So I recently updated to 5.1 and have since noticed lots of issues with the UI system. It appears to revolve around this new class UGameViewportSubsystem. For one, AddToViewport just doesn’t seem to work. The widget instance will be created and code inside the widget will run, but it simply won’t render to the screen. Here’s an example of the code I’m using to create and draw the widgets:
UUserWidget* WidgetInstance = CreateWidget<UUserWidget>(GetWorld(), WidgetClass);
if (WidgetInstance) WidgetInstance->AddToViewport(0);
This does not work in 5.1 despite working just fine in 5.0 and older.
I found this thread on the same issue but the solution of calling Super::Init() on the GameInstance didn’t solve it for me as I was already doing this. Changing the GameInstance class to the engine default doesn’t help either.
Another thing I’ve noticed is that in the UUserWidget::AddToViewport() method, this line sometimes returns null
UGameViewportSubsystem* Subsystem = UGameViewportSubsystem::Get(GetWorld()) // Subsystem == nullptr
It doesn’t help that the Unreal Doc’s entry for UGameViewportSubsystem is basically barren so I can’t really figure out exactly how this class operates without digging in to the source myself. Any ideas on fixes?