Initial Commit

.gitignore

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+.DS_Store
+/.build
+/Packages
+/*.xcodeproj
+xcuserdata/

.swiftpm/xcode/package.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

Package.swift

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+// swift-tools-version:5.3
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "ParallaxSwiftUI",
+    platforms: [
+        .iOS(.v13)
+    ],
+    products: [
+        // Products define the executables and libraries a package produces, and make them visible to other packages.
+        .library(
+            name: "ParallaxSwiftUI",
+            targets: ["ParallaxSwiftUI"]),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages this package depends on.
+        .target(
+            name: "ParallaxSwiftUI",
+            dependencies: []),
+    ]
+)

README.md

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+# ParallaxSwiftUI
+
+A description of this package.

Sources/ParallaxSwiftUI/ParallaxSwiftUI.swift

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+import SwiftUI
+
+extension View {
+    func parallax(amount: CGFloat = 10) -> some View {
+        ParallaxView(view: AnyView(self), amount: amount)
+    }
+}
+
+/// A wrapper view to add a parallax effect to a SwiftUI view.
+struct ParallaxView: View {
+
+    /// The view to apply the parallax too.
+    let view: AnyView
+
+    /// The amount of the parallax effect to be applied.
+    let amount: CGFloat
+
+    var body: some View {
+        /// Using geometry reader we can get the proposed width and height of the view normally. Then we can pass that to the view controller.
+        GeometryReader { geometry in
+            ParallaxRepresentable(view: view, width: geometry.size.width, height: geometry.size.height, amount: amount)
+        }
+    }
+}
+
+/// Converts SwiftUI view to UIKit controller.
+struct ParallaxRepresentable: UIViewControllerRepresentable {
+
+    let view: AnyView
+    let width: CGFloat
+    let height: CGFloat
+    let amount: CGFloat
+
+    func makeUIViewController(context: Context) -> ParallaxController {
+
+        let controller = ParallaxController()
+
+        let hostingController = UIHostingController(rootView: view)
+
+        controller.viewWidth = width
+        controller.viewHeight = height
+        controller.amount = amount
+        controller.viewToChange = hostingController
+
+        return controller
+    }
+
+    func updateUIViewController(_ uiViewController: ParallaxController, context: Context) {
+        uiViewController.viewWidth = width
+        uiViewController.viewHeight = height
+        uiViewController.updateView()
+    }
+}
+
+/// View controller that adds parallax effect to view of another view controller.
+class ParallaxController: UIViewController {
+
+    var viewToChange: UIViewController?
+    var viewWidth: CGFloat = 0
+    var viewHeight: CGFloat = 0
+    var amount: CGFloat = 10
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        // Add SwiftUI view to view controller
+        addChild(viewToChange!)
+        view.addSubview(viewToChange!.view)
+        viewToChange!.didMove(toParent: self)
+
+        // Set frame
+        viewToChange!.view.frame = CGRect(x: 0, y: 0, width: viewWidth, height: viewHeight)
+        view.frame = viewToChange!.view.frame
+
+        // Clear background colour
+        viewToChange!.view.backgroundColor = .clear
+    }
+
+    func updateView() {
+        viewToChange!.view.frame = CGRect(x: 0, y: 0, width: viewWidth, height: viewHeight)
+        view.frame = viewToChange!.view.frame
+    }
+
+    let horizontal = UIInterpolatingMotionEffect(keyPath: "center.x", type: .tiltAlongHorizontalAxis)
+    let vertical = UIInterpolatingMotionEffect(keyPath: "center.y", type: .tiltAlongVerticalAxis)
+    let group = UIMotionEffectGroup()
+
+    override func viewWillLayoutSubviews() {
+
+        horizontal.minimumRelativeValue = -amount
+        horizontal.maximumRelativeValue = amount
+
+        vertical.minimumRelativeValue = -amount
+        vertical.maximumRelativeValue = amount
+
+        group.motionEffects = [horizontal, vertical]
+        viewToChange!.view.addMotionEffect(group)
+    }
+
+}
+