Skiasharp: Wrong Text Size on Windows Desktop

[joreg]

This is similar to: SkiaSharp Text Size on Xamarin Forms

The question: How does the TextSize property on an SKPaint object relate to the 'standard' Windows Forms FontSize on windows desktop?

In the screenshot you see left the text as rendered by SKCanvas (which has no scaling applied) and right i put the windows system dialog "userdefined scaling" for comparison where you see that the string "9-Punkt Segoe UI" is written significantly larger. Also my dpi settings are at 100%.

In the question referenced above, @mattleibow answers with applying a scaling factor but doesn't clarify what the variables mean, in the code he shows: specifically what does "viewWidth" refer to?

var scale = canvasWidth / viewWidth;

[mattleibow]

To be honest, I am not particularly sure - and I know this is not exactly encouraging. This is because there are many factors at play here:

• System settings:
  
  
  
  • the screen dpi
  
  
  • whether scaling is enabled
  
  
  • OS version
  
  
• WinForms settings:
  
  
  
  • autosize mode
  
  
  • autosize enabled
  
  
  • target framework version
  
  
  • app.config settings
  
  
  • app.manifest settings
  
  
• Other factors:
  
  
  
  • WinForms (GDI) fonts are points (pt)
  
  
  • SkiaSharp is pixels (px)
  
  

Important thing about SkiaSharp is that it will ALWAYS draw text with pixels and will do so regardless of DPI/scaling. On machines that have scaling, you will probably have to scale up. The reason this is not so well supported for SkiaSharp is that you are one of the first people that I know that have tried WinForms.

I will try and get to the bottom of this, but in the meantime - here are some docs:

• https://docs.microsoft.com/en-us/dotnet/framework/winforms/adjusting-the-size-and-scale-of-windows-forms
• https://docs.microsoft.com/en-us/dotnet/framework/winforms/high-dpi-support-in-windows-forms
• https://msdn.microsoft.com/en-us/library/windows/desktop/ff684173
• https://msdn.microsoft.com/en-us/library/ms838191.aspx

Not the greatest of results, but I hope this helps a bit. This is fundamentally an issue with WinForms (I believe) as it is a very old framework and much support has been added on later.

[joreg]

thanks for the elaborate answer. i'll dig into these..

[joreg]

finally got back to this and what helped me was:

WinForms (GDI) fonts are points (pt)
SkiaSharp is pixels (px)

so i now convert my pts to px and all is good.
thanks again!

[mattleibow]

NICE! Glad to have helped.