Basics · Events

Key events

Element events cover clicks and form controls, but a keyboard app also wants the raw key stream. Declare a function named handleKey taking a sumi.Event and it becomes the component’s raw handler. The wiring is by name — only handleKey is picked up. The onkey="handleKey" attribute on the root documents that intent; it is not what does the wiring.

The event carries Kind (EventKey, EventSpecial, EventSignal, …), Rune for a printable key, and Special for the named keys. Printable keys arrive as EventKey with Rune set; arrows and the like arrive as EventSpecial — match them by value against sumi.KeyUp, sumi.KeyDown, and the other re-exported constants.

You do not have to wire quitting. Ctrl+C already ends the app — it is the default exit chord (ExitOn). What doesn’t stop on its own is an OS signal: a SIGINT/SIGTERM arrives as an EventSignal and is ignored unless you handle it, which is why every handler starts with the same line.

Your turn

Move the selection with j/k and the arrow keys. The % keeps the index inside the list:

func handleKey(evt sumi.Event) {
    if evt.Kind == sumi.EventSignal { sumi.Quit(); return }
    n := len(todos.Get())
    if n == 0 { return }
    if evt.Rune == 'j' || evt.Special == sumi.KeyDown {
        selected.Set((selected.Get() + 1) % n)
    }
    if evt.Rune == 'k' || evt.Special == sumi.KeyUp {
        selected.Set((selected.Get() + n - 1) % n)
    }
}

Press Run, click into the terminal, and move the > marker with the keyboard.