Touch Improvements to TextBox

src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs

@@ -33,6 +33,7 @@ public class ScrollGestureRecognizer : GestureRecognizer
         private TimeSpan _lastTime;
         private TimeSpan _inertiaStartTime;
         private int _currentInertiaGestureId;
+        private Point _delta;
 
         /// <summary>
         /// Defines the <see cref="CanHorizontallyScroll"/> property.
@@ -133,21 +134,30 @@ protected override void PointerMoved(PointerEventArgs e)
                         _trackedRootPoint = new Point(
                             _trackedRootPoint.X - (_trackedRootPoint.X >= rootPoint.X ? ScrollStartDistance : -ScrollStartDistance),
                             _trackedRootPoint.Y - (_trackedRootPoint.Y >= rootPoint.Y ? ScrollStartDistance : -ScrollStartDistance));
-
-                        Capture(e.Pointer);
                     }
                 }
 
                 if (_scrolling)
                 {
                     var vector = _trackedRootPoint - rootPoint;
 
-                    _velocityTracker?.AddPosition(TimeSpan.FromMilliseconds(e.Timestamp), _pointerPressedPoint - rootPoint);
+                    var oldDelta = _delta;
+                    _delta = _pointerPressedPoint - rootPoint;
+
+                    if (oldDelta == _delta)
+                        return;
+
+                    _velocityTracker?.AddPosition(TimeSpan.FromMilliseconds(e.Timestamp), _delta);
 
                     _lastMoveTimestamp = e.Timestamp;
-                    Target!.RaiseEvent(new ScrollGestureEventArgs(_gestureId, vector));
+                    var scrollEventArgs = new ScrollGestureEventArgs(_gestureId, vector);
+                    Target!.RaiseEvent(scrollEventArgs);
                     _trackedRootPoint = rootPoint;
-                    e.Handled = true;
+                    e.Handled = scrollEventArgs.Handled;
+                    if(e.Handled)
+                    {
+                        Capture(e.Pointer);
+                    }
                 }
             }
         }
@@ -166,7 +176,10 @@ void EndGesture()
                 _stopWatch?.Stop();
                 _stopWatch = null;
                 _inertia = default;
+                _delta = default;
                 _scrolling = false;
+                _velocityTracker?.Dispose();
+                _velocityTracker = null;
                 Target!.RaiseEvent(new ScrollGestureEndedEventArgs(_gestureId));
                 _gestureId = 0;
                 _lastMoveTimestamp = null;

src/Avalonia.Base/Input/GestureRecognizers/VelocityTracker.cs

@@ -59,7 +59,7 @@ internal record struct PointAtTime(bool Valid, Vector Point, TimeSpan Time);
     ///
     /// The quality of the velocity estimation will be better if more data points
     /// have been received.
-    internal class VelocityTracker
+    internal class VelocityTracker : IDisposable
     {
         private const int AssumePointerMoveStoppedMilliseconds = 40;
         private const int HistorySize = 20;
@@ -71,13 +71,16 @@ internal class VelocityTracker
         private readonly PointAtTime[] _samples = new PointAtTime[HistorySize];
         private int _index = 0;
 
+        private Stopwatch _sinceLastSample = new Stopwatch();
+
         /// <summary>
         /// Adds a position as the given time to the tracker.
         /// </summary>
         /// <param name="time"></param>
         /// <param name="position"></param>
         public void AddPosition(TimeSpan time, Vector position)
         {
+            _sinceLastSample.Restart();
             _index++;
             if (_index == HistorySize)
             {
@@ -94,6 +97,11 @@ public void AddPosition(TimeSpan time, Vector position)
         /// Returns null if there is no data on which to base an estimate.
         protected virtual VelocityEstimate? GetVelocityEstimate()
         {
+            if (_sinceLastSample.ElapsedMilliseconds > AssumePointerMoveStoppedMilliseconds)
+            {
+                return new VelocityEstimate(default, 1.0, default, default);
+            }
+
             Span<double> x = stackalloc double[HistorySize];
             Span<double> y = stackalloc double[HistorySize];
             Span<double> w = stackalloc double[HistorySize];
@@ -159,17 +167,6 @@ public void AddPosition(TimeSpan time, Vector position)
                     }
                 }
             }
-            else if(sampleCount > 1)
-            {
-                // Return linear velocity if we don't have enough samples
-                var distance = newestSample.Point - oldestSample.Point;
-                return new VelocityEstimate(
-                  PixelsPerSecond: new Vector(distance.X / duration.Milliseconds * 1000, distance.Y / duration.Milliseconds * 1000),
-                  Confidence: 1,
-                  Duration: duration,
-                  Offset: offset
-                );
-            }
 
             // We're unable to make a velocity estimate but we did have at least one
             // valid pointer position.
@@ -205,6 +202,11 @@ internal virtual Velocity GetFlingVelocity()
         {
             return GetVelocity().ClampMagnitude(MinFlingVelocity, MaxFlingVelocity);
         }
+
+        public void Dispose()
+        {
+            _sinceLastSample.Stop();
+        }
     }
 
     /// An nth degree polynomial fit to a dataset.
@@ -302,7 +304,7 @@ internal sealed class LeastSquaresSolver
             // Solve R B = Qt W Y to find B. This is easy because R is upper triangular.
             // We just work from bottom-right to top-left calculating B's coefficients.
             // "m" isn't expected to be bigger than HistorySize=20, so allocation on stack is safe.
-            Span<double> wy = stackalloc double[m];  
+            Span<double> wy = stackalloc double[m];
             for (int h = 0; h < m; h += 1)
             {
                 wy[h] = y[h] * w[h];
@@ -360,7 +362,7 @@ private static double Multiply(Span<double> v1, Span<double> v2)
             }
             return result;
         }
-        
+
         private static double Norm(Span<double> v)
         {
             return Math.Sqrt(Multiply(v, v));

src/Avalonia.Base/Platform/DefaultPlatformSettings.cs

@@ -14,11 +14,13 @@ namespace Avalonia.Platform
     [PrivateApi]
     public class DefaultPlatformSettings : IPlatformSettings
     {
+        private const int TouchTapSize = 10;
+        private const int TouchDoubleTapSize = 50; // Default TouchModeN_DtapDist value on win32
         public virtual Size GetTapSize(PointerType type)
         {
             return type switch
             {
-                PointerType.Touch or PointerType.Pen => new(10, 10),
+                PointerType.Touch or PointerType.Pen => new(TouchTapSize, TouchTapSize),
                 _ => new(4, 4),
             };
         }
@@ -27,7 +29,7 @@ public virtual Size GetDoubleTapSize(PointerType type)
         {
             return type switch
             {
-                PointerType.Touch or PointerType.Pen => new(16, 16),
+                PointerType.Touch or PointerType.Pen => new(TouchDoubleTapSize, TouchDoubleTapSize),
                 _ => new(4, 4),
             };
         }

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -535,6 +535,8 @@ private void OnScrollGesture(object? sender, ScrollGestureEventArgs e)
                 var scrollable = Child as ILogicalScrollable;
                 var isLogical = scrollable?.IsLogicalScrollEnabled == true;
                 var logicalScrollItemSize = new Vector(1, 1);
+                var canXScroll = false;
+                var canYScroll = false;
 
                 double x = Offset.X;
                 double y = Offset.Y;
@@ -565,6 +567,8 @@ private void OnScrollGesture(object? sender, ScrollGestureEventArgs e)
                     y += dy;
                     y = Math.Max(y, 0);
                     y = Math.Min(y, Extent.Height - Viewport.Height);
+
+                    canYScroll = dy != 0;
                 }
 
                 if (Extent.Width > Viewport.Width)
@@ -581,6 +585,8 @@ private void OnScrollGesture(object? sender, ScrollGestureEventArgs e)
                     x += dx;
                     x = Math.Max(x, 0);
                     x = Math.Min(x, Extent.Width - Viewport.Width);
+
+                    canXScroll = dx != 0;
                 }
 
                 if (isLogical)
@@ -615,6 +621,12 @@ private void OnScrollGesture(object? sender, ScrollGestureEventArgs e)
 
                 e.Handled = !IsScrollChainingEnabled || offsetChanged;
 
+                if(!e.Handled)
+                {
+                    // Gesture may cause an overscroll so we mark the event as handled if it did.
+                    e.Handled = canXScroll || canYScroll;
+                }
+
                 e.ShouldEndScrollGesture = !IsScrollChainingEnabled && !offsetChanged;
             }
         }

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -1,14 +1,14 @@
 using System;
 using System.Collections.Generic;
-using System.Data;
 using Avalonia.Controls.Documents;
 using Avalonia.Controls.Primitives;
-using Avalonia.Interactivity;
+using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Metadata;
+using Avalonia.Platform;
 using Avalonia.Threading;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
@@ -334,6 +334,7 @@ public int SelectionEnd
         protected override bool BypassFlowDirectionPolicies => true;
 
         internal TextSelectionHandleCanvas? TextSelectionHandleCanvas { get; set; }
+        internal TextBoxTextInputMethodClient? CurrentImClient { get; set; }
 
         /// <summary>
         /// Creates the <see cref="TextLayout"/> used to render the text.
@@ -496,7 +497,6 @@ public void ShowCaret()
         public void HideCaret()
         {
             _caretBlink = false;
-            RemoveTextSelectionCanvas();
             _caretTimer?.Stop();
             InvalidateTextLayout();
         }
@@ -944,7 +944,7 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
             ResetCaretTimer();
         }
 
-        private void EnsureTextSelectionLayer()
+        internal void EnsureTextSelectionLayer()
         {
             if (TextSelectionHandleCanvas == null)
             {
@@ -963,7 +963,7 @@ private void EnsureTextSelectionLayer()
                 _layer?.Add(TextSelectionHandleCanvas);
         }
 
-        private void RemoveTextSelectionCanvas()
+        internal void RemoveTextSelectionCanvas()
         {
             if(_layer != null && TextSelectionHandleCanvas is { } canvas)
             {
@@ -977,11 +977,8 @@ private void RemoveTextSelectionCanvas()
         protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
         {
             base.OnDetachedFromVisualTree(e);
-            if (TextSelectionHandleCanvas is { } c)
-            {
-                _layer?.Remove(c);
-                c.SetPresenter(null);
-            }
+
+            RemoveTextSelectionCanvas();
 
             if (_caretTimer != null)
             {
@@ -1026,15 +1023,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 OnPreeditChanged(PreeditText, PreeditTextCursorPosition);
             }
 
-            if(change.Property == TextProperty)
-            {
-                if (!string.IsNullOrEmpty(PreeditText))
-                {
-                    SetCurrentValue(PreeditTextProperty, null);
-                }
-            }
-
-            if(change.Property == CaretIndexProperty)
+            if(change.Property == TextProperty || change.Property == CaretIndexProperty)
             {
                 if (!string.IsNullOrEmpty(PreeditText))
                 {
@@ -1067,7 +1056,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 case nameof(SelectionStart):
                 case nameof(SelectionEnd):
                 case nameof(SelectionForegroundBrush):
-                case nameof(ShowSelectionHighlightProperty):
+                case nameof(ShowSelectionHighlight):
 
                 case nameof(PasswordChar):
                 case nameof(RevealPassword):