Add Composition Start and End properties to TextEditable

src/Android/Avalonia.Android/InputEditable.cs

@@ -26,6 +26,7 @@ namespace Avalonia.Android
 
         public event EventHandler TextChanged;
         public event EventHandler SelectionChanged;
+        public event EventHandler CompositionChanged;
 
         public InputEditable(TopLevelImpl topLevel, IAndroidInputMethod inputMethod, AvaloniaInputConnection avaloniaInputConnection)
         {
@@ -54,8 +55,6 @@ namespace Avalonia.Android
         {
         }
 
-        public bool IsInBatchEdit => _currentBatchLevel > 0;
-
         public TextPresenter Presenter { get => _presenter; }
 
 
@@ -90,6 +89,10 @@ namespace Avalonia.Android
             }
         }
 
+        public int CompositionStart => BaseInputConnection.GetComposingSpanStart(this);
+
+        public int CompositionEnd => BaseInputConnection.GetComposingSpanEnd(this);
+
         public void BeginBatchEdit()
         {
             _currentBatchLevel++;
@@ -120,6 +123,11 @@ namespace Avalonia.Android
             _currentBatchLevel--;
         }
 
+        public void RaiseCompositionChanged()
+        {
+            CompositionChanged?.Invoke(this, EventArgs.Empty);
+        }
+
         void IDisposable.Dispose()
         {
             _presenter = null;

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

@@ -28,6 +28,7 @@ using Math = System.Math;
 using AndroidRect = Android.Graphics.Rect;
 using Window = Android.Views.Window;
 using Android.Graphics.Drawables;
+using Java.Util;
 
 namespace Avalonia.Android.Platform.SkiaPlatform
 {
@@ -411,8 +412,6 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         private readonly TopLevelImpl _topLevel;
         private readonly IAndroidInputMethod _inputMethod;
         private readonly InputEditable _editable;
-        private bool _hasComposingRegion;
-        private int _compositionStart;
 
         public AvaloniaInputConnection(TopLevelImpl topLevel, IAndroidInputMethod inputMethod) : base(inputMethod.View, true)
         {
@@ -427,12 +426,11 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public override bool SetComposingRegion(int start, int end)
         {
-            _inputMethod.Client.SetComposingRegion(new Media.TextFormatting.TextRange(start, end));
+            var ret = base.SetComposingRegion(start, end);
 
-            _hasComposingRegion = true;
-            _compositionStart = start;
+            InputEditable.RaiseCompositionChanged();
 
-            return base.SetComposingRegion(start, end);
+            return ret;
         }
 
         public override bool SetComposingText(ICharSequence text, int newCursorPosition)
@@ -447,13 +445,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             {
                 var ret = base.SetComposingText(text, newCursorPosition);
 
-                if (!_hasComposingRegion)
-                {
-                    _compositionStart = _editable.SelectionEnd - composingText.Length;
-                    _hasComposingRegion = true;
-                }
-
-                _inputMethod.Client.SetComposingRegion(new Media.TextFormatting.TextRange(_compositionStart, _compositionStart + composingText.Length));
+                InputEditable.RaiseCompositionChanged();
 
                 return ret;
             }
@@ -476,19 +468,16 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public override bool FinishComposingText()
         {
-            _inputMethod.Client?.SetComposingRegion(null);
-            _hasComposingRegion = false;
-            _compositionStart = -1;
-            return base.FinishComposingText();
+            var ret = base.FinishComposingText();
+            InputEditable.RaiseCompositionChanged();
+            return ret;
         }
 
         public override bool CommitText(ICharSequence text, int newCursorPosition)
         {
-            _inputMethod.Client?.SetComposingRegion(null);
-            _hasComposingRegion = false;
-            _compositionStart = -1;
-
-            return base.CommitText(text, newCursorPosition);
+            var ret = base.CommitText(text, newCursorPosition);
+            InputEditable.RaiseCompositionChanged();
+            return ret;
         }
 
         public override bool PerformEditorAction([GeneratedEnum] ImeAction actionCode)

src/Avalonia.Base/Input/TextInput/ITextEditable.cs

@@ -12,8 +12,11 @@ namespace Avalonia.Input.TextInput
     {
         event EventHandler TextChanged;
         event EventHandler SelectionChanged;
+        event EventHandler CompositionChanged;
         int SelectionStart { get; set; }
         int SelectionEnd { get; set; }
+        int CompositionStart { get; }
+        int CompositionEnd { get; }
         
         string? Text { get; set; }
     }

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -81,6 +81,7 @@ namespace Avalonia.Controls
                 {
                     _textEditable.TextChanged -= TextEditable_TextChanged;
                     _textEditable.SelectionChanged -= TextEditable_SelectionChanged;
+                    _textEditable.CompositionChanged -= TextEditable_CompositionChanged;
                 }
 
                 _textEditable = value;
@@ -89,6 +90,7 @@ namespace Avalonia.Controls
                 {
                     _textEditable.TextChanged += TextEditable_TextChanged;
                     _textEditable.SelectionChanged += TextEditable_SelectionChanged;
+                    _textEditable.CompositionChanged += TextEditable_CompositionChanged;
 
                     if (_presenter != null)
                     {
@@ -100,6 +102,14 @@ namespace Avalonia.Controls
             }
         }
 
+        private void TextEditable_CompositionChanged(object? sender, EventArgs e)
+        {
+            if (_presenter != null && _textEditable != null)
+            {
+                _presenter.CompositionRegion = new TextRange(_textEditable.CompositionStart, _textEditable.CompositionEnd);
+            }
+        }
+
         private void TextEditable_SelectionChanged(object? sender, EventArgs e)
         {
             if(_parent != null && _textEditable != null)