The wglGetProcAddress function returns the address of an OpenGL extension function for use with the current OpenGL rendering context.
Points to a null-terminated string that is the name of the extension function. The name of the extension function must be identical to a corresponding function implemented by OpenGL.
When the function succeeds, the return value is the address of the extension function.
The OpenGL library supports multiple implementations of its functions. Extension functions supported in one rendering context are not necessarily available in a separate rendering context. Thus, for a given rendering context in an application, use the function addresses returned by the wglGetProcAddress function only.
The spelling and the case of the extension function pointed to by extension must be identical to that of a function supported and implemented by OpenGL. Because extension functions are not exported by OpenGL, you must use wglGetProcAddress to get the addresses of vendor-specific extension functions.
The extension function addresses are unique for each pixel format. All rendering contexts of a given pixel format share the same extension function addresses.