Marque horizontal view

Marque.swift

import Foundation
import SwiftUI

extension View {
    
    func marque() -> some View {
        modifier(HorizontalMarqueModifier())
    }
    
}

fileprivate struct HorizontalMarqueModifier: ViewModifier {
    
    func body(content: Content) -> some View {
        HorizontalMarqueView {
            content
        }
    }
    
}

fileprivate struct HorizontalMarqueViewState {
    
    var parentSize: CGSize?
    var childSize: CGSize?
    var isActive = false
    
    var isFit: Bool {
        guard let p = parentSize, let c = childSize else {
            return true
        }
        return c.width < p.width
    }
    
    var xOffset: CGFloat {
        guard let p = parentSize, let c = childSize else {
            return 0
        }
        guard !isFit else {
            return 0
        }
        return p.width - c.width
    }
}

fileprivate struct HorizontalMarqueView<Content: View>: View {
    
    @State var state = HorizontalMarqueViewState()
    let content: () -> Content
    
    var body: some View {
        GeometryReader { parent in
            ScrollView(.horizontal, showsIndicators: false) {
                content()
                    .disabled(false)
                    .background(
                        GeometryReader { (child) in
                            Path()
                                .onAppear {
                                    state.childSize = child.size
                                }
                        }
                    )
                    .offset(x: state.isActive ? state.xOffset : 0)
                    .animation(state.isFit ? nil : Animation.linear(duration: 1.5).repeatForever(autoreverses: false))
                .onAppear {
                    state.parentSize = parent.size
                }
            }
            .disabled(true)
        }
        .onChange(of: state.childSize) { (cz) in
            state.isActive = !state.isFit
        }
        .onChange(of: state.parentSize) { (pz) in
            state.isActive = !state.isFit
        }
        .frame(width: state.parentSize?.width, height: state.childSize?.height)
    }
    
    
}