Introduce IPlatformSettings to the public API

src/Avalonia.Base/Input/IInputRoot.cs

@@ -1,4 +1,5 @@
 using Avalonia.Metadata;
+using Avalonia.Platform;
 
 namespace Avalonia.Input
 {
@@ -17,10 +18,18 @@ namespace Avalonia.Input
         /// Gets focus manager of the root.
         /// </summary>
         /// <remarks>
-        /// Focus manager can be null only if application wasn't initialized yet.
+        /// Focus manager can be null only if window wasn't initialized yet.
         /// </remarks>
         IFocusManager? FocusManager { get; }
         
+        /// <summary>
+        /// Represents a contract for accessing platform-specific settings and information.
+        /// </summary>
+        /// <remarks>
+        /// Focus manager can be null only if window wasn't initialized yet.
+        /// </remarks>
+        IPlatformSettings? PlatformSettings { get; }
+        
         /// <summary>
         /// Gets or sets the input element that the pointer is currently over.
         /// </summary>

src/Avalonia.Base/Platform/DefaultPlatformSettings.cs

@@ -1,12 +1,14 @@
 using System;
 using Avalonia.Input;
 using Avalonia.Media;
+using Avalonia.Metadata;
 
 namespace Avalonia.Platform
 {
     /// <summary>
     /// A default implementation of <see cref="IPlatformSettings"/> for platforms.
     /// </summary>
+    [PrivateApi]
     public class DefaultPlatformSettings : IPlatformSettings
     {
         public virtual Size GetTapSize(PointerType type)

src/Avalonia.Base/Platform/IPlatformSettings.cs

@@ -4,7 +4,11 @@ using Avalonia.Metadata;
 
 namespace Avalonia.Platform
 {
-    [Unstable]
+    /// <summary>
+    /// The <see cref="IPlatformSettings"/> interface represents a contract for accessing platform-specific settings and information.
+    /// Some of these settings might be changed by used globally in the OS in runtime.
+    /// </summary>
+    [NotClientImplementable]
     public interface IPlatformSettings
     {
         /// <summary>

src/Avalonia.Controls/TopLevel.cs

@@ -487,6 +487,9 @@ namespace Avalonia.Controls
         /// <inheritdoc />
         public IFocusManager? FocusManager => AvaloniaLocator.Current.GetService<IFocusManager>();
 
+        /// <inheritdoc />
+        public IPlatformSettings? PlatformSettings => AvaloniaLocator.Current.GetService<IPlatformSettings>();
+        
         /// <inheritdoc/>
         Point IRenderRoot.PointToClient(PixelPoint p)
         {