Rainbow tree-sitter matches 🌈

[the-mikedavis]

This is #2857 based on the tree-house bindings. (Recreated after that PR closed unexpectedly)

Configurable, themable, nesting rainbow highlights:

This approach uses the syntax tree to guide nesting levels and highlights so it ends up being much more flexible than a naive pair-matching implementation. For example, we can highlight </> when used in Rust type parameters like struct MyStruct<'a> { .. } and not mistakenly highlight </> comparison operators. We can also capture multiple nodes, for example the #, [ and ] characters in a Rust attribute like #[cfg(windows)] and none of these characters are required to be adjacent.

The cherry on top is that we can highlight according to the syntax tree's nesting information rather than whether characters surround each other. For example, in this TOML table, characters is a sub-table of editor.whitespace and the rainbow highlights reflect that fact.

theme = "default"

[editor.whitespace]
# <- red          ^ red
render = "all"
characters = { tab = "▸", newline = "◂" }
#            ^ yellow                   ^ yellow (comes after red in base16)

It also works across injected languages like javascript injected into HTML script tags.

(You can see each of these things in action in the gif above.)

How does it work?...

This implementation leverages tree-sitter queries. We use a QueryCaptures Iterator very similar to the existing one for syntax highlights to query the parsed syntax tree for new rainbows.scm patterns.

Two new captures - @rainbow.scope and @rainbow.bracket - track nesting level and capture syntax nodes for highlighting with rainbows. Specifically: @rainbow.scope pushes a RainbowScope on a stack. When @rainbow.bracket matches, we test that the captured node is a direct descendant of the current scope. If it is, we emit highlights for it according to the scope's level of nesting.

---

Configuration...

In the theme we add a rainbow key that takes a list of Styles. You can have however many you want and you can re-use colors from the palette or even throw modifiers in there:

# ~/.config/helix/themes/my_theme.toml

rainbow = ["#fc6b59", { fg = "lavender", bg = "comet" }, "lilac", { modifiers = ["reversed"] }]

[palette]
lavender = "#a4a0e8"
comet = "#5a5977"
lilac = "#dbbfef"

A default rainbow using the red, yellow, green, blue, cyan, and magenta terminal colors is used as a fallback.

Enable the rendering of rainbow brackets in your config.toml

# ~/.config/helix/config.toml
[editor]
rainbow-brackets = true

Or enable rendering per-language in languages.toml (this overrides the config.toml setting for any languages that set this value):

# ~/.config/helix/languages.toml
[[language]]
name = "scheme"
rainbow-brackets = true

[[language]]
name = "commonlisp"
rainbow-brackets = true

When the rainbow-brackets option is disabled, rainbow brackets are not rendered or computed.

---

Closes #695

[yerlaser]

This doesn't seem to work any more when rebased against latest changes.
All my brackets are simply black now.

Is there a more up-to-date branch or repo with this feature?

[the-mikedavis]

I don't see any issues after rebasing. Did you :set rainbow-brackets true? It's off by default.

I carry this in https://github.com/the-mikedavis/helix/tree/driver - that may be more up-to-date than this branch at any given time since I rebase that often

[yerlaser]

I don't see any issues after rebasing. Did you :set rainbow-brackets true? It's off by default.

Yep, as you said there were no issues rebasing except a minor conflict in languages support doc.
And, yes, I set the rainbow-brackets = true in my config.

But, maybe, there's something wrong with how I built it or my config.
I'll check.

[yerlaser]

Hmm, nope.
I've just rebuilt this, but still doesn't work.
I also opened helix with empty config, ran :set rainbow-brackets true
Open a Rust file which supposedly should have best support with this.
Tried different themes.
No luck :(

[the-mikedavis]

If the rainbow colors aren't specified in a theme the base16 colors you have set for your terminal colorscheme are used. Maybe those aren't set and are defaulting to black. You can customize those colors in the theme when using this PR:

helix/book/src/themes.md

Lines 133 to 140 in f4c43e6

	### Rainbow
	The `rainbow` key is used for rainbow highlight for matching brackets.
	The key is a list of styles.
	```toml
	rainbow = ["#ff0000", "#ffa500", "#fff000", { fg = "#00ff00", modifiers = ["bold"] }]
	```

[yerlaser]

If the rainbow colors aren't specified in a theme the base16 colors you have set for your terminal colorscheme are used. Maybe those aren't set and are defaulting to black. You can customize those colors in the theme when using this PR:

helix/book/src/themes.md

Lines 133 to 140 in f4c43e6

	### Rainbow
	The `rainbow` key is used for rainbow highlight for matching brackets.
	The key is a list of styles.
	```toml
	rainbow = ["#ff0000", "#ffa500", "#fff000", { fg = "#00ff00", modifiers = ["bold"] }]
	```

After some research I seem to understand why things doesn't work for me.
But, things are quite specific to my setup, so I won't waste your time describing them.

Thanks a lot for this great feature. Very sad that it takes so long to be reviewed and merged.

[qm3ster]

@yerlaser please waste the time, it would be very insightful for all

[yerlaser]

Basically it boils down to the fact that I am trying (still unsuccessfuly) to add support for moonbitlang and so my runtime folder is tainted.
I didn't realize that when rebasing.