improve:多指书写

优化性能

Ink Canvas/Helpers/MultiTouchInput.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Windows;
 using System.Windows.Ink;
 using System.Windows.Input;
@@ -8,18 +9,19 @@ namespace Ink_Canvas.Helpers
 {
     public class VisualCanvas : FrameworkElement
     {
+        private readonly List<DrawingVisual> _visuals = new List<DrawingVisual>();
+
         protected override Visual GetVisualChild(int index)
         {
-            return Visual;
+            if (index < 0 || index >= _visuals.Count)
+                throw new ArgumentOutOfRangeException(nameof(index));
+            return _visuals[index];
         }
 
-        protected override int VisualChildrenCount => 1;
+        protected override int VisualChildrenCount => _visuals.Count;
 
-        public VisualCanvas(DrawingVisual visual)
+        public VisualCanvas()
         {
-            Visual = visual;
-            AddVisualChild(visual);
-            
             CacheMode = new BitmapCache();
             
             RenderOptions.SetBitmapScalingMode(this, BitmapScalingMode.LowQuality); 
@@ -27,17 +29,32 @@ namespace Ink_Canvas.Helpers
             RenderOptions.SetCachingHint(this, CachingHint.Cache); 
         }
 
-        public DrawingVisual Visual { get; }
+        public void AddVisual(DrawingVisual visual)
+        {
+            if (visual == null) return;
+            _visuals.Add(visual);
+            AddVisualChild(visual);
+        }
+        public void Clear()
+        {
+            foreach (var visual in _visuals)
+            {
+                RemoveVisualChild(visual);
+            }
+            _visuals.Clear();
+        }
+
+        public IReadOnlyList<DrawingVisual> Visuals => _visuals;
     }
 
     /// <summary>
     /// 用于显示笔迹的类 
     /// </summary>
-    public class StrokeVisual : DrawingVisual
+    public class StrokeVisual
     {
-        private bool _needsRedraw = true;
+        private int _lastDrawnPointCount = 0; 
-        private int _lastPointCount = 0;
+        private const int INCREMENTAL_DRAW_THRESHOLD = 2; 
-        private const int REDRAW_THRESHOLD = 3;
+        private VisualCanvas _visualCanvas; 
 
         /// <summary>
         ///     创建显示笔迹的类
@@ -59,10 +76,6 @@ namespace Ink_Canvas.Helpers
         public StrokeVisual(DrawingAttributes drawingAttributes)
         {
             _drawingAttributes = drawingAttributes;
-
-            RenderOptions.SetBitmapScalingMode(this, BitmapScalingMode.LowQuality); 
-            RenderOptions.SetEdgeMode(this, EdgeMode.Aliased); 
-            RenderOptions.SetCachingHint(this, CachingHint.Cache); 
         }
 
         /// <summary>
@@ -70,6 +83,14 @@ namespace Ink_Canvas.Helpers
         /// </summary>
         public Stroke Stroke { set; get; }
 
+        /// <summary>
+        /// 设置关联的VisualCanvas
+        /// </summary>
+        public void SetVisualCanvas(VisualCanvas visualCanvas)
+        {
+            _visualCanvas = visualCanvas;
+        }
+
         /// <summary>
         /// 在笔迹中添加点
         /// </summary>
@@ -80,16 +101,61 @@ namespace Ink_Canvas.Helpers
             {
                 var collection = new StylusPointCollection { point };
                 Stroke = new Stroke(collection) { DrawingAttributes = _drawingAttributes };
-                _lastPointCount = 1;
             }
             else
             {
                 Stroke.StylusPoints.Add(point);
-                _lastPointCount++;
+            }
+        }
+
+        /// <summary>
+        /// 绘制点段到新的DrawingVisual
+        /// </summary>
+        private void DrawSegmentToNewVisual(int startIndex, int endIndex)
+        {
+            if (Stroke == null || Stroke.StylusPoints.Count == 0 || _visualCanvas == null) return;
+            if (startIndex >= endIndex || startIndex < 0 || endIndex > Stroke.StylusPoints.Count) return;
+
+            var points = Stroke.StylusPoints;
+            var drawingAttributes = Stroke.DrawingAttributes;
+            
+            // 创建新的DrawingVisual用于绘制这个点段
+            var segmentVisual = new DrawingVisual();
+            
+            RenderOptions.SetBitmapScalingMode(segmentVisual, BitmapScalingMode.LowQuality);
+            RenderOptions.SetEdgeMode(segmentVisual, EdgeMode.Aliased);
+            RenderOptions.SetCachingHint(segmentVisual, CachingHint.Cache);
+
+            using (var dc = segmentVisual.RenderOpen())
+            {
+                var pen = new Pen(new SolidColorBrush(drawingAttributes.Color), drawingAttributes.Width);
+                pen.StartLineCap = PenLineCap.Round;
+                pen.EndLineCap = PenLineCap.Round;
+                pen.LineJoin = PenLineJoin.Round;
+
+                // 绘制指定范围内的点段
+                if (endIndex - startIndex >= 2)
+                {
+                    // 多个点，绘制线段
+                    for (int i = startIndex; i < endIndex - 1 && i < points.Count - 1; i++)
+                    {
+                        var startPoint = new Point(points[i].X, points[i].Y);
+                        var endPoint = new Point(points[i + 1].X, points[i + 1].Y);
+                        dc.DrawLine(pen, startPoint, endPoint);
+                    }
+                }
+                else if (endIndex - startIndex == 1 && startIndex < points.Count)
+                {
+                    // 只有一个点，绘制圆点
+                    var brush = new SolidColorBrush(drawingAttributes.Color);
+                    var point = points[startIndex];
+                    dc.DrawEllipse(brush, null, new Point(point.X, point.Y), 
+                        drawingAttributes.Width / 2, drawingAttributes.Height / 2);
+                }
             }
 
-            // 标记需要重绘
+            // 将新的DrawingVisual添加到VisualCanvas中
-            _needsRedraw = true;
+            _visualCanvas.AddVisual(segmentVisual);
         }
 
         /// <summary>
@@ -97,22 +163,35 @@ namespace Ink_Canvas.Helpers
         /// </summary>
         public void Redraw()
         {
-            if (!_needsRedraw || Stroke == null) return;
+            if (Stroke == null || _visualCanvas == null) return;
 
-            if (_lastPointCount % REDRAW_THRESHOLD != 0 && _lastPointCount > REDRAW_THRESHOLD)
+            var currentPointCount = Stroke.StylusPoints.Count;
-            {
+            if (currentPointCount == 0) return;
-                return;
-            }
 
-            try
+            // 计算新增的点数
+            int newPointCount = currentPointCount - _lastDrawnPointCount;
+
+            // 如果新增点数达到阈值，才进行增量绘制
+            if (newPointCount >= INCREMENTAL_DRAW_THRESHOLD || _lastDrawnPointCount == 0)
             {
-                using (var dc = RenderOpen())
+                try
                 {
-                    Stroke.Draw(dc);
+                    if (_lastDrawnPointCount == 0)
+                    {
+                        // 首次绘制：绘制所有点
+                        DrawSegmentToNewVisual(0, currentPointCount);
+                        _lastDrawnPointCount = currentPointCount;
+                    }
+                    else
+                    {
+                        // 从上次绘制的最后一个点开始
+                        int startIndex = Math.Max(0, _lastDrawnPointCount - 1);
+                        DrawSegmentToNewVisual(startIndex, currentPointCount);
+                        _lastDrawnPointCount = currentPointCount;
+                    }
                 }
-                _needsRedraw = false;
+                catch { }
             }
-            catch { }
         }
 
         /// <summary>
@@ -120,7 +199,11 @@ namespace Ink_Canvas.Helpers
         /// </summary>
         public void ForceRedraw()
         {
-            _needsRedraw = true;
+            if (_visualCanvas != null)
+            {
+                _visualCanvas.Clear();
+            }
+            _lastDrawnPointCount = 0;
             Redraw();
         }
 

Ink Canvas/MainWindow_cs/MW_TouchEvents.cs

@@ -482,8 +482,8 @@ namespace Ink_Canvas
 
             var strokeVisual = new StrokeVisual(inkCanvas.DefaultDrawingAttributes.Clone());
             StrokeVisualList[id] = strokeVisual;
-            StrokeVisualList[id] = strokeVisual;
+            var visualCanvas = new VisualCanvas();
-            var visualCanvas = new VisualCanvas(strokeVisual);
+            strokeVisual.SetVisualCanvas(visualCanvas);
             VisualCanvasList[id] = visualCanvas;
             inkCanvas.Children.Add(visualCanvas);