EmbeddedCommunication.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/Array.h"
#include "Containers/Map.h"
#include "Containers/UnrealString.h"
#include "CoreTypes.h"
#include "Delegates/Delegate.h"
#include "Delegates/MulticastDelegateBase.h"
#include "HAL/CriticalSection.h"
#include "Templates/Function.h"
#include "UObject/NameTypes.h"
#include "UObject/UnrealNames.h"
 
typedef TMap<FString, FString> FEmbeddedCommunicationMap;
 
// wraps parameters and a completion delegate
struct FEmbeddedCallParamsHelper
{
    // the command for this call. something like "console" would be a command for the engine to run a console command
    FString Command;
    
    // a map of arbitrary key-value string pairs.
    FEmbeddedCommunicationMap Parameters;
 
    // a delegate to call back on the other end when the command is completed. if this is set, it is expected it will be called
    // but at least one handler of this
    TFunction<void(const FEmbeddedCommunicationMap&, FString)> OnCompleteDelegate;
};
 
class FEmbeddedDelegates
{
public:
 
    // delegate for calling between native wrapper app and embedded ue
    DECLARE_MULTICAST_DELEGATE_OneParam(FEmbeddedCommunicationParamsDelegate, const FEmbeddedCallParamsHelper&);
 
    // calling in from native wrapper to engine
    static CORE_API FEmbeddedCommunicationParamsDelegate& GetNativeToEmbeddedParamsDelegateForSubsystem(FName SubsystemName);
 
    // calling out from engine to native wrapper
    static CORE_API FEmbeddedCommunicationParamsDelegate& GetEmbeddedToNativeParamsDelegateForSubsystem(FName SubsystemName);
 
    // returns true if NativeToEmbedded delegate for subsystem exists
    static CORE_API bool IsEmbeddedSubsystemAvailable(FName SubsystemName);
    
    // FTSTicker-like delegate, to bind things to be ticked at a regular interval while the game thread is otherwise asleep.
    static CORE_API FSimpleMulticastDelegate SleepTickDelegate;
 
    // get/set an object by name, thread safe
    static CORE_API void SetNamedObject(const FString& Name, void* Object);
    static CORE_API void* GetNamedObject(const FString& Name);
    
private:
 
    // This class is only for namespace use (like FCoreDelegates)
    FEmbeddedDelegates() {}
 
    // the per-subsystem delegates
    static TMap<FName, FEmbeddedCommunicationParamsDelegate> NativeToEmbeddedDelegateMap;
    static TMap<FName, FEmbeddedCommunicationParamsDelegate> EmbeddedToNativeDelegateMap;
 
    // named object registry, with thread protection
    static FCriticalSection NamedObjectRegistryLock;
    static TMap<FString, void*> NamedObjectRegistry;
};
 
 
class FEmbeddedCommunication
{
public:
 
    // called early in UE lifecycle - RunOnGameThread can be called before this is called
    static CORE_API void Init();
 
    // force some ticking to happen - used to process messages during otherwise blocking operations like boot
    static CORE_API void ForceTick(int ID, float MinTimeSlice=0.1f, float MaxTimeSlice=0.5f);
 
    // queue up a function to call on game thread
    static CORE_API void RunOnGameThread(int Priority, TFunction<void()> Lambda);
 
    // wake up the game thread to process something put onto the game thread
    static CORE_API void WakeGameThread();
 
    // called from game thread to pull off
    static CORE_API bool TickGameThread(float DeltaTime);
    
    // tell UE to stay awake (or allow it to sleep when nothing to do). Repeated calls with the same Requester are
    // allowed, but bNeedsRendering must match
    static CORE_API void KeepAwake(FName Requester, bool bNeedsRendering);
    static CORE_API void AllowSleep(FName Requester);
    
    static CORE_API void UELogFatal(const TCHAR* String);
    static CORE_API void UELogError(const TCHAR* String);
    static CORE_API void UELogWarning(const TCHAR* String);
    static CORE_API void UELogDisplay(const TCHAR* String);
    static CORE_API void UELogLog(const TCHAR* String);
    static CORE_API void UELogVerbose(const TCHAR* String);
 
    static CORE_API bool IsAwakeForTicking();
    static CORE_API bool IsAwakeForRendering();
    
    static CORE_API FString GetDebugInfo();
};
 
// RAII for keep awake functionality
// This may seem a bit over engineered, but it needs to have move semantics so that any aggregate that
// includes it doesn't lose move semantics.
class FEmbeddedKeepAwake
{
public:
    // tell UE to stay awake (or allow it to sleep when nothing to do). Repeated calls with the same Requester are
    // allowed, but bNeedsRendering must match
    FEmbeddedKeepAwake(FName InRequester, bool bInNeedsRendering)
        : Requester(InRequester)
        , bNeedsRendering(bInNeedsRendering)
    {
        FEmbeddedCommunication::KeepAwake(Requester, bNeedsRendering);
    }
 
    FEmbeddedKeepAwake(const FEmbeddedKeepAwake& Other)
        : Requester(Other.Requester)
        , bNeedsRendering(Other.bNeedsRendering)
        , bIsValid(Other.bIsValid)
    {
        if (bIsValid)
        {
            FEmbeddedCommunication::KeepAwake(Requester, bNeedsRendering);
        }
    }
 
    FEmbeddedKeepAwake(FEmbeddedKeepAwake&& Other)
    {
        Requester = Other.Requester;
        bNeedsRendering = Other.bNeedsRendering;
        bIsValid = Other.bIsValid;
 
        Other.Requester = NAME_None;
        Other.bNeedsRendering = false;
        Other.bIsValid = false;
    }
 
    ~FEmbeddedKeepAwake()
    {
        if (bIsValid)
        {
            FEmbeddedCommunication::AllowSleep(Requester);
        }
    }
 
    FEmbeddedKeepAwake& operator=(const FEmbeddedKeepAwake& Other) &
    {
        bool bOldIsValid = bIsValid;
        FName OldRequester = Requester;
 
        Requester = Other.Requester;
        bNeedsRendering = Other.bNeedsRendering;
        bIsValid = Other.bIsValid;
        if (bIsValid)
        {
            FEmbeddedCommunication::KeepAwake(Requester, bNeedsRendering);
        }
 
        if (bOldIsValid)
        {
            FEmbeddedCommunication::AllowSleep(OldRequester);
        }
 
        return *this;
    }
 
    FEmbeddedKeepAwake& operator=(FEmbeddedKeepAwake&& Other) &
    {
        if (bIsValid)
        {
            FEmbeddedCommunication::AllowSleep(Requester);
        }
 
        Requester = Other.Requester;
        bNeedsRendering = Other.bNeedsRendering;
        bIsValid = Other.bIsValid;
 
        Other.Requester = NAME_None;
        Other.bNeedsRendering = false;
        Other.bIsValid = false;
        return *this;
    }
 
    bool GetNeedsRendering() const { return bNeedsRendering; }
    FName GetRequester() const { return Requester;  }
 
private:
    FName Requester;
    bool bNeedsRendering = false;
    bool bIsValid = true;
};