So I've got drag & drop working. When a drop occurs, I do some processing, and sometimes there is a result that I want to make the user aware of. Right now I am just outputting to the console which isn't very nice.
What's an appropriate way to display a status result from a drag & drop? Somehow a modal dialog box seems inappropriate, and a status bar is too space-constrained, I think.
Growl and libnotify are good for this. On Windows, just show an icon in the system tray and show a bubble off there, and remove the icon when the bubble is closed (unless you can show a bubble without an icon; I haven't tried so I'm not certain about it).
Add an opaque spinner/progress bar overlay on the drag/drop target. The progress bar grows or spinner spins until the operation is complete.
A modal dialog box is indeed the worst you could do, unless an error occurs, that is.
Popping up something in the system tray seems to me quite distracting as well. I'd go with something along the lines as what Byron Whitlock said: highlight the target for a second or two and maybe blend in a small textual description of what just happened, e.g. "file attached".
Another option would be to put something in a status bar or a "log" window/bar, depending on what your app looks like ...
You can implement a notification bar, which comes and goes, like what Browsers do.
Or you can even make use of audible feedback, and announce: "5 items dropped".
OK, that could be annoying and difficult to implement :)