copy double buffers


I have a double buffers device context. In some situations, I want to copy the contents in the front buffer to the back buffer, then add some minor rendering to the back buffer and finally call SwapBuffers(). Does OpenGL has such a copy buffer command? Please help. Thanks.

(The reason for this is that my 3rd part software is rendering first then call a callback function provided by me)


glCopyPixels(0, 0, width, height, GL_COLOR);

but I think there is a better solution to what you are looking for.