Unify IRuntimePlatform registration across backends

src/Android/Avalonia.Android/AndroidPlatform.cs

@@ -18,6 +18,7 @@ namespace Avalonia
         public static AppBuilder UseAndroid(this AppBuilder builder)
         {
             return builder
+                .UseStandardRuntimePlatformSubsystem()
                 .UseWindowingSubsystem(() => AndroidPlatform.Initialize(), "Android")
                 .UseSkia();
         }

src/Avalonia.Base/Platform/IRuntimePlatform.cs

@@ -18,7 +18,6 @@ namespace Avalonia.Platform
         public bool IsMobile { get; set; }
     }
 
-    [Unstable]
     public enum FormFactorType
     {
         Unknown,

src/Avalonia.Base/Platform/StandardRuntimePlatformServices.cs

@@ -3,18 +3,15 @@ using Avalonia.Compatibility;
 using Avalonia.Platform.Internal;
 using Avalonia.Platform.Interop;
 
-namespace Avalonia.Platform
+namespace Avalonia.Platform;
+
+internal static class StandardRuntimePlatformServices
 {
-    public static class StandardRuntimePlatformServices
+    public static void Register(Assembly? assembly = null)
     {
-        public static void Register(Assembly? assembly = null)
-        {
-            var standardPlatform = new StandardRuntimePlatform();
-
-            AssetLoader.RegisterResUriParsers();
-            AvaloniaLocator.CurrentMutable
-                .Bind<IRuntimePlatform>().ToConstant(standardPlatform)
-                .Bind<IAssetLoader>().ToConstant(new StandardAssetLoader(assembly));
-        }
+        AssetLoader.RegisterResUriParsers();
+        AvaloniaLocator.CurrentMutable
+            .Bind<IRuntimePlatform>().ToSingleton<StandardRuntimePlatform>()
+            .Bind<IAssetLoader>().ToConstant(new StandardAssetLoader(assembly));
     }
 }

src/Avalonia.Controls/AppBuilder.cs

@@ -12,23 +12,23 @@ namespace Avalonia
     /// <summary>
     /// Initializes platform-specific services for an <see cref="Application"/>.
     /// </summary>
-    public class AppBuilder
+    public sealed class AppBuilder
     {
         private static bool s_setupWasAlreadyCalled;
         private Action? _optionsInitializers;
         private Func<Application>? _appFactory;
         private IApplicationLifetime? _lifetime;
-        
-        /// <summary>
-        /// Gets or sets the <see cref="IRuntimePlatform"/> instance.
-        /// </summary>
-        public IRuntimePlatform RuntimePlatform { get; set; }
 
         /// <summary>
         /// Gets or sets a method to call the initialize the runtime platform services (e. g. AssetLoader)
         /// </summary>
-        public Action RuntimePlatformServicesInitializer { get; private set; }
+        public Action? RuntimePlatformServicesInitializer { get; private set; }
 
+        /// <summary>
+        /// Gets the name of the currently selected windowing subsystem.
+        /// </summary>
+        public string? RuntimePlatformServicesName { get; private set; }
+        
         /// <summary>
         /// Gets the <see cref="Application"/> instance being initialized.
         /// </summary>
@@ -70,21 +70,10 @@ namespace Avalonia
         /// <summary>
         /// Initializes a new instance of the <see cref="AppBuilder"/> class.
         /// </summary>
-        public AppBuilder()
-            : this(new StandardRuntimePlatform(),
-                builder => StandardRuntimePlatformServices.Register(builder.ApplicationType?.Assembly))
+        private AppBuilder()
         {
         }
         
-        /// <summary>
-        /// Initializes a new instance of the <see cref="AppBuilder"/> class.
-        /// </summary>
-        protected AppBuilder(IRuntimePlatform platform, Action<AppBuilder> platformServices)
-        {
-            RuntimePlatform = platform;
-            RuntimePlatformServicesInitializer = () => platformServices(this);
-        }
-
         /// <summary>
         /// Begin configuring an <see cref="Application"/>.
         /// </summary>
@@ -96,7 +85,6 @@ namespace Avalonia
             return new AppBuilder()
             {
                 ApplicationType = typeof(TApp),
-                // Needed for CoreRT compatibility
                 _appFactory = () => new TApp()
             };
         }
@@ -155,7 +143,7 @@ namespace Avalonia
                 $"Input type either needs to have BuildAvaloniaApp -> AppBuilder method or inherit Application type.");
         }
         
-        protected AppBuilder Self => this;
+        private AppBuilder Self => this;
 
         public AppBuilder AfterSetup(Action<AppBuilder> callback)
         {
@@ -225,6 +213,30 @@ namespace Avalonia
             RenderingSubsystemName = name;
             return Self;
         }
+        
+        /// <summary>
+        /// Specifies a runtime platform subsystem to use.
+        /// </summary>
+        /// <param name="initializer">The method to call to initialize the runtime platform subsystem.</param>
+        /// <param name="name">The name of the runtime platform subsystem.</param>
+        /// <returns>An <see cref="AppBuilder"/> instance.</returns>
+        public AppBuilder UseRuntimePlatformSubsystem(Action initializer, string name = "")
+        {
+            RuntimePlatformServicesInitializer = initializer;
+            RuntimePlatformServicesName = name;
+            return Self;
+        }
+        
+        /// <summary>
+        /// Specifies a standard runtime platform subsystem to use.
+        /// </summary>
+        /// <returns>An <see cref="AppBuilder"/> instance.</returns>
+        public AppBuilder UseStandardRuntimePlatformSubsystem()
+        {
+            RuntimePlatformServicesInitializer = () => StandardRuntimePlatformServices.Register(ApplicationType?.Assembly);
+            RuntimePlatformServicesName = nameof(StandardRuntimePlatform);
+            return Self;
+        }
 
         /// <summary>
         /// Configures platform-specific options

src/Avalonia.DesignerSupport/Remote/RemoteDesignerEntryPoint.cs

@@ -138,6 +138,7 @@ namespace Avalonia.DesignerSupport.Remote
                 CommandLineArgs args, object obj)
             {
                 var builder = (AppBuilder)obj;
+                builder = builder.UseStandardRuntimePlatformSubsystem();
                 if (args.Method == Methods.AvaloniaRemote)
                     builder.UseWindowingSubsystem(() => PreviewerWindowingPlatform.Initialize(transport));
                 if (args.Method == Methods.Html)

src/Avalonia.Native/AvaloniaNativePlatformExtensions.cs

@@ -8,7 +8,9 @@ namespace Avalonia
     {
         public static AppBuilder UseAvaloniaNative(this AppBuilder builder)
         {
-            builder.UseWindowingSubsystem(() =>
+            builder
+                .UseStandardRuntimePlatformSubsystem()
+                .UseWindowingSubsystem(() =>
             {
                 var platform = AvaloniaNativePlatform.Initialize(
                     AvaloniaLocator.Current.GetService<AvaloniaNativePlatformOptions>() ??

src/Avalonia.X11/X11Platform.cs

@@ -289,7 +289,9 @@ namespace Avalonia
     {
         public static AppBuilder UseX11(this AppBuilder builder)
         {
-            builder.UseWindowingSubsystem(() =>
+            builder
+                .UseStandardRuntimePlatformSubsystem()
+                .UseWindowingSubsystem(() =>
                 new AvaloniaX11Platform().Initialize(AvaloniaLocator.Current.GetService<X11PlatformOptions>() ??
                                                      new X11PlatformOptions()));
             return builder;

src/Browser/Avalonia.Browser/BrowserAppBuilder.cs

@@ -98,6 +98,7 @@ public static class BrowserAppBuilder
         this AppBuilder builder)
     {
         return builder
+            .UseBrowserRuntimePlatformSubsystem()
             .UseWindowingSubsystem(BrowserWindowingPlatform.Register)
             .UseSkia();
     }

src/Browser/Avalonia.Browser/BrowserRuntimePlatform.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Runtime.InteropServices.JavaScript;
 using System.Text.RegularExpressions;
@@ -7,6 +8,23 @@ using Avalonia.Platform;
 
 namespace Avalonia.Browser;
 
+internal static class BrowserRuntimePlatformServices
+{
+    public static AppBuilder UseBrowserRuntimePlatformSubsystem(this AppBuilder builder)
+    {
+        builder.UseRuntimePlatformSubsystem(() => Register(builder.ApplicationType?.Assembly), nameof(BrowserRuntimePlatform));
+        return builder;
+    }
+    
+    public static void Register(Assembly? assembly = null)
+    {
+        AssetLoader.RegisterResUriParsers();
+        AvaloniaLocator.CurrentMutable
+            .Bind<IRuntimePlatform>().ToSingleton<BrowserRuntimePlatform>()
+            .Bind<IAssetLoader>().ToConstant(new StandardAssetLoader(assembly));
+    }
+}
+
 internal class BrowserRuntimePlatform : StandardRuntimePlatform
 {
     private static readonly Lazy<RuntimePlatformInfo> Info = new(() =>

src/Headless/Avalonia.Headless/AvaloniaHeadlessPlatform.cs

@@ -105,8 +105,10 @@ namespace Avalonia.Headless
         public static AppBuilder UseHeadless(this AppBuilder builder, AvaloniaHeadlessPlatformOptions opts)
         {
             if(opts.UseHeadlessDrawing)
-                builder.UseRenderingSubsystem(HeadlessPlatformRenderInterface.Initialize, "Headless");
-            return builder.UseWindowingSubsystem(() => AvaloniaHeadlessPlatform.Initialize(opts), "Headless");
+                builder = builder.UseRenderingSubsystem(HeadlessPlatformRenderInterface.Initialize, "Headless");
+            return builder
+                .UseStandardRuntimePlatformSubsystem()
+                .UseWindowingSubsystem(() => AvaloniaHeadlessPlatform.Initialize(opts), "Headless");
         }
     }
 }

src/Linux/Avalonia.LinuxFramebuffer/LinuxFramebufferPlatform.cs

@@ -76,7 +76,10 @@ namespace Avalonia.LinuxFramebuffer
         internal static LinuxFramebufferLifetime Initialize(AppBuilder builder, IOutputBackend outputBackend, IInputBackend? inputBackend)
         {
             var platform = new LinuxFramebufferPlatform(outputBackend);
-            builder.UseSkia().UseWindowingSubsystem(platform.Initialize, "fbdev");
+            builder
+                .UseStandardRuntimePlatformSubsystem()
+                .UseSkia()
+                .UseWindowingSubsystem(platform.Initialize, "fbdev");
             return new LinuxFramebufferLifetime(platform._fb, inputBackend);
         }
     }

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -25,7 +25,9 @@ namespace Avalonia
     {
         public static AppBuilder UseWin32(this AppBuilder builder)
         {
-            return builder.UseWindowingSubsystem(
+            return builder
+                .UseStandardRuntimePlatformSubsystem()
+                .UseWindowingSubsystem(
                 () => Win32.Win32Platform.Initialize(
                     AvaloniaLocator.Current.GetService<Win32PlatformOptions>() ?? new Win32PlatformOptions()),
                 "Win32");

src/iOS/Avalonia.iOS/Platform.cs

@@ -16,6 +16,7 @@ namespace Avalonia
         public static AppBuilder UseiOS(this AppBuilder builder)
         {
             return builder
+                .UseStandardRuntimePlatformSubsystem()
                 .UseWindowingSubsystem(iOS.Platform.Register, "iOS")
                 .UseSkia();
         }