调用覆盖表面（ Overlay Surfaces）的方法

编者：李国帅

时间：2012.5.10

背景原因:

覆盖表面是具有特殊硬件支持能力的表面，就像一张透明纸贴在主表面，改变看上去的画面。

以前的一个提取代码，可参考理解。

源码：

 

// For create overlay surface
    LPDIRECTDRAW7            m_lpDD;
    LPDIRECTDRAWSURFACE7    m_lpPrimary;
    LPDIRECTDRAWSURFACE7    m_lpOverlay;


    VOID InitOverlays();
    VOID ReleaseOverlay();
    BOOL    CreateOverlay();
    BOOL    AreOverlaysSupported();

VOID CGraphPlayer::InitOverlays()
{
    m_lpDD        = NULL;
    m_lpPrimary = NULL;
    m_lpOverlay = NULL;
    CreateOverlay();
}

BOOL CGraphPlayer::AreOverlaysSupported()
{
    DDCAPS  capsDrv;
    HRESULT ddrval;

    // Get driver capabilities to determine Overlay support.
    ZeroMemory(&capsDrv, sizeof(capsDrv));
    capsDrv.dwSize = sizeof(capsDrv);

    ddrval = m_lpDD->GetCaps(&capsDrv, NULL);
    if (FAILED(ddrval))
    {
        return FALSE;
    }

    // Does the driver support overlays in the current mode?
    // (Currently the DirectDraw emulation layer does not support overlays.
    // Overlay related APIs will fail without hardware support).
    if (!(capsDrv.dwCaps & DDCAPS_OVERLAY))
    {
        return FALSE;
    }

    return TRUE;
}

VOID CGraphPlayer::ReleaseOverlay()
{
    if(NULL != m_lpOverlay)
    {
        lpOverlay->UpdateOverlay(NULL, m_lpPrimary, NULL, DDOVER_HIDE, NULL);
        IDirectDrawSurface_Release(m_lpOverlay);
        m_lpOverlay = NULL;
    }

    if(NULL != m_lpPrimary)
    {
        IDirectDrawSurface_Release(m_lpPrimary);
        m_lpPrimary = NULL;
    }

    if(NULL != m_lpDD)
    {
        IDirectDraw_Release(m_lpDD);
        m_lpDD = NULL;
    }
}
BOOL CGraphPlayer::CreateOverlay()
{
    // Initialize DDraw
    if(FAILED(DirectDrawCreateEx(NULL, (void**)&m_lpDD, IID_IDirectDraw7, NULL)))
    {
        return FALSE;
    }

    if(FAILED(m_lpDD->SetCooperativeLevel(NULL, DDSCL_NORMAL)))
    {
        IDirectDraw_Release(m_lpDD);
        m_lpDD = NULL;
        return FALSE;
    }

    // Try to create an overlay surface using one of the pixel formats
    FailedReturn(AreOverlaysSupported(), FALSE);

    // Create primary surface
    DDSURFACEDESC2 ddsd;
    ZeroMemory(&ddsd, sizeof(ddsd));
    ddsd.dwSize = sizeof(ddsd);
    ddsd.dwFlags = DDSD_CAPS ;
    ddsd.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE;

    HRESULT hr = m_lpDD->CreateSurface(&ddsd, &m_lpPrimary, NULL);
    if(FAILED(hr))
    {
        IDirectDraw_Release(m_lpDD);
        m_lpDD = NULL;
        return FALSE;
    }

    // Create overlay surface
    ZeroMemory(&ddsd, sizeof(ddsd));
    ddsd.dwSize = sizeof(ddsd);
    ddsd.dwWidth = 320;
    ddsd.dwHeight = 240;
    ddsd.dwBackBufferCount = 0;
    ddsd.ddpfPixelFormat = g_ddpfOverlayFormats;
    ddsd.dwFlags = DDSD_CAPS | DDSD_HEIGHT | DDSD_WIDTH | DDSD_PIXELFORMAT;
    ddsd.ddsCaps.dwCaps = DDSCAPS_OVERLAY | DDSCAPS_VIDEOMEMORY;

    hr = m_lpDD->CreateSurface(&ddsd, &m_lpOverlay, NULL);
    if(FAILED(hr))
    {
        IDirectDraw_Release(m_lpDD);
        IDirectDrawSurface_Release(m_lpPrimary);
        m_lpDD = NULL;
        m_lpPrimary    = NULL;
        return FALSE;
    }

    return TRUE;
}