Question

In our C++ code base we keep 99 column lines but 79-some-odd column multiline comments. Is there a good strategy to do this automagically? I assume the modes are already known because of smart comment line-joining and leading * insertion.

Answer 1

Apparently both code and comments use the same textwidth option. As far as I can see, the only trick is to set this option dynamically:

 :autocmd CursorMoved,CursorMovedI * :if match(getline(.), '^\s*\*') == 0 | :setlocal textwidth=79 | :else | :setlocal textwidth=99 | :endif

Here the critical part is detecting when we are in a comment. If you only format comments this way:

/*
 * my comment
 */

my regex should work… unless you have lines in the code starting with * (which I guess can happen in C, less frequently in C++). If you use comments like this:

// comment line 1
// comment line 2

the regex is even simpler to write. If you want to cover all possible situations, including corner cases, well… I guess the best thing would be to define a separate detection function and call that from the :autocmd instead of match().