When I was updating my patch to add a 'document' flag to the formats in order to get rid of the hardcoding in MenuBackend.C, I also wrote the documentation for it and for the autoview feature in Customization.lyx. I had a closer look at the autoview logic in configure.py and format.C, and it is strange:
configure.py writes 'none' when it does not find a viewer/editor. This is then interpreted by fixCommand() in format.C as "use OS default viewer/editor if available) An empty string would mean "Disable viewing/editing". This is confusing, since for other settings (e.g. converter) "" and "none" are equivalent. Then we can change the preferences by hand. We can enter "none" with the same meaning as above, or "auto", which means "pretend that we have an automatic viever/editor and give an error message if that should not be true and a user wants to actually use it". I think that configure.py should write "auto" if no viewer/editor was found and it was not explicitly requested that it should be empty (as needed for the lyx13x format). "none" should be equivalent to "" as it was, and "auto" should be replaced in fixCommand() by an empty string if no auto viever/editor is available. Georg
