Do not observe LogStore on the top level (InspectLayout)

Avoids an infinite view update loop.

Author: ole

Sources/LayoutInspector/DebugLayout.swift

@@ -4,7 +4,7 @@ import SwiftUI
 extension View {
     /// Inspect the layout for this subtree.
     public func inspectLayout() -> some View {
-        modifier(InspectLayout())
+        modifier(InspectLayout(logStore: LogStore()))
     }
 
     /// Monitor the layout proposals and responses for this view and add them

Sources/LayoutInspector/DebugLayoutImpl.swift

@@ -2,7 +2,8 @@ import SwiftUI
 
 @available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 struct InspectLayout: ViewModifier {
-    @StateObject private var logStore: LogStore = .init()
+    // Don't observe LogStore. Avoids an infinite update loop.
+    var logStore: LogStore
     @State private var selectedView: String? = nil
     @State private var generation: Int = 0
     @State private var inspectorFrame: CGRect = CGRect(x: 0, y: 0, width: 300, height: 300)
@@ -31,13 +32,12 @@ struct InspectLayout: ViewModifier {
                 .offset(x: inspectorFrame.minX, y: inspectorFrame.minY)
                 .coordinateSpace(name: Self.coordSpaceName)
         }
-        .environment(\.didCallInspectLayout, true)
-        .environmentObject(logStore)
+        .environment(\.logStore, logStore)
     }
 
     @ViewBuilder private var inspectorUI: some View {
         ScrollView([.vertical, .horizontal]) {
-            LogEntriesGrid(logEntries: logStore.log, highlight: $selectedView)
+            LogEntriesGrid(logStore: logStore, highlight: $selectedView)
                 .measureSize { size in
                     tableSize = size
                 }
@@ -91,18 +91,16 @@ struct InspectLayout: ViewModifier {
     }
 }
 
-enum DidCallInspectLayout: EnvironmentKey {
-    static var defaultValue: Bool = false
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
+enum LogStoreKey: EnvironmentKey {
+    static var defaultValue: LogStore? = nil
 }
 
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 extension EnvironmentValues {
-    /// Marker to signal that a valid LogStore environment object has been injected.
-    /// Clients that use `@EnvironmentObject var logStore: LogStore` must verify that
-    /// this value is true before accessing the environment object because it may be
-    /// missing.
-    var didCallInspectLayout: Bool {
-        get { self[DidCallInspectLayout.self] }
-        set { self[DidCallInspectLayout.self] = newValue }
+    var logStore: LogStore? {
+        get { self[LogStoreKey.self] }
+        set { self[LogStoreKey.self] = newValue }
     }
 }
 
@@ -111,16 +109,11 @@ struct DebugLayoutModifier: ViewModifier {
     var label: String
     var file: StaticString
     var line: UInt
-    @Environment(\.didCallInspectLayout) private var didCallInspectLayout
-    /// The log store for the current inspectLayout() subtree.
-    ///
-    /// - Important: You must verify that `didCallInspectLayout == true` before accessing
-    ///   this property. Failure to do so will result in a crash as the object won't be
-    ///   in the environment.
-    @EnvironmentObject private var logStore: LogStore
+    // Using @Environment rather than @EnvironmentObject because we don't want to observe this.
+    @Environment(\.logStore) var logStore: LogStore?
 
     func body(content: Content) -> some View {
-        if didCallInspectLayout {
+        if let logStore {
             DebugLayout(label: label, logStore: logStore) {
                 content
             }
@@ -196,9 +189,14 @@ struct ClearDebugLayoutLog: Layout {
 
 @available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 public final class LogStore: ObservableObject {
-    @Published public var log: [LogEntry] = []
+    @Published public var log: [LogEntry]
     var viewLabels: Set<String> = []
 
+    init(log: [LogEntry] = []) {
+        self.log = log
+        self.viewLabels = Set(log.map(\.label))
+    }
+
     func registerViewLabelAndWarnIfNotUnique(_ label: String, file: StaticString, line: UInt) {
         DispatchQueue.main.async { [self] in
             if viewLabels.contains(label) {

Sources/LayoutInspector/LogEntriesGrid.swift

@@ -2,14 +2,14 @@ import SwiftUI
 
 @available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 public struct LogEntriesGrid: View {
-    var logEntries: [LogEntry]
+    @ObservedObject var logStore: LogStore
     @Binding var highlight: String?
 
     private static let tableRowHorizontalPadding: CGFloat = 8
     private static let tableRowVerticalPadding: CGFloat = 4
 
-    public init(logEntries: [LogEntry], highlight: Binding<String?>? = nil) {
-        self.logEntries = logEntries
+    public init(logStore: LogStore, highlight: Binding<String?>? = nil) {
+        self._logStore = ObservedObject(initialValue: logStore)
         if let binding = highlight {
             self._highlight = binding
         } else {
@@ -42,7 +42,7 @@ public struct LogEntriesGrid: View {
                 .padding(.horizontal, Self.tableRowHorizontalPadding)
 
             // Table rows
-            ForEach(logEntries) { item in
+            ForEach(logStore.log) { item in
                 let isSelected = highlight == item.label
                 GridRow {
                     HStack(spacing: 0) {
@@ -92,6 +92,7 @@ public struct LogEntriesGrid: View {
 @available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 struct LogEntriesGrid_Previews: PreviewProvider {
     static var previews: some View {
-        LogEntriesGrid(logEntries: sampleLogEntries)
+        let logStore = LogStore(log: sampleLogEntries)
+        LogEntriesGrid(logStore: logStore)
     }
 }