大家帮我看一段源码,创建Overlay对象老失败!!!!!!!!!!!!!!!!(100分)

[admireO]

//先检查硬件是否支持overlay.
BOOL CDDUtil::IsSurportOverlay()
{
DDCAPS HalCaps;
ZeroMemory( &HalCaps,sizeof( HalCaps ) );
HalCaps.dwSize = sizeof(HalCaps);

if( FAILED( lpDD->GetCaps( &HalCaps,NULL ) ) )
{
TRACE( "GetCaps()failed.\n" );
return FALSE;
}
if( !(HalCaps.dwCaps & DDCAPS_OVERLAY) )
{
TRACE( "Don't support overlay.\n" );
return FALSE;
}
return TRUE;
}//上面函数执行返回true.
//然后创建Overlay对象.
BOOL CDDUtil::DD_CreateOverlay(int width,int height)
{
DDSURFACEDESC ddsdOverlay;
HRESULT ddrval;

if (!lpDD || !lpDDSPrimary)
return FALSE;
ddsdOverlay.dwBackBufferCount=0;
ddsdOverlay.ddsCaps.dwCaps=DDSCAPS_OVERLAY|DDSCAPS_VIDEOMEMORY;
ddsdOverlay.dwFlags= DDSD_CAPS|DDSD_HEIGHT|DDSD_WIDTH|DDSD_PIXELFORMAT;

DDPIXELFORMAT ddpfPixelFormat = { 0 };
ddpfPixelFormat.dwSize = sizeof( DDPIXELFORMAT );
ddpfPixelFormat.dwFlags = DDPF_RGB;

ddpfPixelFormat.dwRGBBitCount = 24;
memcpy( &(ddsdOverlay.ddpfPixelFormat),&ddpfPixelFormat,sizeof( DDPIXELFORMAT ) );
DWORD BitCount[5] = { 32,24,16,8,4 };
ddrval = -1;
for( int i = 0;(i < 5)&& ( ddrval != DD_OK );i++ )
{
ddsdOverlay.ddpfPixelFormat.dwRGBBitCount = BitCount[i];
ddrval = lpDD->CreateSurface(&ddsdOverlay, &lpDDSOffScreen, NULL);
#ifdef _DEBUG
if( ddrval == DD_OK )
{
TRACE( "success when Bitcount = %d\n",BitCount[i] );
}
else
{
TRACE( "failed when Bitcount = %d\n",BitCount[i] );
}
#endif
}
//ddrval = lpDD->CreateSurface(&ddsdOverlay, &lpDDSOffScreen2, NULL);


// We just couldn't create an overlay surface. Let's exit.
if(FAILED(ddrval))
{
TRACE( "We just couldn't create an overlay surface.\n" );
return FALSE;
}

return TRUE;
}
//该函数总返回false.

[admireO]

请大家救命了!!!!!!!!!!!1