Home/Cluster/Cluster-Events-in-Cpp.md

+Here is a little example on how to use cluster events in C++, e.g., reacting to UMG user input, or keyboard input which is otherwise not synced yet in the CAVE.
+
+You can now find it in the [Snippets section of the Unreal Template](https://git-ce.rwth-aachen.de/vr-vis/VR-Group/unreal-development/unrealprojecttemplate/-/snippets).
+
+## Code Example
+
+Here is the code you would need to use, if you don't want to use the helper class `DisplayClusterEventWrapper`.
+
+`UserInputSync.h`
+```c++
+#pragma once
+
+#include "CoreMinimal.h"
+#include "GameFramework/Actor.h"
+#include "Cluster/IDisplayClusterClusterManager.h"
+#include "Cluster/DisplayClusterClusterEvent.h"
+
+#include "UserInputSync.generated.h"
+
+UCLASS()
+class DYNDIRUNREAL_API AUserInputSync : public AActor
+{
+  GENERATED_BODY()
+	
+public:	
+
+  void BeginPlay() override;
+  void EndPlay(const EEndPlayReason::Type EndPlayReason) override;
+
+  UFUNCTION(BlueprintCallable)
+  void OnUserInput();
+
+  void ReactOnUserInput();
+
+private:	
+
+  FOnClusterEventListener ClusterEventListenerDelegate;
+  void HandleClusterEvent(const FDisplayClusterClusterEvent& Event);
+
+};
+```
+
+`UserInputSync.cpp`
+```c++
+#include "UserInputSync.h"
+
+#include "IUniversalLogging.h" //just here to give some feedback on the user's action
+#include "Engine.h"
+#include "IDisplayCluster.h"
+
+
+void AUserInputSync::BeginPlay() {
+  Super::BeginPlay();
+  //register the listener
+  IDisplayClusterClusterManager* ClusterManager = IDisplayCluster::Get().GetClusterMgr();
+  if (ClusterManager && !ClusterEventListenerDelegate.IsBound())
+  {
+    ClusterEventListenerDelegate = FOnClusterEventListener::CreateUObject(this, &AUserInputSync::HandleClusterEvent);
+    ClusterManager->AddClusterEventListener(ClusterEventListenerDelegate);
+  }
+  
+  //so the log shows on all slaves on screen
+  UniLog.GetDefaultLogStream()->SetLogOnScreenOnMaster(true);
+  UniLog.GetDefaultLogStream()->SetLogOnScreenOnSlaves(true);
+}
+
+void AUserInputSync::EndPlay(const EEndPlayReason::Type EndPlayReason) {
+  //de-register the listener again
+  IDisplayClusterClusterManager* ClusterManager = IDisplayCluster::Get().GetClusterMgr();
+  if (ClusterManager && ClusterEventListenerDelegate.IsBound())
+  {
+    ClusterManager->RemoveClusterEventListener(ClusterEventListenerDelegate);
+  }
+  Super::EndPlay(EndPlayReason);
+}
+
+void AUserInputSync::ReactOnUserInput() {
+  //some action you want to perform on all nodes, e.g.:
+  UniLog.Log("Input received!");
+}
+
+void AUserInputSync::OnUserInput() {
+  IDisplayClusterClusterManager* const Manager = IDisplayCluster::Get().GetClusterMgr();
+  if (Manager)
+  {
+    if (Manager->IsStandalone()) {
+      //in standalone (e.g., desktop editor play) cluster events are not executed....
+      ReactOnUserInput();
+    }
+    else {
+      // else create a cluster event to react to
+      FDisplayClusterClusterEvent cluster_event;
+      cluster_event.Name = "Some Custom Name, e.g., G pressed";
+      Manager->EmitClusterEvent(cluster_event, true);
+    }
+  }
+}
+
+void AUserInputSync::HandleClusterEvent(const FDisplayClusterClusterEvent& Event) {
+  if (Event.Name == "Some Custom Name, e.g., G pressed") {
+    //now we actually react on all cluster nodes:
+    ReactOnUserInput();
+  }
+}
+```
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