Source code for CodeSlicing episode on simple linear activity indicators

HorizontalAtivityIndicatorDemo.swift

//
//  HorizontalAtivityIndicatorDemo.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.
//
//  Copyright © 2021 Adam Fordyce. All rights reserved.
//

import SwiftUI
import PureSwiftUI

private extension Color {
    static let clearRed = Color.red.opacity(0)
}

struct HorizontalAtivityIndicatorDemo: View {
    var body: some View {
        let numSegments = 15
        GeometryReader { (geo: GeometryProxy) in
            HStack(spacing: 0) {
                ForEach(0..<numSegments) { index in
                    Capsule()
                        .width(geo.widthScaled(0.02))
                    if index < numSegments - 1 {
                        Spacer()
                            .frame(minWidth: 0)
                    }
                }
            }
            .mask(
//            .background(
                HorizontalActivityIndicatorMask(debug: false))
        }
    }
}

private struct HorizontalActivityIndicatorMask: View {
    
    var debug = false
    
    @State private var animating = false
    
    var body: some View {
        GeometryReader { (geo: GeometryProxy) in
            LinearGradient([
                (.clearRed, 0.1),
                (.red, 0.5),
                (.clearRed, 0.9),
            ], to: .trailing)
            .xOffsetIfNot(debug, -geo.width)
            .xOffsetIf(animating && !debug, geo.widthScaled(2))
        }
        .onAppear {
            withAnimation(Animation.linear(duration: 1).repeatForever(autoreverses: true)) {
                animating = true
            }
        }
    }
}

struct HorizontalActivityIndicatorDemo_Previews: PreviewProvider {
    struct HorizontalActivityIndicatorDemo_Harness: View {

        var body: some View {
            HorizontalAtivityIndicatorDemo()
                .frame(250, 30)
                .rotate(90.degrees)
        }
    }

    static var previews: some View {
        HorizontalActivityIndicatorDemo_Harness()
            .previewDevice(.iPhone_12_Pro_Max)
    }
}