direct3d9 OnLostDevice

[Feoggou]

Hi!

I have a fullscreen d3d9 application, with an image displayed on the screen. if I press alt-tab to switch to another window, and then I try to get back to my application, I receive D3DERR_INVALIDCALL error at

m_pDevice->Reset(&m_pres_params);

but the problem is that I did not modify m_pres_params structure since the initialization of direct3d (when worked). And I didn't even switch to windowed mode. Can anybody tell me what the problem is and what I can do to solve it?

my code:

main loop:

int CGameApp::Run(void)
{
	MSG msg = {0};

	while (msg.message != WM_QUIT)
	{
		while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}

		if (FALSE == IsLostDevice())
		{
			UpdateScene();
			DrawScene();
		}
	}

	return (int)msg.wParam;
}

here, the function IsLostDevice:

bool CGameApp::IsLostDevice(void)
{
	HRESULT hr = m_pDevice->TestCooperativeLevel();

	if (hr == D3DERR_DEVICELOST)
	{
		Sleep(20);
		return true;
	}

	if (hr == D3DERR_DRIVERINTERNALERROR) D3DErrorMessage(hr);

	if (hr == D3DERR_DEVICENOTRESET)
	{
		OnLostDevice();//here I call OnLost on the sprite
		HRESULT hr = m_pDevice->Reset(&m_pres_params);
		if (hr != D3D_OK) D3DErrorMessage(hr);
		OnResetDevice();//here I call OnReset on the sprite
		return false;
	}

	return false;
}

and here is how I initialized present parameters:

ZeroMemory(&m_pres_params, sizeof(m_pres_params));

m_pres_params.BackBufferWidth            = m_nWidth;//that is, 800
m_pres_params.BackBufferHeight           = m_nHeight;//that is, 600
m_pres_params.BackBufferFormat           = D3DFMT_X8R8G8B8;
m_pres_params.BackBufferCount            = 1;
m_pres_params.MultiSampleType            = D3DMULTISAMPLE_NONE;
m_pres_params.MultiSampleQuality         = 0;
m_pres_params.SwapEffect                 = D3DSWAPEFFECT_DISCARD;
m_pres_params.hDeviceWindow              = m_hWnd;
m_pres_params.Windowed                   = bWindowed;
m_pres_params.EnableAutoDepthStencil     = true;
m_pres_params.AutoDepthStencilFormat     = D3DFMT_D24S8;
m_pres_params.Flags                      = 0;
m_pres_params.FullScreen_RefreshRateInHz = D3DPRESENT_RATE_DEFAULT;

can anybody please help me?