如何在 c++ 中复制指针值并防止崩溃

Question

我有一个 function 使用 DirectX 11 返回屏幕特定 X、Y 坐标的像素颜色。

function 使用方法“AcquireNextFrame”，如果当前帧等于前一帧，不幸失败 (DXGI_ERROR_WAIT_TIMEOUT)。

因此，一些用户建议复制“IDXGIOutputDuplication”值，但经过一些尝试，我看到开始不稳定，就像其他用户在这些情况下所说的那样。

出于这个原因，我尝试使用以下变量对代码的其他部分进行“备份”：“gpuTexPrevious”和“cpuTexPrevious”：

ID3D11Texture2D* gpuTexPrevious = nullptr;
ID3D11Texture2D* cpuTexPrevious = nullptr;

RGBTRIPLE CaptureNext(int X, int Y) {

    bool NewFrame;

    RGBTRIPLE rgb;

    rgb.rgbtBlue = 0;
    rgb.rgbtGreen = 0;
    rgb.rgbtBlue = 0;

    HRESULT hr;

    IDXGIResource* deskRes = nullptr;
    DXGI_OUTDUPL_FRAME_INFO frameInfo;
    
    hr = DeskDupl->AcquireNextFrame(0, &frameInfo, &deskRes);
    if (hr == DXGI_ERROR_WAIT_TIMEOUT) {
        LF::Log_Update(" DXGI_ERROR_WAIT_TIMEOUT");

        NewFrame = false;
    }
    else
        NewFrame = true;

    ID3D11Texture2D* gpuTex = nullptr;
    ID3D11Texture2D* cpuTex = nullptr;

    if (NewFrame)
    {
        hr = deskRes->QueryInterface(__uuidof(ID3D11Texture2D), (void**)&gpuTex);
        deskRes->Release();
        deskRes = nullptr;
        if (FAILED(hr)) {
            // not expected
            return rgb;
        }

        D3D11_TEXTURE2D_DESC desc;
        gpuTex->GetDesc(&desc);
        desc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE | D3D11_CPU_ACCESS_READ;
        desc.Usage = D3D11_USAGE_STAGING;
        desc.BindFlags = 0;
        desc.MiscFlags = 0; // D3D11_RESOURCE_MISC_GDI_COMPATIBLE ?
        hr = D3DDeviceTest->CreateTexture2D(&desc, nullptr, &cpuTex);
        memcpy(&cpuTexPrevious, &cpuTex, sizeof(ID3D11Texture2D));
    }
    else
    {
        memcpy(&gpuTex, &gpuTexPrevious, sizeof(ID3D11Texture2D));
        memcpy(&cpuTex, &cpuTexPrevious, sizeof(ID3D11Texture2D));
    }

    D3D11_BOX srcBox;
    srcBox.left = X;
    srcBox.right = X + 1;
    srcBox.bottom = Y + 1;
    srcBox.top = Y;
    srcBox.front = 0;
    srcBox.back = 1;

    D3DDeviceContextTest->CopySubresourceRegion(cpuTex, 0, 0, 0, 0, gpuTex, 0, &srcBox);

    memcpy(&gpuTexPrevious, &gpuTex,sizeof(ID3D11Texture2D));

    D3D11_MAPPED_SUBRESOURCE sr;
    
    // crash here when NewFrame = false
    hr = D3DDeviceContextTest->Map(cpuTex, 0, D3D11_MAP_READ, 0, &sr);

    COLORREF* pPixels = (COLORREF*)sr.pData;

    rgb.rgbtRed = (pPixels[0] >> 16) & 0xff;
    rgb.rgbtGreen = (pPixels[0] >> 8) & 0xff;
    rgb.rgbtBlue = pPixels[0] & 0xff;

    D3DDeviceContextTest->Unmap(cpuTex, 0);

    cpuTex->Release();
    gpuTex->Release();

    hr = DeskDupl->ReleaseFrame();

    return rgb;
}

直到“AcquireNextFrame”返回 OK 我的代码工作正常，但是当返回“DXGI_ERROR_WAIT_TIMEOUT”

在这一行崩溃：

hr = D3DDeviceContextTest->Map(cpuTex, 0, D3D11_MAP_READ, 0, &sr);

所以我认为我的不是复制指针值的正确方法。

你能建议我另一种方式吗？

谢谢 ！