On Mon, Jan 6, 2025 at 4:41 PM Michel Dänzer <michel.daenzer@xxxxxxxxxxx> wrote:
> Yeah, that's not how double-buffering works in GL. The draw buffer is always GL_BACK, SwapBuffers doesn't affect that (it just may internally change which actual buffer GL_BACK refers to).
>
> I don't see more context about the issue you're investigating, any pointers?
> Yeah, that's not how double-buffering works in GL. The draw buffer is always GL_BACK, SwapBuffers doesn't affect that (it just may internally change which actual buffer GL_BACK refers to).
>
> I don't see more context about the issue you're investigating, any pointers?
I'm sort of a fan of Michael Abrash, as he inspired me to learn programming assembly language a long time ago, but in his Graphics Programming Black Book, Chapter 23 he shows how the CRTC Index Register is used to change what is shown on the screen by alternating between two memory pages at PAGE0_OFFSET and PAGE1_OFFSET. I was under the impression that OpenGL used a similar approach with GL_FRONT and GL_BACK, hence I was expecting GL_DRAW_BUFFER to alternate between the two. On closer inspection of the glXSwapBuffers() reference page, it indeed does not say anything about alternating GL_DRAW_BUFFERs. I must have misread, with the above concept in mind. The glDrawBuffer() reference page however does speak of initial values for double buffered contexts and the use of both front and back buffers.
Can you explain to me why we are only drawing in GL_BACK and how that relates to what portion of memory is shown on the screen?
