Updating UMG from different thread

Development Programming & Scripting UI
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1

Hello,

I’m trying to create UI where there is lot of processing happens in background and UI gets updated and I wanted to use multi threading to do the processing. So I came up with this method to dynamically create and update UI from different threads.

Create scene will create a small widget and put it into a vertical panel in the UI this is all done in blueprint.

I know UE4 crashes if I try to create a UObject from any thread other than game thread so every time I want to create a UObject I can create a ASync from thread on game thread and create UObject inside the ASync.

Header file:

class COOPGAMETOOLS_API UCoOpToolsWidget : public UUserWidget
{
	GENERATED_BODY()
public:
	void AsyncCreateScene();

protected:
	UFUNCTION(BlueprintImplementableEvent, Category = "CoOpToolsWidget")
	USceneWidget* CreateScene();
};


class FCreateSceneWorker : public FRunnable 
{

	bool ShouldThreadRun;

	/** Thread to run the worker FRunnable on */
	FRunnableThread* Thread;

public:
	FCreateSceneWorker(UCoOpToolsWidget* pCoOpToolsWidget);
	~FCreateSceneWorker();

	// Begin FRunnable interface.
	virtual bool Init();
	virtual uint32 Run();
	virtual void Stop();

	UCoOpToolsWidget* CoOpToolsWidget;
};

Code:

void UCoOpToolsWidget::AsyncCreateScene()
{
	AsyncTask(ENamedThreads::GameThread, [&]() {
		USceneWidget* SceneWidget = CreateScene();
	});

}

FCreateSceneWorker::FCreateSceneWorker(UCoOpToolsWidget* pCoOpToolsWidget) :
	CoOpToolsWidget(pCoOpToolsWidget)
{
	Thread = FRunnableThread::Create(this, TEXT("FCreateSceneWorker"), 0, TPri_BelowNormal); 
}

FCreateSceneWorker::~FCreateSceneWorker()
{
	delete Thread;
}

bool FCreateSceneWorker::Init()
{
	ShouldThreadRun = true;
	return true;
}

uint32 FCreateSceneWorker::Run()
{
	//Initial wait before starting
	UE_LOG(LogTemp, Warning, TEXT("Worker Start"));
	FPlatformProcess::Sleep(0.03);

	for (int i = 0; i < 100 && ShouldThreadRun; ++i) 
	{
		FPlatformProcess::Sleep(1.0);
		CoOpToolsWidget->AsyncCreateScene();
	}

	UE_LOG(LogTemp, Warning, TEXT("Worker Done"));
	return 0;
}

void FCreateSceneWorker::Stop()
{
	ShouldThreadRun = false;
}

And I create the thread

FCreateSceneWorker* Runnable = new FCreateSceneWorker(this);

It works, but i want to make sure that there wont be any problems in future.
I do get a warning

LogStats: Warning: MetaData mismatch. Did you assign a stat to two groups? New //STATGROUP_Threads//FCreateSceneWorker///Thread_1ab4_0///####STATCAT_Advanced#### old //STATGROUP_Threads//FCreateSceneWorker///Thread_23dc_0///####STATCAT_Advanced####

I want to know if what i’m doing is correct and if not how can I correct my approach?
What is this warning and how can i remove the warning?

Thanks