const char *glXGetClientString( Display *dpy, int name)
The extensions string is null-terminated and contains a space-separated list of extension names. (The extension names never contain spaces.) If there are no extensions to GLX, then the empty string is returned.
The version string is laid out as follows:
Both the major and minor portions of the version number are of arbitrary length. The vendor-specific information is optional. However, if it is present, the format and contents are implementation specific.
If the GLX version is 1.1 or 1.0, the GL version must be 1.0. If the GLX version is 1.2, then the GL version must be 1.1.
glXGetClientString only returns information about GLX extensions supported by the client. Call glGetString to get a list of GL extensions supported by the server.