Creating a dummy HWND to pass to Direct3D

Question

I'm trying to translate the D3DImage sample to pure C# with SharpDX. Direct3D requires a HWND to initialize, and this is how it's done in C++:

WNDCLASSEX g_wc = { sizeof(WNDCLASSEX), CS_CLASSDC, nullptr, 0L, 0L,
      GetModuleHandle(nullptr), nullptr, nullptr, nullptr, nullptr, L"Foo", nullptr };
HWND g_windowHandle;

// Create invisible window to get HWND
RegisterClassEx(&g_wc);
g_windowHandle = CreateWindow(L"Foo", L"Foo", WS_OVERLAPPEDWINDOW, 
    0, 0, 0, 0, nullptr, nullptr, nullptr, nullptr);

    // then eventually we can create the device
Direct3DCreate9Ex(D3D_SDK_VERSION, &m_d3d);
m_d3d->CreateDeviceEx(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, g_windowHandle,
    vertexProcessing | D3DCREATE_MULTITHREADED | D3DCREATE_FPU_PRESERVE,
    &d3dpp, nullptr, &m_d3dDevice);

What would be the best way of obtaining this dummy HWND in C#? It must be different from the main window's HWND. My application is a WPF project.

wouldn't a dummy windows form form/usercontrol do the job? they should have a handle. — mrvux, Jan 29 '13 at 21:49
It isn't clear why you'd use a dummy window. Just use the regular window that you created in WPF. Use the WindowInteropHelper.Handle property. — Hans Passant, Jan 29 '13 at 22:53
@HansPassant because that's what the MSDN sample I linked to states: "In general, you create a dummy HWND for Direct3D9 to use." — Asik, Jan 29 '13 at 23:20

meklarian · Answer 1 · 2013-01-29T23:40:23.240

The documentation for IDirect3D9Ex::CreateDeviceEx says the HWND parameter is optional if you are in windowed mode and your presentation HWND in your D3DPRESENT_PARAMETERS structure is set (late edit: oops, can't be blank).

From IDirect3D9Ex::CreateDeviceEx @ MSDN

hFocusWindow [in]
Type: HWND
The focus window alerts Direct3D when an application switches from foreground mode to background mode. For full-screen mode, the window specified must be a top-level window. For windowed mode, this parameter may be NULL only if the hDeviceWindow member of pPresentationParameters is set to a valid, non-NULL value.

D3DPRESENT_PARAMETERS struct @ MSDN

To get a window handle for use, you can make another top-level window via regular .NET framework methods and grab its window handle instead of going through the motions with Win32 method calls.

If you find can't use the Handle provided by WPF (per Hans Passant's comment), you can also make a dummy Windows Form and instantiate it as a hidden window, and use its handle instead.

WindowInteropHelper (WPF) @ MSDN

Control.Handle (Windows Forms) @ MSDN

Footnote: Your existing WPF main window handle is probably fine unless some mechanism in SharpDX or an existing Viewport3D has a conflict with using Direct3D9 in this manner.

3-D Graphics Overview (WPF) @ MSDN
Viewport3D Class (WPF) @ MSDN

I just did some tests and apparently it works even without any HWND at all, either to CreateDeviceEx or in the PresentParams. I'm able to instantiate several independent devices that way. So at this point I'm wondering why the MSDN sample suggests creating a dummy HWND to Direct3D or what it's supposed to achieve at all. — Asik, Jan 30 '13 at 16:31
Vista and later do not seem to require a HWND, but the call will fail in Windows XP without a HWND. — dschaeffer, Oct 17 '13 at 16:38

Creating a dummy HWND to pass to Direct3D

1 Answers1