Remove TextBefore, TextAfter

Set surroundingText relative to current line
Raise SurroundingTextChanged on CursorRectangleChanged

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

@@ -49,16 +49,7 @@ namespace Avalonia.Input.TextInput
         /// <param name="afterLength">The length after current selection.</param>
         void DeleteSurroundingText(int beforeLength, int afterLength);
 
-        /// <summary>
-        /// Returns the text before the cursor. Must return a non-empty string if cursor is not at the beginning of the text entry
-        /// </summary>
-        string? TextBeforeCursor { get; }
-        /// <summary>
-        /// Returns the text before the cursor. Must return a non-empty string if cursor is not at the end of the text entry
-        /// </summary>
-        string? TextAfterCursor { get; }
-
-        public void SelectInSurroundingText(int start, int end);
+        void SelectInSurroundingText(int start, int end);
     }
 
     public struct TextInputMethodSurroundingText

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -1,9 +1,6 @@
 using System;
-using System.Diagnostics;
 using Avalonia.Controls.Presenters;
-using Avalonia.Input;
 using Avalonia.Input.TextInput;
-using Avalonia.Media;
 using Avalonia.Threading;
 using Avalonia.VisualTree;
 
@@ -14,6 +11,12 @@ namespace Avalonia.Controls
         private TextBox? _parent;
         private TextPresenter? _presenter;
 
+        public IVisual TextViewVisual => _presenter!;
+
+        public bool SupportsPreedit => true;
+
+        public bool SupportsSurroundingText => true;
+
         public Rect CursorRectangle
         {
             get
@@ -36,10 +39,41 @@ namespace Avalonia.Controls
             }
         }
 
-        public event EventHandler? CursorRectangleChanged;
-        public IVisual TextViewVisual => _presenter!;
+        public TextInputMethodSurroundingText SurroundingText
+        {
+            get
+            {
+                if(_presenter is null)
+                {
+                    return default;
+                }
+
+                var lineIndex = _presenter.TextLayout.GetLineIndexFromCharacterIndex(_presenter.CaretIndex, false);
+
+                var textLine = _presenter.TextLayout.TextLines[lineIndex];
+
+                var lineStart = textLine.FirstTextSourceIndex;
+
+                var lineText = _presenter.Text?.Substring(lineStart, textLine.Length);
+
+                var anchorOffset = Math.Max(0, _presenter.SelectionStart - lineStart);
+
+                var cursorOffset = Math.Max(0, _presenter.SelectionEnd - lineStart);
+
+                return new TextInputMethodSurroundingText
+                {
+                    Text = lineText ?? "",                   
+                    AnchorOffset = anchorOffset,
+                    CursorOffset = cursorOffset
+                };
+            }
+        }
+
         public event EventHandler? TextViewVisualChanged;
-        public bool SupportsPreedit => true;
+
+        public event EventHandler? CursorRectangleChanged;
+
+        public event EventHandler? SurroundingTextChanged;
 
         public void SetPreeditText(string? text)
         {
@@ -51,58 +85,27 @@ namespace Avalonia.Controls
             _presenter.PreeditText = text;
         }
 
-        public bool SupportsSurroundingText => true;
-
-        public event EventHandler? SurroundingTextChanged;
-
-        public TextInputMethodSurroundingText SurroundingText => new()
-        {
-            Text = _presenter?.Text ?? "",
-            CursorOffset = _presenter?.CaretIndex ?? 0,
-            AnchorOffset = _presenter?.SelectionStart ?? 0
-        };
-
-        public string? TextBeforeCursor => null;
-        
-        public string? TextAfterCursor => null;
         public void SelectInSurroundingText(int start, int end)
         {
             if(_parent == null)
-                return;
-            // TODO: Account for the offset
-            _parent.SelectionStart = start;
-            _parent.SelectionEnd = end;
-        }
-
-        private void OnCaretBoundsChanged(object? sender, EventArgs e) =>
-            Dispatcher.UIThread.Post(() => CursorRectangleChanged?.Invoke(this, EventArgs.Empty), DispatcherPriority.Input);
-        
-        private void OnTextBoxPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
-        {
-            if (e.Property == TextBox.TextProperty || e.Property == TextBox.SelectionStartProperty ||
-                e.Property == TextBox.SelectionEndProperty)
             {
-                if (string.IsNullOrEmpty(_presenter?.PreeditText))
-                {
-                    SurroundingTextChanged?.Invoke(this, EventArgs.Empty);
-                }
+                return;
             }
-        }
 
+            //start and end are relative to surroundingText
+            var surroundingText = SurroundingText;
+
+            var selectionStart = surroundingText.AnchorOffset + start;
+            var selectionEnd = surroundingText.AnchorOffset + end;
+             
+            _parent.SelectionStart = selectionStart;
+            _parent.SelectionEnd = selectionEnd;
+        }    
+        
         public void SetPresenter(TextPresenter? presenter, TextBox? parent)
         {
-            if (_parent != null)
-            {
-                _parent.PropertyChanged -= OnTextBoxPropertyChanged;
-            }
-            
             _parent = parent;
 
-            if (_parent != null)
-            {
-                _parent.PropertyChanged += OnTextBoxPropertyChanged;
-            }
-
             if (_presenter != null)
             {
                 _presenter.PreeditText = null;
@@ -118,7 +121,8 @@ namespace Avalonia.Controls
             }
            
             TextViewVisualChanged?.Invoke(this, EventArgs.Empty);
-            CursorRectangleChanged?.Invoke(this, EventArgs.Empty);
+
+            OnCaretBoundsChanged(this, EventArgs.Empty);
         }
 
         public void DeleteSurroundingText(int beforeLength, int afterLength)
@@ -133,5 +137,19 @@ namespace Avalonia.Controls
                 _parent.DeleteSelection(true);
             }
         }
+
+        private void OnCaretBoundsChanged(object? sender, EventArgs e)
+        {
+            Dispatcher.UIThread.Post(() =>
+            {
+                if (SupportsSurroundingText)
+                {
+                    SurroundingTextChanged?.Invoke(sender, e);
+                }
+
+                CursorRectangleChanged?.Invoke(sender, e);
+
+            }, DispatcherPriority.Input);
+        }
     }
 }

src/Web/Avalonia.Web.Blazor/AvaloniaView.razor.cs

@@ -349,12 +349,12 @@ namespace Avalonia.Web.Blazor
                     IsComposing = true;
                     break;
                 case WebCompositionEventArgs.WebCompositionEventType.Update:
-                    _client?.SetPreeditText(e.Data);
+                    _client.SetPreeditText(e.Data);
                     break;
                 case WebCompositionEventArgs.WebCompositionEventType.End:
                     IsComposing = false;
-                    _client?.SetPreeditText(null);
-                    _topLevelImpl.RawTextEvent(e.Data);
+                    _client.SetPreeditText(null);
+                    _topLevelImpl.RawTextEvent(e.Data);              
                     break;
             }
         }
@@ -471,7 +471,7 @@ namespace Avalonia.Web.Blazor
 
         private void SurroundingTextChanged(object? sender, EventArgs e)
         {
-            if(_client != null && IsComposing)
+            if(_client != null)
             {
                 var surroundingText = _client.SurroundingText;
                 
@@ -484,15 +484,8 @@ namespace Avalonia.Web.Blazor
             _inputHelper?.Focus();
             var bounds = new PixelRect((int)rect.X, (int) rect.Y, (int) rect.Width, (int) rect.Height);
             
-            if (_client != null)
-            {
-                var surroundingText = _client.SurroundingText;
-
-                _inputHelper?.SetSurroundingText(surroundingText.Text, surroundingText.AnchorOffset,
-                    surroundingText.CursorOffset);
-                
-                _inputHelper?.SetBounds(bounds, surroundingText.CursorOffset);
-            }
+            _inputHelper?.SetBounds(bounds, _client?.SurroundingText.CursorOffset ?? 0);
+            _inputHelper?.Focus();
         }
 
         public void SetOptions(TextInputOptions options)