Messages in this class are meant to signal unimplemented features, known bugs, etc. They serve as a constant and active reminder of what needs to be done.

Examples: stubs, semi-implemented features, etc.

Messages in this class relate to serious errors in Wine. This sort of messages signal an inconsistent internal state, or more general, a condition which should never happen by design.

Examples: unexpected change in internal state, etc.

These are warning messages. You should report a warning when something unwanted happen but the function behaves properly. That is, output a warning when you encounter something unexpected (ex: could not open a file) but the function deals correctly with the situation (that is, according to the docs). If you do not deal correctly with it, output a fixme.

Examples: fail to access a resource required by the app.

These are detailed debugging messages that are mainly useful to debug a component. These are usually turned off.

Examples: everything else that does not fall in one of the above mentioned categories and the user does not need to know about it.