syntax_style — the style registry

SyntaxStyle is a registry of named styles used for syntax highlighting and token theming. You register styles under names like "keyword" or "markup.link.url", then merge several names together to get the combined fg / bg / attributes for a token. It powers the CodeRenderable widget and is a lighter-weight alternative to driving StyleDefinitions by hand.

let mut styles = SyntaxStyle::create();

The data types

pub struct StyleDefinition {
    pub fg: Option<RGBA>,
    pub bg: Option<RGBA>,
    pub bold: Option<bool>,
    pub italic: Option<bool>,
    pub underline: Option<bool>,
    pub dim: Option<bool>,
}

pub struct StyleDefinitionInput {
    pub fg: Option<ColorInput>,   // accepts strings like "#ffcc00"
    pub bg: Option<ColorInput>,
    pub bold: Option<bool>,
    pub italic: Option<bool>,
    pub underline: Option<bool>,
    pub dim: Option<bool>,
}

pub struct MergedStyle {
    pub fg: Option<RGBA>,
    pub bg: Option<RGBA>,
    pub attributes: u32,          // packed TextAttributes, see types.md
}

pub struct ThemeTokenStyle {
    pub scope: Vec<String>,       // e.g. ["keyword.control", "keyword"]
    pub style: ThemeTokenStyleInner,
}
pub struct ThemeTokenStyleInner {
    pub foreground: Option<ColorInput>,
    pub background: Option<ColorInput>,
    pub bold: Option<bool>,
    pub italic: Option<bool>,
    pub underline: Option<bool>,
    pub dim: Option<bool>,
}

Constructing

convert_theme_to_styles(theme: &[ThemeTokenStyle]) -> HashMap<String, StyleDefinition> is the underlying free function that flattens a theme: every scope in every token becomes a key.

Registering and resolving

styles.register_style("keyword", &StyleDefinitionInput { fg: Some("#ffb464".into()), ..Default::default() }) -> u64
styles.resolve_style_id("keyword") -> Option<u64>   // exact id, or None
styles.get_style_id("keyword.control") -> Option<u64> // falls back to base name before '.'
styles.get_style("keyword.control") -> Option<&StyleDefinition>
styles.get_style_count() -> usize
styles.get_all_styles() -> HashMap<String, StyleDefinition>
styles.get_registered_names() -> Vec<String>

Scoped lookups fall back to the base name: get_style("keyword.control") returns the style registered under "keyword" if no exact match exists. This mirrors how editor token scopes inherit from parent scopes.

Merging

let merged: MergedStyle = styles.merge_styles(&["keyword", "keyword.control"]);

merge_styles overlays the named styles in order — later names override earlier ones field-by-field — packs the resulting booleans into the attributes bitmask via create_text_attributes, and caches the result keyed by the joined name list ("keyword:keyword.control"), so repeated merges of the same set are cheap.

Cache management: clear_cache() empties the merge cache, get_cache_size() reports its size, clear_name_cache() drops the name → id map (ids stay valid), and destroy() frees everything.

Lifecycle guard

All methods assert the registry is not destroyed (SyntaxStyle::destroy()). Calling any method after destroy() panics.

Example — themed tokens for a code widget

use cosh_tui::core::syntax_style::{SyntaxStyle, StyleDefinitionInput, ThemeTokenStyle, ThemeTokenStyleInner};

let theme = vec![
    ThemeTokenStyle {
        scope: vec!["keyword".into(), "keyword.control".into()],
        style: ThemeTokenStyleInner { foreground: Some("#ffb464".into()), ..Default::default() },
    },
    ThemeTokenStyle {
        scope: vec!["string".into()],
        style: ThemeTokenStyleInner { foreground: Some("#96c896".into()), ..Default::default() },
    },
];
let styles = SyntaxStyle::from_theme(&theme);

let merged = styles.merge_styles(&["keyword.control"]);  // inherits "keyword"
// merged.fg == Some(rgba(1.0, 0.71, 0.39, 1.0)), merged.attributes == 0

Next: utils — text attribute helpers.