Lower LayoutInspector deployment target

To make it possible to use the library in an app with a lower deployment target than iOS 16/macOS 13. All APIs are availability-gated, though, so you can only use LayoutInspector APIs in views that are @available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *) or higher.

Author: ole

Package.swift

@@ -4,7 +4,12 @@ import PackageDescription
 
 let package = Package(
     name: "LayoutInspector",
-    platforms: [.macOS(.v13), .iOS(.v16), .tvOS(.v16), .watchOS(.v9)],
+    // LayoutInspector requires iOS 16/macOS 13. We specify a lower deployment
+    // target here to allow integrating the library into an app with a lower
+    // deployment target. The entire LayoutInspector API is availability-gated
+    // to iOS 16/macOS 13, though, so you can only use it in views that are
+    // `@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)` or higher.
+    platforms: [.macOS(.v10_15), .iOS(.v13), .tvOS(.v13), .watchOS(.v6)],
     products: [
         .library(name: "LayoutInspector", targets: ["LayoutInspector"]),
     ],

Sources/LayoutInspector/DebugLayout.swift

@@ -3,6 +3,7 @@
 
 import SwiftUI
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension View {
     /// Start debugging the layout algorithm for this subtree.
     ///
@@ -31,6 +32,7 @@ extension View {
 }
 
 /// A custom layout that adds the layout proposals and responses for a view to a log for display.
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 struct DebugLayout: Layout {
     var label: String
 
@@ -49,6 +51,7 @@ struct DebugLayout: Layout {
 
 /// Draws a highlight (dashed border) around the view that's selected
 /// in the DebugLayout log table.
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 fileprivate struct DebugLayoutSelectionHighlight: ViewModifier {
     var viewID: String
     @Environment(\.debugLayoutSelectedViewID) private var selection: String?
@@ -66,25 +69,29 @@ fileprivate struct DebugLayoutSelectionHighlight: ViewModifier {
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension CGFloat {
     var pretty: String {
         String(format: "%.1f", self)
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension CGSize {
     var pretty: String {
         let thinSpace: Character = "\u{2009}"
         return "\(width.pretty)\(thinSpace)×\(thinSpace)\(height.pretty)"
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension Optional where Wrapped == CGFloat {
     var pretty: String {
         self?.pretty ?? "nil"
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension ProposedViewSize {
     var pretty: String {
         let thinSpace: Character = "\u{2009}"

Sources/LayoutInspector/DebugLayoutLog.swift

@@ -1,5 +1,6 @@
 import SwiftUI
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 func logLayoutStep(_ label: String, step: LogEntry.Step) {
     DispatchQueue.main.async {
         guard let prevEntry = LogStore.shared.log.last else {
@@ -40,6 +41,7 @@ func logLayoutStep(_ label: String, step: LogEntry.Step) {
 
 /// A custom layout that clears the DebugLayout log
 /// at the point where it's placed in the view tree.
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 struct ClearDebugLayoutLog: Layout {
     func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
         assert(subviews.count == 1)
@@ -56,6 +58,7 @@ struct ClearDebugLayoutLog: Layout {
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 public final class LogStore: ObservableObject {
     public static let shared: LogStore = .init()
 
@@ -73,6 +76,7 @@ public final class LogStore: ObservableObject {
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 struct LogEntry: Identifiable {
     enum Step {
         case proposal(ProposedViewSize)
@@ -102,17 +106,20 @@ struct LogEntry: Identifiable {
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 struct DebugLayoutSelectedViewID: EnvironmentKey {
     static var defaultValue: String? { nil }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension EnvironmentValues {
     var debugLayoutSelectedViewID: String? {
         get { self[DebugLayoutSelectedViewID.self] }
         set { self[DebugLayoutSelectedViewID.self] = newValue }
     }
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 public struct DebugLayoutLogView: View {
     @Binding var selection: String?
     @ObservedObject var logStore: LogStore