[Dri-devel] Migration of libGLcore.a to DRI-like interface

[Ian R. <id...@us...>]

On Sunday I researched what it would take to migrate the 
libglx.a-libGLcore.a interface to match the (new) libGL.so-*_dri.so 
interface.  Much to my surprise, I don't think it will be as difficult 
as I had first thought.  There are a few issues.

1. Right now libGLcore has several entry-points for getting GLX visual 
information into the driver.  The file 
programs/Xserver/GL/mesa/X/xf86glx.c contains all of this interface. 
The interface functions are __MESA_initVisuals, __MESA_setVisualConfigs, 
and __MESA_screenProbe.  __MESA_screenProbe is analogous to 
__driCreateNewScreen.  The other two functions server part of the 
purpose of __driCreateNewScreen, but they also do some work not related 
to the driver.  They create a list of X (not GLX) visuals to give back 
to the X server.  That functionality should be moved into libglx.a.

2. Mesa's X11 driver, which is the basis of libGLcore, depends on 
information from an X VisualInfo.  Most of the uses can be eliminated 
trivially, but the depth / nplanes and ColomapEntries / colormap_size 
fields are another story.  The problem here is that the 
__driCreateNewScreen doesn't, and can't, provide VIsualInfo structures 
to the driver.

3. libglx.a calls functions in directly instead of using a dispatch 
table.  Let me clarify this a bit.  On the client-side, the symbol 
glVertex3f is libGL.so.  When an app calls that function, it looks up 
the "real" function and calls it.  On the server-side, the symbol 
glVertex3f is in libGLcore.so (i.e., the driver).  When a glVertex3f 
protocol message comes in, libglx.a calls this function directly.  This 
function then may (or may not, as in the case of the Mac OS X 
libGLcore.a) do a dispatch table look-up.  What should happen is the 
protocol functions should do the dispatch table look-up and call the 
function from the table.

Those are the big issues that I could find.  The rest of it just looks 
like changing function parameters and data structures, or moving code 
from libGLcore to libglx.  I've attached a patch that removes some of 
the dependance on the VisualInfo structure and removes some redundant 
fields from the mesa_visual structure.  Unless there are objections, I 
will commit this soon.  I've only tested this with stand-alone Mesa so far.