I've become moderately intrigued by the notion of a generic drop handler. This would be a useful component for a document management system or to perform some other interesting task with dropped files (for instance, you could use it to send faxes or something). And I know, roughly, how to go about handling drop events from an active app.

It turns out that drop handling in the Windows environment -- on the desktop or from the SendTo folder -- is a horse of a different color. You have to write a shell extension and do a lot of Registry work. Which makes it a nice, compact project, and I started the research today.

A drop handler is registered against a file extension. These extensions are not generally the mere three-letter things used for actual files, but longer descriptive names, because they're not intended for use with actual files. Instead, you create zero-length files with these magical extensions, and those place a convenient icon somewhere in the Explorer (like the SendTo menu).

My drop handler will act on an XML file which encodes a wftk action (or something along those lines), at least potentially. It should also be possible to do without the wftk for general purposes; my initial demo will be a neat utility idea I purloined from the forum at The Software Jedi's place -- it will allow the registration of files in a list with keywords, and the keywords will then be used to format a tag cloud like the ones you can see e.g. at del.icio.us. That's a fun little application of a neat UI trick which won't get in the way of the actual point of the exercise, which is the drop handling itself.

The goal is implementation and documentation within a week. Let's see how I do.