gl.c

static void gl_context_init(HWND hwnd)
{
	HDC h;
	HGLRC tgl, gl;
	HWND fake_window;
	unsigned int nformat;
	int pf;

	WNDCLASS wc = {
		.style = CS_OWNDC,
		.lpfnWndProc = DefWindowProcA,
		.hInstance = GetModuleHandle(0),
		.lpszClassName = "dummy"
	};

	PIXELFORMATDESCRIPTOR pfd = {
		sizeof(PIXELFORMATDESCRIPTOR),
		1,
		PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
		PFD_TYPE_RGBA,
		32,
		0, 0, 0,
		0, 0, 0,
		0, 0,
		0, 0, 0, 0, 0,
		24, 0, 0, 0, 0, 0, 0, 0
	};

	const int attrib[] = {
		WGL_CONTEXT_MAJOR_VERSION_ARB, 4,
		WGL_CONTEXT_MINOR_VERSION_ARB, 5,
		WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
		0, 0
	};

	int pixel_format[] =
	{
		WGL_DRAW_TO_WINDOW_ARB, 1,
		WGL_ACCELERATION_ARB, WGL_FULL_ACCELERATION_ARB,
		WGL_SUPPORT_OPENGL_ARB, 1,
		WGL_COLOR_BITS_ARB, 32,
		WGL_DEPTH_BITS_ARB, 24,
		WGL_ALPHA_BITS_ARB, 8,
		WGL_PIXEL_TYPE_ARB, WGL_TYPE_RGBA_ARB,
		WGL_SAMPLE_BUFFERS_ARB, 1,
		WGL_SAMPLES_ARB, 16,
		0, 0
	};

	/* Create a fake window */
	RegisterClass(&wc);
	fake_window = CreateWindowEx(0, wc.lpszClassName, "dummy window", 0, 0, 0, 0, 0, 0, 0, wc.hInstance, 0);
	
	/* Create a fake DC from fake window */
	h = GetDC(fake_window);
	nformat = ChoosePixelFormat(h, &pfd);

	/* Set a similar pixel format to what we want, and create a fake opengl context */
	SetPixelFormat(h, nformat, &pfd);
	tgl = wglCreateContext(h);
	wglMakeCurrent(h, tgl);

	/* Using the fake context, get the function pointers for the extended functions */
	wglCreateContextAttribsARB = (void *)wglGetProcAddress("wglCreateContextAttribsARB");
	wglChoosePixelFormatARB = (void *)wglGetProcAddress("wglChoosePixelFormatARB");

	/* Destroy the fake window/dc/context */
	wglMakeCurrent(h, 0);
	wglDeleteContext(tgl);
	ReleaseDC(fake_window, h);
	DestroyWindow(fake_window);
	UnregisterClass(wc.lpszClassName, wc.hInstance);

	/* Now the DC of the real window */
	h = GetDC(hwnd);

	/* Set the real pixel format */
	wglChoosePixelFormatARB(h, pixel_format, 0, 1, &pf, &nformat);
	if(!nformat)
	{
		fprintf(stderr, "Fatal: Pixel format unsupported");
		exit(0);
	}
	
	DescribePixelFormat(h, pf, sizeof pfd, &pfd);
	if(!SetPixelFormat(h, pf, &pfd))
	{
		fprintf(stderr, "Fatal: Could not set pixel format");
		exit(0);
	}

	/* Create the real context */
	gl = wglCreateContextAttribsARB(h, 0, attrib);
	if(!gl)
	{
		fprintf(stderr, "Fatal: Couldn't create OpenGL context");
		exit(0);
	}

	wglMakeCurrent(NULL, NULL);
	wglDeleteContext(tgl);
	wglMakeCurrent(h, gl);
	ReleaseDC(hwnd, h);
}