Beating heart source code for CodeSlicing episode on morphing shapes

AnimatedHeartShapeDemo.swift

//
//  AnimatedHeartShapeDemo.swift
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
//  of the Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
//  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
//  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
//  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
//  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
//  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//  Created by Adam Fordyce on 22/02/2021.
//  Copyright © 2020 Adam Fordyce. All rights reserved.
//

import SwiftUI
import PureSwiftUI

private let heartColor = Color(red: 225 / 255, green: 40 / 255, blue: 48 / 255)
private let gridConfig = LayoutGuideConfig.grid(columns: 16, rows: 20)

private typealias Curve = (p: CGPoint, cp1: CGPoint, cp2: CGPoint)

private struct AnimatedHeart: Shape {

    var factor: CGFloat
    
    let debug: Bool
    
    init(animating: Bool, debug: Bool = false) {
        self.factor = animating ? 1 : 0
        self.debug = debug
    }
    
    var animatableData: CGFloat {
        get {
            factor
        }
        set {
            factor = newValue
        }
    }
    
    func path(in rect: CGRect) -> Path {
        var path = Path()
        let g = gridConfig.layout(in: rect)
        
        let p1 = g[0, 6].to(g[2, 6], factor)
        let p2 = g[8, 4].to(g[8, 5], factor)
        let p3 = g[16, 6].to(g[14, 6], factor)
        let p4 = g[8, 20].to(g[8, 19], factor)

        var curves = [Curve]()
        
        //c1
        curves.append(
            Curve(p2,
                  g[0, 0].to(g[3, 2], factor),
                  g[6, -2].to(g[7, 2], factor)))
        //c2
        curves.append(
            Curve(p3,
                  g[10, -2].to(g[9, 2], factor),
                  g[16, 0].to(g[13, 2], factor)))
        //c3
        curves.append(
            Curve(p4,
                  g[16, 10].to(g[15, 10], factor),
                  g[10, 13]))
        //c4
        curves.append(
            Curve(p1,
                  g[6, 13],
                  g[0, 10].to(g[1, 10], factor)))

        path.move(p1)
        
        for curve in curves {
            path.curve(curve.p, cp1: curve.cp1, cp2: curve.cp2, showControlPoints: debug)
        }

        return path
    }
}

struct AnimatedHeartShapeDemo_Previews: PreviewProvider {
    struct AnimatedHeartShapeDemo_Harness: View {
        
        @State private var animating = false
        var body: some View {
            VStack(spacing: 75) {
                Group {
                    AnimatedHeart (animating: animating)
                        .fillColor(heartColor)
                    AnimatedHeart(animating: animating, debug: true)
                        .strokeColor(.black, lineWidth: 2)
                        .layoutGuide(gridConfig)
                }
                .frame(200)
            }
            .onAppear {
                withAnimation(Animation.easeOut(duration: 0.2).repeatForever(autoreverses  : true)) {
                    self.animating = true
                }
            }
        }
    }
    
    static var previews: some View {
        AnimatedHeartShapeDemo_Harness()
            .padding(50)
            .previewSizeThatFits()
            .previewDevice(.iPhone_8)
            .showLayoutGuides(true)
    }
}