How to change Operator highlight color in Vim?

Question

I just switched to iTerm2 on macOS and found some of its options go to Vim as well. That's the case for fonts, I was able to select a Vim font that I like from iTerm options.

It seems iTerm color options also apply to Vim highligh. But in this case highlight situation is not good enogh for my taste. So I tried to change:

:hi Comment ctermfg=gray

Changes font color of comments.

I would like to change =, ::, +, - color, I think these are Operators, so I tried:

:hi Operator ctermfg=blue

But it seems nothing changes. How should I do that?

If it matters I'm playing with .cpp/.h files.

Answer 1

It indeed looks like cppOperator links to Operator which links to Statement (-> :hi cppOperator), but I've never seen these operators displayed differently...

It's just for the keywords. See syn list cppOperator. I guess you'd have to add these symbols to the cppOperator list. You may need a syn match that takes care of not overlapping with cFloat and some other syntax groups. Indeed, if we look closely at $VIMRUNTIME/syntax/c.vim we see that cFloat can match + or - in the possible patterns.

Let's experiment on

42 + 12;
42 foobar 12;

1. :syn keyword cOperator + has no visible effect
2. yet :syn keyword cOperator foobar has a visible effect => syn keyword is not what we're looking for
3. however :syn match cOperator "+" has the effect we are looking for: now we have a match for +

4. better yet, we can have :syn match cOperator "[+/*%^&|<>-]", we can observe:

   • there is no interaction with cFloat: check 12 * 1e-1 -- my fears were unfounded

   • pointers and addresses will also be highlighted -- excluding these cases will require more tweaking.

     void * p = &var;
     12 * *p;
     

Notes:

• Before the modification, the operators belonged to cBlock, now they belong to cOperator. We can change the highlighting of Operator, it will now also affect these operators.
• Put the new :syn... commands into {rtp}/syntax/c/c-highlight-operator.vim for instance. -- by {rtp}, understand any path in your 'rtp' option.