Which vim options should be used in modelines?

Question

I'm wondering which vim options should I be specifying in modelines in my source files (mostly C), and which should not be specified there and rather left for the user to specify.

I believe that the modelines should enforce code-specific policies and/or help vim with the code, while avoiding interfering with user preferences if possible.

When answering, please explain why you believe that a particular option should be enforced via modeline, or not.

Answer 1

Right now, I find the following options useful:

• ft to ensure that vim recognizes the file format correctly,
• noet and sts=0 to disable expanding tabs into spaces (project coding style),
• or alternatively et, ts, sts and sw to enforce project-specific tab expansion,
• maybe tw to suggest line wrapping (but I wouldn't be so sure about that as it is a bit intrusive),
• fenc to indicate the character encoding.

And those are the options I believe I shouldn't be setting:

• ts if the project uses tab-indent — I believe that the user should be able to choose his own tab width,
• folding — user preference,
• indenting — user may have a preferred way of doing indents and changing that may actually cause extra or missing indent out of habit,
• ff because vim should deduce the newline format correctly and if some software (like VCS) transparently converts the file, ff will actually break it.