nodejs keydown/keyup events

Question

I'm interested in seeing if it's possible to bind functions to a user pressing/releasing a key on the keyboard.

So far, I've been able to get key press events with the keypress module and process.stdin's raw mode:

var keypress = require('keypress');
keypress(process.stdin);
process.stdin.on('keypress', function(ch, key) {
    console.log('got "keypress"', key);
    if (key && key.ctrl && key.name == 'c') {
        process.exit();
    }
});
process.stdin.setRawMode(true);
process.stdin.resume();

Are capturing keyboard press and release events even possible in a terminal?

It should be worth noting that I am not interested in any browser implementations; I am looking for something that runs in NodeJS in a terminal.

Thanks, all.

Answer 1

So I figured a workaround the limitations of stdin to get this to work.

Basically I use the SDL library (along with its node bindings) to run a program in the background that listens on the keyboard for input.

To do this:

• Ensure you are running Node version ~0.10. (Apparently the way C bindings on node work a little differently in 0.11?)
• Install sdl, sdl_ttf, and sdl_image through homebrew (on a mac)
• npm install --save https://github.com/creationix/node-sdl/tarball/master

And then something along the lines of:

var sdl = require('sdl');

sdl.init(sdl.INIT.VIDEO);

while (true) {
    var e;
    while (e = sdl.pollEvent()) {
        console.log(e);
    }
}

SDL_PollEvent requires SDL be initialized with SDL_INIT_VIDEO, which in the script above (on a mac) starts a separate application in the dock that draws nothing, but needs to be focused to accept input.

While it's technically true that ANSI terminals simply do not support keyup events, this workaround totally lets one grab keyup events in Node (albeit requiring some GUI-based system to function, i.e. most likely will not work over ssh).