Mixed WPF and winforms project DPI awareness

Question

I have a C# program that uses both winforms and WPF and I'm struggling to get it to work in high DPI environments. Currently, if I remove all WPF projects from the solution and run it, it will scale fine, however as soon as I add any wpf back in (necessary for the functionality) the scaling fails and the UI becomes unusable.

This seems like the exact same issue as previous SO questions: DPI Scaling in .Net 3.5 in Mixed WinForms and WPF Application and Problems getting WinForms to scale correctly with DPI

I followed the advice on these questions and tried adding a manifest file and the dpi aware code provided.

I also upgraded the project to .net framework 4.6.1 (from 4.0) and included the app.config setting: <add key="EnableWindowsFormsHighDpiAutoResizing" value="true" />

This did affect the main shell of the program (so instead of loading up in a small window with all the controls squished, the main program window opens maximised and appears normal) However, when I enter any winforms subform or plugin from the main window, the scaling fails.

When I enter any WPF subform or plugin, or return to the main screen, these render correctly. It is only the winforms features that are failing to scale properly.

Has anyone got any ideas on how to get mixed winforms/WPF projects to scale correctly in high DPI?

Thanks in advance

Answer 1

When WPF is loaded into a project, it promotes the process to be System DPI Aware. In order to get around this, first : 1) set [assembly: DisableDpiAwareness] attribute above the namespace declaration in your entry assembly 2) you can add an app.manifest file in your project and add the following :

 <asmv3:windowsSettings
 xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
       <dpiAware>true/PM</dpiAware> 
 </asmv3:windowsSettings>

This should render your WinForms and WPF content both at the right target DPI. (This will however fail to scale if you have a multi monitor setup with different DPIs).

Answer 2

My colleague finally worked this one out. As none of the config settings etc would work for this project, we attempted to remove the winforms shell and replace it with a WPF shell. Once the main shell project was re-written in WPF, all the 'plugins' appeared in the correct DPI scaling.

Not the best fix I know considering it involves a re-write of existing code, however this was the only thing that sorted the problem for us.

Answer 3

If you do not have a manifest file because you are a WinForms app and not a WPF app, you have to go through AssemblyInfo.cs to make the change. Because it's in the opposite direction, you have to DISABLE DPI awareness to get the worlds in sync, rather than ENABLE it like the above WPF approach.

In AssemblyInfo.cs, add the following line.

[assembly: System.Windows.Media.DisableDpiAwareness]

My question was marked as a duplicate of this, but is not a true duplicate because I have a WinForms app using a WPF component, not the other way around. I am adding this answer for people like me who get directed here for the wrong reason.

Answer 4

Thank you so much for your answer @rohit21agrawal!

I had a quite similar complex Win Forms solution that whenever I opened a docked Form within WeifenLuo's DockPanelSuite, the Form resized and messed-up the whole GUI.

Now, after a couple of years trying different approaches (and none of them working) you saved my life!

In Addition to your answer for every other developer out there wondering how to accomplish your solution:

1. a) (My projects target .NET Framework 4.7.2)
2. b) (all my forms are set to AutoScaleMode = Font)
3. In your WinForms Project, add a Reference to WindowsBase (should be the third last entry in the list of Assemblies)
4. Add "[assembly: System.Windows.Media.DisableDpiAwareness]" to your AssemblyInfo.cs
5. Add "

<application xmlns="urn:schemas-microsoft-com:asm.v3">
  <windowsSettings xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
    <dpiAware>true/PM</dpiAware>
  </windowsSettings>
</application>

" into the parental "<assembly>…</assembly>" section of your app.manifest file

In my case, that worked like a charm :-) Eventually I am able to move the Form between different Displays (one 4K with 175% and another Full HD with 125% Font Scale) and it immediately redraws/re-renders all controls!

Again, thank you very much! Cordt