wglMakeCurrent(): 0xc0070006 error

Don't use a global window's handle to initialize your window DC like shown below. The problem is, WM_CREATE will be sent before your global variable will be initialized ‒ i.e. before returning from CreateWindowW(). Thus, the global variable will be NULL at the moment when window DC is created.

Note that both GetDC() and wglCreateContext() will return non-NULL handles. The problem will become apparent on calling wglMakeCurrent() ‒ it will fail with 0xc0070006, where 6 means "invalid handle".

To deal with this, note that the window procedure has a window handle which you can use. Instead of the global window handle variable, pass the window procedure's hWnd argument to your OpenGL initialization function.

Code demonstrating the problem: