[Mesa-dev] [RFC] st/mesa: Add both front and back buffers for double-buffer visuals

[Józef Kucia]

On Wed, Jan 18, 2017 at 2:25 AM, Boyan Ding <boyan.j.ding at gmail.com> wrote:
> I don't think I find that. The only place in state tracker where
> _mesa_add_renderbuffer is called is st_framebuffer_create and only one
> of the front and back buffers is allocated based on the default
> behavior. When update_framebuffer_state() in state tracker is called
> after draw buffer changes to front, state tracker will find it refers
> to a null renderbuffer and remove it afterwards.

Buffers are allocated on demand in st_DrawBuffers() and
st_ReadBuffer(). The issue is though a bit different. A single GL
context is used with two windows (drawables).
glDrawBuffer/glDrawBuffers() is called when the first window is
current, then after glXMakeCurrent() with the second window a new
st_framebuffer is created but GL_FRONT renderbuffer is never allocated
for the newly created st_framebuffer.