RendererOnScreenNotification.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Internationalization/Text.h"
#include "Misc/CoreDelegates.h"
#include "Misc/LazySingleton.h"
 
class FRendererOnScreenNotification
{
public:
    static FRendererOnScreenNotification& Get()
    {
        return TLazySingleton<FRendererOnScreenNotification>::Get();
    }
 
    static void TearDown()
    {
        TLazySingleton<FRendererOnScreenNotification>::TearDown();
    }
 
    template<typename FunctorType, typename... VarTypes>
    FDelegateHandle AddLambda(FunctorType&& InFunctor, VarTypes... Vars)
    {
        FScopeLock Lock(&DelgateCS);
        return ProxyDelegate.AddLambda(MoveTemp(InFunctor), Vars...);
    }
 
    bool Remove(FDelegateHandle InHandle)
    {
        FScopeLock Lock(&DelgateCS);
        return ProxyDelegate.Remove(InHandle);
    }
 
    void Broadcast()
    {
        // Broadcast using temporary container to reduce any lock contention.
        FCoreDelegates::FSeverityMessageMap MessagesTmp;
        MessagesTmp.Empty(Messages.Num());
        
        {
            FScopeLock Lock(&DelgateCS);
            ProxyDelegate.Broadcast(MessagesTmp);
        }
        {
            FScopeLock Lock(&MessageCS);
            Messages = MoveTemp(MessagesTmp);
        }
    }
 
private:
    friend FLazySingleton;
 
    FRendererOnScreenNotification()
    {
        BaseDelegateHandle = FCoreDelegates::OnGetOnScreenMessages.AddLambda([this](FCoreDelegates::FSeverityMessageMap& OutMessages)
        {
            FScopeLock Lock(&MessageCS);
            OutMessages.Append(Messages);
        });
    }
 
    ~FRendererOnScreenNotification()
    {
        FCoreDelegates::OnGetOnScreenMessages.Remove(BaseDelegateHandle);
    }
 
private:
    FCriticalSection DelgateCS;
    FCriticalSection MessageCS;
    TMulticastDelegate<void(FCoreDelegates::FSeverityMessageMap&)> ProxyDelegate;
    FDelegateHandle BaseDelegateHandle;
    FCoreDelegates::FSeverityMessageMap Messages;
};