LayoutInSwiftUI.swift

LayoutInSwiftUI.swift

import SwiftUI
import Combine

struct ContentView: View {
    var body: some View {
        VStack {
            Section {
                list
                    .frame(height: 150)
            } header: {
                Text("List")
            }

            
            Section {
                grid
                    .frame(height: 150)
            } header: {
                Text("Grid")
            }
            
            Section {
                lazyVGrid
                    .frame(height: 150)
            } header: {
                Text("LazyVGrid")
            }

            Section {
                viewThatFits
                    .frame(height: 150)
            } header: {
                Text("ViewThatFits")
            }
            
            Section {
                layout
                    .frame(height: 150)
            } header: {
                Text("Layout")
            }
        }
    }

    private var viewThatFits: some View {
        ViewThatFits {
            Text("one")
            Text("two")
        }
    }

    private var layout: some View {
        BasicView()
    }

    private var list: some View {
        List {
            Text("one")
            Text("two")
            Text("three")
        }
    }

    private var grid: some View {
        Grid {
            GridRow {
                Text("one")
                Text("two")
            }

            GridRow {
                Text("three")
                Text("four")
                Text("five")
            }
        }
    }

    private var lazyVGrid: some View {
        LazyVGrid(columns: [GridItem(.fixed(50))]) {
            Text("one")
            Text("two")
            Text("three")
            Text("four")
        }
    }
}

struct BasicView: View {
    var body: some View {
        BasicVStack {
            Text("Inside Layout")
        }
    }
}

struct BasicVStack: Layout {
    func placeSubviews(
        in bounds: CGRect,
        proposal: ProposedViewSize,
        subviews: Subviews,
        cache: inout ()
    ) {
        var point = bounds.origin
        for subview in subviews {
            subview.place(at: point, anchor: .topLeading, proposal: .unspecified)
            point.y += subview.dimensions(in: .unspecified).height
        }
    }

    func sizeThatFits(
        proposal: ProposedViewSize,
        subviews: Subviews,
        cache: inout ()
    ) -> CGSize {
        subviews.reduce(CGSize.zero) { result, subview in
            let size = subview.sizeThatFits(.unspecified)
            return CGSize(
                width: max(result.width, size.width),
                height: result.height + size.height)
        }
    }
}