Because the GL does not include queries for the performance characteristics of an implementation, some applications are written to recognize known platforms and modify their GL usage based on known performance characteristics of these platforms. Strings GL_VENDOR and GL_RENDERER together uniquely specify a platform. They do not change from release to release and should be used by platform-recognition algorithms.
Some applications want to make use of features that are not part of the standard GL. These features may be implemented as extensions to the standard GL. The GL_EXTENSIONS string is a space-separated list of supported GL extensions. (Extension names never contain a space character.)
The GL_VERSION string begins with a version number. The version number uses one of these forms:
Vendor-specific information may follow the version number. Its depends on the implementation, but a space always separates the version number and the vendor-specific information.
All strings are null-terminated.
The client and server may support different versions or extensions. glGetString always returns a compatible version number or list of extensions. The release number always describes the server.
GL_INVALID_OPERATION is generated if glGetString is executed between the execution of glBegin and the corresponding execution of glEnd.
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