I’ll try it with alpha from here and get back to you.
Apparently, draw node for metal backend implemented so I just need to check that drawing triangles stays the same at my code. The only complication is that alpha code from metal-backend doesn’t have xcode project so I need to craft one.
upd - checked. no, it dose not currently 
with few lines added I can draw thin lines and triangles but somehow drawSegment at base class DrawNode is behave differently.
I will try to make a patch for metal backend since its currently, as far as I can see, not in production (am I right?)