wpf - 如何将不可见图层添加到线条

Question

我有一个已经实现双击的线条形状，但是线条太细了。我想在它周围添加一个透明的白色填充，这样就不必精确地点击它。

我真的不想增加笔画粗细，我希望它保持形状，因为我不想将它放在内容控件或边框中。

Answer 1

One way of doing this is to override the standard Hit Testing of this line. Unfortunately, the WPF's Line class is sealed, which I personally think is criminal :-)

Here is a piece of code that reproduces the Line behavior, but in another class, and defines a Tolerance property (default value is 5). Feel free to test it:

using System.ComponentModel;
using System.Windows;
using System.Windows.Media;
using System.Windows.Shapes;

namespace MyNamespace
{
    public class HitTolerantLine : Shape
    {
        public static readonly DependencyProperty X1Property = DependencyProperty.Register("X1", typeof(double), typeof(Line), new FrameworkPropertyMetadata(0.0, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure), new ValidateValueCallback(IsDoubleFinite));
        public static readonly DependencyProperty X2Property = DependencyProperty.Register("X2", typeof(double), typeof(Line), new FrameworkPropertyMetadata(0.0, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure), new ValidateValueCallback(IsDoubleFinite));
        public static readonly DependencyProperty Y1Property = DependencyProperty.Register("Y1", typeof(double), typeof(Line), new FrameworkPropertyMetadata(0.0, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure), new ValidateValueCallback(IsDoubleFinite));
        public static readonly DependencyProperty Y2Property = DependencyProperty.Register("Y2", typeof(double), typeof(Line), new FrameworkPropertyMetadata(0.0, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure), new ValidateValueCallback(IsDoubleFinite));
        public static readonly DependencyProperty ToleranceProperty = DependencyProperty.Register("Tolerance", typeof(double), typeof(Line), new FrameworkPropertyMetadata(5.0), new ValidateValueCallback(IsDoubleFinite));

        private LineGeometry _geometry;
        private static readonly Pen _strokePen;

        static HitTolerantLine()
        {
            _strokePen = new Pen(Brushes.Black, 1.0);
            _strokePen.Freeze();
        }

        protected override HitTestResult HitTestCore(PointHitTestParameters hitTestParameters)
        {
            HitTestResult res = base.HitTestCore(hitTestParameters);

            // didn't hit? let's add some tolerance
            if ((res == null) && (_geometry != null) && (Tolerance > 0))
            {
                if (_geometry.StrokeContains(_strokePen, hitTestParameters.HitPoint, Tolerance, ToleranceType.Absolute))
                {
                    res = new PointHitTestResult(this, hitTestParameters.HitPoint);
                }
            }
            return res;
        }

        protected virtual void DefineGeometry()
        {
            Point startPoint = new Point(X1, Y1);
            Point endPoint = new Point(X2, Y2);
            _geometry = new LineGeometry(startPoint, endPoint);
        }

        protected override Size MeasureOverride(Size constraint)
        {
            DefineGeometry();
            return base.MeasureOverride(constraint);
        }

        protected static bool IsDoubleFinite(object o)
        {
            double d = (double)o;
            return (!double.IsInfinity(d) && !double.IsNaN(d));
        }

        protected override Geometry DefiningGeometry
        {
            get
            {
                return _geometry;
            }
        }

        public double Tolerance
        {
            get
            {
                return (double)base.GetValue(ToleranceProperty);
            }
            set
            {
                base.SetValue(ToleranceProperty, value);
            }
        }

        [TypeConverter(typeof(LengthConverter))]
        public double X1
        {
            get
            {
                return (double) base.GetValue(X1Property);
            }
            set
            {
                base.SetValue(X1Property, value);
            }
        }

        [TypeConverter(typeof(LengthConverter))]
        public double X2
        {
            get
            {
                return (double) base.GetValue(X2Property);
            }
            set
            {
                base.SetValue(X2Property, value);
            }
        }

        [TypeConverter(typeof(LengthConverter))]
        public double Y1
        {
            get
            {
                return (double) base.GetValue(Y1Property);
            }
            set
            {
                base.SetValue(Y1Property, value);
            }
        }

        [TypeConverter(typeof(LengthConverter))]
        public double Y2
        {
            get
            {
                return (double) base.GetValue(Y2Property);
            }
            set
            {
                base.SetValue(Y2Property, value);
            }
        }
    }
}

Answer 2

填充区域不可点击。

鉴于您的限制，我能想到的唯一方法是增加笔触厚度并将笔刷管理为透明颜色和可见颜色的渐变

Answer 3

在顶部绘制一条具有较大 StrokeThickness 的透明线，然后对其应用双击行为。