Viewer.  I have an example app called ToolInspector that
ghosts by compositing 50% NX_LTGRAY over the icon, and that's not
bad.  However, in studying File Viewer closely I've noticed that the
ghosting behavior is more complex than that:

   1. When dragging a file icon over an empty shelf slot, the ghosting
      leaves light gray and white alone, turns black into dark gray
      and dark gray into light gray.

   2. A file that I have no permissions for appears on the shelf always
      ghosted, but differently than as described in 1.

   3. I have access to a color machine, but I have no idea how to
      describe how the ghosting is done there, although there is still
      a difference between an icon being dragged over an empty shelf
      slot and an icon for a file I have no permissions to.

I'm a compositing beginner, and I was not able to duplicate any of the
above by experimenting with CompositeLab.  Before I kill more brain
cells trying to figure this out, does anyone know the rules for these? 
I'd like to have my ghosting behavior identical to File Viewer if
possible.   

Thanx,
Michael

--
Michael_Pizolato@afs.com
~18 kyu
Q16
NeXTMail appreciated