keymap-rs

keymap-rs is a lightweight and extensible key mapping library for Rust that simplifies input processing for terminal user interfaces (TUIs), WebAssembly (WASM) applications, and more. It parses keymaps from derive macros or configuration files and maps them to actions from various input backends, including crossterm, termion, and wasm.

📋 Table of Contents

• Installation
• Usage
  • 1. Deriving KeyMap
  • 2. Using External Configuration
  • 3. Compile-Time Validation
  • 4. Direct Key Parsing
• Key Syntax Reference
• Examples
• License
• Contributions

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🔧 Features

• ✅ Declarative Key Mappings: Define keymaps via simple configuration files (e.g., TOML, YAML) or directly in your code using derive macros.
• ⌨️ Key Patterns: Supports single keys (a), combinations (ctrl-b), and multi-key sequences (ctrl-b n).
• 🧠 Key Groups: Use built-in pattern matching for common key groups (@upper, @lower, @alpha, @alnum, and @any).
• 🧬 Compile-Time Safety: The keymap_derive macro validates key syntax at compile time, preventing runtime errors.
• 🌐 Backend-Agnostic: Works with multiple backends, including crossterm, termion, and wasm.
• 🪶 Lightweight & Extensible: Designed to be minimal and easy to extend with new backends or features.

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🕹️ Demo

See keymap-rs in action with the WASM example:

Nyan Jump!	Tur - Turing Machine Language

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📦 Installation

Add keymap to your Cargo.toml, enabling the feature for your chosen backend:

cargo add keymap --feature {crossterm | termion | wasm}

---

🚀 Usage

1. Deriving KeyMap

The easiest way to get started is with the keymap::KeyMap derive macro.

Define your actions:

use keymap::KeyMap;

/// Application actions.
#[derive(KeyMap, Debug, PartialEq, Eq)]
pub enum Action {
    /// Quit the application.
    #[key("q", "esc")]
    Quit,

    /// Move left.
    #[key("left", "h")]
    Left,

    /// Move right.
    #[key("right", "l")]
    Right,

    /// Jump.
    #[key("space")]
    Jump,
}

Use the generated keymap:

The KeyMap derive macro generates an associated keymap_config() method, which returns a Config<Action>.

// Retrieve the config
let config = Action::keymap_config();

// `key` is a key code from the input backend, e.g., `crossterm::event::KeyCode`
match config.get(&key) {
    Some(action) => match action {
        Action::Quit => break,
        Action::Jump => println!("Jump!"),
        _ => println!("Action: {action:?} - {}", action.keymap_item().description),
    }
    _ => {}
}

2. Using External Configuration

keymap-rs also supports loading keymaps from external files (e.g., config.toml). This is useful for user-configurable keybindings.

Example config.toml:

# Override or add new keybindings
Jump = { keys = ["j", "up"], description = "Jump with 'j' or up arrow!" }
Quit = { keys = ["@any"], description = "Quit on any key press." }

This configuration can be loaded in two ways:

Config<T>: Load from File Only

This deserializes only the keybindings from the configuration file, ignoring any #[key("...")] attributes on your enum.

// This config will only contain 'Jump' and 'Quit' from the TOML file.
let config: Config<Action> = toml::from_str(&data)?;

Resulting keybindings:

Key	Action
"j", "up"	Jump
@any	Quit

DerivedConfig<T>: Merge Derived and File Configs

This merges keybindings from the #[key("...")] attributes with those from the configuration file. Keys from the external file will override any conflicting keys defined in the enum.

// This config contains keys from both the derive macro and the TOML file.
let config: DerivedConfig<Action> = toml::from_str(&data)?;

Resulting keybindings:

Key	Action	Source
"j", "up"	Jump	Config file (overrides "space")
"h", "left"	Left	Derive macro
"l", "right"	Right	Derive macro
@any	Quit	Config file (overrides "q", "esc")

Note: When using DerivedConfig<T>, keys from the config file take precedence over derive macro keys for the same action.

3. Compile-Time Validation

The keymap_derive macro validates all key strings at compile time, providing immediate feedback on invalid syntax.

Invalid Key Example:

#[derive(keymap::KeyMap)]
enum Action {
    // "enter2" is not a valid key.
    #[key("enter2", "ctrl-b n")]
    Invalid,
}

Compiler Error:

This code will fail to compile with a clear error message:

error: Invalid key "enter2": Parse error at position 5: expect end of input, found: 2
 --> keymap_derive/tests/derive.rs:7:11
  |
7 |     #[key("enter2", "ctrl-b n")]
  |           ^^^^^^^^

4. Direct Key Parsing

Key strings can also be parsed directly into a KeyMap or a backend-specific key event.

use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
use keymap::{backend::crossterm::parse, Key, KeyMap, Modifier};

// Parse into a generic KeyMap
assert_eq!(
    "ctrl-l".parse::<KeyMap>(),
    Ok(KeyMap::new(Some(Modifier::Ctrl), Key::Char('l')))
);

// Or use the backend-specific parser
assert_eq!(
    parse("ctrl-l").unwrap(),
    KeyEvent::new(KeyCode::Char('l'), KeyModifiers::CONTROL)
);

---

📝 Key Syntax Reference

Type	Description	Example
Single Keys	Individual characters, special keys, arrow keys, and function keys.	a, enter, up, f1
Key Combinations	Keys pressed simultaneously with modifiers (Ctrl, Alt, Shift).	ctrl-c, alt-f4, ctrl-alt-shift-f1
Key Sequences	Multiple keys pressed in order.	g g (press g twice), ctrl-b n (Ctrl+B, then N), ctrl-b c (tmux-style new window)
Key Groups	Predefined patterns matching sets of keys.	@upper (A-Z), @alpha (A-Z, a-z), @any (any key)

Examples in Configuration:

# Single keys
Quit = { keys = ["q", "esc"] }

# Key combinations
Save = { keys = ["ctrl-s"] }
ForceQuit = { keys = ["ctrl-alt-f4"] }

# Key sequences
ShowGitStatus = { keys = ["g s"] }
NewTmuxWindow = { keys = ["ctrl-b c"] }

# Key groups
AnyLetter = { keys = ["@alpha"] }
AnyKey = { keys = ["@any"] }

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📖 Examples

For complete, runnable examples, check out the /examples directory.

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📜 License

This project is licensed under the MIT License.

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🙌 Contributions

Contributions, issues, and feature requests are welcome! Feel free to open an issue or submit a pull request.