Is it possible to choose the default screen in a multi monitor configuration?

Development Programming & Scripting
10

I think all the answers here are incomplete as they assume the following:

  • user has all monitors with the same resolution
  • monitors are aligned from left to right
  • runs only on windows (on linux apparently it does not work properly only in windowed mode)
  • destination monitor also has a native resolution larger or equal to the game resolution

The only information you need is from FMonitorInfo.WorkArea Left/Top.

FDisplayMetrics Display;
FDisplayMetrics::GetDisplayMetrics(Display);
    
// Start on the main display by default
int32 MonitorNumber = 0;
FParse::Value(FCommandLine::Get(), TEXT("monitor="), MonitorNumber);

// Get the correct monitor index
int32 MonitorIndex = INDEX_NONE;
if (MonitorNumber == 0)
{
    // Start monitor on the main screen
    for (int32 Index = 0; Index < DisplayMetrics.MonitorInfo.Num(); Index++)
    {
        if (DisplayMetrics.MonitorInfo[Index].bIsPrimary)
        {
            MonitorIndex = Index;
            break;
        }
    }
}
else
{
    // Normalize
    MonitorIndex = MonitorNumber - 1;
}
 
if (DisplayMetrics.MonitorInfo.IsValidIndex(MonitorIndex))
{
	const FMonitorInfo Monitor = DisplayMetrics.MonitorInfo[MonitorIndex];
    // check if UserSettings.ResolutionSizeX > Monitor.NativeWidth || UserSettings.ResolutionSizeY > Monitor.NativeHeight
    // if true then change your game resolution to Monitor.NativeWidth, Monitor.NativeHeight

    const int32 WindowPosX = Monitor.WorkArea.Left;
	const int32 WindowPosY = Monitor.WorkArea.Top;
    const FVector2D Position(static_cast<float>(WindowPosX), static_cast<float>(WindowPosY));

    if (GEngine && GEngine->GameViewport)
    {
        TSharedPtr<SWindow> Window = GEngine->GameViewport->GetWindow();

        // Hack for linux
#if PLATFORM_LINUX
       const EWindowMode::Type CurrentWindowMode = Window->GetWindowMode();
       Window->SetWindowMode(EWindowMode::Windowed);
#endif

        Window->MoveWindowTo(Position);

#if PLATFORM_LINUX
        // Set back to original
        Window->SetWindowMode(CurrentWindowMode);
#endif
    }
}
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