direct3d9 OnLostDevice

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

Code:

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m_pDevice->Reset(&m_pres_params);

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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:

Code:

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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;
}

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here, the function IsLostDevice:

Code:

---

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;
}

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and here is how I initialized present parameters:

Code:

---

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;

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can anybody please help me?