Merge pull request #7 from GoodRequest/feature/swiftui-readable-content-guide

feat: SwiftUI - readable content guideline modifier

Author: plajdo

Sources/GoodSwiftUI/ReadableContentWidthModifier.swift

@@ -0,0 +1,199 @@
+//
+//  ReadableContentWidthModifier.swift
+//
+//  GoodSwiftUI
+//  Created by Filip Šašala on 31/12/2023.
+//
+
+import SwiftUI
+
+// MARK: - Readable content width view
+
+public struct FittingReadableWidth<Content: View>: View {
+
+    private let alignment: Alignment
+    private let content: () -> Content
+
+    public init(alignment: Alignment = .center, content: @escaping () -> Content) {
+        self.alignment = alignment
+        self.content = content
+    }
+
+    public var body: some View {
+        content().fittingReadableWidth(alignment: alignment)
+    }
+
+}
+
+// MARK: - Readable content width modifier
+
+private struct ReadableContentWidthModifier: ViewModifier {
+
+    let alignment: Alignment
+
+    func body(content: Content) -> some View {
+        content
+            .modifier(ReadableContentWidthPaddingModifier(alignment: alignment))
+            .modifier(ReadableContentWidthMeasurementModifier())
+    }
+
+}
+
+public extension View {
+
+    func fittingReadableWidth(alignment: Alignment = .center) -> some View {
+        modifier(ReadableContentWidthModifier(alignment: alignment))
+    }
+
+}
+
+// MARK: - Environment
+
+private extension EnvironmentValues {
+
+    @Entry var readableContentInsets = EdgeInsets()
+
+}
+
+// MARK: - Padding modifier
+
+private struct ReadableContentWidthPaddingModifier: ViewModifier {
+
+    @Environment(\.readableContentInsets) private var readableContentInsets
+
+    let alignment: Alignment
+
+    func body(content: Content) -> some View {
+        content
+            .frame(maxWidth: .infinity, alignment: alignment)
+            .padding(.leading, readableContentInsets.leading)
+            .padding(.trailing, readableContentInsets.trailing)
+    }
+
+}
+
+// MARK: - Measurement modifier
+
+private struct ReadableContentWidthMeasurementModifier: ViewModifier {
+
+    @State private var readableContentInsets = EdgeInsets()
+
+    func body(content: Content) -> some View {
+        content
+            .environment(\.readableContentInsets, readableContentInsets)
+            .background(LayoutGuides(onChangeOfReadableContentInsets: {
+                readableContentInsets = $0
+            }))
+    }
+
+}
+
+// MARK: - UIKit LayoutGuides view
+
+private struct LayoutGuides: UIViewRepresentable {
+
+    let onChangeOfReadableContentInsets: (EdgeInsets) -> ()
+
+    func makeUIView(context: Context) -> LayoutGuidesView {
+        let uiView = LayoutGuidesView()
+        uiView.onChangeOfReadableContentInsets = self.onChangeOfReadableContentInsets
+        return uiView
+    }
+
+    func updateUIView(_ uiView: LayoutGuidesView, context: Context) {
+        uiView.onChangeOfReadableContentInsets = self.onChangeOfReadableContentInsets
+    }
+
+}
+
+private final class LayoutGuidesView: UIView {
+
+    fileprivate var onChangeOfReadableContentInsets: (EdgeInsets) -> () = { _ in }
+    private var previousReadableContentInsets: EdgeInsets?
+
+    override func layoutMarginsDidChange() {
+        super.layoutMarginsDidChange()
+        updateReadableContent()
+    }
+
+    override func layoutSubviews() {
+        super.layoutSubviews()
+        updateReadableContent()
+    }
+
+    override var frame: CGRect {
+        didSet { updateReadableContent() }
+    }
+
+    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
+        super.traitCollectionDidChange(previousTraitCollection)
+
+        if traitCollection.layoutDirection != previousTraitCollection?.layoutDirection {
+            updateReadableContent()
+        }
+    }
+
+}
+
+private extension LayoutGuidesView {
+
+    func updateReadableContent() {
+        let isRTLLanguage = traitCollection.layoutDirection == .rightToLeft
+        let readableLayoutFrame = readableContentGuide.layoutFrame
+
+        let readableEdgeInsets = UIEdgeInsets(
+            top: readableLayoutFrame.minY - bounds.minY,
+            left: readableLayoutFrame.minX - bounds.minX,
+            bottom: -(readableLayoutFrame.maxY - bounds.maxY),
+            right: -(readableLayoutFrame.maxX - bounds.maxX)
+        )
+        let readableContentInsets = EdgeInsets(
+            top: readableEdgeInsets.top,
+            leading: isRTLLanguage ? readableEdgeInsets.right : readableEdgeInsets.left,
+            bottom: readableEdgeInsets.bottom,
+            trailing: isRTLLanguage ? readableEdgeInsets.left : readableEdgeInsets.right
+        )
+
+        guard previousReadableContentInsets != readableContentInsets else { return }
+        defer { previousReadableContentInsets = readableContentInsets }
+
+        self.onChangeOfReadableContentInsets(readableContentInsets)
+    }
+
+}
+
+// MARK: - Previews
+
+@available(iOS 17.0, *)
+#Preview {
+    FittingReadableWidth {
+        Rectangle()
+            .foregroundStyle(.cyan)
+    }
+}
+
+private final class PreviewViewController: UIViewController {
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        let rectangle = UIView()
+        rectangle.translatesAutoresizingMaskIntoConstraints = false
+        rectangle.backgroundColor = .systemRed
+
+        view.addSubview(rectangle)
+
+        NSLayoutConstraint.activate([
+            rectangle.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
+            rectangle.leadingAnchor.constraint(equalTo: view.readableContentGuide.leadingAnchor),
+            rectangle.trailingAnchor.constraint(equalTo: view.readableContentGuide.trailingAnchor),
+            rectangle.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
+        ])
+    }
+
+}
+
+@available(iOS 17.0, *)
+#Preview {
+    PreviewViewController()
+}