[forum] direct rendering and compatability

[Andrew C Aitchison]

On Tue, 18 Mar 2003, Gregor Burger wrote:

> As far as I understand the x communication:
> 	1. a client makes a request through an api-call
> 	2. the request is translated into the x-protocol and sent over the network
> 	3. the server gets the request and decodes it
> 	4. the server calls a function (probably in a driver to execute the 
> 	    commands from the client. 
> 
> 	and vice versa. 
> 
> What I can see is that step 3 and 4 aren't neccesery
> if you work on the localhost (90% of every x-session).

It is steps 2 and 3 that aren't necessary.
As Alan Coopersmith says, the x-protocol doesn't go over the network when 
it doesn't need to.

On many XFree86 platforms, for OpenGL calls (in the libGL library)
you have the option (usually at run time with LD_LIBRARY_PATH or similar)
of choosing a libGL.so which knows about the Direct Rendering 
Infrastructure (DRI) and skips steps 2 and 3, calling the kernel
routines directly.
So your subject line was right, and the idea is used for some calls.

-- 
Dr. Andrew C. Aitchison		Computer Officer, DPMMS, Cambridge
A.C.Aitchison@dpmms.cam.ac.uk	http://www.dpmms.cam.ac.uk/~werdna