How do I increase performance of FlowDocumentScrollViewer?

Question

In a previous question, I asked how to get real-time logging output in a WPF textbox-like element (WPF append text blocks UI thread heavily but WinForms doesn't?). The a

Answer 1

I execute the sample you've provided, apart from few threading issues the biggest issue is amount of data. which slows down the text rendering as the it grows.

I tried to rewrite your code in a different way. I used Tasks, BlockingCollection and Virtualization to improve the performance with assumptions that main interest of the application is logging speed.

Bridge.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Documents;
using System.Threading;
using System.Collections.Concurrent;
using System.Threading.Tasks;

namespace PerformanceTest
{
    public class Bridge
    {
        int counterLimit;

        public BlockingCollection<string> output;
        public BlockingCollection<string> impOutput;
        public BlockingCollection<string> errors;
        public BlockingCollection<string> impErrors;
        public BlockingCollection<string> logs;


        protected static Bridge controller = new Bridge();

        public static Bridge Controller
        {
            get
            {
                return controller;
            }
        }

        public MainWindow Window
        {
            set
            {
                if (value != null)
                {
                    output = value.outputProducer;
                    impOutput = value.impOutputProducer;
                    errors = value.errorProducer;
                    impErrors = value.impErrorProducer;
                    logs = value.logsProducer;
                }
            }
        }

        public bool Running
        {
            get;
            set;
        }

        private Bridge()
        {
            //20000 lines seems to slow down tabbing enough to prove my point.
            //increase this number to get even worse results.
            counterLimit = 40000;
        }

        public void PrintLotsOfText()
        {
            Task.Run(() => GenerateOutput());
            Task.Run(() => GenerateError());
        }

        private void GenerateOutput()
        {
            //There is tons of output text, so print super fast if possible.
            int counter = 1;
            while (Running && counter < counterLimit)
            {
                PrintOutput("I will never say this horrible word again as long I live. This is confession #" + counter++ + ".");
                //Task.Delay(1).Wait();
            }
        }

        private void GenerateError()
        {
            int counter = 1;
            while (Running && counter < counterLimit)
            {
                PrintError("I will never forgive your errors as long I live. This is confession #" + counter++ + ".");
                //Task.Delay(1).Wait();
            }
        }

        #region Printing
        delegate void StringArgDelegate(String s);
        delegate void InlineArgDelegate(Inline inline);
        public void PrintOutput(String s)
        {
            output.TryAdd(s);
            PrintLog("d " + s);
        }

        public void PrintImportantOutput(String s)
        {
            impOutput.TryAdd(s);
            PrintLog("D " + s);
        }

        public void PrintError(String s)
        {
            errors.TryAdd(s);
            PrintLog("e " + s);
        }

        public void PrintImportantError(String s)
        {
            impErrors.TryAdd(s);
            PrintLog("E " + s);
        }

        public void PrintLog(String s)
        {
            String text = s;
            logs.TryAdd(text);
        }
        #endregion
    }
}

MainWindow.xaml

<Window x:Class="PerformanceTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow"
        WindowStartupLocation="CenterScreen">
    <Grid>
        <TabControl>
            <TabControl.Resources>
                <Style TargetType="ListBox">
                    <Setter Property="TextElement.FontFamily"
                            Value="Consolas" />
                    <Setter Property="TextElement.FontSize"
                            Value="12" />
                    <Setter Property="VirtualizingPanel.IsVirtualizing"
                            Value="True" />
                    <Setter Property="VirtualizingPanel.VirtualizationMode"
                            Value="Recycling" />
                </Style>
            </TabControl.Resources>
            <TabItem Header="Bridge">
                <StackPanel Orientation="Vertical"
                            HorizontalAlignment="Left">
                    <Button Content="Start Test"
                            Click="StartButton_Click" />
                    <Button Content="End Test"
                            Click="EndButton_Click" />
                </StackPanel>
            </TabItem>
            <TabItem Header="Output">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <ListBox Grid.Column="0"
                             ItemsSource="{Binding Output,RelativeSource={RelativeSource FindAncestor,AncestorType=Window}}" />

                    <GridSplitter Grid.Column="1"
                                  Width="5"
                                  ResizeBehavior="PreviousAndNext" />
                    <ListBox Grid.Column="2"
                             ItemsSource="{Binding Errors,RelativeSource={RelativeSource FindAncestor,AncestorType=Window}}" />
                </Grid>

            </TabItem>
            <TabItem Header="Log">
                <Grid>
                    <ListBox Grid.Column="0"
                             ItemsSource="{Binding Logs,RelativeSource={RelativeSource FindAncestor,AncestorType=Window}}" />
                </Grid>
            </TabItem>
        </TabControl>
    </Grid>
</Window>

MainWindow.xaml.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace PerformanceTest
{
    /// 
    /// Interaction logic for MainWindow.xaml
    /// 
    public partial class MainWindow : Window
    {
        public BlockingCollection<string> outputProducer = new BlockingCollection<string>();
        public BlockingCollection<string> impOutputProducer = new BlockingCollection<string>();
        public BlockingCollection<string> errorProducer = new BlockingCollection<string>();
        public BlockingCollection<string> impErrorProducer = new BlockingCollection<string>();
        public BlockingCollection<string> logsProducer = new BlockingCollection<string>();

        public ObservableCollection<object> Output { get; set; }
        public ObservableCollection<object> Errors { get; set; }
        public ObservableCollection<object> Logs { get; set; }

        Dispatcher dispatcher;

        public MainWindow()
        {
            Bridge.Controller.Window = this;
            try
            {
                InitializeComponent();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.InnerException.ToString());
                Console.WriteLine(ex.StackTrace);
            }

            dispatcher = Dispatcher;
            Output = new ObservableCollection<object>();
            Errors = new ObservableCollection<object>();
            Logs = new ObservableCollection<object>();
            Task.Run(() => Print(outputProducer, Output));
            Task.Run(() => Print(errorProducer, Errors));
            Task.Run(() => Print(logsProducer, Logs));
        }

        public void Print(BlockingCollection<string> producer, ObservableCollection<object> target)
        {
            try
            {
                foreach (var str in producer.GetConsumingEnumerable())
                {
                    dispatcher.Invoke(() =>
                    {
                        target.Insert(0, str);
                    }, DispatcherPriority.Background);
                }
            }
            catch (TaskCanceledException)
            {
                //window closing before print finish
            }
        }

        private void StartButton_Click(object sender, RoutedEventArgs e)
        {
            if (!Bridge.Controller.Running)
            {
                Bridge.Controller.Running = true;
                Bridge.Controller.PrintLotsOfText();
            }
        }

        private void EndButton_Click(object sender, RoutedEventArgs e)
        {
            Bridge.Controller.Running = false;
        }
    }
}

For a full working sample download PerformanceTest.zip and see if this is close to what you need. I have only rewritten only some portion. If this example is heading to the desired direction, we can implement rest of the functionality. un-comment Task.Delay(1).Wait(); in Bridge.cs if you may want to slow down the production to see the mixed logs otherwise the logs generation is too fast so it appear one after other in logs tab.

Answer 2

Using FlowDocumentPageViewer will help the performance since it loads document asynchronously.