Android - Initial attempt to fix focus management and implement SurroundingText

src/Android/Avalonia.Android/AndroidInputMethod.cs

@@ -15,12 +15,12 @@ namespace Avalonia.Android
     internal interface IAndroidInputMethod
     {
         public ITextInputMethodClient Client { get; }
-        
+
         public bool IsActive { get; }
     }
-    
+
     class AndroidInputMethod<TView> : ITextInputMethodImpl, IAndroidInputMethod
-        where TView: View, IInitEditorInfo
+        where TView : View, IInitEditorInfo
     {
         private readonly TView _host;
         private readonly InputMethodManager _imm;
@@ -51,16 +51,42 @@ namespace Avalonia.Android
 
         public void SetClient(ITextInputMethodClient client)
         {
+            if(client is null)
+            {
+                _inputConnection?.SetComposingText("", 0);
+            }
+
+            if (_client != null)
+            {
+                _client.SurroundingTextChanged -= SurroundingTextChanged;
+            }
+
+            Reset();
+
             _client = client;
-            
+
             if (IsActive)
             {
+                _client.SurroundingTextChanged += SurroundingTextChanged;
+
                 _host.RequestFocus();
-                Reset();
+
                 _imm.ShowSoftInput(_host, ShowFlags.Implicit);
             }
             else
-                _imm.HideSoftInputFromWindow(_host.WindowToken, HideSoftInputFlags.None);         
+            {
+                _imm.HideSoftInputFromWindow(_host.WindowToken, HideSoftInputFlags.None);
+            }
+        }
+
+        private void SurroundingTextChanged(object sender, EventArgs e)
+        {
+            if (IsActive)
+            {
+                var surroundingText = Client.SurroundingText;
+
+                _imm.UpdateSelection(_host, surroundingText.AnchorOffset, surroundingText.CursorOffset, surroundingText.AnchorOffset, surroundingText.CursorOffset);
+            }
         }
 
         public void SetCursorRect(Rect rect)
@@ -69,10 +95,12 @@ namespace Avalonia.Android
 
         public void SetOptions(TextInputOptions options)
         {
-            _inputConnection = new InputConnectionImpl(_host, this);
-
             _host.InitEditorInfo((_host, outAttrs) =>
             {
+                _inputConnection?.CommitText("", 0);
+
+                _inputConnection = new InputConnectionImpl(_host, this);
+
                 outAttrs.InputType = options.ContentType switch
                 {
                     TextInputContentType.Email => global::Android.Text.InputTypes.TextVariationEmailAddress,

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

@@ -13,6 +13,7 @@ using Avalonia.Android.Platform.Specific;
 using Avalonia.Android.Platform.Specific.Helpers;
 using Avalonia.Android.Platform.Storage;
 using Avalonia.Controls;
+using Avalonia.Controls.Documents;
 using Avalonia.Controls.Platform;
 using Avalonia.Controls.Platform.Surfaces;
 using Avalonia.Input;
@@ -25,6 +26,7 @@ using Avalonia.Platform.Storage;
 using Avalonia.Rendering;
 using Avalonia.Rendering.Composition;
 using Java.Lang;
+using static System.Net.Mime.MediaTypeNames;
 
 namespace Avalonia.Android.Platform.SkiaPlatform
 {
@@ -36,7 +38,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         private readonly AndroidKeyboardEventsHelper<TopLevelImpl> _keyboardHelper;
         private readonly AndroidMotionEventsHelper _pointerHelper;
-        private readonly ITextInputMethodImpl _textInputMethod;
+        private readonly AndroidInputMethod<ViewImpl> _textInputMethod;
         private ViewImpl _view;
 
         public TopLevelImpl(AvaloniaView avaloniaView, bool placeOnTop = false)
@@ -211,7 +213,6 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             }
 
             private Func<View, EditorInfo, InputConnectionImpl> _initEditorInfo;
-            protected InputConnectionImpl _inputConnection;
 
             public void InitEditorInfo(Func<View, EditorInfo, InputConnectionImpl> init)
             {
@@ -257,7 +258,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         }
     }
 
-    internal class InputConnectionImpl: BaseInputConnection
+    internal class InputConnectionImpl: BaseInputConnection, IInputConnection
     {
         private readonly IAndroidInputMethod _inputMethod;
 
@@ -271,11 +272,93 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         {
         }
 
+        public string CompositionText { get; private set; }
+
+        public override bool SetComposingRegion(int start, int end)
+        {
+            if (_inputMethod.IsActive)
+            {
+                var surroundingText = _inputMethod.Client.SurroundingText;
+
+                System.Diagnostics.Debug.WriteLine($"Composing Region: [{start}|{end}] {surroundingText.Text?.Substring(start, end - start)}");
+            }
+
+            return base.SetComposingRegion(start, end);
+        }
+
+        public override bool CommitCorrection(CorrectionInfo correctionInfo)
+        {
+            return base.CommitCorrection(correctionInfo);
+        }
+
+        public override bool DeleteSurroundingTextInCodePoints(int beforeLength, int afterLength)
+        {
+            return base.DeleteSurroundingTextInCodePoints(beforeLength, afterLength);
+        }
+
+        public override bool DeleteSurroundingText(int beforeLength, int afterLength)
+        {
+            if (_inputMethod.IsActive && _inputMethod.Client.SupportsSurroundingText)
+            {
+                _inputMethod.Client.DeleteSurroundingText(beforeLength, afterLength);
+            }
+          
+            return base.DeleteSurroundingText(beforeLength, afterLength);
+        }
+
+        public override ICharSequence GetTextBeforeCursorFormatted(int length, [GeneratedEnum] GetTextFlags flags)
+        {
+            if (_inputMethod.IsActive)
+            {
+                var surroundingText = _inputMethod.Client.SurroundingText;
+
+                if (_inputMethod.IsActive && !string.IsNullOrEmpty(surroundingText.Text))
+                {
+                    var start = System.Math.Max(surroundingText.CursorOffset - length, 0);
+
+                    var end = System.Math.Min(start + length, surroundingText.CursorOffset);
+
+                    var text = surroundingText.Text.Substring(start, end - start);
+
+                    System.Diagnostics.Debug.WriteLine($"Text Before: {text}");
+
+                    return new Java.Lang.String(text);
+                }
+            }
+
+            return base.GetTextBeforeCursorFormatted(length, flags);
+        }
+
+        public override ICharSequence GetTextAfterCursorFormatted(int length, [GeneratedEnum] GetTextFlags flags)
+        {
+            if (_inputMethod.IsActive)
+            {
+                var surroundingText = _inputMethod.Client.SurroundingText;
+
+                if (_inputMethod.IsActive && !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);
+
+                    System.Diagnostics.Debug.WriteLine($"Text After: {text}");
+
+                    return new Java.Lang.String(text);
+                }
+            }
+
+            return base.GetTextAfterCursorFormatted(length, flags);
+        }
+
         public override bool SetComposingText(ICharSequence text, int newCursorPosition)
         {
+            CompositionText = text.ToString();
+
             if (_inputMethod.IsActive)
             {
-                _inputMethod.Client.SetPreeditText(text.ToString());
+                _inputMethod.Client.SetPreeditText(CompositionText);
             }
 
             return base.SetComposingText(text, newCursorPosition);
@@ -283,6 +366,8 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public override bool CommitText(ICharSequence text, int newCursorPosition)
         {
+            CompositionText = null;
+
             if (_inputMethod.IsActive)
             {
                 _inputMethod.Client.SetPreeditText(null);
@@ -290,5 +375,17 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
             return base.CommitText(text, newCursorPosition);
         }
+
+        public override bool FinishComposingText()
+        {
+            CompositionText = null;
+
+            if (_inputMethod.IsActive)
+            {
+                _inputMethod.Client.SetPreeditText(CompositionText);
+            }
+
+            return base.FinishComposingText();
+        }
     }
 }

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

@@ -41,6 +41,14 @@ namespace Avalonia.Input.TextInput
         /// Should be fired when surrounding text changed
         /// </summary>
         event EventHandler? SurroundingTextChanged;
+
+        /// <summary>
+        /// Deletes specified length before and after current selection.
+        /// </summary>
+        /// <param name="beforeLength">The length before current selection.</param>
+        /// <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>

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -9,7 +9,6 @@ using Avalonia.VisualTree;
 using Avalonia.Layout;
 using Avalonia.Media.Immutable;
 using Avalonia.Controls.Documents;
-using Avalonia.Media.TextFormatting.Unicode;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -100,6 +99,7 @@ namespace Avalonia.Controls.Presenters
         private Rect _caretBounds;
         private Point _navigationPosition;
         private string? _preeditText;
+        private CharacterHit _compositionStartHit = new CharacterHit(-1);
 
         static TextPresenter()
         {
@@ -235,7 +235,7 @@ namespace Avalonia.Controls.Presenters
 
                 _textLayout = CreateTextLayout();
 
-                UpdateCaret(_lastCharacterHit);
+                UpdateCaret(_lastCharacterHit, false);
 
                 return _textLayout;
             }
@@ -532,8 +532,8 @@ namespace Avalonia.Controls.Presenters
             {
                 var preeditHighlight = new ValueSpan<TextRunProperties>(_caretIndex, _preeditText.Length,
                         new GenericTextRunProperties(typeface, FontSize,
-                        foregroundBrush: foreground/*,
+                        foregroundBrush: foreground,
-                        textDecorations: TextDecorations.Underline*/));
+                        textDecorations: TextDecorations.Underline));
 
                 textStyleOverrides = new[]
                 {
@@ -573,7 +573,6 @@ namespace Avalonia.Controls.Presenters
             InvalidateMeasure();
         }
 
-
         protected override Size MeasureOverride(Size availableSize)
         {
             _constraint = availableSize;
@@ -800,7 +799,7 @@ namespace Avalonia.Controls.Presenters
             CaretChanged();
         }
 
-        private void UpdateCaret(CharacterHit characterHit)
+        private void UpdateCaret(CharacterHit characterHit, bool updateCaretIndex = true)
         {
             _lastCharacterHit = characterHit;
 
@@ -828,7 +827,10 @@ namespace Avalonia.Controls.Presenters
                 CaretBoundsChanged?.Invoke(this, EventArgs.Empty);
             }
 
-            SetAndRaise(CaretIndexProperty, ref _caretIndex, caretIndex);
+            if (updateCaretIndex)
+            {
+                SetAndRaise(CaretIndexProperty, ref _caretIndex, caretIndex);
+            }
         }
 
         internal Rect GetCursorRectangle()
@@ -845,12 +847,48 @@ namespace Avalonia.Controls.Presenters
             _caretTimer.Tick -= CaretTimerTick;
         }
 
+        protected void OnPreeditTextChanged(string? preeditText)
+        {
+            InvalidateTextLayout();
+
+            if (preeditText is null)
+            {
+                _compositionStartHit = new CharacterHit(-1);
+            }
+            else
+            {
+                if (_compositionStartHit.FirstCharacterIndex == -1)
+                {
+                    _compositionStartHit = _lastCharacterHit;
+                }
+            }
+
+            if (_compositionStartHit.FirstCharacterIndex != -1)
+            {
+                var textPosition = _compositionStartHit.FirstCharacterIndex + _compositionStartHit.TrailingLength + preeditText?.Length ?? 0;
+
+                var lineIndex = TextLayout.GetLineIndexFromCharacterIndex(textPosition, true);
+
+                var textLine = TextLayout.TextLines[lineIndex];
+
+                var characterHit = textLine.GetNextCaretCharacterHit(new CharacterHit(textPosition - 1));
+
+                UpdateCaret(characterHit, false);
+            }
+        }
+
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
             base.OnPropertyChanged(change);
 
             switch (change.Property.Name)
             {
+                case nameof(PreeditText):
+                    {
+                        OnPreeditTextChanged(change.NewValue as string);
+                        break;
+                    }
+
                 case nameof(Foreground):
                 case nameof(FontSize):
                 case nameof(FontStyle):
@@ -859,7 +897,6 @@ namespace Avalonia.Controls.Presenters
                 case nameof(FontStretch):
 
                 case nameof(Text):
-                case nameof(PreeditText):
                 case nameof(TextAlignment):
                 case nameof(TextWrapping):
 

src/Avalonia.Controls/TextBox.cs

@@ -1482,7 +1482,7 @@ namespace Avalonia.Controls
             SelectionEnd = Text?.Length ?? 0;
         }
 
-        private bool DeleteSelection(bool raiseTextChanged = true)
+        internal bool DeleteSelection(bool raiseTextChanged = true)
         {
             if (IsReadOnly)
                 return true;

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -3,6 +3,7 @@ using System.Diagnostics;
 using Avalonia.Controls.Presenters;
 using Avalonia.Input;
 using Avalonia.Input.TextInput;
+using Avalonia.Media;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
@@ -56,7 +57,7 @@ namespace Avalonia.Controls
         public TextInputMethodSurroundingText SurroundingText => new()
         {
             Text = _presenter?.Text ?? "",
-            CursorOffset = _presenter?.CaretIndex ?? 0,
+            CursorOffset = _presenter?.SelectionEnd ?? 0,
             AnchorOffset = _presenter?.SelectionStart ?? 0
         };
 
@@ -78,10 +79,14 @@ namespace Avalonia.Controls
         {
             if (e.Property == TextBox.TextProperty || e.Property == TextBox.SelectionStartProperty ||
                 e.Property == TextBox.SelectionEndProperty)
-                SurroundingTextChanged?.Invoke(this, EventArgs.Empty);
+            {
+                if (string.IsNullOrEmpty(_presenter?.PreeditText))
+                {
+                    SurroundingTextChanged?.Invoke(this, EventArgs.Empty);
+                }
+            }
         }
 
-
         public void SetPresenter(TextPresenter? presenter, TextBox? parent)
         {
             if (_parent != null)
@@ -98,6 +103,8 @@ namespace Avalonia.Controls
 
             if (_presenter != null)
             {
+                _presenter.PreeditText = null;
+
                 _presenter.CaretBoundsChanged -= OnCaretBoundsChanged;
             }
            
@@ -107,14 +114,22 @@ namespace Avalonia.Controls
             {
                 _presenter.CaretBoundsChanged += OnCaretBoundsChanged;
             }
+           
+            TextViewVisualChanged?.Invoke(this, EventArgs.Empty);
+            CursorRectangleChanged?.Invoke(this, EventArgs.Empty);
+        }
 
-            if(presenter == null)
+        public void DeleteSurroundingText(int beforeLength, int afterLength)
+        {
+            if (_parent != null && _presenter != null && string.IsNullOrEmpty(_presenter.PreeditText))
             {
-                SetPreeditText(null);
+                var start = _presenter.SelectionStart;
+
+                _parent.SelectionStart = start - beforeLength;
+                _parent.SelectionEnd = start + afterLength;
+
+                _parent.DeleteSelection(true);
             }
-            
-            TextViewVisualChanged?.Invoke(this, EventArgs.Empty);
-            CursorRectangleChanged?.Invoke(this, EventArgs.Empty);
         }
     }
 }