Plugins: Is API prepared for folders?

I read some pages about developing DO plugins and even managed to compile the lightweight TARGA plugin sourcecode and have it showing beside the v4 version, hooray! o)
But after looking at the code and taking account of gathered information up to now, I think you cannot write a viewer plugin for displaying something if a folder is selected, am I right or wrong?

I was thinking about a very simple plugin that would show a folder.jpg file in the viewer pane, if it is contained in a selected folder.

Thanks! o)

The viewer itself does not handle folders.

So if I understood correctly, the API does not support folders to be handled by plugins?