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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/rive-app/rive-ios/llms.txt

Use this file to discover all available pages before exploring further.

Rive provides powerful layout options to control how your animations scale and align within their container views. Use RiveFit to determine scaling behavior and RiveAlignment to position content.

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RiveFit

The RiveFit enum controls how Rive content scales to fit within its container.

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Fit Modes

public enum RiveFit: Int {
    case fill        // Fills the container, may distort aspect ratio
    case contain     // Fits inside container, maintains aspect ratio
    case cover       // Covers container, maintains aspect ratio (may crop)
    case fitWidth    // Matches container width, maintains aspect ratio
    case fitHeight   // Matches container height, maintains aspect ratio
    case scaleDown   // Contains content, never scales up
    case noFit       // No fitting, uses artboard's natural size
    case layout      // Resizes artboard to match container
}

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Fit Mode Details

Stretches the content to fill the entire container. This may distort the aspect ratio of your animation.
viewModel.fit = .fill
Use when: You want content to exactly fill the container, and aspect ratio isn’t critical.
Scales content to fit inside the container while maintaining aspect ratio. The entire animation will be visible.
viewModel.fit = .contain
Use when: You want the entire animation visible without distortion.
Scales content to cover the entire container while maintaining aspect ratio. Content may be cropped.
viewModel.fit = .cover
Use when: You want to fill the container without distortion, and cropping is acceptable.
Scales content to match the container’s width while maintaining aspect ratio.
viewModel.fit = .fitWidth
Use when: You want content to span the full width, allowing vertical scrolling if needed.
Scales content to match the container’s height while maintaining aspect ratio.
viewModel.fit = .fitHeight
Use when: You want content to span the full height, allowing horizontal scrolling if needed.
Like contain, but never scales content larger than its natural size.
viewModel.fit = .scaleDown
Use when: You want to prevent low-resolution content from appearing pixelated.
Content is rendered at its natural artboard size with no scaling.
viewModel.fit = .noFit
Use when: You want pixel-perfect rendering at the designed size.
Resizes the artboard itself to match the container dimensions.
viewModel.fit = .layout
viewModel.layoutScaleFactor = 2.0 // Optional scale factor
Use when: You want the Rive artboard to dynamically resize with the container.

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RiveAlignment

The RiveAlignment enum controls where content is positioned within its container.

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Alignment Options

public enum RiveAlignment: Int {
    case topLeft
    case topCenter
    case topRight
    case centerLeft
    case center      // Default
    case centerRight
    case bottomLeft
    case bottomCenter
    case bottomRight
}

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Alignment Grid

┌─────────────────────────────┐
│ topLeft  topCenter  topRight│
│                             │
│centerLeft  center centerRight│
│                             │
│bottomLeft bottomCenter bottomRight│
└─────────────────────────────┘

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Using with RiveViewModel

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Setting Fit and Alignment

import RiveRuntime

// Initialize with fit and alignment
let viewModel = RiveViewModel(
    fileName: "animation",
    fit: .contain,
    alignment: .center
)

// Change at runtime
viewModel.fit = .cover
viewModel.alignment = .topLeft

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SwiftUI Example

import SwiftUI
import RiveRuntime

struct LayoutView: View {
    @StateObject private var viewModel = RiveViewModel(
        fileName: "layout_test",
        fit: .contain
    )
    @State private var fit: RiveFit = .contain
    @State private var alignment: RiveAlignment = .center
    
    var body: some View {
        VStack {
            viewModel.view()
                .onChange(of: fit) { newValue in
                    viewModel.fit = newValue
                }
                .onChange(of: alignment) { newValue in
                    viewModel.alignment = newValue
                }
            
            // Fit controls
            HStack {
                Button("Fill") { fit = .fill }
                Button("Contain") { fit = .contain }
                Button("Cover") { fit = .cover }
            }
            
            HStack {
                Button("Fit Width") { fit = .fitWidth }
                Button("Fit Height") { fit = .fitHeight }
                Button("Scale Down") { fit = .scaleDown }
            }
            
            // Alignment controls
            VStack {
                HStack {
                    Button("⬉") { alignment = .topLeft }
                    Button("⬆") { alignment = .topCenter }
                    Button("⬈") { alignment = .topRight }
                }
                HStack {
                    Button("⬅") { alignment = .centerLeft }
                    Button("●") { alignment = .center }
                    Button("➡") { alignment = .centerRight }
                }
                HStack {
                    Button("⬋") { alignment = .bottomLeft }
                    Button("⬇") { alignment = .bottomCenter }
                    Button("⬊") { alignment = .bottomRight }
                }
            }
        }
    }
}

​
Layout Scale Factor

When using RiveFit.layout, you can control the scale factor: 
viewModel.fit = .layout

// Automatic scaling (default)
viewModel.layoutScaleFactor = RiveViewModel.layoutScaleFactorAutomatic

// Custom scale factor
viewModel.layoutScaleFactor = 2.0 // Render at 2x resolution
viewModel.layoutScaleFactor = 1.0 // Render at 1x resolution

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Dynamic Scale Factor Example

@State private var scaleFactor: Double = RiveViewModel.layoutScaleFactorAutomatic

Stepper {
    Text("Scale factor: \(scaleFactor == RiveViewModel.layoutScaleFactorAutomatic ? "Automatic" : "\(Int(scaleFactor))")
} onIncrement: {
    if scaleFactor == RiveViewModel.layoutScaleFactorAutomatic {
        scaleFactor = 1
    } else {
        scaleFactor += 1
    }
} onDecrement: {
    guard scaleFactor > RiveViewModel.layoutScaleFactorAutomatic else { return }
    scaleFactor -= 1
    if scaleFactor == 0 {
        scaleFactor = RiveViewModel.layoutScaleFactorAutomatic
    }
}
.onChange(of: scaleFactor) { newValue in
    viewModel.layoutScaleFactor = newValue
}

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Using with RiveRenderer

For manual rendering, use the RiveRenderer alignment method: 
let context = // your CGContext
let renderer = RiveRenderer(context: context)

// Align content
renderer.align(
    with: containerRect,
    withContentRect: artboardBounds,
    withAlignment: .center,
    withFit: .contain
)

// Draw artboard
artboard.draw(renderer)

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Responsive Layout Example

import SwiftUI
import RiveRuntime

struct ResponsiveRiveView: View {
    @StateObject private var viewModel = RiveViewModel(
        fileName: "responsive",
        fit: .contain
    )
    @State private var collapsed = false
    
    var body: some View {
        VStack {
            viewModel.view()
                .frame(
                    width: collapsed ? 150 : 400,
                    height: collapsed ? 300 : 400
                )
                .animation(.default, value: collapsed)
            
            Button("Toggle Size") {
                collapsed.toggle()
            }
        }
    }
}

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Best Practices

The .contain fit mode is the most common choice as it ensures the entire animation is visible without distortion.
let viewModel = RiveViewModel(
    fileName: "animation",
    fit: .contain,
    alignment: .center
)
When using Rive content as a background, .cover ensures the container is filled without distortion.
viewModel.fit = .cover
viewModel.alignment = .center
The .layout fit mode allows your artboard to resize dynamically, perfect for responsive interfaces.
viewModel.fit = .layout
viewModel.layoutScaleFactor = 2.0 // High DPI displays
Always test your fit and alignment choices on different screen sizes and orientations to ensure content displays correctly.

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Common Patterns

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Full-Screen Background

let backgroundVM = RiveViewModel(
    fileName: "background",
    fit: .cover,
    alignment: .center
)

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Centered Icon

let iconVM = RiveViewModel(
    fileName: "icon",
    fit: .scaleDown,
    alignment: .center
)

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Hero Image

let heroVM = RiveViewModel(
    fileName: "hero",
    fit: .fitWidth,
    alignment: .topCenter
)
  • RiveViewModel - High-level view model with layout support
  • Artboards - Understand artboard dimensions
  • RiveView - Native view rendering

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