wglGetProcAddress

wglGetProcAddress is a Windows-specific function used in OpenGL to obtain pointers to OpenGL extension functions and newer core functions that may not be exported by the system library. It is provided by opengl32.dll and is commonly used to access functions introduced after OpenGL 1.1 or functions added by graphics drivers as extensions.

The function signature is typically described as PROC wglGetProcAddress(const char* lpszProc); The return value is a generic function pointer that must be cast to the appropriate type, for example PFNGLGENBUFFERSPROC for glGenBuffers. If the requested function is not available from the driver, the function returns NULL.

Usage and context requirements: A current OpenGL rendering context must be made current on the calling thread before invoking wglGetProcAddress. The returned address may be context-specific and can vary between contexts or driver reloads, so pointers should be queried per context as needed. Core OpenGL functions that are supported by the installed context may be returned as well, but the common practice is to query functions not exported by opengl32.dll or only available via extensions.

Limitations and best practices: wglGetProcAddress relies on the driver’s support, so the result should be checked for NULL before use. It is not a cross-platform mechanism; for portability, loader libraries such as GLEW, GLAD, or GL3W are often used to encapsulate the querying process. On Windows, opengl32.dll provides OpenGL 1.1 functions directly, while newer or extension functions are typically retrieved through wglGetProcAddress.

Example usage: a function pointer is retrieved and cast to the appropriate type, then used if non-NULL.