axiom-swiftui-layout

# SwiftUI Adaptive Layout

## Overview

Discipline-enforcing skill for building layouts that respond to available space rather than device assumptions. Covers tool selection, size class limitations, iOS 26 free-form windows, and common anti-patterns.

**Core principle:** Your layout should work correctly if Apple ships a new device tomorrow, or if iPadOS adds a new multitasking mode next year. Respond to your container, not your assumptions about the device.

## When to Use This Skill

- "How do I make this layout work on iPad and iPhone?"
- "Should I use GeometryReader or ViewThatFits?"
- "My layout breaks in Split View / Stage Manager"
- "Size classes aren't giving me what I need"
- "Designer wants different layout for portrait vs landscape"
- "Preparing app for iOS 26 window resizing"

## Decision Tree

```
"I need my layout to adapt..."
│
├─ TO AVAILABLE SPACE (container-driven)
│   │
│   ├─ "Pick best-fitting variant"
│   │   → ViewThatFits
│   │
│   ├─ "Animated switch between H↔V"
│   │   → AnyLayout + condition
│   │
│   ├─ "Read size for calculations"
│   │   → onGeometryChange (iOS 16+)
│   │
│   └─ "Custom layout algorithm"
│       → Layout protocol
│
├─ TO PLATFORM TRAITS
│   │
│   ├─ "Compact vs Regular width"
│   │   → horizontalSizeClass (⚠️ iPad limitations)
│   │
│   ├─ "Accessibility text size"
│   │   → dynamicTypeSize.isAccessibilitySize
│   │
│   └─ "Platform differences"
│       → #if os() / Environment
│
└─ TO WINDOW SHAPE (aspect ratio)
    │
    ├─ "Portrait vs Landscape semantics"
    │   → Geometry + custom threshold
    │
    ├─ "Auto show/hide columns"
    │   → NavigationSplitView (automatic in iOS 26)
    │
    └─ "Window lifecycle"
        → @Environment(\.scenePhase)
```

## Tool Selection

### Quick Decision

```
Do you need a calculated value (width, height)?
├─ YES → onGeometryChange
└─ NO → Do you need animated transitions?
         ├─ YES → AnyLayout + condition
         └─ NO → ViewThatFits
```

### When to Use Each Tool

| I n