Xgl server

[David Reveman]

I've been doing some work to get an X server running on top of
OpenGL/glitz and I've got something that works pretty well now. I stuck
the code into the "xserver" tree and './configure --enable-xglserver'
should compile the common xgl code along with an Xglx server that can
run on top of an existing X server with GLX.

With a good OpenGL driver and some luck, you should be able to run most
applications on it. However, you should know that the Xglx server is
really simple, there's no real cursor and compared to the Xnest server,
Xglx must always run on top of all other windows as the back buffer is
used for pixmap memory.

There's a screenshot from running a complete gnome desktop on top of
Xglx here:
http://www.cs.umu.se/~c99drn/pics/xgl-shot.png
I was actually running Xglx on top of software mesa when I took that
screenshot. That's of course quite slow, but not completely unusable. :)

A lot of operations are accelerated, some operations can be accelerated
better, some operations are not accelerated but can be accelerated and
some operations can never be accelerated.

Here's a list of things that I think most importantly need some work:

* Get the fb layer to operate on pixel data with scan-line order
bottom-to-top. This will make software fall-backs A LOT faster. As
keithp told me, all we really need to do is to use negative strides and
I'll give that a try within in a few days, hopefully that will work just
fine.
* Replace or improve the current xgl offscreen memory manager, it wastes
huge amounts of memory right now.
* Improve xrender text performance.
* Accelerate bitmap text. Performance of applications that use bitmap
text is terrible right now. :(

The following things could also needs some work. They are probably not
as important but they would be interesting and fun to get working:

* Hook up glitz's convolution filters. This should be really easy, all
we need is a software fall-back.
* GLX and accelerated indirect rendering.
* Add Xagl and Xwgl servers.
* Add a miniglx or mesa-solo server.

Have fun playing with it. If you find any bugs (and you will), please
let me know.
 
-David