Apply optimizations in Avalonia Android (#20968)

* Apply optimizations around Avalonia Android

* More changes

* Move benchmarks to run on Android

* Remove Android Benchmark from build

* More changes

* Removed Android Benchmarks project

src/Android/Avalonia.Android/AndroidDispatcherImpl.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics;
+using System.Threading;
 using Android.OS;
 using Avalonia.Controls.Documents;
 using Avalonia.Threading;
@@ -19,8 +20,7 @@ namespace Avalonia.Android
         private readonly Runnable _timerSignaler;
         private readonly Runnable _wakeupSignaler;
         private readonly MessageQueue _queue;
-        private readonly object _lock = new();
+        private int _signaled;
-        private bool _signaled;
         private bool _backgroundProcessingRequested;
         
 
@@ -46,8 +46,7 @@ namespace Avalonia.Android
         public event Action? Signaled;
         private void OnSignaled()
         {
-            lock (_lock)
+            Interlocked.Exchange(ref _signaled, 0);
-                _signaled = false;
             Signaled?.Invoke();
         }
 
@@ -68,13 +67,11 @@ namespace Avalonia.Android
 
         public void Signal()
         {
-            lock (_lock)
+            if (Interlocked.CompareExchange(ref _signaled, 1, 0) != 0)
             {
-                if(_signaled)
+                return;
-                    return;
-                _signaled = true;
-                _handler.Post(_signaler);
             }
+            _handler.Post(_signaler);
         }
 
         readonly Stopwatch _clock = Stopwatch.StartNew();
@@ -133,11 +130,9 @@ namespace Avalonia.Android
                 // "background" jobs not being processed
                 // So we need to examine the queue state to prevent that scenario
                 
-                lock (_lock)
+                if (Volatile.Read(ref _signaled) != 0)
                 {
-                    // There are higher priority jobs enqueued, we'll be called again
+                    return;
-                    if (_signaled)
-                        return;
                 }
                 
                 if (CanQueryPendingInput)

src/Android/Avalonia.Android/AvaloniaAccessHelper.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
+
 using Android.OS;
 using AndroidX.Core.View.Accessibility;
 using AndroidX.CustomView.Widget;
@@ -134,9 +134,18 @@ namespace Avalonia.Android
 
         protected override bool OnPerformActionForVirtualView(int virtualViewId, int action, Bundle? arguments)
         {
-            return (GetNodeInfoProvidersFromVirtualViewId(virtualViewId) ?? [])
+            var providers = GetNodeInfoProvidersFromVirtualViewId(virtualViewId);
-                .Select(x => TryPerformNodeAction(x, action, arguments))
+            if (providers == null)
-                .Aggregate(false, (a, b) => a | b);
+            {
+                return false;
+            }
+
+            var result = false;
+            foreach (var provider in providers)
+            {
+                result |= TryPerformNodeAction(provider, action, arguments);
+            }
+            return result;
         }
 
         private static bool TryPerformNodeAction(INodeInfoProvider nodeInfoProvider, int action, Bundle? arguments)

src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs

@@ -4,6 +4,7 @@ using Android.App;
 using Android.Content;
 using Android.Graphics;
 using Android.Graphics.Drawables;
+using Android.OS;
 using Android.Runtime;
 using Android.Views;
 using AndroidX.AppCompat.App;
@@ -144,6 +145,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             private readonly TopLevelImpl _tl;
             private Size _oldSize;
             private double _oldScaling;
+            private Paint? _clearPaint;
 
             public SurfaceViewImpl(Context context, TopLevelImpl tl, bool placeOnTop) : base(context)
             {
@@ -159,11 +161,13 @@ namespace Avalonia.Android.Platform.SkiaPlatform
                 // can be seen below, but it does not.
                 if (OperatingSystem.IsAndroidVersionAtLeast(29))
                 {
-                    // Android 10+ does this (BlendMode was new)
+                    if (_clearPaint == null)
-                    var paint = new Paint();
+                    {
-                    paint.SetColor(0);
+                        _clearPaint = new Paint();
-                    paint.BlendMode = BlendMode.Clear;
+                        _clearPaint.SetColor(0);
-                    canvas.DrawRect(0, 0, Width, Height, paint);
+                        _clearPaint.BlendMode = BlendMode.Clear;
+                    }
+                    canvas.DrawRect(0, 0, Width, Height, _clearPaint);
                 }
                 else
                 {
@@ -384,7 +388,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         {
             if(Input != null)
             {
-                var args = new RawTextInputEventArgs(AndroidKeyboardDevice.Instance!, (ulong)DateTime.Now.Ticks, InputRoot!, text);
+                var args = new RawTextInputEventArgs(AndroidKeyboardDevice.Instance!, (ulong)SystemClock.UptimeMillis(), InputRoot!, text);
 
                 Input(args);
             }

src/Android/Avalonia.Android/Platform/Specific/Helpers/AndroidKeyboardEventsHelper.cs

@@ -10,6 +10,18 @@ namespace Avalonia.Android.Platform.Specific.Helpers
 {
     internal class AndroidKeyboardEventsHelper<TView> : IDisposable where TView : TopLevelImpl
     {
+        private static readonly string[] s_asciiStringCache = InitAsciiStringCache();
+
+        private static string[] InitAsciiStringCache()
+        {
+            var cache = new string[128];
+            for (int i = 0; i < 128; i++)
+            {
+                cache[i] = ((char)i).ToString();
+            }
+            return cache;
+        }
+
         private readonly TView _view;
 
         public bool HandleEvents { get; set; }
@@ -79,7 +91,7 @@ namespace Avalonia.Android.Platform.Specific.Helpers
                   AndroidKeyboardDevice.Instance!,
                   Convert.ToUInt64(e.EventTime),
                   inputRoot,
-                  unicodeTextInput ?? Convert.ToChar(e.UnicodeChar).ToString()
+                  unicodeTextInput ?? CharToString(e.UnicodeChar)
                   );
                 _view.Input?.Invoke(rawTextEvent);
 
@@ -107,6 +119,15 @@ namespace Avalonia.Android.Platform.Specific.Helpers
             return rv;
         }
 
+        private static string CharToString(int unicodeChar)
+        {
+            if (unicodeChar >= 0 && unicodeChar < s_asciiStringCache.Length)
+            {
+                return s_asciiStringCache[unicodeChar];
+            }
+            return char.ConvertFromUtf32(unicodeChar);
+        }
+
         private static string? GetKeySymbol(int unicodeChar, PhysicalKey physicalKey)
         {
             // Handle a very limited set of control characters so that we're consistent with other platforms
@@ -126,7 +147,7 @@ namespace Avalonia.Android.Platform.Specific.Helpers
                     if (unicodeChar <= 0x7F)
                     {
                         var asciiChar = (char)unicodeChar;
-                        return KeySymbolHelper.IsAllowedAsciiKeySymbol(asciiChar) ? asciiChar.ToString() : null;
+                        return KeySymbolHelper.IsAllowedAsciiKeySymbol(asciiChar) ? s_asciiStringCache[asciiChar] : null;
                     }
                     return char.ConvertFromUtf32(unicodeChar);
             }