glextensions.h Example File
demos/boxes/glextensions.h

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 #ifndef GLEXTENSIONS_H
 #define GLEXTENSIONS_H

 #include <QtOpenGL>

 /*
 Functions resolved:

 glGenFramebuffersEXT
 glGenRenderbuffersEXT
 glBindRenderbufferEXT
 glRenderbufferStorageEXT
 glDeleteFramebuffersEXT
 glDeleteRenderbuffersEXT
 glBindFramebufferEXT
 glFramebufferTexture2DEXT
 glFramebufferRenderbufferEXT
 glCheckFramebufferStatusEXT

 glActiveTexture
 glTexImage3D

 glGenBuffers
 glBindBuffer
 glBufferData
 glDeleteBuffers
 glMapBuffer
 glUnmapBuffer
 */

 #ifndef Q_WS_MAC
 # ifndef APIENTRYP
 #   ifdef APIENTRY
 #     define APIENTRYP APIENTRY *
 #   else
 #     define APIENTRY
 #     define APIENTRYP *
 #   endif
 # endif
 #else
 # define APIENTRY
 # define APIENTRYP *
 #endif

 #ifndef GL_VERSION_1_2
 #define GL_TEXTURE_3D 0x806F
 #define GL_TEXTURE_WRAP_R 0x8072
 #define GL_CLAMP_TO_EDGE 0x812F
 #define GL_BGRA 0x80E1
 #endif

 #ifndef GL_VERSION_1_3
 #define GL_TEXTURE0 0x84C0
 #define GL_TEXTURE1 0x84C1
 #define GL_TEXTURE2 0x84C2
 #define GL_TEXTURE_CUBE_MAP 0x8513
 #define GL_TEXTURE_CUBE_MAP_POSITIVE_X 0x8515
 //#define GL_TEXTURE_CUBE_MAP_NEGATIVE_X 0x8516
 //#define GL_TEXTURE_CUBE_MAP_POSITIVE_Y 0x8517
 //#define GL_TEXTURE_CUBE_MAP_NEGATIVE_Y 0x8518
 //#define GL_TEXTURE_CUBE_MAP_POSITIVE_Z 0x8519
 //#define GL_TEXTURE_CUBE_MAP_NEGATIVE_Z 0x851A
 #endif

 #ifndef GL_ARB_vertex_buffer_object
 typedef ptrdiff_t GLsizeiptrARB;
 #endif

 #ifndef GL_VERSION_1_5
 #define GL_ARRAY_BUFFER 0x8892
 #define GL_ELEMENT_ARRAY_BUFFER 0x8893
 #define GL_READ_WRITE 0x88BA
 #define GL_STATIC_DRAW 0x88E4
 #endif

 #ifndef GL_EXT_framebuffer_object
 #define GL_RENDERBUFFER_EXT 0x8D41
 #define GL_FRAMEBUFFER_EXT 0x8D40
 #define GL_FRAMEBUFFER_COMPLETE_EXT 0x8CD5
 #define GL_COLOR_ATTACHMENT0_EXT 0x8CE0
 #define GL_DEPTH_ATTACHMENT_EXT 0x8D00
 #endif

 typedef void (APIENTRY *_glGenFramebuffersEXT) (GLsizei, GLuint *);
 typedef void (APIENTRY *_glGenRenderbuffersEXT) (GLsizei, GLuint *);
 typedef void (APIENTRY *_glBindRenderbufferEXT) (GLenum, GLuint);
 typedef void (APIENTRY *_glRenderbufferStorageEXT) (GLenum, GLenum, GLsizei, GLsizei);
 typedef void (APIENTRY *_glDeleteFramebuffersEXT) (GLsizei, const GLuint*);
 typedef void (APIENTRY *_glDeleteRenderbuffersEXT) (GLsizei, const GLuint*);
 typedef void (APIENTRY *_glBindFramebufferEXT) (GLenum, GLuint);
 typedef void (APIENTRY *_glFramebufferTexture2DEXT) (GLenum, GLenum, GLenum, GLuint, GLint);
 typedef void (APIENTRY *_glFramebufferRenderbufferEXT) (GLenum, GLenum, GLenum, GLuint);
 typedef GLenum (APIENTRY *_glCheckFramebufferStatusEXT) (GLenum);

 typedef void (APIENTRY *_glActiveTexture) (GLenum);
 typedef void (APIENTRY *_glTexImage3D) (GLenum, GLint, GLenum, GLsizei, GLsizei, GLsizei, GLint, GLenum, GLenum, const GLvoid *);

 typedef void (APIENTRY *_glGenBuffers) (GLsizei, GLuint *);
 typedef void (APIENTRY *_glBindBuffer) (GLenum, GLuint);
 typedef void (APIENTRY *_glBufferData) (GLenum, GLsizeiptrARB, const GLvoid *, GLenum);
 typedef void (APIENTRY *_glDeleteBuffers) (GLsizei, const GLuint *);
 typedef void *(APIENTRY *_glMapBuffer) (GLenum, GLenum);
 typedef GLboolean (APIENTRY *_glUnmapBuffer) (GLenum);

 struct GLExtensionFunctions
 {
         bool resolve(const QGLContext *context);

     bool fboSupported();
     bool openGL15Supported(); // the rest: multi-texture, 3D-texture, vertex buffer objects

         _glGenFramebuffersEXT GenFramebuffersEXT;
         _glGenRenderbuffersEXT GenRenderbuffersEXT;
         _glBindRenderbufferEXT BindRenderbufferEXT;
         _glRenderbufferStorageEXT RenderbufferStorageEXT;
         _glDeleteFramebuffersEXT DeleteFramebuffersEXT;
         _glDeleteRenderbuffersEXT DeleteRenderbuffersEXT;
         _glBindFramebufferEXT BindFramebufferEXT;
         _glFramebufferTexture2DEXT FramebufferTexture2DEXT;
         _glFramebufferRenderbufferEXT FramebufferRenderbufferEXT;
         _glCheckFramebufferStatusEXT CheckFramebufferStatusEXT;

         _glActiveTexture ActiveTexture;
         _glTexImage3D TexImage3D;

         _glGenBuffers GenBuffers;
         _glBindBuffer BindBuffer;
         _glBufferData BufferData;
         _glDeleteBuffers DeleteBuffers;
         _glMapBuffer MapBuffer;
         _glUnmapBuffer UnmapBuffer;
 };

 inline GLExtensionFunctions &getGLExtensionFunctions()
 {
         static GLExtensionFunctions funcs;
         return funcs;
 }

 #define glGenFramebuffersEXT getGLExtensionFunctions().GenFramebuffersEXT
 #define glGenRenderbuffersEXT getGLExtensionFunctions().GenRenderbuffersEXT
 #define glBindRenderbufferEXT getGLExtensionFunctions().BindRenderbufferEXT
 #define glRenderbufferStorageEXT getGLExtensionFunctions().RenderbufferStorageEXT
 #define glDeleteFramebuffersEXT getGLExtensionFunctions().DeleteFramebuffersEXT
 #define glDeleteRenderbuffersEXT getGLExtensionFunctions().DeleteRenderbuffersEXT
 #define glBindFramebufferEXT getGLExtensionFunctions().BindFramebufferEXT
 #define glFramebufferTexture2DEXT getGLExtensionFunctions().FramebufferTexture2DEXT
 #define glFramebufferRenderbufferEXT getGLExtensionFunctions().FramebufferRenderbufferEXT
 #define glCheckFramebufferStatusEXT getGLExtensionFunctions().CheckFramebufferStatusEXT

 #define glActiveTexture getGLExtensionFunctions().ActiveTexture
 #define glTexImage3D getGLExtensionFunctions().TexImage3D

 #define glGenBuffers getGLExtensionFunctions().GenBuffers
 #define glBindBuffer getGLExtensionFunctions().BindBuffer
 #define glBufferData getGLExtensionFunctions().BufferData
 #define glDeleteBuffers getGLExtensionFunctions().DeleteBuffers
 #define glMapBuffer getGLExtensionFunctions().MapBuffer
 #define glUnmapBuffer getGLExtensionFunctions().UnmapBuffer

 #endif