glReadBuffer(...)/glDrawBuffer(...)/glDrawBuffers(...) access part of a framebuffer's state.For reading the default framebuffer, this is GL_FRONT or GL_BACK.  However, the documentation doesn't say what it is for FBOs.  The only thing I found was an offhand comment here stating that the default is GL_COLOR_ATTACHMENT0 (which is what I would guess).  Can I rely on that?For writing, I didn't immediately find any claims what what color buffers are enabled.
What Are The Default Values of `glReadBuffer/glDrawBuffer(s)` for an FBO?
opengl