How to align label in an HStack with the result of the labels in a Form?

Question

I am trying to include a custom HStack row in a SwiftUI Form as follows:

var body: some View {
    Form {
        TextField("Text", text: .constant("test"))
        Toggle("Toggle", isOn: .constant(true))
            .toggleStyle(SwitchToggleStyle())
        HStack {
            Text("Label")
            MenuButton("Menu") {
                Button(action: {
                    print("Clicked Pizza")
                }) { Text("Pizza") }
                Button(action: {
                    print("Clicked Pasta")
                }) { Text("Pasta") }
            }
            TextField("Topping", text: .constant("Cheese"))
                .labelsHidden()
        }
        
    }
    .padding()
}

resulting in

However, I would like Label to be vertically aligned with Toggle, and Menu vertically aligned with the toggle.

Is there a standard way of choosing the alignment mode for the custom HStack row?

Answer 1

macOS 13 only

The new LabeledContent view in SwiftUI will help you:

LabeledContent("Label") {
  MenuButton("Menu") {
    Button(action: {
      print("Clicked Pizza")
    }) { Text("Pizza") }
    Button(action: {
      print("Clicked Pasta")
    }) { Text("Pasta") }
  }
  TextField("Topping", text: .constant("Cheese"))
    .labelsHidden()
  }
}

However, this view has not been backported to earlier versions of macOS, so if you need to support earlier versions you'll need another approach.

---

Earlier versions of macOS

Building on the preference key code from @Nhat Nguyen Duc, the key is to use alignment guides rather than padding. Creating a custom view, and with a customised preference that only measures the width:

struct LabeledHStack<Content: View>: View {
    var label: String
    var content: () -> Content
    @State var labelWidth: CGFloat = 0

    init(_ label: String, @ViewBuilder content: @escaping () -> Content) {
        self.label = label
        self.content = content
    }

    var body: some View {
        HStack {
            Text(label)
                .readWidth { self.labelWidth = $0 }
            content()
        }
        .alignmentGuide(.leading) { _ in labelWidth + 10 } // see note
    }
}

struct WidthPreferenceKey: PreferenceKey {
    static var defaultValue: CGFloat = 0
    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) { }
}

extension View {
    func readWidth(onChange: @escaping (CGFloat) -> Void) -> some View {
        background(
            GeometryReader { geometryProxy in
                Color.clear
                    .preference(key: WidthPreferenceKey.self, value: geometryProxy.size.width)
            }
        )
        .onPreferenceChange(WidthPreferenceKey.self, perform: onChange)
    }
}

Note that in the custom view I've added 10 pixels to quickly emulate the spacing between a label and its form elements. There is probably a better way to make this work for accessibility sizes, etc., (e.g., the use of a @ScaledMetric value). You might also wish to apply this as padding rather than in the alignment guide calculation.

Below has a line with macOS13's LabeledContent, followed by LabeledHStack:

Answer 2

macOS 13

LabeledContent {
    HStack { 
        // ...
    }
} label: {
    Text("Count")
}

• Read more about LabeledContent here

---

Previous version

Idea: Calculate the size of the label using GeometryReader, and offset the view by its width.

@State private var textSize = CGSize.zero

var body: some View {
    Form {
        TextField("Text", text: .constant("test"))
            .padding(.leading, -textSize.width)
        Toggle("Toggle", isOn: .constant(true))
            .toggleStyle(SwitchToggleStyle())
            .padding(.leading, -textSize.width)
        HStack {
            Text("Label")
                .readSize { textSize in
                    self.textSize = textSize
                }
            MenuButton("Menu") {
                Button("Pizza") {
                    print("Clicked Pizza")
                }
                Button("Pasta") {
                    print("Clicked Pasta")
                }
            }
            TextField("Topping", text: .constant("Cheese"))
                .labelsHidden()
        }
        .padding(.leading, -textSize.width - 10)
        .frame(maxWidth: .infinity)
    }
    .padding(.leading, textSize.width + 10)
    .padding()
}

• extension View

extension View {
    func readSize(onChange: @escaping (CGSize) -> Void) -> some View {
        background(
            GeometryReader { geometryProxy in
                Color.clear
                    .preference(key: SizePreferenceKey.self, value: geometryProxy.size)
            }
        )
        .onPreferenceChange(SizePreferenceKey.self, perform: onChange)
    }
}

• struct SizePreferenceKey

struct SizePreferenceKey: PreferenceKey {
    static var defaultValue: CGSize = .zero
    static func reduce(value: inout CGSize, nextValue: () -> CGSize) { }
}

• Bonus: For a button that contains only label, you can use

Button(<#String#>) { <#Action#> }

instead of

Button(action: { <#Action#> }) { Text(<#String#>) }