Ability to highlight a pair's content

[SamirHafez]

paren gives you an overlay that matches pairs and their content if you set its matching style to expression. smartparens doesn't support this matching style therefore there is no way to highlight the content of a pair.

In this PR I'm proposing a new customizable face sp-show-pair-match-content-face that will operate solely on the contents of a pair.

This has an advantage over the paren implementation as paren is too rigid in that it doesn't allow you to highlight pairs and their contents independently.

Here's a look at a possible configuration

And a working scenario (should have used a more visible colour for this example :D)

[Fuco1]

I like how you implemented this, this way we can have both or neither or just the enclosing pairs.

Can you also edit the documentation https://github.com/Fuco1/smartparens/wiki/Show-smartparens-mode or do you need some special permissions for that? (In which case I can do that).

👍

[SamirHafez]

@Fuco1 thanks.
Can't edit the wiki though, no permissions, sorry.

[Fuco1]

@SamirHafez OK, I'll leave this open until I fix the docs so that I won't forget. If it takes too much time feel free to poke me!

Otherwise LGTM.

[kqr]

Maybe something like this, appended to the bottom of the existing page?

In addition, smartparens has a third face which is used for the expression between matching pairs. This face is named:

sp-show-pair-match-content-face

By default, show-smartparens-mode does not highlight the contained expression at all. Setting sp-show-pair-match-content-face to the same thing as sp-show-pair-match-face emulates setting show-paren-style to expression when using show-paren-mode.

However, it may also be useful to use a different colour for the matching pairs and the contained expression. This is of course possible with show-smartparens-mode but not with regular show-paren-mode.

[kqr]

Sorry a bit tired so I realise it may have all been junk. Oh well, it didn't cost me anything!

Thank you, @SamirHafez for implementing this!

[Fuco1]

@kqr Why junk, I think it makes perfect sense. I'll copy the text there right away. Thanks for the contribution!

[Fuco1]

Ok, the docs are live https://github.com/Fuco1/smartparens/wiki/Show-smartparens-mode#customizing-the-looks so I'm merging this.

Thank you both for the work again!