Skiasharp: [BUG] macOS NullReferenceException when using SKGLView control

[aodpi]

Description
The SKGLView control doesn't seem to work on macOS. It crashes with a NullReferenceException that narrows down to the platform SKGLView in the DrawRect method. I believe that when you just have a SKGLView control without painting anything on it it would crash.

Stacktrace:

at SkiaSharp.Views.Mac.SKGLView.DrawRect (CoreGraphics.CGRect dirtyRect) [0x000d0] in <f196d3fbe68d4774a19d9220fd09cf57>:0 at (wrapper managed-to-native) AppKit.NSApplication.NSApplicationMain(int,string[]) at AppKit.NSApplication.Main (System.String[] args) [0x00040] in /Library/Frameworks/Xamarin.Mac.framework/Versions/5.2.1.16/src/Xamarin.Mac/AppKit/NSApplication.cs:100 at TestProject.Mac.MainClass.Main (System.String[] args) [0x00017] in /Users/localusr/Projects/TestProject/TestProject.Mac/Main.cs:11
Expected Behavior
The SKGLView should work and drawing on it should be supported.

Actual Behavior
The app crashes whenever you have a SKGLView control in your xamarin.forms app.

Basic Information

• Version with issue: 1.68.0
• Last known good version: unknown.
• IDE: Visual Studio for Mac 7.8.3 (build 2)

• Platform Target Frameworks:

  • macOS: macOS Mojave: 10.14.4

• Target Devices:

  • Mac mini (Late 2014)

Reproduction Link

Here is a sample project:

TestProject.zip

[aodpi]

After testing it on a macbook pro with a discrete video card it does work. The difference is that mac mini doesn't have a discrete video card.

[nor0x]

I have the same issue on a MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports)

[nor0x]

I just tested this in a blank project, here is a repro for the issue (Xamarin.Forms on macOS).
https://github.com/nor0x/SkiaSharp_PerfomanceExperiments/tree/master/Xamarin.Forms

Stacktrace

at SkiaSharp.Views.Mac.SKGLView.DrawRect (CoreGraphics.CGRect dirtyRect) [0x000d0] in <f196d3fbe68d4774a19d9220fd09cf57>:0
at (wrapper managed-to-native) AppKit.NSApplication.NSApplicationMain(int,string[])
at AppKit.NSApplication.Main (System.String[] args) [0x00040] in /Library/Frameworks/Xamarin.Mac.framework/Versions/5.10.0.157/src/Xamarin.Mac/AppKit/NSApplication.cs:100 
at SkiaXFPlayground.macOS.MainClass.Main (System.String[] args) [0x00017] in /Users/johnny/SkiaPlayground/Xamarin.Forms/SkiaXFPlayground.macOS/Main.cs:11

Any updates on this one @mattleibow ?
Thanks

[aodpi]

@nor0x Does your MacBook Pro have a discrete videocard?

[nor0x]

@aodpi no it doesn't. In the hardware infos the only entry is.
Intel Iris Plus Graphics 655 1536 MB graphics

[aodpi]

@nor0x I took the code for SKGLView and created a new view and used it natively on macOS and it works with no issues, no crashes event on a mac with no dedicated gpu, so GPU is not the issue here 😞.

[aodpi]

After some more digging, this line causes the issue:
https://github.com/mono/SkiaSharp/blob/5e8dc3e2c9e72f2ad0d9feecefbef503ca9fcc15/source/SkiaSharp.Views/SkiaSharp.Views.Mac/SKGLView.cs#L100

The SKSurface.Create method with the signature above returns null thus causing the NullReferenceException. I've also installed the early access build v1.68.1-rc.138 and it works well. Changes to SKSurface from the last release (v 1.68.0) seem to have fixed this issue.

[aodpi]

Actually, changes in the mac SKGLView diff have fixed this issue. It's related to the way the surface samples count read.

[aodpi]

Yep, it has been fixed here https://github.com/mono/SkiaSharp/issues/727#issuecomment-448425962 #727 . I think I will close this issue.

[nor0x]

thanks for the response and closing, it’s great to see this fixed