Add conceal support for \(sub)*sections

[lervag]

See #1978 for context.

Some things to discuss before merging:

• This direction of conceals is full of edge cases. For instance, how should we treat \chapter? I would perhaps claim we should only allow this particular type of concealment to the specific family \(sub)*section.

• I suspect this conceal feature will be much more opinionated. Perhaps it should be off by default? If so, then the g:vimtex_syntax_conceal_default becomes "obsolete", but it might have been a bad way to customize things anyways. Perhaps it is better to show the defaults explicitly, allow some defaults to be off, and instead add g:vimtex_syntax_conceal_disable to make it easy to disable all conceal features for whomever wants that.

• And, of course: is the current implementation satisfactory?

[mawkler]

Looks good! Your conceal implementation looks way cleaner than my proof of concept hehe.

how should we treat \chapter?

I personally don't use \chapter{} so perhaps I shouldn't be the one answering this, but perhaps it simply shouldn't be concealed like you suggest, or it could be concealed like \section{} but with another symbol than #, for instance §. I.e. \chapter{Test} would be concealed into § Test.

Perhaps it should be off by default?

I agree.

If so, then the g:vimtex_syntax_conceal_default becomes "obsolete"

Yeah I think g:vimtex_syntax_conceal is a perfectly fine way to control the conceals. You could write out its default values in the docs, for instance:

g:vimtex_syntax_conceal = {
  \ 'styles': 1,
  \ 'accents': 1,
  \ 'greek': 1,
  \ 'math_fracs': 1,
  \ 'math_symbols': 1,
  \ 'math_super_sub': 1,
  \ 'cites': 1,
  \ 'fancy': 1,
  \ 'sections': 0,
  \ 'math_delimiters': 1,
  \ 'math_bounds': 1
  \ }

Adding g:vimtex_syntax_conceal_disable makes sense to me too.

[lervag]

Thanks for your thoughts. I've pushed corresponding updates now. I propose to merge this, but I would be happy to hear a second opinion. Not sure if there may be "lurkers" reading this that would be interested in commenting? :)

[Schmiddiii]

Hi, random "lurker" here.
This seems pretty good, but I still have some ideas for minor improvements.

First consider \section*{Title}. This is currently concealed as # * Title.
Would it be possible to leave out the * as I think this information is not neccessary.
In my experience, either all sections are section or section*, not a mix.
This of course also applies for all (sub)*sections.

My next request is a conceal for label, as many (sub)*sections have a label beneath.
This is for example the case in the snippets for Ultisnips here.
This could either be integrated into the (sub)*section conceal (if possible), e.g. # Title (label), or be a new conceal, e.g.

# Title
↪ label

My last request would be the (sub)*paragraph.
The current conceal of \paragraph{Text} is \paragraph Text (just left out the {}).
This probably might be improved, but I have no idea how to conceal it.
To my information, makrdown does not have any character for a paragraph.
Also consider paragraph*. This is currently not concealed at all.
This is inconsistent and should probably be changed.

[lervag]

Hi, random "lurker" here.

Great, happy to "meet" you :)

First consider \section*{Title}. ...
In my experience, either all sections are section or section*, not a mix.

I've mixed things several times. Typically with things like adding a \section*{Acknowledgement}. However, I also tend to agree that the # * does not look so good, so I can agree on simply hiding the star as well.

My next request is a conceal for label, as many (sub)*sections have a label beneath.
This is for example the case in the snippets for Ultisnips here.
This could either be integrated into the (sub)*section conceal (if possible), e.g. # Title (label), or be a new conceal, e.g.

Unfortunately, this may be more tricky: 1) I don't think we can conceal multiple lines, and 2) conceals generally only allow to conceal a single "matched part/region" with a single character. More complex conceals are all "hacks" that combine syntax rules in more or less twisted ways. :\

My last request would be the (sub)*paragraph.
The current conceal of \paragraph{Text} is \paragraph Text (just left out the {}).

Ah, that was actually an unintended side effect; a bug. Thanks for reporting. I'll revert this immediately.

[lervag]

I'm sorry about the delay here; I've merged this now.