Liquid Glass Design

# Liquid Glass Design System (iOS 26)

Patterns for implementing Apple's Liquid Glass — a dynamic material that blurs content behind it, reflects color and light from surrounding content, and reacts to touch and pointer interactions. Covers SwiftUI, UIKit, and WidgetKit integration.

## When to Activate

- Building or updating apps for iOS 26+ with the new design language
- Implementing glass-style buttons, cards, toolbars, or containers
- Creating morphing transitions between glass elements
- Applying Liquid Glass effects to widgets
- Migrating existing blur/material effects to the new Liquid Glass API

## Core Pattern — SwiftUI

### Basic Glass Effect

The simplest way to add Liquid Glass to any view:

```swift
Text("Hello, World!")
    .font(.title)
    .padding()
    .glassEffect()  // Default: regular variant, capsule shape
```

### Customizing Shape and Tint

```swift
Text("Hello, World!")
    .font(.title)
    .padding()
    .glassEffect(.regular.tint(.orange).interactive(), in: .rect(cornerRadius: 16.0))
```

Key customization options:
- `.regular` — standard glass effect
- `.tint(Color)` — add color tint for prominence
- `.interactive()` — react to touch and pointer interactions
- Shape: `.capsule` (default), `.rect(cornerRadius:)`, `.circle`

### Glass Button Styles

```swift
Button("Click Me") { /* action */ }
    .buttonStyle(.glass)

Button("Important") { /* action */ }
    .buttonStyle(.glassProminent)
```

### GlassEffectContainer for Multiple Elements

Always wrap multiple glass views in a container for performance and morphing:

```swift
GlassEffectContainer(spacing: 40.0) {
    HStack(spacing: 40.0) {
        Image(systemName: "scribble.variable")
            .frame(width: 80.0, height: 80.0)
            .font(.system(size: 36))
            .glassEffect()

        Image(systemName: "eraser.fill")
            .frame(width: 80.0, height: 80.0)
            .font(.system(size: 36))
            .glassEffect()
    }
}
```

The `spacing` parameter controls merge distance — closer elements blend their glass shapes together.

### Uniting Glass Effects

Combine multiple views into a single glass shape with `glassEffectUnion`:

```swift
@Namespace private var namespace

GlassEffectContainer(spacing: 20.0) {
    HStack(spacing: 20.0) {
        ForEach(symbolSet.indices, id: \.self) { item in
            Image(systemName: symbolSet[item])
                .frame(width: 80.0, height: 80.0)
                .glassEffect()
                .glassEffectUnion(id: item < 2 ? "group1" : "group2", namespace: namespace)
        }
    }
}
```

### Morphing Transitions

Create smooth morphing when glass elements appear/disappear:

```swift
@State private var isExpanded = false
@Namespace private var namespace

GlassEffectContainer(spacing: 40.0) {
    HStack(spacing: 40.0) {
        Image(systemName: "scribble.variable")
            .frame(width: 80.0, height: 80.0)
            .glassEffect()
            .glassEffectID("pencil", in: namespace)

        if isExpanded {
            Image(systemName: "eraser.fill")
                .frame(width: 80.0, height: 80.0)
                .glassEffect()
                .glassEffectID("eraser", in: namespace)
        }
    }
}

Button("Toggle") {
    withAnimation { isExpanded.toggle() }
}
.buttonStyle(.glass)
```

### Extending Horizontal Scrolling Under Sidebar

To allow horizontal scroll content to extend under a sidebar or inspector, ensure the `ScrollView` content reaches the leading/trailing edges of the container. The system automatically handles the under-sidebar scrolling behavior when the layout extends to the edges — no additional modifier is needed.

## Core Pattern — UIKit

### Basic UIGlassEffect

```swift
let glassEffect = UIGlassEffect()
glassEffect.tintColor = UIColor.systemBlue.withAlphaCompone