The issue is not access to an external texture, it's access to an external texture on the right thread in the right GL context. We did look at writing a new bac

The issue is not access to an external texture, it's access to an external texture on the right thread in the right GL context. We did look at writing a new backend for surfman to integrate directly, but it's a bit of work and not at all cross-platform, so this was not a goal of the project at this stage. I'd like to find a way to avoid the blit though, so I'm continuing to experiment in this direction.