Document that readline.emitKeypressEvents only works when tty is in raw mode

[arve0]

• Version: 6.0.0
• Platform: osx 10.11.4, uname -a: 15.4.0 Darwin Kernel Version 15.4.0: Fri Feb 26 22:08:05 PST 2016; root:xnu-3248.40.184~3/RELEASE_X86_64 x86_64
• Subsystem: readline.emitKeypressEvents

process.stdin does not emit keypress after readline.emitKeypressEvents(process.stdin), but does when a readline interface created.

const readline = require('readline')

// const rl = readline.createInterface({
//  input: process.stdin,
//  output: process.stdout
// })
readline.emitKeypressEvents(process.stdin)
process.stdin.on('keypress', () => {
    process.stdout.write('.')
})

What happens: On keypress, event handler is not called. If a readline interface is created, the event handler is called.
Expected: stdin to start emitting keypress-events.

[addaleax]

Does setting process.stdin.setRawMode(true); help you?

[arve0]

@addaleax Yes, it does. The event handler is called, and terminal echo turns off.

[addaleax]

That is expected in raw mode, yes. I am not sure whether there’s another way to make process.stdin unbuffered/return characters as they are typed…

Is your question answered by this?

[arve0]

Kind of. I guess the documentation should state that raw mode or a readline interface is needed.

A drawback with raw mode though, is that SIGINT is disabled. Any way around that, without implementing it oneself?

This does not seem to work:

process.stdin.on('keypress', (str, key) => {
    if (key.ctrl && key.name === 'c') {
        process.emit('SIGINT')
    }
})

Any idea why?

[arve0]

To be more clear, this is needed in raw mode

process.on('SIGINT', () => {
    process.exit()
})

but not when using a readline interface.

[addaleax]

I guess the documentation should state that raw mode or a readline interface is needed.

Yeah, I guess so… The readline interface sets raw mode itself if the input is a terminal, that’s why that’s working.

To be more clear, this is needed in raw mode

If you “just” want as close to the original Ctrl+C behaviour as possible, you may want to use process.kill(process.pid, 'SIGINT') rather than process.emit('SIGINT'). The latter one does not actually send the signal, just emits the event to any JS listeners for it.

[arve0]

Aha, thanks!