wglMakeCurrent

wglMakeCurrent is a Windows-specific function in the WGL API that binds an OpenGL rendering context to a device context for the calling thread. It allows subsequent OpenGL commands issued by that thread to render to the specified device context using the specified rendering context. The function is typically declared as BOOL wglMakeCurrent(HDC hdc, HGLRC hglrc); and returns a nonzero value on success or zero on failure.

When both hdc and hglrc are non-NULL, wglMakeCurrent binds the given rendering context to the given device context for the calling thread. If both parameters are NULL, the function releases the current rendering context from the thread, meaning no GL context is current for that thread. If only one parameter is NULL, the call generally fails and leaves the current context unchanged.

Usage in a typical OpenGL flow involves obtaining a device context, selecting a suitable pixel format, creating a GL rendering context, and then calling wglMakeCurrent(hdc, hglrc) to begin rendering. To stop rendering and detach the context, a common step is to call wglMakeCurrent(NULL, NULL). Proper cleanup also includes releasing the device context and destroying the GL context when it is no longer needed.

Important considerations include thread ownership: a GL context may be current on only one thread at a time, and a thread may have at most one current GL context. Errors can arise from invalid or mismatched device contexts or rendering contexts, or from attempting to use GL commands when no context is current. Retrieve extended error information via system APIs if wglMakeCurrent fails.