macOS & SwiftUI 2: simplest way to turn off beep on keystroke

Question

The following trivial macOS app is written in SwiftUI 2.0.

import SwiftUI

@main
struct TempApp: App {
  var body: some Scene {
    WindowGroup { ContentView() }
  }
}

struct ContentView: View {
  var body: some View {
    Text("Hello, beep!").padding()
  }
}

When in the foreground, this app will emit an error beep on certain keystrokes (like "a"). What's the simplest way to suppress this beep?

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An Xcode project illustrating this (and the answer) can be found here.

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There are many older related questions on SO, but none of these are specifically about doing this in SwiftUI 2.0.

Answer 1

You can suppress the beep by adding a local monitor for the .keyDown event at the top level. This can be done simply in ContentView.init(), like so:

struct ContentView: View {
  var body: some View {
    Text("Hello, silence!").padding()
  }

  init() {
    NSEvent.addLocalMonitorForEvents(matching: .keyDown) { _ in return nil }
  }
}

This technique was inspired by this answer.