问题
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.
回答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().
回答2:
I came across this same problem and think that I have found a suitable solution.
What I wanted my comments to word wrap so that when I'm typing I don't have to worry about formating text. This works well with comment text. But I wasn't comfortable with having vim format my code. So I wanted vim to highlight every thing in red after x column.
To do this with only cpp code you would add the following to your ~/.vim/ftdetect/cpp.vim file.
set textwidth=79
match ErrorMsg '\%>99v.\+'
note: You may have to create the file and folders if they don't exist.
If you have problems with this make sure that you have formatoptions set to:
formatoptions=croql
You can see this by running :set formatoptions inside of vim.
来源：https://stackoverflow.com/questions/3475072/vim-different-textwidth-for-multiline-c-comments