Layout

SwiftUI Layout (watchOS)

Glanceable design: users interact with Apple Watch for 1-2 seconds. Every view must communicate its purpose instantly.

Watch Screen Constraints

• Screen sizes: 40mm (162pt), 41mm (176pt), 44mm (184pt), 45mm (198pt), 49mm Ultra (205pt)
• Always design for the smallest screen, let larger screens breathe
• No landscape orientation — always portrait
• No split views, no multi-column layouts

Layout Principles

Vertical Stacking

// Good - simple vertical stack, fills naturally
VStack(spacing: 8) {
    Text("Heart Rate")
        .font(AppTheme.Fonts.caption2)
        .foregroundStyle(.secondary)
    Text("72")
        .font(AppTheme.Fonts.largeTitle)
    Text("BPM")
        .font(AppTheme.Fonts.caption)
        .foregroundStyle(.secondary)
}

Full-Width Elements

// Good - buttons fill width on watch
Button("Start Workout") {
    startWorkout()
}
.buttonStyle(.borderedProminent)
// Buttons naturally fill width on watchOS — no .frame(maxWidth:) needed

containerRelativeFrame (preferred over GeometryReader)

Image("chart")
    .resizable()
    .containerRelativeFrame(.horizontal) { width, _ in
        width * 0.9
    }
    .aspectRatio(contentMode: .fit)

View Structure

Prefer Modifiers Over Conditional Views

// Good - same view, different states
SomeView()
    .opacity(isVisible ? 1 : 0)

// Avoid - creates/destroys view identity
if isVisible {
    SomeView()
}

Extract Subviews Into Separate Structs

// Good - separate struct, SwiftUI can skip body when inputs unchanged
struct MetricDisplay: View {
    let value: Int
    let unit: String

    var body: some View {
        VStack {
            Text("\(value)")
                .font(AppTheme.Fonts.title2)
            Text(unit)
                .font(AppTheme.Fonts.caption2)
                .foregroundStyle(.secondary)
        }
    }
}

What NOT to Use on watchOS

• No GeometryReader — use containerRelativeFrame or let stacks fill naturally
• No UIScreen.main.bounds — doesn't exist on watchOS
• No size classes — watch has one size class
• No NavigationSplitView — watch is single-column only
• No adaptive grids with many columns — use simple VStack or single-column List
• No .frame(maxWidth: 700) readability constraints — the screen is already small
• No AnyLayout switching — there's only one layout direction on watch

Layout Rules

1. Keep views shallow — 2-3 levels of nesting maximum
2. Use List for scrollable content, ScrollView for custom layouts
3. Large text (.title, .largeTitle) for primary information
4. Small text (.caption, .caption2) for labels and secondary info
5. Minimum tap target: 44pt (Apple requirement, critical on small screen)
6. Use @ScaledMetric for custom dimensions that respect Dynamic Type