DiagnosticView Ordering

src/Uno.Foundation/Diagnostics/DiagnosticViewRegistry.cs

@@ -12,7 +12,7 @@ internal static class DiagnosticViewRegistry
 {
 	internal static EventHandler<IImmutableList<DiagnosticViewRegistration>>? Added;
 
-	private static ImmutableArray<DiagnosticViewRegistration> _registrations = ImmutableArray<DiagnosticViewRegistration>.Empty;
+	private static ImmutableArray<DiagnosticViewRegistration> _registrations = [];
 
 	/// <summary>
 	/// Gets the list of registered diagnostic providers.
@@ -24,26 +24,46 @@ internal static class DiagnosticViewRegistry
 	/// </summary>
 	/// <param name="view">A diagnostic view to display.</param>
 	/// <param name="mode">Defines when the registered diagnostic view should be displayed.</param>
-	public static void Register(IDiagnosticView view, DiagnosticViewRegistrationMode mode = default)
+	public static void Register(IDiagnosticView view, DiagnosticViewRegistrationMode mode = default, DiagnosticViewRegistrationPosition position = default)
 	{
 		ImmutableInterlocked.Update(
 			ref _registrations,
 			static (providers, provider) => providers.Add(provider),
-			new DiagnosticViewRegistration(mode, view));
+			new DiagnosticViewRegistration(mode, position, view));
 
 		Added?.Invoke(null, _registrations);
 	}
 }
 
-internal record DiagnosticViewRegistration(DiagnosticViewRegistrationMode Mode, IDiagnosticView View);
+internal sealed record DiagnosticViewRegistration(
+	DiagnosticViewRegistrationMode Mode,
+	DiagnosticViewRegistrationPosition Position,
+	IDiagnosticView View) : IComparable<DiagnosticViewRegistration>
+{
+	public int CompareTo(DiagnosticViewRegistration? other)
+	{
+		if (other is null)
+		{
+			return 1;
+		}
+
+		if (Position == other.Position)
+		{
+			// If the position is the same, we compare the view id to ensure a stable order.
+			return string.Compare(View.Id, other.View.Id, StringComparison.Ordinal);
+		}
+
+		return (int)Position - (int)other.Position;
+	}
+}
 
 public enum DiagnosticViewRegistrationMode
 {
 	/// <summary>
 	/// Diagnostic is being display on at least one window.
 	/// I.e. only the main/first opened but move to the next one if the current window is closed.
 	/// </summary>
-	One,
+	One, // Default
 
 	/// <summary>
 	/// Diagnostic is being rendered as overlay on each window.
@@ -55,3 +75,18 @@ public enum DiagnosticViewRegistrationMode
 	/// </summary>
 	OnDemand
 }
+
+public enum DiagnosticViewRegistrationPosition
+{
+	Normal = 0, // Default
+
+	/// <summary>
+	/// Register as the first diagnostic view, ensuring it is displayed first.
+	/// </summary>
+	First = -1,
+
+	/// <summary>
+	/// Register as the last diagnostic view, ensuring it is displayed last.
+	///	</summary>
+	Last = 1,
+}

src/Uno.UI.RemoteControl/RemoteControlClient.cs

@@ -33,7 +33,63 @@ public partial class RemoteControlClient : IRemoteControlClient
 	public delegate void RemoteControlClientEventEventHandler(object sender, ClientEventEventArgs args);
 	public delegate void SendMessageFailedEventHandler(object sender, SendMessageFailedEventArgs args);
 
-	public static RemoteControlClient? Instance { get; private set; }
+	public static RemoteControlClient? Instance
+	{
+		get => _instance;
+		private set
+		{
+			_instance = value;
+
+			if (value is { })
+			{
+				while (Interlocked.Exchange(ref _waitingList, null) is { } waitingList)
+				{
+					foreach (var action in waitingList)
+					{
+						action(value);
+					}
+				}
+			}
+		}
+	}
+
+	private static IReadOnlyCollection<Action<RemoteControlClient>>? _waitingList;
+
+	/// <summary>
+	/// Add a callback to be called when the Instance is available.
+	/// </summary>
+	/// <remarks>
+	/// Will be called synchronously if the instance is already available, no need to check for it before.
+	/// </remarks>
+	public static void OnRemoteControlClientAvailable(Action<RemoteControlClient> action)
+	{
+		if (Instance is { })
+		{
+			action(Instance);
+		}
+		else
+		{
+			// Thread-safe way to add the action to a waiting list for the client to be available
+			while (true)
+			{
+				var waitingList = _waitingList;
+				IReadOnlyCollection<Action<RemoteControlClient>> newList = waitingList is null
+					? [action]
+					: [.. waitingList, action];
+
+				if (Instance is { } i) // Last chance to avoid the waiting list
+				{
+					action(i);
+					break;
+				}
+
+				if (ReferenceEquals(Interlocked.CompareExchange(ref _waitingList, newList, waitingList), waitingList))
+				{
+					break;
+				}
+			}
+		}
+	}
 
 	public static RemoteControlClient Initialize(Type appType)
 		=> Instance = new RemoteControlClient(appType);
@@ -59,6 +115,7 @@ internal static RemoteControlClient Initialize(Type appType, ServerEndpointAttri
 
 	private readonly StatusSink _status;
 	private static readonly TimeSpan _keepAliveInterval = TimeSpan.FromSeconds(30);
+	private static RemoteControlClient? _instance;
 	private readonly (string endpoint, int port)[]? _serverAddresses;
 	private readonly Dictionary<string, IClientProcessor> _processors = new();
 	private readonly List<IRemoteControlPreProcessor> _preprocessors = new();

src/Uno.UI.Toolkit/Diagnostics/DiagnosticsOverlay.cs

@@ -2,6 +2,7 @@
 #if WINUI || HAS_UNO_WINUI
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Linq;
 using System.Runtime.CompilerServices;
@@ -462,10 +463,10 @@ private void EnqueueUpdate(bool forceUpdate = false)
 				var viewsThatShouldBeMaterialized = DiagnosticViewRegistry
 					.Registrations
 					.Where(ShouldMaterialize)
+					.Order() // See DiagnosticViewRegistration.CompareTo
 					.Select(reg => reg.View)
-					.Concat(_localRegistrations)
-					.Distinct()
-					.ToList();
+					.Concat(_localRegistrations) // They are at the end of the list.
+					.Distinct();
 
 				foreach (var view in viewsThatShouldBeMaterialized)
 				{

src/Uno.UI/Diagnostics/DiagnosticView.Factories.cs

@@ -21,11 +21,16 @@ partial class DiagnosticView
 	/// </remarks>
 	/// <typeparam name="TView">Type of the control.</typeparam>
 	/// <param name="friendlyName">The user-friendly name of the diagnostics view.</param>
-	public static DiagnosticView<TView> Register<TView>(string friendlyName)
+	/// <param name="mode">Defines when the registered diagnostic view should be displayed.</param>
+	/// <param name="position">Defines where the item should be placed in the overlay.</param>
+	public static DiagnosticView<TView> Register<TView>(
+		string friendlyName,
+		DiagnosticViewRegistrationMode mode = default,
+		DiagnosticViewRegistrationPosition position = default)
 		where TView : UIElement, new()
 	{
 		var provider = new DiagnosticView<TView>(typeof(TView).Name, friendlyName, () => new TView());
-		DiagnosticViewRegistry.Register(provider);
+		DiagnosticViewRegistry.Register(provider, mode, position);
 		return provider;
 	}
 
@@ -43,11 +48,16 @@ public static DiagnosticView<TView> Register<TView>(string friendlyName)
 	/// <param name="friendlyName">The user-friendly name of the diagnostics view.</param>
 	/// <param name="factory">Factory to create an instance of the control.</param>
 	/// <param name="mode">Defines when the registered diagnostic view should be displayed.</param>
-	public static DiagnosticView<TView> Register<TView>(string friendlyName, Func<TView> factory, DiagnosticViewRegistrationMode mode = default)
+	/// <param name="position">Defines where the item should be placed in the overlay.</param>
+	public static DiagnosticView<TView> Register<TView>(
+		string friendlyName,
+		Func<TView> factory,
+		DiagnosticViewRegistrationMode mode = default,
+		DiagnosticViewRegistrationPosition position = default)
 		where TView : UIElement
 	{
 		var provider = new DiagnosticView<TView>(typeof(TView).Name, friendlyName, factory);
-		DiagnosticViewRegistry.Register(provider, mode);
+		DiagnosticViewRegistry.Register(provider, mode, position);
 		return provider;
 	}
 
@@ -62,17 +72,21 @@ public static DiagnosticView<TView> Register<TView>(string friendlyName, Func<TV
 	/// <param name="friendlyName">The user-friendly name of the diagnostics view.</param>
 	/// <param name="update">Delegate to use to update the <typeparamref name="TView"/> when the <typeparamref name="TState"/> is being updated.</param>
 	/// <param name="details">Optional delegate used to show more details about the diagnostic info when user taps on the view.</param>
+	/// <param name="mode">Defines when the registered diagnostic view should be displayed.</param>
+	/// <param name="position">Defines where the item should be placed in the overlay.</param>
 	/// <returns>A diagnostic view helper class which can be used to push updates of the state (cf. <see cref="DiagnosticView{TView,TState}.Update"/>).</returns>
 	public static DiagnosticView<TView, TState> Register<TView, TState>(
 		string friendlyName,
 		Action<TView, TState> update,
-		Func<TState, object?>? details = null)
+		Func<TState, object?>? details = null,
+		DiagnosticViewRegistrationMode mode = default,
+		DiagnosticViewRegistrationPosition position = default)
 		where TView : FrameworkElement, new()
 	{
 		var provider = details is null
 			? new DiagnosticView<TView, TState>(typeof(TView).Name, friendlyName, _ => new TView(), update)
 			: new DiagnosticView<TView, TState>(typeof(TView).Name, friendlyName, _ => new TView(), update, (ctx, state, ct) => new(details(state)));
-		DiagnosticViewRegistry.Register(provider);
+		DiagnosticViewRegistry.Register(provider, mode, position);
 		return provider;
 	}
 
@@ -88,18 +102,22 @@ public static DiagnosticView<TView, TState> Register<TView, TState>(
 	/// <param name="factory">Factory to create an instance of the generic element.</param>
 	/// <param name="update">Delegate to use to update the <typeparamref name="TView"/> when the <typeparamref name="TState"/> is being updated.</param>
 	/// <param name="details">Optional delegate used to show more details about the diagnostic info when user taps on the view.</param>
+	/// <param name="mode">Defines when the registered diagnostic view should be displayed.</param>
+	/// <param name="position">Defines where the item should be placed in the overlay.</param>
 	/// <returns>A diagnostic view helper class which can be used to push updates of the state (cf. <see cref="DiagnosticView{TView,TState}.Update"/>).</returns>
 	public static DiagnosticView<TView, TState> Register<TView, TState>(
 		string friendlyName,
 		Func<IDiagnosticViewContext, TView> factory,
 		Action<TView, TState> update,
-		Func<TState, object?>? details = null)
+		Func<TState, object?>? details = null,
+		DiagnosticViewRegistrationMode mode = default,
+		DiagnosticViewRegistrationPosition position = default)
 		where TView : FrameworkElement
 	{
 		var provider = details is null
 			? new DiagnosticView<TView, TState>(typeof(TView).Name, friendlyName, factory, update)
 			: new DiagnosticView<TView, TState>(typeof(TView).Name, friendlyName, factory, update, (ctx, state, ct) => new(details(state)));
-		DiagnosticViewRegistry.Register(provider);
+		DiagnosticViewRegistry.Register(provider, mode, position);
 		return provider;
 	}
 }