You can expect drawing a WebGL canvas to a 2D canvas to do a GPU copy. It’s not particularly slow, at least on desktop GPUs with plenty of bandwidth. And in the hopefully-not-too-distant future, transferToImageBitmap is intended to enable a similar operation without any copying at all.
From: email@example.com [mailto:firstname.lastname@example.org]
On Behalf Of Florian Bösch
On Sat, Apr 28, 2018 at 4:50 AM, Ken Russell <email@example.com> wrote:
That's the first I've heard about that, I'm not sure that's how it was meant. Regardless, sharing resources would happen between contexts living within one live page. All WebGL contexts there are virtual, even on platforms that do not have a dedicated GPU process. What the actual context can share or not is of no relevance, because you just overlay whatever sharing semantic you want since you all operate within the same actual context.
Afaik this would be pretty slow as it'll perform a readback to obtain pixel data to put into the 2D canvas buffer does it not?