SwiftUI animation demo

swiftui-logo-animation.swift

import SwiftUI

struct Vector: VectorArithmetic {
    static func -= (lhs: inout Vector, rhs: Vector) {
        lhs = lhs - rhs
    }

    static func - (lhs: Vector, rhs: Vector) -> Vector {
        Vector(points: zip(lhs.points, rhs.points).map { $0.0 - $0.1 } )
    }

    static func += (lhs: inout Vector, rhs: Vector) {
        lhs = lhs + rhs
    }

    static func + (lhs: Vector, rhs: Vector) -> Vector {
        Vector(points: zip(lhs.points, rhs.points).map { $0.0 + $0.1 } )
    }

    mutating func scale(by rhs: Double) {
        points = points.map { $0 * rhs }
    }

    var magnitudeSquared: Double {
        self.points.reduce(1, { $0 + $1 * $1 })
    }

    static var zero: Vector { Vector(points: []) }

    var points: [Double]

}

struct Elevation: Shape {

    var data: Vector


    var animatableData: Vector {
        get { data }
        set { data = newValue }
    }

    func path(in rect: CGRect) -> Path {
        let path = Path { p in

            let start = CGPoint(x: 0, y: 1)

            p.move(to: start)

            if !data.points.isEmpty {

                for (i, l) in data.points.dropLast().enumerated() {
                    let pp = CGPoint(x: Double(i) * Double(1) / Double(data.points.count), y: l)
                    p.addLine(to: pp)
                }
                
                p.addLine(to: CGPoint(x: 1, y: data.points.last!))
            }
            p.addLine(to: CGPoint(x: 1, y: 1))

        }

        .applying(CGAffineTransform(scaleX: rect.width, y: rect.height))

        return path
    }


}


struct ContentView: View {

    var timer = Timer.publish(every: 0.2, on: .main, in: .common).autoconnect()
    
    @State var trail = Vector(points: (1...50).map( { _ in Double.random(in: 0.5...0.8)}))

    func randomize() {
        trail = Vector(points: (1...130).map( { _ in Double.random(in: 0.3...0.7)}))
    }

    var body: some View {

                ZStack {

                    Color.black.edgesIgnoringSafeArea(.all)


                    Text("SwiftUI")
                        .foregroundColor(.white)
                        .font(.system(size: 70))
                        .offset(x: 0, y: 40)
                        .rotationEffect(Angle(degrees: 180))

                    Elevation(data: trail)
                        .foregroundColor(.blue)
                        .frame(width: 300, height: 1000)
                        .clipShape(
                            Circle()

                    )
                    .animation(.interpolatingSpring(stiffness: 50, damping: 10))



                    Elevation(data: trail)
                        .foregroundColor(.yellow)
                        .frame(width: 300, height: 800)
                        .clipShape(
                            Circle()

                    )
                    .animation(.interpolatingSpring(stiffness: 50, damping: 10))

                    Elevation(data: trail)
                        .foregroundColor(.orange)
                        .frame(width: 300, height: 600)
                        .clipShape(
                            Circle()

                    )
                    .animation(.interpolatingSpring(stiffness: 50, damping: 10))


                    Elevation(data: trail)
                        .foregroundColor(.red)
                        .frame(width: 300, height: 400)
                        .clipShape(
                            Circle()

                    )
                    .animation(.interpolatingSpring(stiffness: 50, damping: 10))





            }.rotationEffect(Angle(degrees: -180))


        .onReceive(timer) { _ in
            self.randomize()
        }
    }
}




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