'webgl' context still not working

[GarasChan]

When I use html2canvas to parse canvas with 'webgl' or 'webgl2' context, the generated image is empty.

[fneumeyer]

It's possible that WebGL cleared your canvas' buffer before html2canvas can access it. Try to use the WebGLContextAttribute preserveDrawingBuffer = true. Note that you'll have to clear the buffer yourself before rendering the next frame then, if necessary.

Another way could be to take the screenshot exactly after rendering. So exactly after each other
renderToCanvas()
takeScreenshot()