add comments

src/Android/Avalonia.Android/AndroidPlatform.cs

@@ -33,7 +33,11 @@ namespace Avalonia.Android
     {
         public static readonly AndroidPlatform Instance = new AndroidPlatform();
         public static AndroidPlatformOptions Options { get; private set; }
+
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickSize"/>
         public Size TouchDoubleClickSize => new Size(4, 4);
+
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickTime"/>
         public TimeSpan TouchDoubleClickTime => TimeSpan.FromMilliseconds(200);
 
         public static void Initialize(Type appType, AndroidPlatformOptions options)

src/Avalonia.Native/AvaloniaNativePlatform.cs

@@ -26,8 +26,10 @@ namespace Avalonia.Native
 
         public TimeSpan DoubleClickTime => TimeSpan.FromMilliseconds(500); //TODO
 
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickSize"/>
         public Size TouchDoubleClickSize => new Size(16, 16);
 
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickTime"/>
         public TimeSpan TouchDoubleClickTime => DoubleClickTime;
 
         public static AvaloniaNativePlatform Initialize(IntPtr factory, AvaloniaNativePlatformOptions options)

src/Avalonia.Visuals/Platform/ITouchPlatformSettings.cs

@@ -4,8 +4,14 @@ namespace Avalonia.Platform
 {
     public interface ITouchPlatformSettings
     {
+        /// <summary>
+        /// Determines the size of the area within that you should click twice in order for a double click to be counted.
+        /// </summary>
         Size TouchDoubleClickSize { get; }
 
+        /// <summary>
+        /// Determines the time span that what will be used to determine the double-click.
+        /// </summary>
         TimeSpan TouchDoubleClickTime { get; }
     }
 }

src/Avalonia.X11/Stubs.cs

@@ -8,8 +8,10 @@ namespace Avalonia.X11
         public Size DoubleClickSize { get; } = new Size(2, 2);
         public TimeSpan DoubleClickTime { get; } = TimeSpan.FromMilliseconds(500);
 
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickSize"/>
         public Size TouchDoubleClickSize => new Size(16, 16);
 
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickTime"/>
         public TimeSpan TouchDoubleClickTime => DoubleClickTime;
     }
 }

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -133,7 +133,11 @@ namespace Avalonia.Win32
             UnmanagedMethods.GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CYDOUBLECLK));
 
         public TimeSpan DoubleClickTime => TimeSpan.FromMilliseconds(UnmanagedMethods.GetDoubleClickTime());
+
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickSize"/>
         public Size TouchDoubleClickSize => new Size(16,16);
+
+        /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickTime"/>
         public TimeSpan TouchDoubleClickTime => DoubleClickTime;
         public static void Initialize()
         {

src/iOS/Avalonia.iOS/Platform.cs

@@ -15,7 +15,10 @@ namespace Avalonia.iOS
         public static DisplayLinkTimer Timer;
         class PlatformSettings : ITouchPlatformSettings
         {
+            /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickSize"/>
             public Size TouchDoubleClickSize => new Size(10, 10);
+
+            /// <inheritdoc cref="ITouchPlatformSettings.TouchDoubleClickTime"/>
             public TimeSpan TouchDoubleClickTime => TimeSpan.FromMilliseconds(500);
         }