Recommended Engine Changes

This document lists sets of publicly available recommended engine changes, along with the reasons for the changes and their impact. Some engine changes for specific platforms may require private requests due to NDA restrictions.

Note that we tag our engine changes internally with surrounding //$$ BEGIN and //$$ END blocks. These are preserved here to ensure that our internal tests match the code presented here.

General Engine Changes

There are no generic engine changes recommended or required at this time

Steam

The Engine’s OnlineSubsystemSteam is missing some key features, and is not set up to be extensible so that those features can be easily added. As such, while our OnlineSubsystemSteamV2 does add some missing features (such as Steam Inventory), some features are more easily added to the base engine directly.

FindSessionById Implementation

Reason: the OnlineSubsystemSteam base implementation of this function trivially triggers its delegate with a failure.

Impact: the lack of implemtation in this function prevents looking up Steam Sessions by their ID, preventing some flows for joining or rejoining a Steam Session from functioning.

Notes: this change embeds a helper object, to make it easier to communicate and drop into the engine. The helper can be moved out to match other similar implementations if you wish.

Replace the following in OnlineSessionInterfaceSteam.cpp:

bool FOnlineSessionSteam::FindSessionById(const FUniqueNetId& SearchingUserId, const FUniqueNetId& SessionId, const FUniqueNetId& FriendId, const FOnSingleSessionResultCompleteDelegate& CompletionDelegates)
{
	FOnlineSessionSearchResult EmptyResult;
	CompletionDelegates.ExecuteIfBound(0, false, EmptyResult);
	return true;
}

With the following code (the original implementation is left commented out for reference):

bool FOnlineSessionSteam::FindSessionById(const FUniqueNetId& SearchingUserId, const FUniqueNetId& SessionId, const FUniqueNetId& FriendId, const FOnSingleSessionResultCompleteDelegate& CompletionDelegates)
{
	//$$ BEGIN
	
	DECLARE_DELEGATE_TwoParams(FOnlineAsyncTaskSteamFindLobbyDelegate, const bool, const class FOnlineSessionSearchResult&);

	class FOnlineAsyncTaskSteamFindLobby : public FOnlineAsyncTaskSteamFindLobbiesBase
	{
	public:
		/** Constructor */
		FOnlineAsyncTaskSteamFindLobby(class FOnlineSubsystemSteam* InSubsystem, const FUniqueNetIdSteam& InLobbyId, const TSharedPtr<FOnlineSessionSearch>& InSearchSettings, const FOnlineAsyncTaskSteamFindLobbyDelegate& InFindLobbyCompleteDelegate) :
			FOnlineAsyncTaskSteamFindLobbiesBase(InSubsystem, InSearchSettings),
			OnFindLobbyCompleteDelegate(InFindLobbyCompleteDelegate)
		{
			LobbyIDs.Add(CSteamID(*(uint64*)InLobbyId.GetBytes()));
			FindLobbiesState = FOnlineAsyncTaskSteamFindLobbiesBase::EFindLobbiesState::RequestLobbyData;
		}

		/**
		*	Get a human readable description of task
		*/
		FString ToString() const override
		{
			return FString::Printf(TEXT("FOnlineAsyncTaskSteamFindLobby bWasSuccessful: %d Lobby ID: %llu"), WasSuccessful(), LobbyIDs[0].ConvertToUint64());
		}

		/**
		*	Async task is given a chance to trigger it's delegates
		*/
		void TriggerDelegates() override
		{
			if (bWasSuccessful && SearchSettings->SearchResults.Num() > 0)
			{
				OnFindLobbyCompleteDelegate.ExecuteIfBound(bWasSuccessful, SearchSettings->SearchResults[0]);
			}
			else
			{
				FOnlineSessionSearchResult EmptyResult;
				OnFindLobbyCompleteDelegate.ExecuteIfBound(bWasSuccessful, EmptyResult);
			}
		}

	private:

		FOnlineAsyncTaskSteamFindLobbyDelegate OnFindLobbyCompleteDelegate;
	};

	// Create a search settings object 
	this->CurrentSessionSearch = MakeShareable(new FOnlineSessionSearch());
	this->CurrentSessionSearch->SearchState = EOnlineAsyncTaskState::InProgress;

	FOnlineAsyncTaskSteamFindLobbyDelegate completeDelegate = FOnlineAsyncTaskSteamFindLobbyDelegate::CreateLambda([CompletionDelegates](const bool success, const class FOnlineSessionSearchResult& result) {
		CompletionDelegates.ExecuteIfBound(0, success, result);
		});

	const FUniqueNetIdSteam& SteamSessionId = (const FUniqueNetIdSteam&)SessionId;
	FOnlineAsyncTaskSteamFindLobby* NewTask = new FOnlineAsyncTaskSteamFindLobby(SteamSubsystem, SteamSessionId, this->CurrentSessionSearch, completeDelegate);
	SteamSubsystem->QueueAsyncTask(NewTask);
	/* Original Engine Implementation
	FOnlineSessionSearchResult EmptyResult;
	CompletionDelegates.ExecuteIfBound(0, false, EmptyResult);
	*/
	return true;

	//$$ END
}