IPlatformRenderInterface - This interface or abstract class is -not- implementable by user code !

[MihaMarkic]

If I were to implement a custom platform, how would I implement IPlatformRenderInterface as it whines that all members cannot implicitly implement an inaccessible member and ends with Error CS0535 : 'PlatformRenderInterface' does not implement interface member 'IPlatformRenderInterface.(This interface or abstract class is -not- implementable by user code !)()'

[maxkatz6]

You can set AvaloniaAccessUnstablePrivateApis, see https://github.com/AvaloniaUI/Avalonia/wiki/Using-private-apis-in-nuget-packages

[MihaMarkic]

Awesome, thanks

[Matubil]

Hey! That error is expected if you try to implement IPlatformRenderInterface from normal application code.

Avalonia intentionally hides some platform/backend interfaces behind its private/unstable API surface. For a custom rendering/platform backend, you need to opt in explicitly in your project file:

<PropertyGroup>
  <AvaloniaAccessUnstablePrivateApis>true</AvaloniaAccessUnstablePrivateApis>
</PropertyGroup>

After enabling that, the inaccessible members / NotClientImplementable-style errors should no longer block you in the same way.

Just keep in mind that these APIs are considered unstable, so they may change between Avalonia versions and you may need to adapt your backend after upgrades.

Also, if your goal is only platform-specific functionality rather than a complete custom rendering backend, it may be much simpler to keep Avalonia’s normal renderer and isolate the platform-specific parts behind interfaces or native interop instead.

[MihaMarkic]

I have a custom backend where there is no Skia and a custom drawing stack. So I guess I have to implement the whole enchilada. So I've used Avalonia.Skia as a template and created minimal functional code that does not throw an exception.
Now I'm wondering how does Avalonia actually draw content from Skia on its window. Any pointers appreciated.