#key #parse #parser

crokey

Parse and describe keys - helping incorporate keybindings in terminal applications

18 releases (1 stable)

1.0.0 Apr 24, 2024
0.6.4 Mar 30, 2024
0.6.3 Jan 26, 2024
0.5.1 Aug 30, 2022
0.4.0 Feb 7, 2022

#53 in Command-line interface

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MIT license

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Crokey

Crokey helps incorporate configurable keybindings in crossterm based terminal applications by providing functions

  • parsing key combinations from strings
  • describing key combinations in strings
  • parsing key combinations at compile time
  • combining Crossterm key events in key combinations

The KeyCombination

A KeyCombination is made of 1 to 3 "normal" keys with some optional modifiers (alt, shift, ctrl).

It can be parsed, ergonomically built with the key! macro, obtained from key events.

The Combiner

With a Combiner, you can change raw Crossterm key events into key combinations.

When the terminal is modern enough and supports the Kitty protocol, complex combinations with up to three non-modifier keys may be formed, for example Ctrl-Alt-Shift-g-y or Space-!.

For standard ANSI terminals, only regular combinations are available, like Shift-o, Ctrl-Alt-Shift-g or i.

The combiner works in both cases: if you presses the ctrl, i, and u keys at the same time, it will result in one combination (ctrl-i-u) on a kitty-compatible terminal, and as a sequence of 2 key combinations (ctrl-i then ctrl-u assuming you started pressing the i before the u) in other terminals.

The print_key example shows how to deal with that:

let fmt = KeyCombinationFormat::default();
let mut combiner = Combiner::default();
let combines = combiner.enable_combining().unwrap();
if combines {
    println!("Your terminal supports combining keys");
} else {
    println!("Your terminal doesn't support combining non-modifier keys");
}
println!("Type any key combination");
loop {
    terminal::enable_raw_mode().unwrap();
    let e = read();
    terminal::disable_raw_mode().unwrap();
    match e {
        Ok(Event::Key(key_event)) => {
            if let Some(key_combination) = combiner.transform(key_event) {
                match key_combination {
                    key!(ctrl-c) | key!(ctrl-q) => {
                        println!("quitting");
                        break;
                    }
                    _ => {
                        println!("You typed {}", fmt.to_string(key_combination));
                    }
                }
            }
        },
        ...
    }
}

Parse a string

Those strings are usually provided by a configuration file.

use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
assert_eq!(
    crokey::parse("alt-enter").unwrap(),
    KeyEvent::new(KeyCode::Enter, KeyModifiers::ALT),
);
assert_eq!(
    crokey::parse("shift-F6").unwrap(),
    KeyEvent::new(KeyCode::F(6), KeyModifiers::SHIFT),
);

Use key combination "literals" thanks to procedural macros

Those key combinations are parsed at compile time and have zero runtime cost.

They're efficient and convenient for matching events or defining hardcoded keybindings.

match key_event.into() {
    key!(ctrl-c) => {
        println!("Arg! You savagely killed me with a {}", fmt.to_string(key_event).red());
        break;
    }
    key!(ctrl-q) => {
        println!("You typed {} which gracefully quits", fmt.to_string(key_event).green());
        break;
    }
    _ => {
        println!("You typed {}", fmt.to_string(key_event).blue());
    }
}

Complete example in /examples/print_key:

print_key

The key! macro can be called in const contexts:

const quit: KeyCombination = key!(ctrl-q);

Display a string with a configurable format

use crokey::*;
use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};

// The default format
let format = KeyCombinationFormat::default();
assert_eq!(format.to_string(key!(shift-a)), "Shift-a");
assert_eq!(format.to_string(key!(ctrl-c)), "Ctrl-c");

// A more compact format
let format = KeyCombinationFormat::default()
    .with_implicit_shift()
    .with_control("^");
assert_eq!(format.to_string(key!(shift-a)), "A");
assert_eq!(format.to_string(key!(ctrl-c)), "^c");

Deserialize keybindings using Serde

With the "serde" feature enabled, you can read configuration files in a direct way:

use {
    crokey::*,
    crossterm::event::KeyEvent,
    serde::Deserialize,
    std::collections::HashMap,
};
#[derive(Debug, Deserialize)]
struct Config {
    keybindings: HashMap<KeyCombination, String>,
}
static CONFIG_HJSON: &str = r#"
{
    keybindings: {
        a: aardvark
        shift-b: babirussa
        ctrl-k: koala
        alt-j: jaguar
    }
}
"#;
let config: Config = deser_hjson::from_str(CONFIG_HJSON).unwrap();
let key: KeyCombination = key!(shift-b);
assert_eq!(
    config.keybindings.get(&key).unwrap(),
    "babirussa",
);

You can use any Serde compatible format such as JSON or TOML.

Crossterm Compatibility

Crokey includes and reexports Crossterm, so you don't have to import it and to avoid conflicts.

Dependencies

~2.1–7.5MB
~61K SLoC