wpf-利用装饰器制作 彩色字体+可选中+可复制 的textblock

效果如下图所示：

实现要点：

• 彩色字体可以用TextBlock的Run实现
• “可选中”可以通过装饰器实现
• 注意鼠标事件处理

前台

<ScrollViewer Width="400" x:Name="colorScrollViewer" HorizontalScrollBarVisibility="Visible" >
    <TextBlock x:Name="colorSeq" ScrollViewer.CanContentScroll="True"
               VirtualizingPanel.IsVirtualizing="True" VirtualizingPanel.ScrollUnit="Pixel" 		
               VirtualizingPanel.VirtualizationMode="Recycling" 
               MouseLeftButtonDown="colorSeq_MouseLeftButtonDown"
               PreviewMouseLeftButtonDown="colorSeq_PreviewMouseLeftButtonDown"
               PreviewMouseLeftButtonUp="colorSeq_PreviewMouseLeftButtonUp"
               />
</ScrollViewer>

后台

    public partial class WPInfoWindow : Window
    {
        private Point _startMousePosition { set; get; }
        private TextPointer _startPt { set; get; }
        private TextBlockSelectedAdorner _tbsAdorner { set; get; }
        
        public WPInfoWindow()
        {
            InitializeComponent();
            string t = "";
            string[] dict = new string[] {"A","C","G","T" };
            // 搞点随机字符串
            Random rd = new Random();
            for (int i = 0; i < 4000; i++) {
                string c = dict[rd.Next(0, 4)];
                Run r = new Run();
                r.Text = c;
                // 给点不同的颜色
                switch (c) {
                    case "A":
                        r.Foreground = Brushes.Green;
                        break;
                    case "C":
                        r.Foreground = Brushes.Blue;
                        break;
                    case "G":
                        r.Foreground = Brushes.Black;
                        break;
                    case "T":
                        r.Foreground = Brushes.Red;
                        break;
                }
                this.colorSeq.Inlines.Add(r);
            }  
        }
...
        private void colorSeq_PreviewMouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            Point lastMousePosition = e.GetPosition(this.colorSeq);
            TextPointer tp = this.colorSeq.GetPositionFromPoint(lastMousePosition, true);
            TextRange tr = new TextRange(_startPt, tp);
            string selectedText = tr.Text;
            AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this.colorSeq);
            Rect rect = new Rect(_startMousePosition.X, 0.0, lastMousePosition.X-_startMousePosition.X, 30);
            this._tbsAdorner = new TextBlockSelectedAdorner(this.colorSeq, rect);
            adornerLayer.Add(this._tbsAdorner);
            // 省去复制到剪贴板那步，自己想咋处理咋处理
            MessageBox.Show(selectedText);
        }

        private void colorSeq_PreviewMouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            _startMousePosition = e.GetPosition(this.colorSeq);
            _startPt = this.colorSeq.GetPositionFromPoint(_startMousePosition, true);
            AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this.colorSeq);
            
            if (this._tbsAdorner != null)
            {
                adornerLayer.Remove(this._tbsAdorner);
            }
        }

        private void colorSeq_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this.colorSeq);
            _cursorAdorner = new TextBlockSelectedAdorner(this.colorSeq, new Rect(_startMousePosition.X, 0.0, 0, 30));
            adornerLayer.Add(_cursorAdorner);
        }

...

    public class TextBlockSelectedAdorner : Adorner {
        // 被装饰的元素
        Rect _maskRect;
        
        // 基类初始化
        public TextBlockSelectedAdorner(UIElement element, Rect rect) : base(element) {
            this._maskRect = rect;
        }
        
        // 实现装饰器呈现的行为
        protected override void OnRender(DrawingContext drawingContext)
        {
            base.OnRender(drawingContext);
            Pen renderPen = new Pen(new SolidColorBrush(Colors.Red), 0);
            SolidColorBrush brush = new SolidColorBrush(Color.FromArgb(30,0,0,255));
            drawingContext.DrawRectangle(brush, renderPen, this._maskRect);
        }
    }