NSOpenGL* and etc

[Frederic De Jaeger]

This is a repost of a mail I sent to gnustep-dev and gnu3dkit-dev.


I have started implementating NSOpenGLContext and NSOpenGLPixelFormat
for the X backend using glx.  Here is the first screen shot.

http://thoran.free.fr/screen1.png

Some details:
I drop the idea of the GSXView.  It is a bad idea in fact.  Brent
Gulanowski pointed me that a GLContext  can be attached to any view
and this does not play well with this approach.

I wrote a class in the backend that can attach an X window to any view
that belongs to an NSWindow.  The new window is a direct descendant of
the X window containing the NSWindow.  

This class may be used for other purposes than implementing openGL.

With this, it's easy to attach a glx context to such window.
What I observed, while looking at the spec, was that the NSOpenGL API
is very close to GLX 1.3.  Even the tokens have the same numerical values.
We have the following correspondences:
 NSOpenGLPixelFormat  <--->  GLXFBConfig
 NSOpenGLContext <---> GLXContext
and they are functionally equivalent (almost)

I write, for the gui, two classes that implement the visible part of
the API (NSOpenGLContext and NSOpenGLPixelFormat).  When they are sent 
allocWithZone: they ask the current GSDisplayServer for a concrete
implementation of themselves and forward the invocation to it.

Because my drivers (NVidia, closed source) are completely buggy (the X
server crashes)  I could not write a clean implementation using the
nice GLX 1.3 API.  Now, it's an ugly mix between GLX 1.0 and GLX 1.3.

current status:
- The only things that is working is a GL context attached to a mapped
NSView (the view really needs to belong to a view hierarchy that is
attached to an NSWindow (and this window must be mapped on the
screen))
- [NSOpenGLPixelFormat initWithAttributes] just considers the most
important attributes (the one I fully understand)


things that need to be implemented:
- fullscreen and offscreen gl context
- sharing of textures and display list name spaces.
- methods related to NSOpenGLContextParameter.
- case when there are several virtual screens
- multithread.
- NSOpenGLView (should be easy, now)

and a lot of other things.

Here is the patch, if someone wants to play with.
It is very unstable.

http://thoran.free.fr/gl.tgz

There is no instruction.  
For the backend, you need to regenerate configure with autoconf, and
config.h.in with autoheader.

Cheers,

        Frederic De Jaeger