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Using Themes

Select a theme for syntax highlighting and access theme colors.

Pass a theme name in CodeToHTMLOptions.Theme to color tokens from a VS Code theme.

Select a theme

Go
html, err := h.CodeToHTML(ctx, code, nuri.CodeToHTMLOptions{
  Lang:  "typescript",
  Theme: "github-dark",
})

The theme resolves colors from a VS Code theme JSON bundled in the filesystem. Themes load lazily on first use.

Swap the name to change the color scheme:

Go
html, err := h.CodeToHTML(ctx, code, nuri.CodeToHTMLOptions{
  Lang:  "typescript",
  Theme: "dracula",
})

The same theme name works across all output methods (h.CodeToANSI(), h.CodeToSVG(), etc.).

Available themes

65 themes ship in both the core and full bundles. A sample of the included names:

andromeeda, ayu-dark, catppuccin-mocha, dark-plus, dracula, everforest-dark, github-dark, github-light, min-dark, monokai, nord, one-dark-pro, rose-pine, slack-dark, solarized-dark, tokyo-night, vitesse-dark, and more.

For the complete list, see Bundled Languages & Themes.

h.LoadedThemes() returns the names of themes that have been loaded into the cache so far:

Go
names := h.LoadedThemes()
fmt.Println(names) // e.g. ["github-dark"]

This reflects cached themes, not the full set of available themes. A theme enters the cache the first time it is used in a highlighting call or loaded explicitly.

Theme colors

h.GetThemeColors() returns the UI colors for a loaded theme. Use these to style code block chrome (title bars, copy buttons, terminal frames) consistently with the highlighted code:

Go
colors, err := h.GetThemeColors("github-dark")
if err != nil {
  log.Fatal(err)
}
fmt.Println(colors.Type)       // "dark"
fmt.Println(colors.Background) // "#24292e"
fmt.Println(colors.Foreground) // "#e1e4e8"
Field Type Description
Type string "dark" or "light"
Background string Editor background color
Foreground string Editor foreground color
SelectionBackground string Selection highlight color
LineHighlightBg string Current-line highlight color
Colors map[string]string Full VS Code color map (editor.*, terminal.*, etc.)

The Colors map contains all color keys defined in the theme JSON. Access specific keys when the top-level fields are not enough:

Go
tabBorder := colors.Colors["editorGroupHeader.tabsBorder"]

Contrast correction

Nuri adjusts token foreground colors that fail a WCAG 2.1 contrast check against the theme background. The default ratio is 5.5 (WCAG AA enhanced). Adjusted themes are cached, so there is no per-token cost. h.GetThemeColors() returns contrast-adjusted colors.

See the Contrast Correction guide to configure or disable this behavior.

Next steps

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