WPF FlowDocumentScrollViewer example

MainWindow.xaml

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <FlowDocumentScrollViewer Name="ChatPanel" Block.LineHeight="2">
            <!--<RichTextBox x:Name="rtbChatlog1" IsReadOnly="True" >
                    <RichTextBox.ContextMenu>
                        <ContextMenu>
                            <MenuItem Header="복사" Command="ApplicationCommands.Copy"/>
                            <MenuItem Header="Custom Item" Click="MenuItem_Click"/>
                        </ContextMenu>
                    </RichTextBox.ContextMenu>
                </RichTextBox>-->
        </FlowDocumentScrollViewer>
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Media;

namespace WpfApp1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private FlowDocument _chatDocument;

        public MainWindow()
        {
            InitializeComponent();

            // Initialize the FlowDocument that will contain all chat messages
            _chatDocument = new FlowDocument();
            ChatPanel.Document = _chatDocument;
        }

        private void AddMessage(string message)
        {
            var paragraph = new Paragraph(new Run(message))
            {
                Foreground = Brushes.Blue,
                FontWeight = FontWeights.Bold
            };

            // Create and attach a custom context menu to the paragraph
            var contextMenu = new ContextMenu();
            
            var menuItem = new MenuItem { Header = "Custom Action" };
            menuItem.Click += MenuItem_Click;
            // Store the Paragraph object in the Tag property of the MenuItem
            menuItem.Tag = paragraph;
            contextMenu.Items.Add(menuItem);

            var menuItemReplace = new MenuItem { Header = "Replace" };
            menuItemReplace.Click += MenuItemReplace_Click;
            menuItemReplace.Tag = paragraph;
            contextMenu.Items.Add(menuItemReplace);
            
            paragraph.ContextMenu = contextMenu;

            _chatDocument.Blocks.Add(paragraph);
        }

        private static int count = 1;
        private void MenuItemReplace_Click(object sender, RoutedEventArgs e)
        {
            // Retrieve the Paragraph object from the Tag property of the MenuItem
            var paragraph = ((MenuItem)sender).Tag as Paragraph;
            if (paragraph != null)
            {
                string newMessage = $"replaced! ({count++})";
                ReplaceTextInParagraph(paragraph, newMessage);
                MessageBox.Show($"Custom action triggered for paragraph: {newMessage}");
            }
        }

        private void MenuItem_Click(object sender, RoutedEventArgs e)
        {
            // Retrieve the Paragraph object from the Tag property of the MenuItem
            var paragraph = ((MenuItem)sender).Tag as Paragraph;
            if (paragraph != null)
            {
                string paragraphText = GetTextFromParagraph(paragraph);
                MessageBox.Show($"Custom action triggered for paragraph: {paragraphText}");
            }
        }

        private string GetTextFromParagraph(Paragraph paragraph)
        {
            StringBuilder sb = new StringBuilder();
            foreach (Inline inline in paragraph.Inlines)
            {
                if (inline is Run run)
                {
                    sb.Append(run.Text);
                }
                else if (inline is Span span)
                {
                    foreach (Inline childInline in span.Inlines)
                    {
                        if (childInline is Run childRun)
                        {
                            sb.Append(childRun.Text);
                        }
                    }
                }
                // Handle other types of Inline elements if necessary
            }
            return sb.ToString();
        }

        private void ReplaceTextInParagraph(Paragraph paragraph, string newText)
        {
            // Clear existing inlines
            paragraph.Inlines.Clear();

            // Add new text
            paragraph.Inlines.Add(new Run(newText));
        }

        protected override void OnContentRendered(EventArgs e)
        {
            base.OnContentRendered(e);

            // Example usage: Add multiple messages
            for (int i = 0; i < 500; i++)
            {
                AddMessage($"Lorem ipsum dolor sit amet, consectetur adipiscing elit. ({i + 1})");
            }
        }
    }
}