Spline Demo in SwiftUI

SplineDemo.swift

//
//  ContentView.swift
//  Spline Demo
//
//  Created by Anton Heestand on 2022-08-27.
//

import SwiftUI

struct ContentView: View {
    
    @State private var leadingFrame: CGRect?
    @State private var trailingFrame: CGRect?
    
    @State private var location: CGPoint?
    @State private var interacting: Bool = false

    var body: some View {
        
        ZStack {
            
            RoundedRectangle(cornerRadius: 16, style: .continuous)
                .read(frame: $leadingFrame)
                .frame(width: 100,
                       height: 100)
                .offset(x: -200)
            
            RoundedRectangle(cornerRadius: 16, style: .continuous)
                .foregroundColor(interacting ? .accentColor : .primary)
                .read(frame: $trailingFrame)
                .frame(width: 100,
                       height: 100)
                .offset(x: -50,
                        y: -50)
                .offset(x: location?.x ?? 200,
                        y: location?.y ?? -100)
                .gesture(
                    DragGesture()
                        .onChanged { value in
                            interacting = true
                            location = value.location
                        }
                        .onEnded { _ in
                            interacting = false
                        }
                )
            
            Path { path in
                
                guard let leadingFrame,
                      let trailingFrame
                else { return }
                
                let leadingPoint = CGPoint(x: leadingFrame.maxX,
                                           y: leadingFrame.midY)
                let trailingPoint = CGPoint(x: trailingFrame.minX,
                                            y: trailingFrame.midY)
                                            
                let controlPoint1 = CGPoint(x: (leadingPoint.x + trailingPoint.x) / 2,
                                            y: leadingPoint.y)
                let controlPoint2 = CGPoint(x: (leadingPoint.x + trailingPoint.x) / 2,
                                            y: trailingPoint.y)
                
                path.move(to: leadingPoint)
                
                path.addCurve(to: trailingPoint,
                              control1: controlPoint1,
                              control2: controlPoint2)
            }
            .stroke()
        }
        .coordinateSpace(name: "main")
        .frame(maxWidth: .infinity,
               maxHeight: .infinity)
    }
}

extension View {
    
    func read(frame: Binding<CGRect?>) -> some View {
        self.background {
            GeometryReader { geometry in
                Color.clear
                    .onAppear {
                        frame.wrappedValue = geometry.frame(in: .named("main"))
                    }
                    .onChange(of: geometry.frame(in: .named("main"))) { newFrame in
                        frame.wrappedValue = newFrame
                    }
                
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

https://twitter.com/heestand_xyz/status/1563563766511325185?s=21&t=a2qOmPHwv8qAXnkRbPGePw