* \param buffer buffer token such as GL_LEFT or GL_FRONT_AND_BACK, etc.
*
* Note that the behaviour of this function depends on whether the
* \param buffer buffer token such as GL_LEFT or GL_FRONT_AND_BACK, etc.
*
* Note that the behaviour of this function depends on whether the
* In the former case, we update the per-context ctx->Color.DrawBuffer
* state var _and_ the FB's ColorDrawBuffer state.
* In the later case, we update the FB's ColorDrawBuffer state only.
* In the former case, we update the per-context ctx->Color.DrawBuffer
* state var _and_ the FB's ColorDrawBuffer state.
* In the later case, we update the FB's ColorDrawBuffer state only.