highlight enemies

Source/Aura/Private/Character/AuraEnemy.cpp

@@ -5,8 +5,10 @@
 
 void AAuraEnemy::HighlightActor()
 {
+	bHighlighted = true;
 }
 
 void AAuraEnemy::UnHighlightActor()
 {
+	bHighlighted = false;
 }

Source/Aura/Private/Player/AuraPlayerController.cpp

@@ -5,12 +5,75 @@
 
 #include "EnhancedInputSubsystems.h"
 #include "EnhancedInputComponent.h"
+#include "Interaction/EnemyInterface.h"
 
 AAuraPlayerController::AAuraPlayerController()
 {
 	bReplicates = true;
 }
 
+void AAuraPlayerController::PlayerTick(float DeltaTime)
+{
+	Super::PlayerTick(DeltaTime);
+
+	CursorTrace();
+}
+
+void AAuraPlayerController::CursorTrace()
+{
+	FHitResult CursorHit;
+	GetHitResultUnderCursor(ECC_Visibility, false, CursorHit);
+	if (!CursorHit.bBlockingHit)
+		return;
+
+	LastActor = ThisActor;
+	ThisActor = CursorHit.GetActor();
+
+	/*
+	 * Line tracer from cursor. There are several scenarios:
+	 *  A. LastActor is null && ThisActor is null
+	 *    - Do nothing.
+	 *  B. LastActor is null && ThisActor is valid
+	 *    - Highlight ThisActor.
+	 *  C. LastActor is valid && ThisActor is null
+	 *    - UnHighlight LastActor
+	 *  D. Both actors are valid, but LastActor != ThisActor
+	 *    - UnHighlight LastActor.
+	 *    - Highlight ThisActor.
+	 *  E. Both actors are valid, and are the same actor
+	 *    - Do nothing.
+	 */
+
+	if (!LastActor)
+	{
+		if (ThisActor)
+		{
+			// Case B
+			ThisActor->HighlightActor();
+		}
+		// else Case A
+	}
+	else // LastActor is valid
+	{
+		if (!ThisActor)
+		{
+			// Case C
+			LastActor->UnHighlightActor();
+		}
+		else
+		{
+			// Both Actors are valid
+			if (LastActor != ThisActor)
+			{
+				// Case D
+				LastActor->UnHighlightActor();
+				ThisActor->HighlightActor();
+			}
+			// else do nothing
+		}
+	}
+}
+
 void AAuraPlayerController::BeginPlay()
 {
 	Super::BeginPlay();

Source/Aura/Public/Character/AuraEnemy.h

@@ -18,4 +18,7 @@ class AURA_API AAuraEnemy : public AAuraCharacterBase, public IEnemyInterface
 public:
 	virtual void HighlightActor() override;
 	virtual void UnHighlightActor() override;
+	
+	UPROPERTY (BlueprintReadOnly)
+	bool bHighlighted = false;
 };

Source/Aura/Public/Player/AuraPlayerController.h

@@ -9,6 +9,8 @@
 class UInputMappingContext;
 class UInputAction;
 
+class IEnemyInterface;
+
 struct FInputActionValue;
 
 UCLASS()
@@ -18,6 +20,7 @@ class AURA_API AAuraPlayerController : public APlayerController
 
 public:
 	AAuraPlayerController ();
+	virtual void PlayerTick(float DeltaTime) override;
 
 protected:
 	virtual void BeginPlay() override;
@@ -31,4 +34,10 @@ private:
 	TObjectPtr<UInputAction> MoveAction;
 
 	void Move (const FInputActionValue &InputActionValue);
+
+	void CursorTrace ();
+
+	// for highlighting
+	TScriptInterface<IEnemyInterface> LastActor; // TScriptInterface must be used to hold interfaces
+	TScriptInterface<IEnemyInterface> ThisActor;
 };