I want to Understand the Rendering Modes in WPF application.

Question

Recently i came across this section of code on Stackoverflow.

void myClass_SourceInitialized(object sender, EventArgs e)

    {

        Log.Info("myClass_SourceInitialized");

        System.Windows.Interop.HwndSource source = System.Windows.Interop.HwndSource.FromHwnd(new System.Windows.Interop.WindowInteropHelper(this).Handle);

        source.AddHook(new System.Windows.Interop.HwndSourceHook(WndProc));

        var ss = source.CompositionTarget;

        ss.RenderMode = RenderMode.Default;

        Log.Info(ss.TransformFromDevice.ToString());

    }

To my surprise if i set Render mode to RenderMode.SoftwareOnly my application lags but with default mode it runs perfectly. On Stack overflow i saw some answers that default mode is used to avoid the DUCE error. So can you briefly explain it.

Answer 1

Hi,@Vishal2 Bansal. Welcome to Microsoft Q&A. 

WPF's internal architecture has two rendering pipelines, hardware and software.

 

Hardware rendering pipeline: Use hardware (GPU) accelerated rendering. RenderMode.Default, WPF renders in hardware if possible; otherwise in software.

 

Software rendering pipeline: Rendering using CPU only. RenderMode.SoftwareOnly, WPF renders only in software.

 

Related Documents: Optimizing Performance: Taking Advantage of Hardware - WPF .NET Framework | Microsoft Learn

 

Reasons for program lag: When only CPU rendering is used without GPU acceleration, the rendering speed is very slow because the CPU rendering efficiency is not high

 

System.Windows.Media.Composition.DUCE.Channel.SyncFlush()

Reasons why switching rendering mode could handle the above errors: 1. When the CPU rendering capacity is not enough to meet the demand (memory), hardware (GPU) could be used for accelerated rendering. 2. Switching rendering mode could detect whether there is a problem with the driver.

 

A more detailed explanation: WPF render thread failures - .NET Framework | Microsoft Learn

 

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