Common How-To

• Get top level window

C++

FSlateApplication::Get().GetActiveTopLevelWindow()
FSlateApplication::Get().GetInteractiveTopLevelWindows()
FSlateApplication::Get().GetAllVisibleWindowsOrdered(AllWindows);
TSharedPtr<SWindow> ParentWindow = FSlateApplication::Get().FindWidgetWindow(AsShared());

// If the main frame exists parent the window to it
TSharedPtr< SWindow > ParentWindow;
if (FModuleManager::Get().IsModuleLoaded( "MainFrame" ) )
{
  IMainFrameModule& MainFrame = FModuleManager::GetModuleChecked<IMainFrameModule>( "MainFrame" );
  ParentWindow = MainFrame.GetParentWindow();
}

TSharedPtr<SWindow> ParentWindow = FGlobalTabmanager::Get()->GetRootWindow();
if (ParentWindow.IsValid())
{
    // Parent the window to the main frame
    FSlateApplication::Get().AddWindowAsNativeChild(NewSlateWindow, ParentWindow.ToSharedRef());
}
else
{
    FSlateApplication::Get().AddWindow(NewSlateWindow);
}

• Destroy window

C++

FSlateApplicationBase::Get().RequestDestroyWindow(Window);

• Add as child window

C++

FSlateApplication::Get().AddWindowAsNativeChild(BrowserWindowWidget, ParentWindow.ToSharedRef());

• Get Application Slate Renderer (D3D, OpenGL, etc)

C++

FSlateApplication::Get().GetRenderer()

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

Reference From https://answers.unrealengine.com/questions/294650/is-it-possible-to-choose-the-default-screen-in-a-m.html

C++

 // Move window to the corresponding monitor

 if (GEngine && GEngine->GameViewport) {

 int MonitorNumber = 1;

 FParse::Value(FCommandLine::Get(), L"monitor=", MonitorNumber);

 FDisplayMetrics Display;

 FDisplayMetrics::GetDisplayMetrics(Display);



 int8 MonitorIndex = MonitorNumber - 1;

int32 CurrentMonitorWidth = Display.MonitorInfo[MonitorIndex].NativeWidth;

 float WidthPosition = (MonitorIndex)*Display.PrimaryDisplayWidth - CurrentMonitorWidth;


 float HeightPosition = 0.0f;


FVector2D WindowPosition = FVector2D(WidthPosition, 0.f);

 GEngine->GameViewport->GetWindow()->MoveWindowTo(WindowPosition);

 }

Reference From https://answers.unrealengine.com/questions/294650/is-it-possible-to-choose-the-default-screen-in-a-m.html

Everything happens in UGameEngine::CreateGameViewport() which can be found in Engine\Source\Runtime\Engine\Private\GameEngine.cpp. Now look at the following lines of code :

C++

// SAVEWINPOS tells us to load/save window positions to user settings (this is disabled by default)
int32 SaveWinPos;
if (FParse::Value(FCommandLine::Get(), TEXT("SAVEWINPOS="), SaveWinPos) && SaveWinPos > 0 )
{

You can see the Window->MoveWindowTo() function call which is exactly what we want. So after these lines I added the following :

C++

FDisplayMetrics DisplayMetrics;
    FSlateApplication::Get().GetDisplayMetrics(DisplayMetrics);
 
    int MonitorNumber = 0;
    FParse::Value(FCommandLine::Get(), L"monitor=", MonitorNumber);
 
    //Reset to primary if the monitor index is invalid
    if( MonitorNumber >= DisplayMetrics.MonitorInfo.Num() || MonitorNumber < 0 )
    {
        FString Message = "_____ Incorrect monitor index, will use primary screen instead";
        UE_LOG(LogTemp, Warning, TEXT( "%s" ), *Message);
        MonitorNumber = 0;
    }
 
    //If monitor index is 0, we default to primary screen
    if( MonitorNumber == 0 )
    {
        for( int i = 0; i < DisplayMetrics.MonitorInfo.Num(); i++ )
        {
            FString MonitorInfo = "_____ Found monitor \"" + DisplayMetrics.MonitorInfo[i].Name + "\" (is primary : ";
            MonitorInfo += FString::FromInt( DisplayMetrics.MonitorInfo[i].bIsPrimary ) + FString(")");
            UE_LOG(LogTemp, Warning, TEXT( "%s" ), *MonitorInfo);
 
            if( DisplayMetrics.MonitorInfo[i].bIsPrimary )
            {
                MonitorNumber = i + 1;
            }
        }
    }

Reference From http://www.froyok.fr/blog/2018-01-ue4-specify-default-monitor-at-launch