Responding to keyboard modifiers on macOS in SwiftUI

New in macOS 15, we can now use onModifierKeysChanged(mask:initial:_:) to update our views when keyboard modifiers are held down.

On macOS, it is common to reveal additional details and advanced settings when the user holds down the option key. Here is a view that shows a button to access advanced settings only while the user is holding down option.

struct ContentView: View {
    @State var optionPressed = false
    
    var body: some View {
        VStack(alignment: .trailing) {
            Toggle("Show emoji", isOn: .constant(false))
            Spacer()
            if optionPressed {
                Button("Advanced") {
                    /// TODO: open advance settings sheet
                }
            }
        }
        .onModifierKeysChanged(mask: .option) { old, new in
            optionPressed = new.contains(.option)
        }
    }
}

Screenshot macOS view showing the advanced button visible while the option key is held down.

The new onModifierKeysChanged() method is only available on the latest macOS, so if you need to respond to modifier keys on iPadOS or older macOS versions, check out my other post Reading keyboard modifiers on iPad in SwiftUI.

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