This was a leftover from some not-well-thought-out design decision. The
function is now used exclusively for binding for draw, as all
framebuffer reading functions (blit(), read()) are doing the read
binding internally. Moreover it required the user to be extra careful on
ES2, because in many cases there are no separate binding points for
reading and drawing.
The function is now parameter-less and always bind the framebuffer for
drawing. The logic for internal binding was also simplified and on ES2
there are separate implementations for single/separate binding points.
For *Framebuffer::checkStatus() the documentation was updated to explain
the meaning of the parameter on ES2 implementation. Also removed the
need for FramebufferTarget::ReadDraw binding, as it was rather
confusing.
Old *Framebuffer::bind(FramebufferTarget) is now just an alias to the
parameter-less function, ignoring the parameter. Along with
FramebufferTarget::ReadDraw it is marked as deprecated and will be
removed in some future release.
The documentation of ARB_invalidate_subdata mentions that all the
functions are really just a hint for the implementation to make some
performance optimizations and they are not affecting behavior at all. So
it's perfectly fine to do nothing if the extension is not supported.
I didn't do this originally as I mistakenly thought that invalidating
depth buffer would somehow behave the same as clearing it, but that's
not the case.
The previous way was half-working at best, as it handled array textures
improperly. Now there is overload for each texture type. The old way
with attachTexture*D() is marked as deprecated and will be removed in
future release.
Vladimír Vondruš