Merge pull request #10328 from AvaloniaUI/ime_improvements

Android/Browser - IME improvements

samples/MobileSandbox/MainView.xaml

@@ -5,8 +5,8 @@
              x:DataType="mobileSandbox:MainView">
   <StackPanel Margin="100 50" Spacing="50">
     <TextBlock Text="Login" Foreground="White" />
-    <TextBox Watermark="Text" />
-    <TextBox Watermark="Username" TextInputOptions.ContentType="Email" AcceptsReturn="True" TextInputOptions.ReturnKeyType="Search" />
+    <TextBox TextInputOptions.Multiline="True" AcceptsReturn="True" Watermark="Text" Height="200" TextWrapping="Wrap"/>
+    <TextBox Watermark="Username" TextInputOptions.ContentType="Email" TextInputOptions.ReturnKeyType="Done" />
     <TextBox Watermark="Password" PasswordChar="*" TextInputOptions.ContentType="Password" />
     <TextBox Watermark="Pin" PasswordChar="*" TextInputOptions.ContentType="Digits" />
     <Button Content="Login" Command="{Binding ButtonCommand}" />

src/Android/Avalonia.Android/AndroidInputMethod.cs

@@ -5,8 +5,10 @@ using Android.Text;
 using Android.Views;
 using Android.Views.InputMethods;
 using Avalonia.Android.Platform.SkiaPlatform;
+using Avalonia.Controls.Presenters;
 using Avalonia.Input;
 using Avalonia.Input.TextInput;
+using Avalonia.Reactive;
 
 namespace Avalonia.Android
 {
@@ -68,23 +70,10 @@ namespace Avalonia.Android
 
         public void SetClient(ITextInputMethodClient client)
         {
-            if (_client != null)
-            {
-                _client.SurroundingTextChanged -= SurroundingTextChanged;
-            }
-
-            if(_inputConnection != null)
-            {
-                _inputConnection.ComposingText = null;
-                _inputConnection.ComposingRegion = default;
-            }
-
             _client = client;
 
             if (IsActive)
             {
-                _client.SurroundingTextChanged += SurroundingTextChanged;
-
                 _host.RequestFocus();
 
                 _imm.RestartInput(View);              
@@ -101,24 +90,6 @@ namespace Avalonia.Android
             }
         }
 
-        private void SurroundingTextChanged(object sender, EventArgs e)
-        {
-            if (IsActive && _inputConnection != null)
-            {
-                var surroundingText = Client.SurroundingText;
-
-                _inputConnection.SurroundingText = surroundingText;
-
-                _imm.UpdateSelection(_host, surroundingText.AnchorOffset, surroundingText.CursorOffset, surroundingText.AnchorOffset, surroundingText.CursorOffset);
-
-                if (_inputConnection.ComposingText != null && !_inputConnection.IsCommiting && surroundingText.AnchorOffset == surroundingText.CursorOffset)
-                {
-                    _inputConnection.CommitText(_inputConnection.ComposingText, 0);
-                    _inputConnection.SetSelection(surroundingText.AnchorOffset, surroundingText.CursorOffset);
-                }
-            }
-        }
-
         public void SetCursorRect(Rect rect)
         {
             
@@ -157,11 +128,14 @@ namespace Avalonia.Android
                     TextInputReturnKeyType.Search => (ImeFlags)CustomImeFlags.ActionSearch,
                     TextInputReturnKeyType.Next => (ImeFlags)CustomImeFlags.ActionNext,
                     TextInputReturnKeyType.Previous => (ImeFlags)CustomImeFlags.ActionPrevious,
-                    _ => (ImeFlags)CustomImeFlags.ActionDone
+                    TextInputReturnKeyType.Done => (ImeFlags)CustomImeFlags.ActionDone,
+                    _ => options.Multiline ? ImeFlags.NoEnterAction : (ImeFlags)CustomImeFlags.ActionDone
                 };
 
                 outAttrs.ImeOptions |= ImeFlags.NoFullscreen | ImeFlags.NoExtractUi;
 
+                _client.TextEditable = _inputConnection.InputEditable;
+
                 return _inputConnection;
             });
         }

src/Android/Avalonia.Android/InputEditable.cs

@@ -0,0 +1,127 @@
+using System;
+using Android.Runtime;
+using Android.Text;
+using Android.Views;
+using Android.Views.InputMethods;
+using Avalonia.Android.Platform.SkiaPlatform;
+using Avalonia.Controls.Presenters;
+using Avalonia.Input;
+using Avalonia.Input.Raw;
+using Avalonia.Input.TextInput;
+using Java.Lang;
+using static System.Net.Mime.MediaTypeNames;
+
+namespace Avalonia.Android
+{
+    internal class InputEditable : SpannableStringBuilder, ITextEditable
+    {
+        private readonly TopLevelImpl _topLevel;
+        private readonly IAndroidInputMethod _inputMethod;
+        private readonly AvaloniaInputConnection _avaloniaInputConnection;
+        private int _currentBatchLevel;
+        private string _previousText;
+        private int _previousSelectionStart;
+        private int _previousSelectionEnd;
+
+        public event EventHandler TextChanged;
+        public event EventHandler SelectionChanged;
+        public event EventHandler CompositionChanged;
+
+        public InputEditable(TopLevelImpl topLevel, IAndroidInputMethod inputMethod, AvaloniaInputConnection avaloniaInputConnection)
+        {
+            _topLevel = topLevel;
+            _inputMethod = inputMethod;
+            _avaloniaInputConnection = avaloniaInputConnection;
+        }
+
+        public InputEditable(ICharSequence text) : base(text)
+        {
+        }
+
+        public InputEditable(string text) : base(text)
+        {
+        }
+
+        public InputEditable(ICharSequence text, int start, int end) : base(text, start, end)
+        {
+        }
+
+        public InputEditable(string text, int start, int end) : base(text, start, end)
+        {
+        }
+
+        protected InputEditable(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
+        {
+        }
+
+        public int SelectionStart
+        {
+            get => Selection.GetSelectionStart(this); set
+            {
+                var end = SelectionEnd < 0 ? 0 : SelectionEnd;
+                _avaloniaInputConnection.SetSelection(value, end);
+                _inputMethod.IMM.UpdateSelection(_topLevel.View, value, end, value, end);
+            }
+        }
+        public int SelectionEnd
+        {
+            get => Selection.GetSelectionEnd(this); set
+            {
+                var start = SelectionStart < 0 ? 0 : SelectionStart;
+                _avaloniaInputConnection.SetSelection(start, value);
+                _inputMethod.IMM.UpdateSelection(_topLevel.View, start, value, start, value);
+            }
+        }
+
+        public string? Text
+        {
+            get => ToString(); set
+            {
+                if (Text != value)
+                {
+                    Clear();
+                    Insert(0, value ?? "");
+                }
+            }
+        }
+
+        public int CompositionStart => BaseInputConnection.GetComposingSpanStart(this);
+
+        public int CompositionEnd => BaseInputConnection.GetComposingSpanEnd(this);
+
+        public void BeginBatchEdit()
+        {
+            _currentBatchLevel++;
+
+            if (_currentBatchLevel == 1)
+            {
+                _previousText = ToString();
+                _previousSelectionStart =  SelectionStart;
+                _previousSelectionEnd = SelectionEnd;
+            }
+        }
+
+        public void EndBatchEdit()
+        {
+            if (_currentBatchLevel == 1)
+            {
+                if(_previousText != Text)
+                {
+                    TextChanged?.Invoke(this, EventArgs.Empty);
+                }
+
+                if (_previousSelectionStart != SelectionStart || _previousSelectionEnd != SelectionEnd)
+                {
+                    SelectionChanged?.Invoke(this, EventArgs.Empty);
+                }
+            }
+
+            _currentBatchLevel--;
+        }
+
+        public void RaiseCompositionChanged()
+        {
+            CompositionChanged?.Invoke(this, EventArgs.Empty);
+        }
+    }
+}

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
 {
@@ -410,159 +411,73 @@ namespace Avalonia.Android.Platform.SkiaPlatform
     {
         private readonly TopLevelImpl _topLevel;
         private readonly IAndroidInputMethod _inputMethod;
+        private readonly InputEditable _editable;
 
         public AvaloniaInputConnection(TopLevelImpl topLevel, IAndroidInputMethod inputMethod) : base(inputMethod.View, true)
         {
             _topLevel = topLevel;
             _inputMethod = inputMethod;
+            _editable = new InputEditable(_topLevel, _inputMethod, this);
         }
 
-        public TextInputMethodSurroundingText SurroundingText { get; set; }
+        public override IEditable Editable => _editable;
 
-        public string ComposingText { get; internal set; }
-
-        public ComposingRegion? ComposingRegion { get; internal set; }
-
-        public bool IsComposing => !string.IsNullOrEmpty(ComposingText);
-        public bool IsCommiting { get; private set; }
+        internal InputEditable InputEditable => _editable;
 
         public override bool SetComposingRegion(int start, int end)
         {
-            //System.Diagnostics.Debug.WriteLine($"Composing Region: [{start}|{end}] {SurroundingText.Text?.Substring(start, end - start)}");
+            var ret = base.SetComposingRegion(start, end);
 
-            ComposingRegion = new ComposingRegion(start, end);
+            InputEditable.RaiseCompositionChanged();
 
-            return base.SetComposingRegion(start, end);
+            return ret;
         }
 
         public override bool SetComposingText(ICharSequence text, int newCursorPosition)
         {
             var composingText = text.ToString();
 
-            ComposingText = composingText;
-
-            _inputMethod.Client?.SetPreeditText(ComposingText);
-
-            return base.SetComposingText(text, newCursorPosition);
-        }
-
-        public override bool FinishComposingText()
-        {
-            if (!string.IsNullOrEmpty(ComposingText))
+            if (string.IsNullOrEmpty(composingText))
             {
-                CommitText(ComposingText, ComposingText.Length);
+                return CommitText(text, newCursorPosition);
             }
             else
             {
-                ComposingRegion = new ComposingRegion(SurroundingText.CursorOffset, SurroundingText.CursorOffset);
-            }
-
-            return base.FinishComposingText();
-        }
-
-        public override ICharSequence GetTextBeforeCursorFormatted(int length, [GeneratedEnum] GetTextFlags flags)
-        {
-            if (!string.IsNullOrEmpty(SurroundingText.Text) && length > 0)
-            {
-                var start = System.Math.Max(SurroundingText.CursorOffset - length, 0);
+                var ret = base.SetComposingText(text, newCursorPosition);
 
-                var end = System.Math.Min(start + length - 1, SurroundingText.CursorOffset);
+                InputEditable.RaiseCompositionChanged();
 
-                var text = SurroundingText.Text.Substring(start, end - start);
-
-                //System.Diagnostics.Debug.WriteLine($"Text Before: {text}");
-
-                return new Java.Lang.String(text);
+                return ret;
             }
-
-            return null;
         }
 
-        public override ICharSequence GetTextAfterCursorFormatted(int length, [GeneratedEnum] GetTextFlags flags)
+        public override bool BeginBatchEdit()
         {
-            if (!string.IsNullOrEmpty(SurroundingText.Text))
-            {
-                var start = SurroundingText.CursorOffset;
-
-                var end = System.Math.Min(start + length, SurroundingText.Text.Length);
-
-                var text = SurroundingText.Text.Substring(start, end - start);
+            _editable.BeginBatchEdit();
 
-                //System.Diagnostics.Debug.WriteLine($"Text After: {text}");
-
-                return new Java.Lang.String(text);
-            }
-
-            return null;
+            return base.BeginBatchEdit();
         }
 
-        public override bool CommitText(ICharSequence text, int newCursorPosition)
+        public override bool EndBatchEdit()
         {
-            IsCommiting = true;
-            var committedText = text.ToString();
-
-            _inputMethod.Client.SetPreeditText(null);
+            var ret = base.EndBatchEdit();
+            _editable.EndBatchEdit();
 
-            int? start, end;
-
-            if(SurroundingText.CursorOffset != SurroundingText.AnchorOffset)
-            {
-                start = Math.Min(SurroundingText.CursorOffset, SurroundingText.AnchorOffset);
-                end = Math.Max(SurroundingText.CursorOffset, SurroundingText.AnchorOffset);
-            }
-            else if (ComposingRegion != null)
-            {
-                start = ComposingRegion?.Start;
-                end = ComposingRegion?.End;
-
-                ComposingRegion = null;
-            }
-            else
-            {
-                start = end = _inputMethod.Client.SurroundingText.CursorOffset;
-            }
-
-            _inputMethod.Client.SelectInSurroundingText((int)start, (int)end);
-
-            var time = DateTime.Now.TimeOfDay;
-
-            var rawTextEvent = new RawTextInputEventArgs(KeyboardDevice.Instance, (ulong)time.Ticks, _topLevel.InputRoot, committedText);
-
-            _topLevel.Input(rawTextEvent);
-
-            ComposingText = null;
-
-            ComposingRegion = new ComposingRegion(newCursorPosition, newCursorPosition);
-
-            return base.CommitText(text, newCursorPosition);
+            return ret;
         }
 
-        public override bool DeleteSurroundingText(int beforeLength, int afterLength)
+        public override bool FinishComposingText()
         {
-            var surroundingText = _inputMethod.Client.SurroundingText;
-
-            var selectionStart = surroundingText.CursorOffset;
-
-            _inputMethod.Client.SelectInSurroundingText(selectionStart - beforeLength, selectionStart + afterLength);
-
-            _inputMethod.View.DispatchKeyEvent(new KeyEvent(KeyEventActions.Down, Keycode.ForwardDel));
-
-            surroundingText = _inputMethod.Client.SurroundingText;
-
-            selectionStart = surroundingText.CursorOffset;
-
-            ComposingRegion = new ComposingRegion(selectionStart, selectionStart);
-
-            return base.DeleteSurroundingText(beforeLength, afterLength);
+            var ret = base.FinishComposingText();
+            InputEditable.RaiseCompositionChanged();
+            return ret;
         }
 
-        public override bool SetSelection(int start, int end)
+        public override bool CommitText(ICharSequence text, int newCursorPosition)
         {
-            _inputMethod.Client.SelectInSurroundingText(start, end);
-
-            ComposingRegion = new ComposingRegion(start, end);
-
-            return base.SetSelection(start, end);
+            var ret = base.CommitText(text, newCursorPosition);
+            InputEditable.RaiseCompositionChanged();
+            return ret;
         }
 
         public override bool PerformEditorAction([GeneratedEnum] ImeAction actionCode)

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

@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Avalonia.Metadata;
+
+namespace Avalonia.Input.TextInput
+{
+    [NotClientImplementable]
+    public interface ITextEditable
+    {
+        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.Base/Input/TextInput/ITextInputMethodClient.cs

@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Media.TextFormatting;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Input.TextInput
@@ -30,6 +31,11 @@ namespace Avalonia.Input.TextInput
         /// </summary>
         void SetPreeditText(string? text);
 
+        /// <summary>
+        /// Sets the current composing region. This doesn't remove the composing text from the commited text.
+        /// </summary>
+        void SetComposingRegion(TextRange? region);
+
         /// <summary>
         /// Indicates if text input client is capable of providing the text around the cursor
         /// </summary>
@@ -43,6 +49,11 @@ namespace Avalonia.Input.TextInput
         /// </summary>
         event EventHandler? SurroundingTextChanged;
 
+        /// <summary>
+        /// Gets or sets a platform editable. Text and selection changes made in the editable are forwarded to the IM client.
+        /// </summary>
+        ITextEditable? TextEditable { get; set; }
+
         void SelectInSurroundingText(int start, int end);
     }
 

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -63,6 +63,15 @@ namespace Avalonia.Controls.Presenters
                 o => o.PreeditText,
                  (o, v) => o.PreeditText = v);
 
+        /// <summary>
+        /// Defines the <see cref="CompositionRegion"/> property.
+        /// </summary>
+        public static readonly DirectProperty<TextPresenter, TextRange?> CompositionRegionProperty =
+            AvaloniaProperty.RegisterDirect<TextPresenter, TextRange?>(
+                nameof(CompositionRegion),
+                o => o.CompositionRegion,
+                 (o, v) => o.CompositionRegion = v);
+
         /// <summary>
         /// Defines the <see cref="TextAlignment"/> property.
         /// </summary>
@@ -106,6 +115,7 @@ namespace Avalonia.Controls.Presenters
         private Rect _caretBounds;
         private Point _navigationPosition;
         private string? _preeditText;
+        private TextRange? _compositionRegion;
 
         static TextPresenter()
         {
@@ -146,6 +156,12 @@ namespace Avalonia.Controls.Presenters
             set => SetAndRaise(PreeditTextProperty, ref _preeditText, value);
         }
 
+        public TextRange? CompositionRegion
+        {
+            get => _compositionRegion;
+            set => SetAndRaise(CompositionRegionProperty, ref _compositionRegion, value);
+        }
+
         /// <summary>
         /// Gets or sets the font family.
         /// </summary>
@@ -548,7 +564,20 @@ namespace Avalonia.Controls.Presenters
 
             var foreground = Foreground;
 
-            if (!string.IsNullOrEmpty(_preeditText))
+            if(_compositionRegion != null)
+            {
+                var preeditHighlight = new ValueSpan<TextRunProperties>(_compositionRegion?.Start ?? 0, _compositionRegion?.Length ?? 0,
+                        new GenericTextRunProperties(typeface, FontSize,
+                        foregroundBrush: foreground,
+                        textDecorations: TextDecorations.Underline));
+
+                textStyleOverrides = new[]
+                {
+                    preeditHighlight
+                };
+
+            }
+            else if (!string.IsNullOrEmpty(_preeditText))
             {
                 var preeditHighlight = new ValueSpan<TextRunProperties>(_caretIndex, _preeditText.Length,
                         new GenericTextRunProperties(typeface, FontSize,
@@ -911,6 +940,7 @@ namespace Avalonia.Controls.Presenters
                         break;
                     }
 
+                case nameof(CompositionRegion):
                 case nameof(Foreground):
                 case nameof(FontSize):
                 case nameof(FontStyle):
@@ -931,7 +961,6 @@ namespace Avalonia.Controls.Presenters
 
                 case nameof(PasswordChar):
                 case nameof(RevealPassword):
-
                 case nameof(FlowDirection):
                     {
                         InvalidateTextLayout();

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -5,6 +5,7 @@ using Avalonia.Media.TextFormatting;
 using Avalonia.Threading;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
+using static System.Net.Mime.MediaTypeNames;
 
 namespace Avalonia.Controls
 {
@@ -12,6 +13,7 @@ namespace Avalonia.Controls
     {
         private TextBox? _parent;
         private TextPresenter? _presenter;
+        private ITextEditable? _textEditable;
 
         public Visual TextViewVisual => _presenter!;
 
@@ -45,7 +47,7 @@ namespace Avalonia.Controls
         {
             get
             {
-                if(_presenter is null || _parent is null)
+                if (_presenter is null || _parent is null)
                 {
                     return default;
                 }
@@ -71,13 +73,70 @@ namespace Avalonia.Controls
             }
         }
 
+        public ITextEditable? TextEditable
+        {
+            get => _textEditable; set
+            {
+                if(_textEditable != null)
+                {
+                    _textEditable.TextChanged -= TextEditable_TextChanged;
+                    _textEditable.SelectionChanged -= TextEditable_SelectionChanged;
+                    _textEditable.CompositionChanged -= TextEditable_CompositionChanged;
+                }
+
+                _textEditable = value;
+
+                if(_textEditable != null)
+                {
+                    _textEditable.TextChanged += TextEditable_TextChanged;
+                    _textEditable.SelectionChanged += TextEditable_SelectionChanged;
+                    _textEditable.CompositionChanged += TextEditable_CompositionChanged;
+
+                    if (_presenter != null)
+                    {
+                        _textEditable.Text = _presenter.Text;
+                        _textEditable.SelectionStart = _presenter.SelectionStart;
+                        _textEditable.SelectionEnd = _presenter.SelectionEnd;
+                    }
+                }
+            }
+        }
+
+        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)
+            {
+                _parent.SelectionStart = _textEditable.SelectionStart;
+                _parent.SelectionEnd = _textEditable.SelectionEnd;
+            }
+        }
+
+        private void TextEditable_TextChanged(object? sender, EventArgs e)
+        {
+            if (_parent != null)
+            {
+                if (_parent.Text != _textEditable?.Text)
+                {
+                    _parent.Text = _textEditable?.Text;
+                }
+            }
+        }
+
         private static string GetTextLineText(TextLine textLine)
         {
             var builder = StringBuilderCache.Acquire(textLine.Length);
 
             foreach (var run in textLine.TextRuns)
             {
-                if(run.Length > 0)
+                if (run.Length > 0)
                 {
 #if NET6_0_OR_GREATER
                     builder.Append(run.Text.Span);
@@ -110,9 +169,18 @@ namespace Avalonia.Controls
             _presenter.PreeditText = text;
         }
 
+        public void SetComposingRegion(TextRange? region)
+        {
+            if (_presenter == null)
+            {
+                return;
+            }
+            _presenter.CompositionRegion = region;
+        }
+
         public void SelectInSurroundingText(int start, int end)
         {
-            if(_parent is null ||_presenter is null)
+            if (_parent is null || _presenter is null)
             {
                 return;
             }
@@ -125,21 +193,21 @@ namespace Avalonia.Controls
 
             var selectionStart = lineStart + start;
             var selectionEnd = lineStart + end;
-             
+
             _parent.SelectionStart = selectionStart;
             _parent.SelectionEnd = selectionEnd;
-        }    
-        
+        }
+
         public void SetPresenter(TextPresenter? presenter, TextBox? parent)
         {
-            if(_parent != null)
+            if (_parent != null)
             {
                 _parent.PropertyChanged -= OnParentPropertyChanged;
             }
 
             _parent = parent;
 
-            if(_parent != null)
+            if (_parent != null)
             {
                 _parent.PropertyChanged += OnParentPropertyChanged;
             }
@@ -148,16 +216,18 @@ namespace Avalonia.Controls
             {
                 _presenter.PreeditText = null;
 
-                _presenter.CaretBoundsChanged -= OnCaretBoundsChanged;             
+                _presenter.CompositionRegion = null;
+
+                _presenter.CaretBoundsChanged -= OnCaretBoundsChanged;
             }
-           
+
             _presenter = presenter;
-            
+
             if (_presenter != null)
             {
                 _presenter.CaretBoundsChanged += OnCaretBoundsChanged;
             }
-           
+
             TextViewVisualChanged?.Invoke(this, EventArgs.Empty);
 
             OnCaretBoundsChanged(this, EventArgs.Empty);
@@ -165,12 +235,33 @@ namespace Avalonia.Controls
 
         private void OnParentPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
-            if(e.Property == TextBox.SelectionStartProperty || e.Property == TextBox.SelectionEndProperty)
+            if (e.Property == TextBox.SelectionStartProperty || e.Property == TextBox.SelectionEndProperty)
             {
                 if (SupportsSurroundingText)
                 {
                     SurroundingTextChanged?.Invoke(this, e);
                 }
+                if (_textEditable != null)
+                {
+                    var value = (int)(e.NewValue ?? 0);
+                    if (e.Property == TextBox.SelectionStartProperty)
+                    {
+                        _textEditable.SelectionStart = value;
+                    }
+
+                    if (e.Property == TextBox.SelectionEndProperty)
+                    {
+                        _textEditable.SelectionEnd = value;
+                    }
+                }
+            }
+
+            if(e.Property == TextBox.TextProperty)
+            {
+                if(_textEditable != null)
+                {
+                    _textEditable.Text = (string?)e.NewValue;
+                }
             }
         }
 

src/Browser/Avalonia.Browser/AvaloniaView.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Reflection;
 using System.Runtime.InteropServices.JavaScript;
 using Avalonia.Browser.Interop;
@@ -15,6 +16,7 @@ using Avalonia.Platform;
 using Avalonia.Rendering.Composition;
 using Avalonia.Threading;
 using SkiaSharp;
+using static System.Runtime.CompilerServices.RuntimeHelpers;
 
 namespace Avalonia.Browser
 {
@@ -94,6 +96,7 @@ namespace Avalonia.Browser
 
             InputHelper.SubscribeTextEvents(
                 _inputElement,
+                OnBeforeInput,
                 OnTextInput,
                 OnCompositionStart,
                 OnCompositionUpdate,
@@ -316,6 +319,30 @@ namespace Avalonia.Browser
             return _topLevelImpl.RawTextEvent(data);
         }
 
+        private bool OnBeforeInput(JSObject arg, int start, int end)
+        {
+            var type = arg.GetPropertyAsString("inputType");
+            if (type != "deleteByComposition")
+            {
+                if (type == "deleteContentBackward")
+                {
+                    start = _inputElement.GetPropertyAsInt32("selectionStart");
+                    end = _inputElement.GetPropertyAsInt32("selectionEnd");
+                }
+                else
+                {
+                    start = -1;
+                    end = -1;
+                }
+            }
+
+            if(start != -1 && end != -1 && _client != null)
+            {
+                _client.SelectInSurroundingText(start, end);
+            }
+            return false;
+        }
+
         private bool OnCompositionStart (JSObject args)
         {
             if (_client == null)

src/Browser/Avalonia.Browser/Interop/InputHelper.cs

@@ -18,6 +18,8 @@ internal static partial class InputHelper
     [JSImport("InputHelper.subscribeTextEvents", AvaloniaModule.MainModuleName)]
     public static partial void SubscribeTextEvents(
         JSObject htmlElement,
+        [JSMarshalAs<JSType.Function<JSType.Object, JSType.Number, JSType.Number, JSType.Boolean>>]
+        Func<JSObject, int, int, bool> onBeforeInput,
         [JSMarshalAs<JSType.Function<JSType.String, JSType.String, JSType.Boolean>>]
         Func<string, string?, bool> onInput,
         [JSMarshalAs<JSType.Function<JSType.Object, JSType.Boolean>>]

src/Browser/Avalonia.Browser/webapp/modules/avalonia/input.ts

@@ -47,6 +47,7 @@ export class InputHelper {
 
     public static subscribeTextEvents(
         element: HTMLInputElement,
+        beforeInputCallback: (args: InputEvent, start: number, end: number) => boolean,
         inputCallback: (type: string, data: string | null) => boolean,
         compositionStartCallback: (args: CompositionEvent) => boolean,
         compositionUpdateCallback: (args: CompositionEvent) => boolean,
@@ -68,6 +69,25 @@ export class InputHelper {
         };
         element.addEventListener("compositionstart", compositionStartHandler);
 
+        const beforeInputHandler = (args: InputEvent) => {
+            const ranges = args.getTargetRanges();
+            let start = -1;
+            let end = -1;
+            if (ranges.length > 0) {
+                start = ranges[0].startOffset;
+                end = ranges[0].endOffset;
+            }
+
+            if (args.inputType === "insertCompositionText") {
+                start = 2;
+                end = start + 2;
+            }
+            if (beforeInputCallback(args, start, end)) {
+                args.preventDefault();
+            }
+        };
+        element.addEventListener("beforeinput", beforeInputHandler);
+
         const compositionUpdateHandler = (args: CompositionEvent) => {
             if (compositionUpdateCallback(args)) {
                 args.preventDefault();