Here are pointers to the relevant MSDN docs. The top-level topic
is "Shell Basics: Extending the Shell"
You'll want to read the "Creating a File Association" and "Extending
Shortcut Menus" sub-topics.
The summary is that you'll need to fiddle with the registry to register
your file types and specify your app's command line; that can be done
at install time if you have a good installer package.
I don't know if the commercial Lisps provide shell extension functionality
directly, but Allegro and LispWorks both have interfaces for DDE and
COM/ActiveX, if you want to dive into the deep end.
Sorry that I don't have any Lisp code for this myself, but you've
prompted me to add another topic to my long-term todo list :-)
--
Jack Unrue
1. Install NewLisp.
2. Write the three lines of NewLisp code for my application.
(My own quirky way of doing file bkups.)
3. Figure out link.lsp (well documented in the NewLisp doc) and
create a NewLisp executable.
4. Follow the MSDN doc to hook it into the filebrowser menu.
(This was the hardest part -- just bcs it's somewhat complex.)
Et voila! -- new functionality!
Thanks!!