syntax

Syntax styles for OpenTUI’s highlighted-text renderables: markdown, code, and diff. Each of them resolves every span of text through an OpenTUI SyntaxStyle: a lookup table from tree-sitter capture name — "default", "markup.strong", "keyword", … — to a colour and a set of text attributes.

A theme is a List(Style), declared on the config under a name with opentui.register_syntax_style and selected per element by that name with opentui/attribute.syntax_style.

opentui.default_config()
|> opentui.register_syntax_style("handbook", [
  syntax.style("default") |> syntax.fg("#E6EDF3"),
  syntax.style("markup.heading.1")
    |> syntax.fg("#58A6FF")
    |> syntax.bold(True),
  syntax.style("markup.link.url")
    |> syntax.fg("#A5D6FF")
    |> syntax.underline(True),
  syntax.style("conceal") |> syntax.dim(True),
])

Capture names

Capture names come from the grammar, so the full set is whatever @opentui/core’s assets/<grammar>/highlights.scm emits — not a closed list. The ones worth styling first, for markdown: default, conceal, markup.heading plus markup.heading.1 through markup.heading.6, markup.strong, markup.italic, markup.strikethrough, markup.raw, markup.link, markup.link.label, markup.link.url, markup.list, and markup.quote. code adds the usual code captures — keyword, string, comment, function, number, and so on — for whichever filetype it is given. A capture with no entry contributes nothing to the span.

Lookup drops everything after the first dot

A capture resolves to the entry registered under its exact name; failing that, to the entry registered under the segment before its first dot. markup.heading.1 falls back to markup, not to markup.heading, so register every level you want to style. default applies to a span only when none of the captures covering it contributed anything.

Attributes you never set are left out

An entry that never calls bold sends no bold at all; bold(False) sends an explicit false. That matters where two different captures cover one span — markdown’s spell sits under every paragraph, and an emphasis capture like markup.strong sits on a run inside it. The highlighter merges those least-specific first, field by field, skipping fields an entry does not carry, so a colour-only markup.strong leaves spell’s attributes standing. An explicit false switches them off.

This is merging between captures, not inheritance along one. A capture resolves to exactly one entry, by the rule above, and keyword.import registered on its own therefore replaces keyword rather than adding to it.

Types

Style

opaque </>

A style for one tree-sitter capture name: a foreground and background colour, and the four text attributes. Seed one with style and pipe it through the setters below.

pub opaque type Style

Values

bg

</>

pub fn bg(style: Style, value: String) -> Style

Set the background colour. OpenTUI parses this as a ColorInput, so a hex string like "#0D1117" and a CSS colour name like "black" both work.

bold

</>

pub fn bold(style: Style, value: Bool) -> Style

Render matching text bold.

dim

</>

pub fn dim(style: Style, value: Bool) -> Style

Render matching text dimmed.

fg

</>

pub fn fg(style: Style, value: String) -> Style

Set the foreground colour. OpenTUI parses this as a ColorInput, so a hex string like "#58A6FF" and a CSS colour name like "cyan" both work.

italic

</>

pub fn italic(style: Style, value: Bool) -> Style

Render matching text italic.

style

</>

pub fn style(capture: String) -> Style

Create a style for a tree-sitter capture name, with no colours and no attributes set. Capture names are the grammar’s own: "default", "conceal", "markup.strong", "keyword", and so on.

to_json

</>

pub fn to_json(styles: List(Style)) -> json.Json

Encode a theme as the JSON object OpenTUI wants: one entry per capture name, under OpenTUI’s own field names, carrying only the fields that were set.

You should not need to call this yourself — opentui.register_syntax_style does it for you. It is public only because Config is opaque, so that function has to live in opentui, where it cannot reach inside a Style.

underline

</>

pub fn underline(style: Style, value: Bool) -> Style

Render matching text underlined.