rdev

rdev

Simple library to listen and send events globally to keyboard and mouse on macOS, Windows and Linux (x11).

You can also check out Enigo which is another crate which helped me write this one.

This crate is so far a pet project for me to understand the Rust ecosystem.

Listening to global events

use rdev::{listen, Event};

// This will block.
if let Err(error) = listen(callback) {
    println!("Error: {:?}", error)
}

fn callback(event: Event) {
    println!("My callback {:?}", event);
    match event.name {
        Some(string) => println!("User wrote {:?}", string),
        None => (),
    }
}

OS Caveats:

When using the listen function, the following caveats apply:

macOS

The process running the blocking listen function (loop) needs to be the parent process (no fork before). The process needs to be granted access to the Accessibility API (i.e. if you're running your process inside Terminal.app, then Terminal.app needs to be added in System Preferences > Security & Privacy > Privacy > Accessibility) If the process is not granted access to the Accessibility API, macOS will silently ignore rdev's listen callback and will not trigger it with events. No error will be generated.

Linux

The listen function uses X11 APIs, and so will not work in Wayland or in the Linux kernel virtual console

Sending some events

…

Main structs

Event

In order to detect what a user types, we need to plug to the OS level management of keyboard state (modifiers like shift, CTRL, but also dead keys if they exist).

EventType corresponds to a physical event, corresponding to QWERTY layout Event corresponds to an actual event that was received and Event.name reflects what key was interpreted by the OS at that time, it will respect the layout.

/// When events arrive from the system we can add some information
/// time is when the event was received.
#[derive(Debug)]
pub struct Event {
    pub time: SystemTime,
    pub name: Option,
    pub event_type: EventType,
}

Be careful, Event::name, might be None, but also String::from(""), and might contain not displayable Unicode characters. We send exactly what the OS sends us, so do some sanity checking before using it. Caveat: Dead keys don't function yet on Linux

EventType

In order to manage different OS, the current EventType choices is a mix and match to account for all possible events. There is a safe mechanism to detect events no matter what, which are the Unknown() variant of the enum which will contain some OS specific value. Also, not that not all keys are mapped to an OS code, so simulate might fail if you try to send an unmapped key. Sending Unknown() variants will always work (the OS might still reject it).

…

Getting the main screen size

use rdev::{display_size};

let (w, h) = display_size().unwrap();
assert!(w > 0);
assert!(h > 0);

Keyboard state

We can define a dummy Keyboard, that we will use to detect what kind of EventType trigger some String. We get the currently used layout for now ! Caveat : This is layout dependent. If your app needs to support layout switching, don't use this! Caveat: On Linux, the dead keys mechanism is not implemented. Caveat: Only shift and dead keys are implemented, Alt+Unicode code on Windows won't work.

use rdev::{Keyboard, EventType, Key, KeyboardState};

let mut keyboard = Keyboard::new().unwrap();
let string = keyboard.add(&EventType::KeyPress(Key::KeyS));
// string == Some("s")

Grabbing global events. (Requires unstable_grab feature)

Installing this library with the unstable_grab feature adds the grab function which hooks into the global input device event stream. By supplying this function with a callback, you can intercept all keyboard and mouse events before they are delivered to applications / window managers. In the callback, returning None ignores the event and returning the event lets it pass. There is no modification of the event possible here (yet).

Note: the use of the word unstable here refers specifically to the fact that the grab API is unstable and subject to change

#[cfg(feature = "unstable_grab")]
use rdev::{grab, Event, EventType, Key};

#[cfg(feature = "unstable_grab")]
let callback = |event: Event| -> Option {
    if let EventType::KeyPress(Key::CapsLock) = event.event_type {
        println!("Consuming and cancelling CapsLock");
        None  // CapsLock is now effectively disabled
    }
    else { Some(event) }
};
// This will block.
#[cfg(feature = "unstable_grab")]
if let Err(error) = grab(callback) {
    println!("Error: {:?}", error)
}

OS Caveats:

When using the listen and/or grab functions, the following caveats apply:

macOS

The process running the blocking grab function (loop) needs to be the parent process (no fork before). The process needs to be granted access to the Accessibility API (i.e. if you're running your process inside Terminal.app, then Terminal.app needs to be added in System Preferences > Security & Privacy > Privacy > Accessibility) If the process is not granted access to the Accessibility API, the grab call will fail with an EventTapError (at least in macOS 10.15, possibly other versions as well)

Linux

The grab function use the evdev library to intercept events, so they will work with both X11 and Wayland In order for this to work, the process running the listen or grab loop needs to either run as root (not recommended), or run as a user who's a member of the input group (recommended) Note: on some distros, the group name for evdev access is called plugdev, and on some systems, both groups can exist. When in doubt, add your user to both groups if they exist.

Serialization

Event data returned by the listen and grab functions can be serialized and deserialized with Serde if you install this library with the serialize feature.