How to render a window with an OpenGlControl to RenderTargetBitmap?

[marklam]

I'm running on Windows with Skia and UseWgl=true.

I have a MainWindow which uses a control derived from OpenGlControlBase, and when I try to render to RenderTargetBitmap:

            use bmp = new RenderTargetBitmap(psize, Vector(96,96))
            this.Measure(size);
            this.Arrange(new Rect(size));
            bmp.Render(this)

I get an ArgumentNullException under OpenGlBitmapImp.cs line 44

 	SkiaSharp.dll!SkiaSharp.SKSurface.Create(SkiaSharp.GRRecordingContext context, SkiaSharp.GRBackendTexture texture, SkiaSharp.GRSurfaceOrigin origin, int sampleCount, SkiaSharp.SKColorType colorType, SkiaSharp.SKColorSpace colorspace, SkiaSharp.SKSurfaceProperties props)	Unknown
 	SkiaSharp.dll!SkiaSharp.SKSurface.Create(SkiaSharp.GRRecordingContext context, SkiaSharp.GRBackendTexture texture, SkiaSharp.GRSurfaceOrigin origin, SkiaSharp.SKColorType colorType)	Unknown
 	SkiaSharp.dll!SkiaSharp.SKSurface.Create(SkiaSharp.GRContext context, SkiaSharp.GRBackendTexture texture, SkiaSharp.GRSurfaceOrigin origin, SkiaSharp.SKColorType colorType)	Unknown
>	Avalonia.Skia.dll!Avalonia.Skia.GlOpenGlBitmapImpl.Draw(Avalonia.Skia.DrawingContextImpl context, SkiaSharp.SKRect sourceRect, SkiaSharp.SKRect destRect, SkiaSharp.SKPaint paint) Line 44	C#

context.GrContext is null - do I need to do something before I can render the OpenGL control to RenderTargetBitmap?

Thanks for any help.

[kekekeks]

Unfortunately right now RenderTargetBitmap is always software-only, so it's not possible to use GPU-backend surfaced to render into it.
We are reworking our rendering stack to make them GPU backed, but that effort is temporally stalled due to recent events.

[marklam]

Thanks @kekekeks. Good to know I wasn't just doing it wrong :-)

For background, I was trying to turn an Avalonia animation into a video, without skipping any frames, by using a custom clock to advance each frame as it was captured into a RenderTargetBitmap and encoded with an ffmpeg wrapper.

[atticus-lv]

4 years pass, is there any progress on this issue? @kekekeks