Tree paints before decompile; AssemblyTreeNode observes load

Two ordering fixes for startup so the user sees the assembly tree before any
decompiled content shows up in the document area, and so the lazy-load story
actually holds.

Assisted-by: Claude:claude-opus-4-7:Claude Code

ICSharpCode.ILSpyX/LoadedAssembly.cs

@@ -65,6 +65,20 @@ namespace ICSharpCode.ILSpyX
 		// demand (any caller that awaits or reads .Result). Status checks below use
 		// IsValueCreated so they don't accidentally trigger the load just by polling.
 		Task<LoadResult> loadingTask => lazyLoadingTask.Value;
+
+		/// <summary>
+		/// Fires once when the lazy load task transitions to a completed state (success
+		/// or failure). Subscribers use it to refresh derived state (tree-node icons,
+		/// cached metadata pointers) without themselves calling
+		/// <see cref="GetLoadResultAsync"/>, which would trigger the load.
+		///
+		/// If the load has already finished by the time you subscribe, the event will
+		/// not fire retroactively — check <see cref="IsLoaded"/> after subscribing and
+		/// invoke your handler manually if it returns true.
+		/// </summary>
+		public event Action? Loaded;
+
+		void RaiseLoaded() => Loaded?.Invoke();
 		readonly AssemblyList assemblyList;
 		readonly string fileName;
 		readonly string shortName;
@@ -94,9 +108,18 @@ namespace ICSharpCode.ILSpyX
 			// callers (e.g. AssemblyListTreeNode) construct LoadedAssembly entries en masse
 			// without flooding the thread pool with metadata-loading tasks; the active
 			// assembly's path-restore awaits first and gets a clean run.
+			//
+			// Continuation hooks the Loaded event so subscribers can refresh their display
+			// (icon / tooltip / lazy children) without themselves triggering the load — they
+			// observe completion rather than start it.
 			var localStream = stream;
 			this.lazyLoadingTask = new Lazy<Task<LoadResult>>(
-				() => Task.Run(() => LoadAsync(localStream)),
+				() => {
+					var task = Task.Run(() => LoadAsync(localStream));
+					task.ContinueWith(static (_, state) => ((LoadedAssembly)state!).RaiseLoaded(),
+						this, TaskScheduler.Default);
+					return task;
+				},
 				LazyThreadSafetyMode.ExecutionAndPublication); // requires that this.fileName is set
 			this.shortName = Path.GetFileNameWithoutExtension(fileName);
 		}

ILSpy/AssemblyTree/AssemblyListPane.axaml.cs

@@ -50,7 +50,20 @@ namespace ILSpy.AssemblyTree
 			AppEnv.StartupLog.Mark("AssemblyListPane ctor entered");
 			InitializeComponent();
 			AttachedToVisualTree += (_, _) => AppEnv.StartupLog.Mark("AssemblyListPane attached to visual tree");
-			Loaded += (_, _) => AppEnv.StartupLog.Mark("AssemblyListPane Loaded");
+			Loaded += (_, _) => {
+				AppEnv.StartupLog.Mark("AssemblyListPane Loaded");
+				if (DataContext is AssemblyTreeModel m)
+					m.MarkTreeReady();
+			};
+			// One-shot mark on the first DataGridRow being prepared — that's the
+			// observable "tree has rows on screen" moment we compare against decompiler
+			// output appearing.
+			void OnFirstRowLoaded(object? sender, DataGridRowEventArgs args)
+			{
+				AppEnv.StartupLog.Mark("Assembly tree DataGrid: first row realised");
+				TreeGrid.LoadingRow -= OnFirstRowLoaded;
+			}
+			TreeGrid.LoadingRow += OnFirstRowLoaded;
 			TreeGrid.DoubleTapped += OnTreeGridDoubleTapped;
 			TreeGrid.KeyDown += OnTreeGridKeyDown;
 			// Bubble + handledEventsToo: ProDataGrid's row-level pointer handlers mark

ILSpy/AssemblyTree/AssemblyTreeModel.cs

@@ -145,6 +145,27 @@ namespace ILSpy.AssemblyTree
 				NotifyTextChanged(child);
 		}
 
+		readonly TaskCompletionSource<bool> treeReadyTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
+
+		/// <summary>
+		/// Completes when the assembly-tree view (<c>AssemblyListPane</c>) has fired its
+		/// <c>Loaded</c> event for the first time. <c>RestoreSelectedPathAsync</c> awaits
+		/// this before assigning <see cref="SelectedItem"/> so the saved-selection path
+		/// (which kicks off a decompilation through the dock workspace) doesn't paint
+		/// the document area before the tree itself is on screen.
+		/// </summary>
+		public Task TreeReady => treeReadyTcs.Task;
+
+		/// <summary>
+		/// Called by <c>AssemblyListPane</c> from its <c>Loaded</c> handler to resolve
+		/// <see cref="TreeReady"/>. Idempotent — only the first call wins.
+		/// </summary>
+		internal void MarkTreeReady()
+		{
+			if (treeReadyTcs.TrySetResult(true))
+				AppEnv.StartupLog.Mark("AssemblyTreeModel.TreeReady completed");
+		}
+
 		public void Initialize()
 		{
 			using var _ = AppEnv.StartupLog.Phase("AssemblyTreeModel.Initialize body");
@@ -214,6 +235,17 @@ namespace ILSpy.AssemblyTree
 						node.EnsureLazyChildren();
 					node = node.Children.FirstOrDefault(c => c.ToString() == element);
 				}
+				// Wait for the tree view to be Loaded before assigning SelectedItem. Without
+				// this, the SelectedItem assignment runs ShowSelectedNode → CurrentNodes →
+				// async decompilation, and the user can see the decompiled output appear
+				// BEFORE the assembly tree has rendered — a confusing reverse order.
+				// The 5-second timeout is a safety net for environments where the pane
+				// never loads (headless tests, design-time previews).
+				using (AppEnv.StartupLog.Phase("await TreeReady before SelectedItem assignment"))
+				{
+					await Task.WhenAny(TreeReady, Task.Delay(TimeSpan.FromSeconds(5)))
+						.ConfigureAwait(true);
+				}
 				if (node != null && node != Root && ReferenceEquals(SelectedItem, initialSelection))
 					SelectedItem = node;
 			}

ILSpy/TextView/DecompilerTabPageModel.cs

@@ -54,6 +54,19 @@ namespace ILSpy.TextView
 		[ObservableProperty]
 		private string text = string.Empty;
 
+		// Diagnostics: stamp the first non-empty Text assignment so we can correlate when
+		// decompiled output becomes visible against the tree-render path. The check is
+		// idempotent — only the first assignment for the lifetime of the process gets marked.
+		static int firstTextMarked;
+		partial void OnTextChanged(string? oldValue, string newValue)
+		{
+			if (!string.IsNullOrEmpty(newValue)
+				&& System.Threading.Interlocked.Exchange(ref firstTextMarked, 1) == 0)
+			{
+				ILSpy.AppEnv.StartupLog.Mark("DecompilerTabPageModel: first non-empty Text set");
+			}
+		}
+
 		/// <summary>
 		/// File extension driving syntax highlighting (e.g. ".cs"). Updated alongside <see cref="Text"/>.
 		/// </summary>

ILSpy/TreeNodes/AssemblyTreeNode.cs

@@ -62,22 +62,30 @@ namespace ILSpy.TreeNodes
 			this.assembly = assembly;
 			this.PackageEntry = packageEntry;
 			LazyLoading = true;
-			_ = InitAsync();
+			// Observe the load OUTCOME without triggering it — the cooldown sweep and
+			// explicit user actions (path-restore, expand) are what start the load.
+			// If we called GetLoadResultAsync here we'd flatten the lazy strategy and
+			// every assembly in the list would load the moment its tree node is built.
+			assembly.Loaded += OnAssemblyLoaded;
+			if (assembly.IsLoaded)
+				OnAssemblyLoaded(); // already finished before we subscribed — catch up
 		}
 
-		// Assemblies nested in NuGet packages can't be unloaded individually — the parent
-		// package entry owns them.
-		public override bool CanDelete() => PackageEntry == null;
-
-		public override void Delete() => DeleteCore();
-
-		public override void DeleteCore() => assembly.AssemblyList.Unload(assembly);
+		void OnAssemblyLoaded()
+		{
+			// The Loaded event fires from a thread-pool ContinueWith. Marshal to the UI
+			// thread before mutating tree-node state and raising change notifications;
+			// SharpTreeNode's RaisePropertyChanged is not thread-safe.
+			global::Avalonia.Threading.Dispatcher.UIThread.Post(InitFromLoadResult,
+				global::Avalonia.Threading.DispatcherPriority.Background);
+		}
 
-		async Task InitAsync()
+		void InitFromLoadResult()
 		{
 			try
 			{
-				var loadResult = await assembly.GetLoadResultAsync();
+				// GetLoadResultAsync is a no-op now — the load is already complete.
+				var loadResult = assembly.GetLoadResultAsync().GetAwaiter().GetResult();
 				cachedModule = loadResult.MetadataFile;
 				if (cachedModule == null && loadResult.Package == null)
 				{
@@ -96,6 +104,14 @@ namespace ILSpy.TreeNodes
 			RaisePropertyChanged(nameof(ShowExpander));
 		}
 
+		// Assemblies nested in NuGet packages can't be unloaded individually — the parent
+		// package entry owns them.
+		public override bool CanDelete() => PackageEntry == null;
+
+		public override void Delete() => DeleteCore();
+
+		public override void DeleteCore() => assembly.AssemblyList.Unload(assembly);
+
 		public override object Text => assembly.Text;
 
 		// ToString is the stable identity used by SessionSettings.ActiveTreeViewPath — must not