text: #ifndef __SIEGE_INTERNAL_GL_H__
  #define __SIEGE_INTERNAL_GL_H__
  
  #if defined(APPLE) || defined(_APPLE) || defined(__APPLE__)
  #include <OpenGL/gl.h>
  #include <OpenGL/glu.h>
  #include <OpenGL/glext.h>
  #else   /* not Apple */
  #include <GL/gl.h>
  #include <GL/glu.h>
  #include <GL/glext.h>
  #endif  /* Apple */
  
  #ifndef GL_EXT_framebuffer_object
  #error "SIEGE requires EXT_framebuffer_object"
  #endif /* GL_EXT_framebuffer_object */
  PFNGLISRENDERBUFFERPROC                         glIsRenderbufferEXT;
  PFNGLBINDRENDERBUFFERPROC                       glBindRenderbufferEXT;
  PFNGLDELETERENDERBUFFERSPROC                    glDeleteRenderbuffersEXT;
  PFNGLGENRENDERBUFFERSPROC                       glGenRenderbuffersEXT;
  PFNGLRENDERBUFFERSTORAGEPROC                    glRenderbufferStorageEXT;
  PFNGLGETRENDERBUFFERPARAMETERIVPROC             glGetRenderbufferParameterivEXT;
  PFNGLISFRAMEBUFFERPROC                          glIsFramebufferEXT;
  PFNGLBINDFRAMEBUFFERPROC                        glBindFramebufferEXT;
  PFNGLDELETEFRAMEBUFFERSPROC                     glDeleteFramebuffersEXT;
  PFNGLGENFRAMEBUFFERSPROC                        glGenFramebuffersEXT;
  PFNGLCHECKFRAMEBUFFERSTATUSPROC                 glCheckFramebufferStatusEXT;
  PFNGLFRAMEBUFFERTEXTURE1DPROC                   glFramebufferTexture1DEXT;
  PFNGLFRAMEBUFFERTEXTURE2DPROC                   glFramebufferTexture2DEXT;
  PFNGLFRAMEBUFFERTEXTURE3DPROC                   glFramebufferTexture3DEXT;
  PFNGLFRAMEBUFFERRENDERBUFFERPROC                glFramebufferRenderbufferEXT;
  PFNGLGETFRAMEBUFFERATTACHMENTPARAMETERIVPROC    glGetFramebufferAttachmentParameterivEXT;
  PFNGLGENERATEMIPMAPPROC                         glGenerateMipmapEXT;
  
  #ifndef GL_EXT_blend_minmax
  #error "SIEGE requires EXT_blend_minmax"
  #endif /* GL_EXT_blend_minmax */
  PFNGLBLENDEQUATIONPROC                          glBlendEquationEXT;
  
  #define GLTEX(x) (*(GLuint*)(x)->handle)
  #define GLFBO(x) (*(GLuint*)(x)->fboid)
  #define GLRB(x) (*(GLuint*)(x)->rbid)
  
  #endif /* __SIEGE_INTERNAL_GL_H__ */
  