How to get current display mode (resolution, refresh rate) of a monitor/output in DXGI?

Question

I am creating a multi-monitor full screen DXGI/D3D application. I am enumerating through the available outputs and adapters in preparation of creating their swap chains.

When creating my swap chain using DXGI's IDXGIFactory::CreateSwapChain method, I need to provide a swap chain description which includes a buffer description of type DXGI_MODE_DESC that details the width, height, refresh rate, etc. How can I find out what the output is currently set to (or how can I find out what the display mode of the output currently is)? I don't want to change the user's resolution or refresh rate when I go to full screen with this swap chain.

Answer 1

After looking around some more I stumbled upon the EnumDisplaySettings legacy GDI function, which allows me to access the current resolution and refresh rate. Combining this with the IDXGIOutput::FindClosestMatchingMode function I can get pretty close to the current display mode:

void getClosestDisplayModeToCurrent(IDXGIOutput* output, DXGI_MODE_DESC* outCurrentDisplayMode)
{
  DXGI_OUTPUT_DESC outputDesc;
  output->GetDesc(&outputDesc);
  HMONITOR hMonitor = outputDesc.Monitor;
  MONITORINFOEX monitorInfo;
  monitorInfo.cbSize = sizeof(MONITORINFOEX);
  GetMonitorInfo(hMonitor, &monitorInfo);
  DEVMODE devMode;
  devMode.dmSize = sizeof(DEVMODE);
  devMode.dmDriverExtra = 0;
  EnumDisplaySettings(monitorInfo.szDevice, ENUM_CURRENT_SETTINGS, &devMode);

  DXGI_MODE_DESC current;
  current.Width = devMode.dmPelsWidth;
  current.Height = devMode.dmPelsHeight;
  bool useDefaultRefreshRate = 1 == devMode.dmDisplayFrequency || 0 == devMode.dmDisplayFrequency;
  current.RefreshRate.Numerator = useDefaultRefreshRate ? 0 : devMode.dmDisplayFrequency;
  current.RefreshRate.Denominator = useDefaultRefreshRate ? 0 : 1;
  current.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
  current.ScanlineOrdering = DXGI_MODE_SCANLINE_ORDER_UNSPECIFIED;
  current.Scaling = DXGI_MODE_SCALING_UNSPECIFIED;

  output->FindClosestMatchingMode(&current, outCurrentDisplayMode, NULL);
}

...But I don't think that this is really the correct answer because I'm needing to use legacy functions. Is there any way to do this with DXGI to get the exact current display mode rather than using this method?

Answer 2

I saw solution here: http://www.rastertek.com/dx11tut03.html

In folow part:

   // Now go through all the display modes and find the one that matches the screen width and height.
    // When a match is found store the numerator and denominator of the refresh rate for that monitor.
    for(i=0; i<numModes; i++)
    {
        if(displayModeList[i].Width == (unsigned int)screenWidth)
        {
            if(displayModeList[i].Height == (unsigned int)screenHeight)
            {
                numerator = displayModeList[i].RefreshRate.Numerator;
                denominator = displayModeList[i].RefreshRate.Denominator;
            }
        }
    }

Is my understanding correct, the available resolution is in the displayModeList.