Gameplay Debugger broken in ShooterGame PIE dedicated server

Development Programming & Scripting
1

Gameplay Debugger UI does not appear when pressing apostrophe key (’) in PIE in the [ShooterGame][1] example when Run Dedicated Server is checked in the Play menu.

Some other observations:

  • Gameplay Debugger UI appears if Run Dedicated Server is not checked.
  • Gameplay Debugger UI appears in an empty project even if Run Dedicated Server is not checked.

276148-run-dedicated-server.jpg

Related Bug: UE-74446

2

Bug is tracked by UE-74446.

3

The Issue is caused by the Replication Graph code in ShooterGame example!

4

We solved a similar problem with this PR: https://github.com/EpicGames/UnrealEngine/pull/7720

bAlwaysRelevant was false in AGameplayDebuggerCategoryReplicator, so the replication graph didn’t replicate it to the client.

5

Thanks to @FilipeTessaro and @JonasKjellstrom for pointing me in the right direction. The bug is in UShooterReplicationGraph::OnGameplayDebuggerOwnerChange. The lambda in the function incorrectly captured and used OldOwner when it should have used Controller.

Below in the broken and fixed code.

BROKEN

void UShooterReplicationGraph::OnGameplayDebuggerOwnerChange(AGameplayDebuggerCategoryReplicator* Debugger, APlayerController* OldOwner)
{
	auto GetAlwaysRelevantForConnectionNode = [&](APlayerController* Controller) -> UShooterReplicationGraphNode_AlwaysRelevant_ForConnection*
	{
		if (OldOwner)
		{
			if (UNetConnection* NetConnection = OldOwner->GetNetConnection())
			{
				if (UNetReplicationGraphConnection* GraphConnection = FindOrAddConnectionManager(NetConnection))
				{
					for (UReplicationGraphNode* ConnectionNode : GraphConnection->GetConnectionGraphNodes())
					{
						if (UShooterReplicationGraphNode_AlwaysRelevant_ForConnection* AlwaysRelevantConnectionNode = Cast<UShooterReplicationGraphNode_AlwaysRelevant_ForConnection>(ConnectionNode))
						{
							return AlwaysRelevantConnectionNode;
						}
					}

				}
			}
		}

		return nullptr;
	};

	if (UShooterReplicationGraphNode_AlwaysRelevant_ForConnection* AlwaysRelevantConnectionNode = GetAlwaysRelevantForConnectionNode(OldOwner))
	{
		AlwaysRelevantConnectionNode->GameplayDebugger = nullptr;
	}

	if (UShooterReplicationGraphNode_AlwaysRelevant_ForConnection* AlwaysRelevantConnectionNode = GetAlwaysRelevantForConnectionNode(Debugger->GetReplicationOwner()))
	{
		AlwaysRelevantConnectionNode->GameplayDebugger = Debugger;
	}
}

FIXED

void UShooterReplicationGraph::OnGameplayDebuggerOwnerChange(AGameplayDebuggerCategoryReplicator* Debugger, APlayerController* OldOwner)
{
	auto GetAlwaysRelevantForConnectionNode = [&](APlayerController* Controller) -> UShooterReplicationGraphNode_AlwaysRelevant_ForConnection*
	{
		if (Controller)
		{
			if (UNetConnection* NetConnection = Controller->GetNetConnection())
			{
				if (UNetReplicationGraphConnection* GraphConnection = FindOrAddConnectionManager(NetConnection))
				{
					for (UReplicationGraphNode* ConnectionNode : GraphConnection->GetConnectionGraphNodes())
					{
						if (UShooterReplicationGraphNode_AlwaysRelevant_ForConnection* AlwaysRelevantConnectionNode = Cast<UShooterReplicationGraphNode_AlwaysRelevant_ForConnection>(ConnectionNode))
						{
							return AlwaysRelevantConnectionNode;
						}
					}

				}
			}
		}

		return nullptr;
	};

	if (UShooterReplicationGraphNode_AlwaysRelevant_ForConnection* AlwaysRelevantConnectionNode = GetAlwaysRelevantForConnectionNode(OldOwner))
	{
		AlwaysRelevantConnectionNode->GameplayDebugger = nullptr;
	}

	if (UShooterReplicationGraphNode_AlwaysRelevant_ForConnection* AlwaysRelevantConnectionNode = GetAlwaysRelevantForConnectionNode(Debugger->GetReplicationOwner()))
	{
		AlwaysRelevantConnectionNode->GameplayDebugger = Debugger;
	}
}
6

Let this be a lesson to everyone: & lambda capture is evil.