Enable nullable and fix almost all warnings in iOS project

src/Avalonia.Controls/ApplicationLifetimes/IActivatableApplicationLifetime.cs

@@ -11,13 +11,13 @@ public interface IActivatableApplicationLifetime
     /// An event that is raised when the application is Activated for various reasons
     /// as described by the <see cref="ActivationKind"/> enumeration.
     /// </summary>
-    event EventHandler<ActivatedEventArgs> Activated;
+    event EventHandler<ActivatedEventArgs>? Activated;
     
     /// <summary>
     /// An event that is raised when the application is Deactivated for various reasons
     /// as described by the <see cref="ActivationKind"/> enumeration.
     /// </summary>
-    event EventHandler<ActivatedEventArgs> Deactivated;
+    event EventHandler<ActivatedEventArgs>? Deactivated;
 
     /// <summary>
     /// Tells the application that it should attempt to leave its background state.

src/iOS/Avalonia.iOS/Avalonia.iOS.csproj

@@ -1,9 +1,15 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>net7.0-ios16.0</TargetFramework>
-    <SupportedOSPlatformVersion>13.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">13.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'tvos'">13.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">13.1</SupportedOSPlatformVersion>
     <MSBuildEnableWorkloadResolver>true</MSBuildEnableWorkloadResolver>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+
+    <!-- Compatibility attributes are pretty much broken for iOS-like platforms. Verify by hand. -->
+    <!-- Workaround: https://github.com/dotnet/roslyn-analyzers/issues/6158 -->
+    <NoWarn>$(NoWarn);CA1416</NoWarn>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\Avalonia.Base\Avalonia.Base.csproj" />
@@ -12,4 +18,5 @@
 
   <Import Project="..\..\..\build\DevAnalyzers.props" />
   <Import Project="..\..\..\build\TrimmingEnable.props" />
+  <Import Project="..\..\..\build\NullableEnable.props" />
 </Project>

src/iOS/Avalonia.iOS/AvaloniaAppDelegate.cs

@@ -15,7 +15,7 @@ namespace Avalonia.iOS
     public class AvaloniaAppDelegate<TApp> : UIResponder, IUIApplicationDelegate, IAvaloniaAppDelegate
         where TApp : Application, new()
     {
-        private EventHandler<ActivatedEventArgs> _onActivated, _onDeactivated;
+        private EventHandler<ActivatedEventArgs>? _onActivated, _onDeactivated;
 
         public AvaloniaAppDelegate()
         {
@@ -37,7 +37,7 @@ namespace Avalonia.iOS
         protected virtual AppBuilder CustomizeAppBuilder(AppBuilder builder) => builder;
         
         [Export("window")]
-        public UIWindow Window { get; set; }
+        public UIWindow? Window { get; set; }
 
         [Export("application:didFinishLaunchingWithOptions:")]
         public bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
@@ -64,7 +64,7 @@ namespace Avalonia.iOS
 
             builder.SetupWithLifetime(lifetime);
 
-            Window.MakeKeyAndVisible();
+            Window!.MakeKeyAndVisible();
 
             return true;
         }

src/iOS/Avalonia.iOS/AvaloniaView.Text.cs

@@ -1,4 +1,3 @@
-#nullable enable
 using Avalonia.Input.TextInput;
 using UIKit;
 

src/iOS/Avalonia.iOS/AvaloniaView.cs

@@ -1,7 +1,6 @@
-#nullable enable
-
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.Versioning;
 using Avalonia.Controls;
 using Avalonia.Controls.Embedding;
@@ -12,7 +11,6 @@ using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Input.Raw;
 using Avalonia.Input.TextInput;
-using Avalonia.iOS.Storage;
 using Avalonia.Platform;
 using Avalonia.Platform.Storage;
 using Avalonia.Rendering.Composition;
@@ -24,6 +22,9 @@ using IInsetsManager = Avalonia.Controls.Platform.IInsetsManager;
 
 namespace Avalonia.iOS
 {
+    /// <summary>
+    /// Root view container for Avalonia content, that can be embedded into iOS visual tree.
+    /// </summary>
     public partial class AvaloniaView : UIView, ITextInputMethodImpl
     {
         internal IInputRoot InputRoot
@@ -35,7 +36,7 @@ namespace Avalonia.iOS
         private TextInputMethodClient? _client;
         private IAvaloniaViewController? _controller;
         private IInputRoot? _inputRoot;
-        private MetalRenderTarget? _currentRenderTarget;
+        private Metal.MetalRenderTarget? _currentRenderTarget;
 
         public AvaloniaView()
         {
@@ -49,13 +50,14 @@ namespace Avalonia.iOS
 
             InitLayerSurface();
 #if !TVOS
-            MultipleTouchEnabled = true;
+            if (OperatingSystem.IsIOS() || OperatingSystem.IsMacCatalyst())
+            {
+                MultipleTouchEnabled = true;
+            }
 #endif
         }
 
-        [ObsoletedOSPlatform("ios12.0", "Use 'Metal' instead.")]
-        [SupportedOSPlatform("ios")]
-        [UnsupportedOSPlatform("maccatalyst")]
+        [SuppressMessage("Interoperability", "CA1422:Validate platform compatibility")]
         private void InitLayerSurface()
         {
             var l = Layer;
@@ -68,13 +70,13 @@ namespace Avalonia.iOS
                     OpenGLES.EAGLDrawableProperty.RetainedBacking, false,
                     OpenGLES.EAGLDrawableProperty.ColorFormat, OpenGLES.EAGLColorFormat.RGBA8
                 );
-                _topLevelImpl.Surfaces = new[] { new EaglLayerSurface(eaglLayer) };
+                _topLevelImpl.Surfaces = new[] { new Eagl.EaglLayerSurface(eaglLayer) };
             }
             else
 #endif
             if (l is CAMetalLayer metalLayer)
             {
-                _topLevelImpl.Surfaces = new[] { new MetalPlatformSurface(metalLayer, this) };
+                _topLevelImpl.Surfaces = new[] { new Metal.MetalPlatformSurface(metalLayer, this) };
             }
         }
 
@@ -85,6 +87,12 @@ namespace Avalonia.iOS
         public override bool CanResignFirstResponder => true;
 
         /// <inheritdoc />
+        [ObsoletedOSPlatform("ios17.0", "Use the 'UITraitChangeObservable' protocol instead.")]
+        [ObsoletedOSPlatform("maccatalyst17.0", "Use the 'UITraitChangeObservable' protocol instead.")]
+        [ObsoletedOSPlatform("tvos17.0", "Use the 'UITraitChangeObservable' protocol instead.")]
+        [SupportedOSPlatform("ios")]
+        [SupportedOSPlatform("tvos")]
+        [SupportedOSPlatform("maccatalyst")]
         public override void TraitCollectionDidChange(UITraitCollection? previousTraitCollection)
         {
             base.TraitCollectionDidChange(previousTraitCollection);
@@ -125,8 +133,12 @@ namespace Avalonia.iOS
             {
                 _view = view;
                 _nativeControlHost = new NativeControlHostImpl(view);
-#if !TVOS
-                _storageProvider = new IOSStorageProvider(view);
+#if TVOS
+                _storageProvider = null;
+                _clipboard = null;
+                _inputPane = null;
+#else
+                _storageProvider = new Storage.IOSStorageProvider(view);
                 _clipboard = new ClipboardImpl();
                 _inputPane = UIKitInputPane.Instance;
 #endif
@@ -152,7 +164,8 @@ namespace Avalonia.iOS
                 // No-op
             }
 
-            public Compositor Compositor => Platform.Compositor;
+            public Compositor Compositor => Platform.Compositor
+                ?? throw new InvalidOperationException("iOS backend wasn't initialized. Make sure UseiOS was called.");
 
             public void Invalidate(Rect rect)
             {
@@ -237,7 +250,6 @@ namespace Avalonia.iOS
                     return _insetsManager;
                 }
 
-#if !TVOS
                 if (featureType == typeof(IClipboard))
                 {
                     return _clipboard;
@@ -252,7 +264,6 @@ namespace Avalonia.iOS
                 {
                     return _inputPane;
                 }
-#endif
 
                 return null;
             }
@@ -262,7 +273,7 @@ namespace Avalonia.iOS
         public static Class LayerClass()
         {
 #if !MACCATALYST
-            if (Platform.Graphics is EaglPlatformGraphics)
+            if (Platform.Graphics is Eagl.EaglPlatformGraphics)
             {
                 return new Class(typeof(CAEAGLLayer));
             }
@@ -299,7 +310,7 @@ namespace Avalonia.iOS
             set => _topLevel.Content = value;
         }
 
-        internal void SetRenderTarget(MetalRenderTarget target)
+        internal void SetRenderTarget(Metal.MetalRenderTarget target)
         {
             _currentRenderTarget = target;
         }

src/iOS/Avalonia.iOS/ClipboardImpl.cs

@@ -1,20 +1,22 @@
 #if !TVOS
 using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
+using Foundation;
 using UIKit;
 
 namespace Avalonia.iOS
 {
     internal class ClipboardImpl : IClipboard
     {
-        public Task<string> GetTextAsync()
+        public Task<string?> GetTextAsync()
         {
             return Task.FromResult(UIPasteboard.General.String);
         }
 
-        public Task SetTextAsync(string text)
+        public Task SetTextAsync(string? text)
         {
             UIPasteboard.General.String = text;
             return Task.CompletedTask;
@@ -22,15 +24,40 @@ namespace Avalonia.iOS
 
         public Task ClearAsync()
         {
-            UIPasteboard.General.String = "";
+            UIPasteboard.General.Items = Array.Empty<NSDictionary>();
             return Task.CompletedTask;
         }
 
-        public Task SetDataObjectAsync(IDataObject data) => Task.CompletedTask;
+        public Task SetDataObjectAsync(IDataObject data)
+        {
+            if (data.Contains(DataFormats.Text))
+            {
+                UIPasteboard.General.String = data.GetText();
+            }
+
+            return Task.CompletedTask;
+        }
+
+        public Task<string[]> GetFormatsAsync()
+        {
+            var formats = new List<string>();
+            if (UIPasteboard.General.HasStrings)
+            {
+                formats.Add(DataFormats.Text);
+            }
 
-        public Task<string[]> GetFormatsAsync() => Task.FromResult(Array.Empty<string>());
+            return Task.FromResult(formats.ToArray());
+        }
 
-        public Task<object> GetDataAsync(string format) => Task.FromResult<object>(null);
+        public Task<object?> GetDataAsync(string format)
+        {
+            if (format == DataFormats.Text)
+            {
+                return Task.FromResult<object?>(UIPasteboard.General.String);
+            }
+
+            return Task.FromResult<object?>(null);
+        }
     }
 }
 #endif

src/iOS/Avalonia.iOS/DispatcherImpl.cs

@@ -1,5 +1,3 @@
-#nullable enable
-
 using System;
 using System.Diagnostics;
 using System.Runtime.InteropServices;

src/iOS/Avalonia.iOS/DisplayLinkTimer.cs

@@ -11,7 +11,7 @@ namespace Avalonia.iOS
 {
     class DisplayLinkTimer : IRenderTimer
     {
-        public event Action<TimeSpan> Tick;
+        public event Action<TimeSpan>? Tick;
         private Stopwatch _st = Stopwatch.StartNew();
 
         public DisplayLinkTimer()
@@ -36,4 +36,4 @@ namespace Avalonia.iOS
             Tick?.Invoke(_st.Elapsed);
         }
     }
-}
+}

src/iOS/Avalonia.iOS/Eagl/EaglDisplay.cs

@@ -8,10 +8,13 @@ using Avalonia.Platform;
 using Avalonia.Reactive;
 using OpenGLES;
 
-namespace Avalonia.iOS
+namespace Avalonia.iOS.Eagl
 {
     [ObsoletedOSPlatform("ios12.0", "Use 'Metal' instead.")]
+    [ObsoletedOSPlatform("tvos12.0", "Use 'Metal' instead.")]
+    [UnsupportedOSPlatform("maccatalyst")]
     [SupportedOSPlatform("ios")]
+    [SupportedOSPlatform("tvos")]
     class EaglPlatformGraphics : IPlatformGraphics
     {
         public IPlatformGraphicsContext GetSharedContext() => Context;
@@ -32,7 +35,7 @@ namespace Avalonia.iOS
             Context = new(iface, null);
         }
         
-        public static EaglPlatformGraphics TryCreate()
+        public static EaglPlatformGraphics? TryCreate()
         {
             try
             {
@@ -47,12 +50,14 @@ namespace Avalonia.iOS
     }
 
     [ObsoletedOSPlatform("ios12.0", "Use 'Metal' instead.")]
+    [ObsoletedOSPlatform("tvos12.0", "Use 'Metal' instead.")]
     [SupportedOSPlatform("ios")]
+    [SupportedOSPlatform("tvos")]
     class GlContext : IGlContext
     {
-        public EAGLContext Context { get; private set; }
+        public EAGLContext? Context { get; private set; }
         
-        public GlContext(GlInterface glInterface, EAGLSharegroup sharegroup)
+        public GlContext(GlInterface glInterface, EAGLSharegroup? sharegroup)
         {
             GlInterface = glInterface;
             Context = sharegroup == null ?
@@ -68,10 +73,10 @@ namespace Avalonia.iOS
 
         class ResetContext : IDisposable
         {
-            private EAGLContext _old;
+            private EAGLContext? _old;
             private bool _disposed;
 
-            public ResetContext(EAGLContext old)
+            public ResetContext(EAGLContext? old)
             {
                 _old = old;
             }
@@ -102,7 +107,7 @@ namespace Avalonia.iOS
         {
             if (Context == null)
                 throw new PlatformGraphicsContextLostException();
-            if(EAGLContext.CurrentContext == Context)
+            if (EAGLContext.CurrentContext == Context)
                 return Disposable.Empty;
             return MakeCurrent();
         }
@@ -110,8 +115,10 @@ namespace Avalonia.iOS
         public bool IsSharedWith(IGlContext context) => context is GlContext other
             && ReferenceEquals(other.Context?.ShareGroup, Context?.ShareGroup);
         public bool CanCreateSharedContext => true;
-        public IGlContext CreateSharedContext(IEnumerable<GlVersion> preferredVersions = null)
+        public IGlContext CreateSharedContext(IEnumerable<GlVersion>? preferredVersions = null)
         {
+            if (Context == null)
+                throw new PlatformGraphicsContextLostException();
             return new GlContext(GlInterface, Context.ShareGroup);
         }
 
@@ -134,7 +141,7 @@ namespace Avalonia.iOS
             }
         }
 
-        public object TryGetFeature(Type featureType) => null;
+        public object? TryGetFeature(Type featureType) => null;
     }
 }
 #endif

src/iOS/Avalonia.iOS/Eagl/EaglLayerSurface.cs

@@ -5,14 +5,14 @@ using System.Threading;
 using Avalonia.OpenGL;
 using Avalonia.OpenGL.Surfaces;
 using CoreAnimation;
-using Foundation;
-using OpenGLES;
-using UIKit;
 
-namespace Avalonia.iOS
+namespace Avalonia.iOS.Eagl
 {
     [ObsoletedOSPlatform("ios12.0", "Use 'Metal' instead.")]
+    [ObsoletedOSPlatform("tvos12.0", "Use 'Metal' instead.")]
     [SupportedOSPlatform("ios")]
+    [SupportedOSPlatform("tvos")]
+    [UnsupportedOSPlatform("maccatalyst")]
     class EaglLayerSurface : IGlPlatformSurface
     {
         private readonly CAEAGLLayer _layer;
@@ -80,19 +80,19 @@ namespace Avalonia.iOS
 
         static void CheckThread()
         {
-            if (Platform.Timer.TimerThread != Thread.CurrentThread)
+            if (Platform.Timer!.TimerThread != Thread.CurrentThread)
                 throw new InvalidOperationException("Invalid thread, go away");
         }
         
         public IGlPlatformSurfaceRenderTarget CreateGlRenderTarget(IGlContext context)
         {
             CheckThread();
-            var ctx = ((EaglPlatformGraphics)Platform.Graphics).Context;
+            var ctx = ((EaglPlatformGraphics)Platform.Graphics!).Context;
             if (ctx != context)
                 throw new InvalidOperationException("Platform surface is only usable with tha main context");
             using (ctx.MakeCurrent())
             {
-                var fbo = new SizeSynchronizedLayerFbo(ctx.Context, ctx.GlInterface, _layer);
+                var fbo = new SizeSynchronizedLayerFbo(ctx.Context!, ctx.GlInterface, _layer);
                 if (!fbo.Sync())
                     throw new InvalidOperationException("Unable to create render target");
                 return new RenderTarget(ctx, fbo);

src/iOS/Avalonia.iOS/Eagl/LayerFbo.cs

@@ -5,10 +5,13 @@ using Avalonia.OpenGL;
 using CoreAnimation;
 using OpenGLES;
 
-namespace Avalonia.iOS
+namespace Avalonia.iOS.Eagl
 {
     [ObsoletedOSPlatform("ios12.0", "Use 'Metal' instead.")]
+    [ObsoletedOSPlatform("tvos12.0", "Use 'Metal' instead.")]
     [SupportedOSPlatform("ios")]
+    [SupportedOSPlatform("tvos")]
+    [UnsupportedOSPlatform("maccatalyst")]
     internal class LayerFbo
     {
         private readonly EAGLContext _context;
@@ -29,7 +32,7 @@ namespace Avalonia.iOS
             _depthBuffer = depthBuffer;
         }
 
-        public static LayerFbo TryCreate(EAGLContext context, GlInterface gl, CAEAGLLayer layer)
+        public static LayerFbo? TryCreate(EAGLContext context, GlInterface gl, CAEAGLLayer layer)
         {
             if (context != EAGLContext.CurrentContext)
                 return null;
@@ -78,7 +81,7 @@ namespace Avalonia.iOS
         public void Present()
         {
             Bind();
-            var success = _context.PresentRenderBuffer(GlConsts.GL_RENDERBUFFER);
+            _context.PresentRenderBuffer(GlConsts.GL_RENDERBUFFER);
         }
 
         public void Dispose()
@@ -95,13 +98,16 @@ namespace Avalonia.iOS
     }
 
     [ObsoletedOSPlatform("ios12.0", "Use 'Metal' instead.")]
+    [ObsoletedOSPlatform("tvos12.0", "Use 'Metal' instead.")]
     [SupportedOSPlatform("ios")]
+    [SupportedOSPlatform("tvos")]
+    [UnsupportedOSPlatform("maccatalyst")]
     class SizeSynchronizedLayerFbo : IDisposable
     {
         private readonly EAGLContext _context;
         private readonly GlInterface _gl;
         private readonly CAEAGLLayer _layer;
-        private LayerFbo _fbo;
+        private LayerFbo? _fbo;
         private double _oldLayerWidth, _oldLayerHeight, _oldLayerScale;
         
         public SizeSynchronizedLayerFbo(EAGLContext context, GlInterface gl, CAEAGLLayer layer)
@@ -139,10 +145,10 @@ namespace Avalonia.iOS
         {
             if(!Sync())
                 throw new InvalidOperationException("Unable to create a render target");
-            _fbo.Bind();
+            _fbo!.Bind();
         }
 
-        public void Present() => _fbo.Present();
+        public void Present() => _fbo!.Present();
 
         public int Width => _fbo?.Width ?? 0;
         public int Height => _fbo?.Height ?? 0;

src/iOS/Avalonia.iOS/InsetsManager.cs

@@ -3,7 +3,6 @@ using Avalonia.Controls.Platform;
 using Avalonia.Media;
 
 namespace Avalonia.iOS;
-#nullable enable
 
 internal class InsetsManager : IInsetsManager
 {

src/iOS/Avalonia.iOS/Metal/MetalDevice.cs

@@ -1,9 +1,10 @@
 using System;
+using System.Runtime.Versioning;
 using Avalonia.Metal;
 using Avalonia.Utilities;
 using Metal;
 
-namespace Avalonia.iOS;
+namespace Avalonia.iOS.Metal;
 
 internal class MetalDevice : IMetalDevice
 {
@@ -12,7 +13,8 @@ internal class MetalDevice : IMetalDevice
     public MetalDevice(IMTLDevice device)
     {
         Device = device;
-        Queue = device.CreateCommandQueue();
+        Queue = device.CreateCommandQueue()
+            ?? throw new InvalidOperationException("IMTLCommandQueue is not available");
     }
 
     public IMTLDevice Device { get; }
@@ -23,7 +25,7 @@ internal class MetalDevice : IMetalDevice
     public bool IsLost => false;
 
     public IDisposable EnsureCurrent() => _syncRoot.Lock();
-    public object TryGetFeature(Type featureType) => null;
+    public object? TryGetFeature(Type featureType) => null;
 
     public void Dispose()
     {

src/iOS/Avalonia.iOS/Metal/MetalDrawingSession.cs

@@ -2,7 +2,7 @@ using System;
 using Avalonia.Metal;
 using CoreAnimation;
 
-namespace Avalonia.iOS;
+namespace Avalonia.iOS.Metal;
 
 internal class MetalDrawingSession : IMetalPlatformSurfaceRenderingSession
 {
@@ -21,7 +21,7 @@ internal class MetalDrawingSession : IMetalPlatformSurfaceRenderingSession
     public void Dispose()
     {
         var buffer = _device.Queue.CommandBuffer();
-        buffer.PresentDrawable(_drawable);
+        buffer!.PresentDrawable(_drawable);
         buffer.Commit();
     }
 

src/iOS/Avalonia.iOS/Metal/MetalPlatformGraphics.cs

@@ -1,20 +1,26 @@
 using System;
+using System.Runtime.Versioning;
 using Avalonia.Platform;
 using Metal;
 using SkiaSharp;
 
-namespace Avalonia.iOS;
-#nullable enable
+namespace Avalonia.iOS.Metal;
 
+[SupportedOSPlatform("ios")]
+[SupportedOSPlatform("macos")]
+[SupportedOSPlatform("maccatalyst")]
+[SupportedOSPlatform("tvos")]
 internal class MetalPlatformGraphics : IPlatformGraphics
 {
-    private MetalPlatformGraphics()
+    private readonly IMTLDevice _defaultDevice;
+
+    private MetalPlatformGraphics(IMTLDevice defaultDevice)
     {
-        
+        _defaultDevice = defaultDevice;
     }
     
     public bool UsesSharedContext => false;
-    public IPlatformGraphicsContext CreateContext() => new MetalDevice(MTLDevice.SystemDefault);
+    public IPlatformGraphicsContext CreateContext() => new MetalDevice(_defaultDevice);
 
     public IPlatformGraphicsContext GetSharedContext() => throw new NotSupportedException();
 
@@ -38,6 +44,6 @@ internal class MetalPlatformGraphics : IPlatformGraphics
         }
 #endif
 
-        return new MetalPlatformGraphics();
+        return new MetalPlatformGraphics(device);
     }
 }

src/iOS/Avalonia.iOS/Metal/MetalPlatformSurface.cs

@@ -1,7 +1,7 @@
 using Avalonia.Metal;
 using CoreAnimation;
 
-namespace Avalonia.iOS;
+namespace Avalonia.iOS.Metal;
 
 internal class MetalPlatformSurface : IMetalPlatformSurface
 {

src/iOS/Avalonia.iOS/Metal/MetalRenderTarget.cs

@@ -2,9 +2,8 @@ using Avalonia.Metal;
 using Avalonia.Platform;
 using CoreAnimation;
 using CoreGraphics;
-using Foundation;
 
-namespace Avalonia.iOS;
+namespace Avalonia.iOS.Metal;
 
 internal class MetalRenderTarget : IMetalPlatformSurfaceRenderTarget
 {
@@ -28,7 +27,7 @@ internal class MetalRenderTarget : IMetalPlatformSurfaceRenderTarget
     public IMetalPlatformSurfaceRenderingSession BeginRendering()
     {
         // Flush all existing rendering
-        var buffer = _device.Queue.CommandBuffer();
+        var buffer = _device.Queue.CommandBuffer()!;
         buffer.Commit();
         buffer.WaitUntilCompleted();
         _size = PendingSize;

src/iOS/Avalonia.iOS/NativeControlHostImpl.cs

@@ -1,6 +1,4 @@
-#nullable enable
-
-using System;
+using System;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Platform;
 using Avalonia.Platform;

src/iOS/Avalonia.iOS/Platform.cs

@@ -46,10 +46,10 @@ namespace Avalonia.iOS
 {
     static class Platform
     {
-        public static iOSPlatformOptions Options;
-        public static IPlatformGraphics Graphics;
-        public static DisplayLinkTimer Timer;
-        internal static Compositor Compositor { get; private set; }
+        public static iOSPlatformOptions? Options;
+        public static IPlatformGraphics? Graphics;
+        public static DisplayLinkTimer? Timer;
+        internal static Compositor? Compositor { get; private set; }
 
         public static void Register()
         {
@@ -84,14 +84,17 @@ namespace Avalonia.iOS
             {
 #if !MACCATALYST
                 if (renderingMode == iOSRenderingMode.OpenGl
-                    && EaglPlatformGraphics.TryCreate() is { } eaglGraphics)
+                    && !OperatingSystem.IsMacCatalyst()
+#pragma warning disable CA1422
+                    && Eagl.EaglPlatformGraphics.TryCreate() is { } eaglGraphics)
+#pragma warning restore CA1422
                 {
                     return eaglGraphics;
                 }
 #endif
 
                 if (renderingMode == iOSRenderingMode.Metal
-                    && MetalPlatformGraphics.TryCreate() is { } metalGraphics)
+                    && Metal.MetalPlatformGraphics.TryCreate() is { } metalGraphics)
                 {
                     return metalGraphics;
                 }

src/iOS/Avalonia.iOS/PlatformSettings.cs

@@ -1,4 +1,3 @@
-#nullable enable
 using System;
 using Avalonia.Media;
 using Avalonia.Platform;

src/iOS/Avalonia.iOS/SingleViewLifetime.cs

@@ -12,16 +12,16 @@ internal class SingleViewLifetime : ISingleViewApplicationLifetime, IActivatable
         avaloniaAppDelegate.Deactivated += (_, args) => Deactivated?.Invoke(this, args);
     }
             
-    public AvaloniaView View;
+    public AvaloniaView? View;
 
-    public Control MainView
+    public Control? MainView
     {
-        get => View.Content;
-        set => View.Content = value;
+        get => View!.Content;
+        set => View!.Content = value;
     }
 
-    public event EventHandler<ActivatedEventArgs> Activated;
-    public event EventHandler<ActivatedEventArgs> Deactivated;
+    public event EventHandler<ActivatedEventArgs>? Activated;
+    public event EventHandler<ActivatedEventArgs>? Deactivated;
     public bool TryLeaveBackground() => false;
     public bool TryEnterBackground() => false;
 }

src/iOS/Avalonia.iOS/Storage/IOSStorageItem.cs

@@ -10,8 +10,6 @@ using Foundation;
 
 using UIKit;
 
-#nullable enable
-
 namespace Avalonia.iOS.Storage;
 
 internal abstract class IOSStorageItem : IStorageBookmarkItem
@@ -57,7 +55,10 @@ internal abstract class IOSStorageItem : IStorageBookmarkItem
 
         var properties = attributes is null ?
             new StorageItemProperties() :
-            new StorageItemProperties(attributes.Size, (DateTime)attributes.CreationDate, (DateTime)attributes.ModificationDate);
+            new StorageItemProperties(
+                attributes.Size,
+                attributes.CreationDate is { } creationDate ? (DateTime)creationDate : null,
+                attributes.ModificationDate is { } modificationDate ? (DateTime)modificationDate : null);
 
         return Task.FromResult(properties);
     }

src/iOS/Avalonia.iOS/Storage/IOSStorageProvider.cs

@@ -13,8 +13,6 @@ using UniformTypeIdentifiers;
 using UTTypeLegacy = MobileCoreServices.UTType;
 using UTType = UniformTypeIdentifiers.UTType;
 
-#nullable enable
-
 namespace Avalonia.iOS.Storage;
 
 internal class IOSStorageProvider : IStorageProvider
@@ -69,8 +67,10 @@ internal class IOSStorageProvider : IStorageProvider
             var allowedUtils = options.FileTypeFilter?.SelectMany(f => f.AppleUniformTypeIdentifiers ?? Array.Empty<string>())
                 .ToArray() ?? new[]
             {
+#pragma warning disable CA1422
                 UTTypeLegacy.Content,
                 UTTypeLegacy.Item,
+#pragma warning restore CA1422
                 "public.data"
             };
             documentPicker = new UIDocumentPickerViewController(allowedUtils, UIDocumentPickerMode.Open);
@@ -149,7 +149,9 @@ internal class IOSStorageProvider : IStorageProvider
     {
         using var documentPicker = OperatingSystem.IsIOSVersionAtLeast(14) ?
             new UIDocumentPickerViewController(new[] { UTTypes.Folder }, false) :
+#pragma warning disable CA1422
             new UIDocumentPickerViewController(new string[] { UTTypeLegacy.Folder }, UIDocumentPickerMode.Open);
+#pragma warning restore CA1422
 
         if (OperatingSystem.IsIOSVersionAtLeast(13))
         {

src/iOS/Avalonia.iOS/Stubs.cs

@@ -12,6 +12,7 @@ namespace Avalonia.iOS
 
         private class CursorImplStub : ICursorImpl
         {
+            public CursorImplStub(){}
             public void Dispose() { }
         }
     }
@@ -22,7 +23,7 @@ namespace Avalonia.iOS
 
         public IWindowImpl CreateEmbeddableWindow() => throw new NotSupportedException();
 
-        public ITrayIconImpl CreateTrayIcon() => null;
+        public ITrayIconImpl? CreateTrayIcon() => null;
     }
     
     internal class PlatformIconLoaderStub : IPlatformIconLoader

src/iOS/Avalonia.iOS/TextInputResponder.Properties.cs

@@ -1,4 +1,3 @@
-#nullable enable
 using Avalonia.Input.TextInput;
 using Foundation;
 using UIKit;

src/iOS/Avalonia.iOS/TextInputResponder.cs

@@ -14,8 +14,6 @@ using UIKit;
 
 namespace Avalonia.iOS;
 
-#nullable enable
-
 partial class AvaloniaView
 {
 
@@ -110,7 +108,9 @@ partial class AvaloniaView
             {
                 UITextInputMode? mode = null;
 #if !TVOS
+#pragma warning disable CA1422
                 mode = UITextInputMode.CurrentInputMode;
+#pragma warning restore CA1422
 #endif
                 // Can be empty see https://developer.apple.com/documentation/uikit/uitextinputmode/1614522-activeinputmodes
                 if (mode is null && UITextInputMode.ActiveInputModes.Length > 0)

src/iOS/Avalonia.iOS/TouchHandler.cs

@@ -11,7 +11,7 @@ namespace Avalonia.iOS
     {
         private readonly AvaloniaView _view;
         private readonly ITopLevelImpl _tl;
-        public TouchDevice _device = new TouchDevice();
+        public TouchDevice _device = new();
 
         public TouchHandler(AvaloniaView view, ITopLevelImpl tl)
         {
@@ -19,12 +19,12 @@ namespace Avalonia.iOS
             _tl = tl;
         }
 
-        static ulong Ts(UIEvent evt) => (ulong) (evt.Timestamp * 1000);
+        static ulong Ts(UIEvent? evt) => evt is null ? 0 : (ulong) (evt.Timestamp * 1000);
         private IInputRoot Root => _view.InputRoot;
         private static long _nextTouchPointId = 1;
         private Dictionary<UITouch, long> _knownTouches = new Dictionary<UITouch, long>();
 
-        public void Handle(NSSet touches, UIEvent evt)
+        public void Handle(NSSet touches, UIEvent? evt)
         {
             foreach (UITouch t in touches)
             {

src/iOS/Avalonia.iOS/UIKitInputPane.cs

@@ -7,7 +7,6 @@ using Avalonia.Controls.Platform;
 using Foundation;
 using UIKit;
 
-#nullable enable
 namespace Avalonia.iOS;
 
 [UnsupportedOSPlatform("tvos")]

src/iOS/Avalonia.iOS/ViewController.cs

@@ -12,7 +12,7 @@ public interface IAvaloniaViewController
 #endif
     bool PrefersStatusBarHidden { get; set; }
     Thickness SafeAreaPadding { get; }
-    event EventHandler SafeAreaPaddingChanged;
+    event EventHandler? SafeAreaPaddingChanged;
 }
 
 /// <inheritdoc cref="IAvaloniaViewController" />
@@ -78,5 +78,5 @@ public class DefaultAvaloniaViewController : UIViewController, IAvaloniaViewCont
     public Thickness SafeAreaPadding { get; private set; }
 
     /// <inheritdoc/>
-    public event EventHandler SafeAreaPaddingChanged;
+    public event EventHandler? SafeAreaPaddingChanged;
 }