wglCreateContext fails with error code 6 (Invalid Handle) - windows

Question

I'm trying to create a wgl context according to the tutorial at https://www.khronos.org/opengl/wiki/Creating_an_OpenGL_Context_(WGL). For whatever reason, wglCreateContext returns null, and GetLastError returns 6, or Invalid Handle. I have used the tutorial before, and it worked just fine.
I'm trying to create a dummy context to a hidden window so that I can create another context for the user window. What's going on?
The Windows API is referred through the winAPI identifier, and wgl is a global struct containing function pointers to OpenGL.
struct WglContext
{
winAPI.HDC hdc;
winAPI.HGLRC handle;
}
__gshared Win32GL wgl;
///WGL-specific global data.
struct Win32GL
{
import oswald : OsWindow, WindowConfig, WindowError;
OsWindow helperWindow;
winAPI.HINSTANCE instance;
PFN_wglCreateContext createContext;
PFN_wglDeleteContext deleteContext;
PFN_wglGetProcAddress getProcAddress;
PFN_wglMakeCurrent makeCurrent;
PFN_wglCreateContextAttribsARB createContextAttribsARB;
PFN_wglGetExtensionStringARB getExtensionStringARB;
PFN_wglGetExtensionStringEXT getExtensionStringEXT;
bool extensionsAreLoaded;
static void initialize()
{
if (wgl.instance !is null)
return; //The library has already been initialized
WindowConfig cfg;
cfg.title = "viewport_gl_helper";
cfg.hidden = true;
auto windowError = OsWindow.createNew(cfg, &wgl.helperWindow);
if (windowError != WindowError.NoError)
{
import std.conv : to;
assert(false, "Failed to create helper window: " ~ windowError.to!string);
}
wgl.instance = winAPI.LoadLibrary("opengl32.dll");
if (wgl.instance is null)
assert(false, "Viweport failed to load opengl32.dll");
wgl.bind(cast(void**)&wgl.createContext, "wglCreateContext\0");
wgl.bind(cast(void**)&wgl.deleteContext, "wglDeleteContext\0");
wgl.bind(cast(void**)&wgl.getProcAddress, "wglGetProcAddress\0");
wgl.bind(cast(void**)&wgl.makeCurrent, "wglMakeCurrent\0");
}
static void terminate()
{
if (!wgl.instance)
return;
winAPI.FreeLibrary(wgl.instance);
wgl.helperWindow.destroy();
}
void bind(void** func, in string name)
{
*func = winAPI.GetProcAddress(this.instance, name.ptr);
}
}
struct WglContext
{
winAPI.HDC hdc;
winAPI.HGLRC handle;
}
WglContext wglCreateTmpContext()
{
assert(wgl.instance);
winAPI.PIXELFORMATDESCRIPTOR pfd;
pfd.nSize = winAPI.PIXELFORMATDESCRIPTOR.sizeof;
pfd.nVersion = 1;
pfd.dwFlags = winAPI.PFD_DRAW_TO_WINDOW | winAPI.PFD_SUPPORT_OPENGL | winAPI.PFD_DOUBLEBUFFER;
pfd.iPixelType = winAPI.PFD_TYPE_RGBA;
pfd.cColorBits = 24;
auto hdc = winAPI.GetDC(wgl.helperWindow.platformData.handle);
const pixelFormat = winAPI.ChoosePixelFormat(hdc, &pfd);
if (winAPI.SetPixelFormat(hdc, pixelFormat, &pfd) == winAPI.FALSE)
assert(false, "Failed to set pixel format for temp context");
writeln(hdc);
writeln(pixelFormat);
winAPI.HGLRC context = wgl.createContext(hdc);
if (context is null)
{
import std.conv: to;
assert(false, "Failed to create temp context: Error Code " ~ winAPI.GetLastError().to!string);
}
if (wgl.makeCurrent(hdc, context) == winAPI.FALSE)
{
wgl.deleteContext(context);
assert(false, "Failed to make temp context current");
}
return WglContext(hdc, context);
}
void main()
{
wgl.initialize(); //Fetches function pointers, and loads opengl32.dll
auto context = wglCreateTmpContext();
wglDeleteContext(context); //Delegates to wgl.deleteContext
wgl.terminate(); //Unloads opengl32.dll and nulls function pointers
}

Answer 1

I know nothing on that winAPI you use. Anyhow, I'm sure of:
You must:
Create a window and get its HWND handle (Windows definition of
HWND, see below). Tipically the window uses WS_CLIPCHILDREN | WS_CLIPSIBLINGS
style; but try also the WS_OVERLAPPEDWINDOW as in the link you
posted.
Verify you get a valid HWND, and a valid HDC from it.
HWND and HDC are defined as *void. I would not trust on auto.