improve:墨迹延迟

Ink Canvas/Helpers/MultiTouchInput.cs

@@ -25,10 +25,14 @@ namespace Ink_Canvas.Helpers
     }
 
     /// <summary>
-    ///     用于显示笔迹的类
+    /// 用于显示笔迹的类 
     /// </summary>
     public class StrokeVisual : DrawingVisual
     {
+        private bool _needsRedraw = true;
+        private int _lastPointCount = 0;
+        private const int REDRAW_THRESHOLD = 3; 
+
         /// <summary>
         ///     创建显示笔迹的类
         /// </summary>
@@ -49,15 +53,20 @@ namespace Ink_Canvas.Helpers
         public StrokeVisual(DrawingAttributes drawingAttributes)
         {
             _drawingAttributes = drawingAttributes;
+            
+            // 启用硬件加速
+            RenderOptions.SetBitmapScalingMode(this, BitmapScalingMode.HighQuality);
+            RenderOptions.SetEdgeMode(this, EdgeMode.Aliased);
+            RenderOptions.SetCachingHint(this, CachingHint.Cache);
         }
 
         /// <summary>
-        ///     设置或获取显示的笔迹
+        /// 设置或获取显示的笔迹
         /// </summary>
         public Stroke Stroke { set; get; }
 
         /// <summary>
-        ///     在笔迹中添加点
+        /// 在笔迹中添加点
         /// </summary>
         /// <param name="point"></param>
         public void Add(StylusPoint point)
@@ -66,28 +75,50 @@ namespace Ink_Canvas.Helpers
             {
                 var collection = new StylusPointCollection { point };
                 Stroke = new Stroke(collection) { DrawingAttributes = _drawingAttributes };
+                _lastPointCount = 1;
             }
             else
             {
                 Stroke.StylusPoints.Add(point);
+                _lastPointCount++;
             }
+            
+            // 标记需要重绘
+            _needsRedraw = true;
         }
 
         /// <summary>
-        ///     重新画出笔迹
+        /// 重新画出笔迹
         /// </summary>
         public void Redraw()
         {
+            if (!_needsRedraw || Stroke == null) return;
+            
+            if (_lastPointCount % REDRAW_THRESHOLD != 0 && _lastPointCount > REDRAW_THRESHOLD)
+            {
+                return;
+            }
+
             try
             {
                 using (var dc = RenderOpen())
                 {
                     Stroke.Draw(dc);
                 }
+                _needsRedraw = false;
             }
             catch { }
         }
 
+        /// <summary>
+        /// 强制重绘
+        /// </summary>
+        public void ForceRedraw()
+        {
+            _needsRedraw = true;
+            Redraw();
+        }
+
         private readonly DrawingAttributes _drawingAttributes;
 
         public static implicit operator Stroke(StrokeVisual v)