fix 粘贴溢出到窗体

CustomRichTextBox.cs

@@ -14,6 +14,13 @@ namespace WpfRichTextBox
         public CustomRichTextBox()
         {
             TextChanged += CustomRichTextBox_TextChanged;
+            DataObject.AddPastingHandler(this, OnPasteHandler);
+        }
+
+        private void OnPasteHandler(object sender, DataObjectPastingEventArgs e)
+        {
+            SyncRichChars();
+            InvalidateVisual();
         }
 
         private void CustomRichTextBox_TextChanged(object sender, TextChangedEventArgs e)
@@ -26,13 +33,15 @@ namespace WpfRichTextBox
         {
             RichChars.Clear();
             var text = new TextRange(Document.ContentStart, Document.ContentEnd).Text;
-            for (int i = 0; i < text.Length; i++)
+            int maxChars = (int)(ActualWidth / 16);
+            int count = Math.Min(text.Length, maxChars);
+            for (int i = 0; i < count; i++)
             {
                 RichChars.Add(new RichChar
                 {
                     Character = text[i],
-                    Position = new Point(i * 16, 10), // 横向排列，纵坐标可调整
-                    Color = Colors.Black // 默认颜色
+                    Position = new Point(i * 16, 10),
+                    Color = Colors.Black
                 });
             }
         }
@@ -42,16 +51,19 @@ namespace WpfRichTextBox
             base.OnRender(drawingContext);
             foreach (var richChar in RichChars)
             {
-                var formattedText = new FormattedText(
-                    richChar.Character.ToString(),
-                    System.Globalization.CultureInfo.CurrentCulture,
-                    FlowDirection.LeftToRight,
-                    new Typeface("Segoe UI"),
-                    16,
-                    new SolidColorBrush(richChar.Color),
-                    VisualTreeHelper.GetDpi(this).PixelsPerDip);
-
-                drawingContext.DrawText(formattedText, richChar.Position);
+                if (richChar.Position.X >= 0 && richChar.Position.X + 16 <= ActualWidth && richChar.Position.Y >= 0 && richChar.Position.Y + 16 <= ActualHeight)
+                {
+                    var formattedText = new FormattedText(
+                        richChar.Character.ToString(),
+                        System.Globalization.CultureInfo.CurrentCulture,
+                        FlowDirection.LeftToRight,
+                        new Typeface("Segoe UI"),
+                        16,
+                        new SolidColorBrush(richChar.Color),
+                        VisualTreeHelper.GetDpi(this).PixelsPerDip);
+
+                    drawingContext.DrawText(formattedText, richChar.Position);
+                }
             }
         }
     }