Vim syntax highlighting: make region only match on one line

Question

I have defined a custom file type with these lines:

syn region SubSubtitle start=+=+ end=+=+
highlight SubSubtitle ctermbg=black ctermfg=DarkGrey

syn region Subtitle start=+==+ end=+==+
highlight Subtitle ctermbg=black ctermfg=DarkMagenta

syn region Title start=+===+ end=+===+
highlight Title ctermbg=black ctermfg=yellow

syn region MasterTitle start=+====+ end=+====+
highlight MasterTitle cterm=bold term=bold ctermbg=black ctermfg=LightBlue

I enclose all of my headings in this kind of document like this:

==== Biggest Heading ==== // this will be bold and light blue

  ===Sub heading === // this will be yellow 

    bla bla bla  // this will be normally formatted

However right now when ever I use an equals sign in my code it thinks that it is a title. Is there anyway that I can force a match to be only on one line?

Answer 1

UPDATE: My previous answer was wrong, you can do this with a region, just do

syn region SubSubtitle start=+=+ end=+=+ oneline

See :help syn-oneline and :help syn-arguments. Guess it shows that I can't actually run vim right now, hunh?

---

Previous answer

According to my reading of the :help syntax, there's no way to do this with a region. However, you could do this with a syn-match:

syn match SubSubtitle /=\@<!=[^=]*==\@!/

The /=\@<!/ says there's no = immediately before your match, and the /=\@!/ says there's no = immediately after, so this matches exactly one =, a bunch of non-= (not including newlines - to include newlines it would have to be \_[^=]), then exactly one =.

The rest are similar

syn match Subtitle    /=\@<!=\{2}[^=]*=\{2}=\@!/
syn match Title       /=\@<!=\{3}[^=]*=\{3}=\@!/
syn match MasterTitle /=\@<!=\{4}[^=]*=\{4}=\@!/

You can still do matches within syn-matches, so if you have any nesting going on, it will still work.

For example

syn match Todo /\<TODO\>/ containedin=SubSubtitle,Subtitle,Title,MasterTitle contained