Don't ignore the result_uncertain flag from g_content_type_guess() as it might cause nautilus to incorrectly think that a particular file is of a certain type, and never check its magic.
- Put multi-page DjVu file on a remote filesystem (file will have
DJVMin the first few bytes of data, rather than
DJVUas used for images)
- Make sure evince is installed with DjVu support
- Double-click on file
What's supposed to happen is nautilus, having only got a "fast" content-type will check the file's magic before choosing whether it's an image or a document, and the file will be launched in evince (maybe it will even get thumbnailed).
This already works correctly on the local filesystem.