如何使用X11从所有显示器中获取屏幕截图？

Question

我正在编写屏幕快照，并在Mac上找到了这个很棒的话题：How can I get screenshot from all displays on MAC?

我想知道是否有人拥有x11库的等效库？要获取所有监视器，然后将它们全部截屏？

我找到了这个主题：https://stackoverflow.com/a/5293559/1828637

但是对于像我这样的新手来说，从那里链接的代码并不容易遵循。

RootWindow(3)会得到所有监视器的总面积吗？然后，我可以查看监视器的尺寸，然后在RootWindow返回时使用XGetImage这些部分？

我遇到过这个主题：How do take a screenshot correctly with xlib?但是我不确定它是否具有多显示器支持。我在ctypes中执行此操作，因此我无法轻松地测试该代码，而无需经历先编写代码的艰巨任务。所以我想知道这是否正确，或者我将如何修改它以处理多星期一？

编辑

那里的海报分享了他的代码，在这里可以看到：https://github.com/Lalaland/ScreenCap/blob/master/src/screenCapturerImpl.cpp#L96，但是它很复杂，我不理解。它使用了XFixesGetCursorImage之类的功能，我在文档中找不到这些功能，而且我看不到多显示器在那儿如何工作。该主题的作者警告说，他不记得该代码了，它可能不适用于现代Linux。

Answer 1

这不是对问题的完美答案，但是可以修改以下代码以获得所需最终结果的快速版本：https://github.com/Clodo76/vr-desktop-mirror/blob/master/DesktopCapture/main.cpp

DesktopCapturePlugin_Initialize方法将所有显示转换为对象：

UNITY_INTERFACE_EXPORT void UNITY_INTERFACE_API DesktopCapturePlugin_Initialize()
{   
    DesksClean();

    g_needReinit = 0;


    IDXGIFactory1* factory;
    CreateDXGIFactory1(__uuidof(IDXGIFactory1), reinterpret_cast<void**>(&factory));

    IDXGIAdapter1* adapter;
    for (int i = 0; (factory->EnumAdapters1(i, &adapter) != DXGI_ERROR_NOT_FOUND); ++i)
    {
        IDXGIOutput* output;
        for (int j = 0; (adapter->EnumOutputs(j, &output) != DXGI_ERROR_NOT_FOUND); j++)
        {
            DXGI_OUTPUT_DESC outputDesc;
            output->GetDesc(&outputDesc);

            MONITORINFOEX monitorInfo;
            monitorInfo.cbSize = sizeof(MONITORINFOEX);
            GetMonitorInfo(outputDesc.Monitor, &monitorInfo);

            // Maybe in future add a function to identify the primary monitor.
            //if (monitorInfo.dwFlags == MONITORINFOF_PRIMARY)
            {
                int iDesk = DeskAdd();

                g_desks[iDesk].g_width = monitorInfo.rcMonitor.right - monitorInfo.rcMonitor.left;                  
                g_desks[iDesk].g_height = monitorInfo.rcMonitor.bottom - monitorInfo.rcMonitor.top;

                auto device = g_unity->Get<IUnityGraphicsD3D11>()->GetDevice();
                IDXGIOutput1* output1;
                output1 = reinterpret_cast<IDXGIOutput1*>(output);
                output1->DuplicateOutput(device, &g_desks[iDesk].g_deskDupl);
            }

            output->Release();
        }
        adapter->Release();
    }

    factory->Release();
}

然后，OnRenderEvent方法将显示中的帧复制到纹理（在这种情况下，由单位提供）：

void UNITY_INTERFACE_API OnRenderEvent(int eventId)
{
    for (int iDesk = 0; iDesk < g_nDesks; iDesk++)
    {
        if (g_desks[iDesk].g_deskDupl == nullptr || g_desks[iDesk].g_texture == nullptr)
        {
            g_needReinit++;
            return;
        }

        IDXGIResource* resource = nullptr;

        const UINT timeout = 0; // ms
        HRESULT resultAcquire = g_desks[iDesk].g_deskDupl->AcquireNextFrame(timeout, &g_desks[iDesk].g_frameInfo, &resource);
        if (resultAcquire != S_OK)
        {
            g_needReinit++;
            return;
        }

        g_desks[iDesk].g_isPointerVisible = (g_desks[iDesk].g_frameInfo.PointerPosition.Visible == TRUE);
        g_desks[iDesk].g_pointerX = g_desks[iDesk].g_frameInfo.PointerPosition.Position.x;
        g_desks[iDesk].g_pointerY = g_desks[iDesk].g_frameInfo.PointerPosition.Position.y;

        ID3D11Texture2D* texture;
        HRESULT resultQuery = resource->QueryInterface(__uuidof(ID3D11Texture2D), reinterpret_cast<void**>(&texture));
        resource->Release();

        if (resultQuery != S_OK)
        {
            g_needReinit++;
            return;
        }

        ID3D11DeviceContext* context;
        auto device = g_unity->Get<IUnityGraphicsD3D11>()->GetDevice();
        device->GetImmediateContext(&context);
        context->CopyResource(g_desks[iDesk].g_texture, texture);

        g_desks[iDesk].g_deskDupl->ReleaseFrame();
    }

    g_needReinit = 0;
}