liquid-glass

What this skill does

# Liquid Glass Design

Implement Apple's Liquid Glass design language across all Apple UI frameworks. Covers SwiftUI (`.glassEffect()`), AppKit (`NSGlassEffectView`), UIKit (`UIGlassEffect` + `UIVisualEffectView`), and WidgetKit (rendering modes, accented content, glass elements in widgets).

## When This Skill Activates

- User wants glass/blur effects on views
- User asks about Liquid Glass or modern Apple design
- User needs transparent, interactive UI elements
- User wants morphing transitions between views
- User is implementing glass effects in UIKit with `UIVisualEffectView`
- User needs `UIGlassEffect` or `UIGlassContainerEffect`
- User asks about scroll view edge effects in UIKit
- User wants Liquid Glass in widgets (WidgetKit)
- User needs to support accented rendering mode in widgets
- User asks about widget textures or mounting styles on visionOS

## Quick Start (SwiftUI)

### Basic Glass Effect

```swift
import SwiftUI

Text("Hello, World!")
    .font(.title)
    .padding()
    .glassEffect()  // Capsule shape by default
```

### Custom Shape

```swift
Text("Hello")
    .padding()
    .glassEffect(in: .rect(cornerRadius: 16))

// Available shapes:
// .capsule (default)
// .rect(cornerRadius: CGFloat)
// .circle
```

### Interactive Glass

```swift
Button("Tap Me") {
    // action
}
.padding()
.glassEffect(.regular.interactive())
```

### Tinted Glass

```swift
Text("Important")
    .padding()
    .glassEffect(.regular.tint(.blue))
```

## Glass Configuration Options

| Option | Description | Example |
|--------|-------------|---------|
| `.regular` | Standard glass effect | `.glassEffect(.regular)` |
| `.tint(Color)` | Add color tint | `.glassEffect(.regular.tint(.orange))` |
| `.interactive()` | React to touch/hover | `.glassEffect(.regular.interactive())` |

## Multiple Glass Effects

### GlassEffectContainer

When using multiple glass elements, wrap them in `GlassEffectContainer` for:
- Better rendering performance
- Proper blending between effects
- Morphing transitions

```swift
GlassEffectContainer(spacing: 40.0) {
    HStack(spacing: 40.0) {
        Image(systemName: "star.fill")
            .frame(width: 80, height: 80)
            .font(.system(size: 36))
            .glassEffect()

        Image(systemName: "heart.fill")
            .frame(width: 80, height: 80)
            .font(.system(size: 36))
            .glassEffect()
    }
}
```

**Spacing Parameter:**
- Controls when effects merge
- Smaller spacing = views must be closer to merge
- Larger spacing = effects merge at greater distances

### Uniting Glass Effects

Combine views into a single glass effect using `glassEffectUnion`:

```swift
@Namespace private var namespace

GlassEffectContainer(spacing: 20.0) {
    HStack(spacing: 20.0) {
        ForEach(items.indices, id: \.self) { index in
            Image(systemName: items[index])
                .frame(width: 60, height: 60)
                .glassEffect()
                .glassEffectUnion(
                    id: index < 2 ? "group1" : "group2",
                    namespace: namespace
                )
        }
    }
}
```

## Morphing Transitions

Create fluid morphing effects when views appear/disappear.

### Setup

1. Create a namespace
2. Assign glass effect IDs
3. Use animations on state changes

```swift
struct MorphingToolbar: View {
    @State private var isExpanded = false
    @Namespace private var namespace

    var body: some View {
        GlassEffectContainer(spacing: 40.0) {
            HStack(spacing: 40.0) {
                // Always visible
                Image(systemName: "pencil")
                    .frame(width: 60, height: 60)
                    .glassEffect()
                    .glassEffectID("pencil", in: namespace)

                // Conditionally visible - will morph in/out
                if isExpanded {
                    Image(systemName: "eraser")
                        .frame(width: 60, height: 60)
                        .glassEffect()
                        .glassEffectID("eraser", in: namespace)

                    Image(systemName: "ruler")
                        .frame(width: 60, height: 60)
                        .glassEffect()
                        .glassEffectID("ruler", in: namespace)
                }
            }
        }

        Button("Toggle") {
            withAnimation(.spring(response: 0.4, dampingFraction: 0.8)) {
                isExpanded.toggle()
            }
        }
        .buttonStyle(.glass)
    }
}
```

## Button Styles

### Glass Button

```swift
Button("Standard") {
    // action
}
.buttonStyle(.glass)
```

### Glass Prominent Button

```swift
Button("Primary Action") {
    // action
}
.buttonStyle(.glassProminent)
```

## Advanced Techniques

### Background Extension

Stretch content under sidebar or inspector:

```swift
NavigationSplitView {
    SidebarView()
} detail: {
    DetailView()
        .background {
            Image("wallpaper")
                .resizable()
                .ignoresSafeArea()
        }
}
```

### Horizontal Scroll Under Sidebar

```swift
ScrollView(.horizontal) {
    HStack {
        ForEach(items) { item in
            ItemView(item: item)
        }
    }
}
.scrollExtensionMode(.underSidebar)
```

## AppKit Implementation

### NSGlassEffectView

```swift
import AppKit

// Create glass effect view
let glassView = NSGlassEffectView(frame: NSRect(x: 20, y: 20, width: 200, height: 100))
glassView.cornerRadius = 16.0
glassView.tintColor = NSColor.systemBlue.withAlphaComponent(0.3)

// Create content
let label = NSTextField(labelWithString: "Glass Content")
label.translatesAutoresizingMaskIntoConstraints = false

// Set content view
glassView.contentView = label

// Add constraints
if let contentView = glassView.contentView {
    NSLayoutConstraint.activate([
        label.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
        label.centerYAnchor.constraint(equalTo: contentView.centerYAnchor)
    ])
}
```

### NSGlassEffectContainerView

```swift
// Create container
let container = NSGlassEffectContainerView(frame: bounds)
container.spacing = 40.0

// Create content view
let contentView = NSView(frame: container.bounds)
container.contentView = contentView

// Add glass views to content
let glass1 = NSGlassEffectView(frame: NSRect(x: 20, y: 50, width: 150, height: 100))
let glass2 = NSGlassEffectView(frame: NSRect(x: 190, y: 50, width: 150, height: 100))

contentView.addSubview(glass1)
contentView.addSubview(glass2)
```

### Interactive AppKit Glass

```swift
class InteractiveGlassView: NSGlassEffectView {
    override init(frame: NSRect) {
        super.init(frame: frame)
        setupTracking()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupTracking()
    }

    private func setupTracking() {
        let options: NSTrackingArea.Options = [
            .mouseEnteredAndExited,
            .activeInActiveApp
        ]
        let trackingArea = NSTrackingArea(
            rect: bounds,
            options: options,
            owner: self,
            userInfo: nil
        )
        addTrackingArea(trackingArea)
    }

    override func mouseEntered(with event: NSEvent) {
        super.mouseEntered(with: event)
        NSAnimationContext.runAnimationGroup { context in
            context.duration = 0.2
            animator().tintColor = NSColor.systemBlue.withAlphaComponent(0.2)
        }
    }

    override func mouseExited(with event: NSEvent) {
        super.mouseExited(with: event)
        NSAnimationContext.runAnimationGroup { context in
            context.duration = 0.2
            animator().tintColor = nil
        }
    }
}
```

## Common Patterns

### Floating Action Bar

```swift
struct FloatingActionBar: View {
    @Namespace private var namespace

    var body: some View {
        GlassEffectContainer(spacing: 20) {
            HStack(spacing: 16) {
                ForEach(actions) { action in
                    Button {