[Xorg] X on OpenGL

[Andy Sy]

Adam Jackson wrote:

>>The one big problem I see with the OpenGL API is that it does not give
>>you any direct pixel-level access to the frame buffer and wouldn't it
>>be extremely kludgy to build a windowing system without such?
> 
> 
> man glReadPixels.
> 
> - - ajax

Right... glReadPixels, glCopyPixels and glDrawPixels... however
everyone says that implementations of these are dog-slow (abuse
of the hardware) and you're better off writing to a texture (which
is kludgy in many contexts)...

http://www.google.com/search?q=glReadPixels+slow&sourceid=mozilla-search&start=0&start=0&ie=utf-8&oe=utf-8
http://www.google.com/search?hl=en&lr=&ie=UTF-8&q=OpenGLBLit&btnG=Search

Why is it that OpenGL drivers seem to universally have this behaviour?

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