Can't use backend.buffer_age() on winit due to new bind() borrowing requirements

[YaLTeR]

df08c6f made bind() mutably borrow the backend, making it impossible to get backend.buffer_age() while it is bound. However, when the backend is not bound, buffer_age() returns None. So effectively you can't use the buffer age on winit currently.

[Drakulix]

I think it actually is possible, since the Renderer doesn't unbind when finishing a Frame, but that is still a super ackward api.

[YaLTeR]

If I'm not mistaken, GlesTarget unbinds on Drop, and it is one of the things borrowing the backend from bind(). So I'm not sure it's possible

[Drakulix]

If I'm not mistaken, GlesTarget unbinds on Drop, and it is one of the things borrowing the backend from bind(). So I'm not sure it's possible

No, I am pretty sure it doesn't. It destroys framebuffer objects, but it doesn't call unbind to save instructions, if the user just binds the same framebuffer again next cycle.

[Drakulix]

#1673