Actually, I was making a very silly error: calling the newFrameDataForContext() method from a thread different from the animation thread (where Processing’s opengl context is created), which resulted in getting nil every time I called [client newFrameImageForContext:CGLGetCurrentContext()] in native code…
Doing all the calls from draw() results in valid id, width and height… I think we are close to having the client working 🙂
Once I get this part working, I will look at replacing SyphonNameboundClient, as you suggest.