如何在RichTextBox中围绕单词绘制边框？

Question

假设我有2个TextPointers.一个指向一个单词的开头,另一个指向单词的结尾.

我想在单词周围绘制单个像素边框.我该怎么做？当用户输入或滚动时,边框应该与单词绑定并随之移动.

我已经尝试过使用DrawingBrush的TextDecorations但是无法提供任何可用的东西.

Answer 1

我做了类似的事情,只在TextBox中加下了文字.校长似乎大致相同.

1. 添加包含RichTextBox但在ScrollViewer中的AdornerDecorator.

   <Border ...>
       <ScrollViewer ... >
           <AdornerDecorator>
               <RichTextBox
                   x:Name="superMagic"
                   HorizontalScrollBarVisibility="Hidden"
                   VerticalScrollBarVisibility="Hidden"
                   BorderBrush="{x:Null}"
                   BorderThickness="0"
                   ...
                   />
           </AdornerDecorator>
       </ScrollViewer>
   </Border>
   

2. 创建一个Adorner来渲染矩形并将其添加到AdornerLayer

   void HostControl_Loaded(object sender, RoutedEventArgs e)
   {
       _adorner = new RectangleAdorner(superMagic);
   
       AdornerLayer layer = AdornerLayer.GetAdornerLayer(superMagic);
       layer.Add(_adorner);
   }
   

3. 装饰器应该挂钩RichTextBox的TextChanged事件.您需要做的就是InvalidateVisuals()通过调度程序调用DispatcherPriority.Background以确保它在文本框之后呈现.我不知道这是否是一个问题RichTextBox,但是TextBox只有当它的内容最后一次更改时,才能获得至少一次的字符坐标.

   class RectangleAdorner : Adorner
   {
       public RectangleAdorner(RichTextBox textbox)
           : base(textbox)
       {
           textbox.TextChanged += delegate
           {
               SignalInvalidate();
           };
       }
   
       void SignalInvalidate()
       {
           RichTextBox box = (RichTextBox)this.AdornedElement;
           box.Dispatcher.BeginInvoke(DispatcherPriority.Background, (Action)InvalidateVisual);
       }
   
       // ...
   }
   

4. 覆盖Adorner.OnRender()以使用框来绘制TextPointer.GetCharacterRect()坐标.

   protected override void OnRender(DrawingContext drawingContext)
   {
       TextPointer start;
       TextPointer end;
   
       // Find the start and end of your word
       // Actually, if you did this in the TextChanged event handler,
       // you could probably save some calculation time on large texts
       // by considering what actually changed relative to an earlier
       // calculation. (TextChangedEventArgs includes a list of changes
       //  - 'n' characters inserted here, 'm' characters deleted there).
   
       Rect startRect = start.GetCharacterRect(LogicalDirection.Backward);
       Rect endRect = end.GetCharacterRect(LogicalDirection.Forward);
   
       drawingContext.DrawRectangle(null, pen, Rect.Union(startRect, endRect));
   }
   

注意:虽然原始代码运行良好,但我很久以前就写过了,并没有测试我对这个答案的适应性.它至少应该帮助你走上正确的道路.

此外,这不处理单词跨行分割的情况,但不应该太难以满足.