GL extension checking/loading

[tigital]

me again,

...at the moment, freespace1/2 doesn't seem to take advantage of any  
opengl extensions, and there are several possible things that should  
give appreciable speed ups, at least on OSX (I'm thinking specifically  
of replacing GL_TEXTURE_2D with GL_TEXTURE_RECTANGLE_EXT, adding  
glTextureRangeAPPLE(), and using GL_UNPACK_CLIENT_STORAGE_APPLE:  all  
of these can select a cpu bypass for direct AGP texture uploads)...all  
of this could easily be #ifdef __APPLE__, but I'd like to set it up so  
that at least future addition of extension-enabled graphic improvements  
is easier...

...here's the code I've used before for cross platform extension  
checking (but also for checking that a particular capability is  
available on a OSX graphic card):

/*
  This is SGI sample code taken directly from OpenGL.org:
   
http://www.opengl.org/developers/code/features/OGLextensions/ 
OGLextensions.html
  */
int OpenGLExtensionIsSupported(const char* extension) {
   const GLubyte *extensions = NULL;
   const GLubyte *start;
   GLubyte *where, *terminator;

   /* Extension names should not have spaces. */
   where = (GLubyte *) strchr(extension, ' ');
   if (where || *extension == '\0')
     return 0;
   extensions = glGetString(GL_EXTENSIONS);
   /* It takes a bit of care to be fool-proof about parsing the
      OpenGL extensions string. Don't be fooled by sub-strings,
      etc. */
   start = extensions;
   for (;;) {
     where = (GLubyte *) strstr((const char *) start, extension);
     if (!where)
       break;
     terminator = where + strlen(extension);
     if (where == start || *(where - 1) == ' ')
       if (*terminator == ' ' || *terminator == '\0')
         return 1;
     start = terminator;
   }
   return 0;
}

...so, anyone have thoughts, pro/con?  I know that the prevailing  
opinion of the icculus port is to maintain the basic integrity of the  
code (meaning no specific changes for mod support, or features that  
break compatibility with the basic campaigns), but I don't think the  
above texture speedups are anything but performance enhancers...

l8r,
jamie
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