Comparing custom HStack with default HStack

hstacks.swift

//: A UIKit based Playground for presenting user interface
  
import SwiftUI
import PlaygroundSupport

struct MyEqualWidthHStack: Layout {
    /// Returns a size that the layout container needs to arrange its subviews
    /// horizontally.
    /// - Tag: sizeThatFitsHorizontal
    func sizeThatFits(
        proposal: ProposedViewSize,
        subviews: Subviews,
        cache: inout Void
    ) -> CGSize {
        guard !subviews.isEmpty else { return .zero }

        let maxSize = maxSize(subviews: subviews)
        let spacing = spacing(subviews: subviews)
        let totalSpacing = spacing.reduce(0) { $0 + $1 }

        return CGSize(
            width: maxSize.width * CGFloat(subviews.count) + totalSpacing,
            height: maxSize.height)
    }

    /// Places the subviews in a horizontal stack.
    /// - Tag: placeSubviewsHorizontal
    func placeSubviews(
        in bounds: CGRect,
        proposal: ProposedViewSize,
        subviews: Subviews,
        cache: inout Void
    ) {
        guard !subviews.isEmpty else { return }

        let maxSize = maxSize(subviews: subviews)
        let spacing = spacing(subviews: subviews)

        let placementProposal = ProposedViewSize(width: maxSize.width, height: maxSize.height)
        var nextX = bounds.minX + maxSize.width / 2

        for index in subviews.indices {
            subviews[index].place(
                at: CGPoint(x: nextX, y: bounds.midY),
                anchor: .center,
                proposal: placementProposal)
            nextX += maxSize.width + spacing[index]
        }
    }

    /// Finds the largest ideal size of the subviews.
    private func maxSize(subviews: Subviews) -> CGSize {
        let subviewSizes = subviews.map { $0.sizeThatFits(.unspecified) }
        let maxSize: CGSize = subviewSizes.reduce(.zero) { currentMax, subviewSize in
            CGSize(
                width: max(currentMax.width, subviewSize.width),
                height: max(currentMax.height, subviewSize.height))
        }

        return maxSize
    }

    /// Gets an array of preferred spacing sizes between subviews in the
    /// horizontal dimension.
    private func spacing(subviews: Subviews) -> [CGFloat] {
        subviews.indices.map { index in
            guard index < subviews.count - 1 else { return 0 }
            return subviews[index].spacing.distance(
                to: subviews[index + 1].spacing,
                along: .horizontal)
        }
    }
}

struct ContentView: View {
    
    var body: some View {
        
        VStack(spacing: 0) {
            
            (MyEqualWidthHStack()) {
                Text("Hi")
                    .frame(maxWidth: .infinity)
                    .background(.blue)
                Text("Hellooooo")
                    .frame(maxWidth: .infinity)
                    .background(.green)
                Text("World")
                    .frame(maxWidth: .infinity)
                    .background(.orange)
            }
            .padding(.vertical)
            .padding(.bottom, 10)
            .font(.headline)
            
            Divider()
            
            HStack {
                Text("Hi")
                    .frame(maxWidth: .infinity)
                    .background(.blue)
                Text("Hellooooo")
                    .frame(maxWidth: .infinity)
                    .background(.green)
                Text("World")
                    .frame(maxWidth: .infinity)
                    .background(.orange)
            }
            .padding(.vertical)
            .padding(.bottom, 10)
            .font(.headline)
        }
        .background(.thinMaterial)
    }
}

let hostingVc = UIHostingController(rootView: ContentView())
hostingVc.view.frame = .init(x: 0, y: 0, width: 500, height: 600)
PlaygroundPage.current.liveView = hostingVc