Properly sync preedit

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -10,6 +10,7 @@ using Avalonia.Layout;
 using Avalonia.Media.Immutable;
 using Avalonia.Controls.Documents;
 using Avalonia.Input.TextInput;
+using Avalonia.Data;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -52,7 +53,7 @@ namespace Avalonia.Controls.Presenters
             AvaloniaProperty.RegisterDirect<TextPresenter, string?>(
                 nameof(Text),
                 o => o.Text,
-                (o, v) => o.Text = v);
+                (o, v) => o.Text = v, defaultBindingMode: BindingMode.OneWay);
 
         /// <summary>
         /// Defines the <see cref="PreeditText"/> property.
@@ -107,7 +108,7 @@ namespace Avalonia.Controls.Presenters
         private int _selectionStart;
         private int _selectionEnd;
         private bool _caretBlink;
-        private string? _text;
+        internal string? _text;
         private TextLayout? _textLayout;
         private Size _constraint;
 
@@ -526,22 +527,22 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
-        private string? GetText()
-        {
-            if (!string.IsNullOrEmpty(_preeditText))
-            {
-                if (string.IsNullOrEmpty(_text) || _caretIndex > _text.Length)
-                {
-                    return _preeditText;
-                }
+        //private string? GetText()
+        //{
+        //    if (!string.IsNullOrEmpty(_preeditText))
+        //    {
+        //        if (string.IsNullOrEmpty(_text) || _caretIndex > _text.Length)
+        //        {
+        //            return _preeditText;
+        //        }
 
-                var text = _text.Substring(0, _caretIndex) + _preeditText + _text.Substring(_caretIndex);
+        //        var text = _text.Substring(0, _caretIndex) + _preeditText + _text.Substring(_caretIndex);
 
-                return text;
-            }
+        //        return text;
+        //    }
 
-            return _text;
-        }
+        //    return _text;
+        //}
 
         /// <summary>
         /// Creates the <see cref="TextLayout"/> used to render the text.
@@ -551,7 +552,7 @@ namespace Avalonia.Controls.Presenters
         {
             TextLayout result;
 
-            var text = GetText();
+            var text = _text;
 
             var typeface = new Typeface(FontFamily, FontStyle, FontWeight);
 
@@ -851,7 +852,7 @@ namespace Avalonia.Controls.Presenters
             CaretChanged();
         }
 
-        private void UpdateCaret(CharacterHit characterHit, bool notify = true)
+        internal void UpdateCaret(CharacterHit characterHit, bool notify = true)
         {
             _lastCharacterHit = characterHit;
 
@@ -883,10 +884,6 @@ namespace Avalonia.Controls.Presenters
             {
                 SetAndRaise(CaretIndexProperty, ref _caretIndex, caretIndex);
             }
-            else
-            {
-                _caretIndex = caretIndex;
-            }
         }
 
         internal Rect GetCursorRectangle()
@@ -903,17 +900,6 @@ namespace Avalonia.Controls.Presenters
             _caretTimer.Tick -= CaretTimerTick;
         }
 
-        private CharacterHit GetCharacterHitFromTextPosition(int textPosition)
-        {
-            var lineIndex = TextLayout.GetLineIndexFromCharacterIndex(textPosition, true);
-
-            var textLine = TextLayout.TextLines[lineIndex];
-
-            var characterHit = textLine.GetNextCaretCharacterHit(new CharacterHit(textPosition - 1));
-
-            return characterHit;
-        }
-
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
             base.OnPropertyChanged(change);

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -1,6 +1,8 @@
 using System;
+using System.Diagnostics;
 using Avalonia.Controls.Presenters;
 using Avalonia.Input.TextInput;
+using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Threading;
 using Avalonia.Utilities;
@@ -75,7 +77,7 @@ namespace Avalonia.Controls
         {
             get => _textEditable; set
             {
-                if(_textEditable != null)
+                if (_textEditable != null)
                 {
                     _textEditable.TextChanged -= TextEditable_TextChanged;
                     _textEditable.SelectionChanged -= TextEditable_SelectionChanged;
@@ -84,7 +86,7 @@ namespace Avalonia.Controls
 
                 _textEditable = value;
 
-                if(_textEditable != null)
+                if (_textEditable != null)
                 {
                     _textEditable.TextChanged += TextEditable_TextChanged;
                     _textEditable.SelectionChanged += TextEditable_SelectionChanged;
@@ -110,7 +112,7 @@ namespace Avalonia.Controls
 
         private void TextEditable_SelectionChanged(object? sender, EventArgs e)
         {
-            if(_parent != null && _textEditable != null)
+            if (_parent != null && _textEditable != null)
             {
                 _parent.SelectionStart = _textEditable.SelectionStart;
                 _parent.SelectionEnd = _textEditable.SelectionEnd;
@@ -157,16 +159,53 @@ namespace Avalonia.Controls
 
         public event EventHandler? SurroundingTextChanged;
 
-        public void SetPreeditText(string? text)
+        private string? _presenterText;
+        private int _compositionStart;
+
+        public void SetPreeditText(string? preeditText)
         {
             if (_presenter == null || _parent == null)
             {
                 return;
             }
 
-            _presenter.CaretIndex = _parent.CaretIndex;
+            if (_presenterText is null)
+            {
+                _presenterText = _parent.Text ?? "";
+                _compositionStart = _parent.CaretIndex;
+            }
+
+            var text = GetText(preeditText);
+
+            Debug.WriteLine(text);
+
+            _presenter._text = text;
+
+            _presenter.PreeditText = preeditText;
+
+            _presenter.UpdateCaret(new CharacterHit(_compositionStart + (preeditText != null ? preeditText.Length : 0)), false);
+
+            if (string.IsNullOrEmpty(preeditText))
+            {
+                _presenterText = null;
+            }
+        }
+
+        private string? GetText(string? preeditText)
+        {
+            if (string.IsNullOrEmpty(preeditText))
+            {
+                return _presenterText;
+            }
+
+            if (string.IsNullOrEmpty(_presenterText))
+            {
+                return preeditText;
+            }
+
+            var text = _presenterText.Substring(0, _compositionStart) + preeditText + _presenterText.Substring(_compositionStart);
 
-            _presenter.PreeditText = text;
+            return text;
         }
 
         public void SetComposingRegion(TextRange? region)
@@ -175,6 +214,7 @@ namespace Avalonia.Controls
             {
                 return;
             }
+
             _presenter.CompositionRegion = region;
         }
 
@@ -256,9 +296,9 @@ namespace Avalonia.Controls
                 }
             }
 
-            if(e.Property == TextBox.TextProperty)
+            if (e.Property == TextBox.TextProperty)
             {
-                if(_textEditable != null)
+                if (_textEditable != null)
                 {
                     _textEditable.Text = (string?)e.NewValue;
                 }

src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs

@@ -713,13 +713,14 @@ namespace Avalonia.Win32
 
                         break;
                     }
+                case WindowsMessage.WM_IME_SELECT:
+                    break;
                 case WindowsMessage.WM_IME_CHAR:
                 case WindowsMessage.WM_IME_COMPOSITIONFULL:
                 case WindowsMessage.WM_IME_CONTROL:
                 case WindowsMessage.WM_IME_KEYDOWN:
                 case WindowsMessage.WM_IME_KEYUP:
                 case WindowsMessage.WM_IME_NOTIFY:
-                case WindowsMessage.WM_IME_SELECT:
                     break;
                 case WindowsMessage.WM_IME_STARTCOMPOSITION:
                     Imm32InputMethod.Current.IsComposing = true;