# What Are The Default Values of glReadBuffer/glDrawBuffer(s) for an FBO?

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.

• glReadBuffer(...) initial value: (default framebuffer: GL_FRONT iff single-buffered, GL_BACK iff double-buffered) (FBO: GL_COLOR_ATTACHMENT0) (see page 506)
• glDrawBuffer(...) initial value: (see glDrawBuffers(...))
• glDrawBuffers(...) initial value: (default framebuffer: fragment color 0 goes to GL_FRONT iff single-buffered, GL_BACK iff double-buffered) (FBO: fragment color 0 goes to GL_COLOR_ATTACHMENT0) (both: fragment colors other than 0 go to GL_NONE) (see page 497)