IDirectDrawSurface7 * DXC_ddraw::pCreateOffScreenSurface(WORD wSzX, WORD wSzY)
{
	DDSURFACEDESC2 ddsd;
	IDirectDrawSurface7 * pdds4;

    ZeroMemory(&ddsd, sizeof(ddsd));
	if ((wSzX % 4) != 0) wSzX += 4 - (wSzX % 4);
    ddsd.dwSize  = sizeof(ddsd);
    ddsd.dwFlags = DDSD_CAPS | DDSD_HEIGHT |DDSD_WIDTH;
	ddsd.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN | DDSCAPS_SYSTEMMEMORY;
	ddsd.dwWidth  = (DWORD)wSzX;
    ddsd.dwHeight = (DWORD)wSzY;
    if (m_lpDD4->CreateSurface(&ddsd, &pdds4, NULL) != DD_OK) return NULL;
	return pdds4;
}

void DXC_ddraw::ChangeDisplayMode(HWND hWnd)
{
	HRESULT        ddVal;
	DDSURFACEDESC2 ddsd;

	if (m_lpBackB4flip != NULL)
	{
		m_lpBackB4flip->Release();
		m_lpBackB4flip = NULL;
	}
	if (m_lpBackB4 != NULL) m_lpBackB4->Release();
	if (m_lpFrontB4 != NULL) m_lpFrontB4->Release();
	if (m_lpDD4 != NULL)
	{
		if (m_bFullMode == TRUE) m_lpDD4->RestoreDisplayMode();
	}

	if( m_bFullMode == TRUE )
	{
		int cx = GetSystemMetrics(SM_CXFULLSCREEN);
		int cy = GetSystemMetrics(SM_CYFULLSCREEN);

		ddVal = m_lpDD4->SetCooperativeLevel(hWnd, DDSCL_NORMAL);
		if (ddVal != DD_OK) return;

		cx = cx/2;
		cy = cy/2;
		if(cy>280) cy -= 40;
		SetWindowPos( hWnd, NULL, cx-320, cy-240, 640, 480, SWP_SHOWWINDOW);

		// Create Front Buffer
		memset( (VOID *)&ddsd, 0, sizeof(ddsd) );
		ddsd.dwSize = sizeof( ddsd );
		ddsd.dwFlags = DDSD_CAPS;
		//ddsd.dwBackBufferCount = 0;
		ddsd.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE;
		
		ddVal = m_lpDD4->CreateSurface(&ddsd, &m_lpFrontB4, NULL);
		if (ddVal != DD_OK) return;

		SetRect(&m_rcFlipping, cx-320, cy-240, cx+320, cy+240); // our fictitious sprite bitmap is... 
		m_bFullMode = FALSE;
	}
	else
	{
		DDSCAPS2       ddscaps;
		// Full Screen Mode
		ddVal = m_lpDD4->SetCooperativeLevel(hWnd, DDSCL_EXCLUSIVE | DDSCL_FULLSCREEN);
		if (ddVal != DD_OK) return;

		ddVal = m_lpDD4->SetDisplayMode(640, 480, 16,0,0);
		if (ddVal != DD_OK) return;
		//Create Front Buffer
		memset( (VOID *)&ddsd, 0, sizeof(ddsd) );
		ddsd.dwSize = sizeof( ddsd );
		ddsd.dwFlags = DDSD_CAPS | DDSD_BACKBUFFERCOUNT;
		ddsd.dwBackBufferCount = 1;//2; //v1.3
		ddsd.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE | DDSCAPS_FLIP | DDSCAPS_COMPLEX;
		
		ddVal = m_lpDD4->CreateSurface(&ddsd, &m_lpFrontB4, NULL);
		if (ddVal != DD_OK) return;

// Learned from:
// http://www.gamedev.net/reference/articles/article608.asp

		ZeroMemory(&ddscaps, sizeof(ddscaps));
		ddscaps.dwCaps = DDSCAPS_BACKBUFFER;
		ddVal = m_lpFrontB4->GetAttachedSurface(&ddscaps, &m_lpBackB4flip);
		if (ddVal != DD_OK) return;
		SetRect(&m_rcFlipping, 0, 0, 640, 480); // our fictitious sprite bitmap is... 
		m_bFullMode = TRUE;
	}
	InitFlipToGDI(hWnd);
	// Create Back Buffer
	m_lpBackB4 = pCreateOffScreenSurface(640, 480);
	if (m_lpBackB4 == NULL) return;

	// Pre-draw background surface create buffer 
	m_lpPDBGS = pCreateOffScreenSurface(640+32, 480+32);
	if (m_lpPDBGS == NULL) return;

	// Getting the back buffer's address and pitch
 
	ddsd.dwSize = sizeof(ddsd);
	if (m_lpBackB4->Lock(NULL, &ddsd, DDLOCK_WAIT, NULL) != DD_OK) return;
	m_pBackB4Addr        = (WORD *)ddsd.lpSurface;
	m_sBackB4Pitch       = (short)ddsd.lPitch >> 1;
	m_lpBackB4->Unlock(NULL);
}