Introduction

Opaline is a token-based theme engine for Rust applications. It gives your app a complete theming system: raw hex colors resolve to semantic tokens, which compose into styles, all driven by TOML configuration. While Opaline ships with first-class ratatui support, adapters for egui, crossterm, owo-colors, syntect, and CSS make it work across terminal, GUI, and web targets.

Why Opaline?

Most Ratatui apps hardcode colors directly in their render functions. This works fine for small projects, but as your app grows you end up with magic color values scattered everywhere:

// The usual approach: colors everywhere
let style = Style::default().fg(Color::Rgb(225, 53, 255)).bold();
let border = Style::default().fg(Color::Rgb(128, 255, 234));

Opaline replaces this with semantic names that resolve through a theme:

use opaline::Theme;

let theme = Theme::default();

// Semantic: the theme decides what "keyword" looks like
let keyword = theme.style("keyword");   // works directly via Into<Style>
let border = theme.style("focused_border");

Change the theme, and every styled element updates automatically. Users can switch between 39 builtin themes or load custom ones from TOML files.

Architecture

Opaline uses a three-layer resolution pipeline:

graph LR
    A[Palette] --> B[Tokens]
    B --> C[Styles]
    B --> D[Gradients]

    style A fill:#e135ff,color:#fff,stroke:#bd93f9
    style B fill:#80ffea,color:#121218,stroke:#50fa7b
    style C fill:#ff6ac1,color:#fff,stroke:#ff6363
    style D fill:#f1fa8c,color:#121218,stroke:#f1fa8c

1. Palette: Named hex colors (purple = "#e135ff")
2. Tokens: Semantic references to palette (accent.primary = "purple")
3. Styles: Composed fg/bg + modifiers (keyword = { fg = "accent.primary", bold = true })

This separation means palette swaps propagate through the entire theme automatically. Change one hex value and every token referencing it updates.

Features at a Glance

Feature	Description
39 builtin themes	SilkCircuit, Catppuccin, GitHub, Monokai Pro, Ayu, Night Owl, Flexoki, Palenight, Rose Pine, Everforest, Tokyo Night, Kanagawa, Dracula, Nord, Gruvbox, Solarized, One
Token system	26 core semantic tokens across generic namespaces
Gradients	Multi-stop color interpolation with at(t) and generate(n)
7 adapters	ratatui, egui, crossterm, owo-colors, syntect, CSS, colored
ThemeBuilder	Programmatic theme construction without TOML
Strict resolver	Cycle detection, unresolvable reference errors
Zero unsafe	unsafe_code = "forbid", no exceptions

Next Steps

• Installation: Add Opaline to your Cargo.toml
• Quick Start: Load a theme and render styled content in 5 minutes