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Plugins/GGS/Source/GenericCameraSystem/Private/GCMS_CameraModeStack.cpp

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+// Copyright 2025 https://yuewu.dev/en  All Rights Reserved.
+
+
+#include "GCMS_CameraModeStack.h"
+
+#include "Engine/Canvas.h"
+
+#include UE_INLINE_GENERATED_CPP_BY_NAME(GCMS_CameraModeStack)
+
+//////////////////////////////////////////////////////////////////////////
+// UGCMS_CameraModeStack
+//////////////////////////////////////////////////////////////////////////
+UGCMS_CameraModeStack::UGCMS_CameraModeStack()
+{
+	bIsActive = true;
+}
+
+void UGCMS_CameraModeStack::ActivateStack()
+{
+	if (!bIsActive)
+	{
+		bIsActive = true;
+
+		// Notify camera modes that they are being activated.
+		for (UGCMS_CameraMode* CameraMode : CameraModeStack)
+		{
+			check(CameraMode);
+			CameraMode->OnActivation();
+		}
+	}
+}
+
+void UGCMS_CameraModeStack::DeactivateStack()
+{
+	if (bIsActive)
+	{
+		bIsActive = false;
+
+		// Notify camera modes that they are being deactivated.
+		for (UGCMS_CameraMode* CameraMode : CameraModeStack)
+		{
+			check(CameraMode);
+			CameraMode->OnDeactivation();
+		}
+	}
+}
+
+void UGCMS_CameraModeStack::PushCameraMode(TSubclassOf<UGCMS_CameraMode> CameraModeClass)
+{
+	if (!CameraModeClass)
+	{
+		return;
+	}
+
+	// get camera from pool.
+	UGCMS_CameraMode* NewCameraMode = GetCameraModeInstance(CameraModeClass);
+	check(NewCameraMode);
+
+	int32 StackSize = CameraModeStack.Num();
+
+	if ((StackSize > 0) && (CameraModeStack[0] == NewCameraMode))
+	{
+		// Already top of stack.
+		return;
+	}
+
+	// See if it's already in the stack and remove it.
+	// Figure out how much it was contributing to the stack.
+	int32 ExistingStackIndex = INDEX_NONE;
+	float ExistingStackContribution = 1.0f;
+
+	for (int32 StackIndex = 0; StackIndex < StackSize; ++StackIndex)
+	{
+		if (CameraModeStack[StackIndex] == NewCameraMode)
+		{
+			ExistingStackIndex = StackIndex;
+			ExistingStackContribution *= NewCameraMode->GetBlendWeight();
+			break;
+		}
+		else
+		{
+			ExistingStackContribution *= (1.0f - CameraModeStack[StackIndex]->GetBlendWeight());
+		}
+	}
+
+	// existing in stack, remove it before add.
+	if (ExistingStackIndex != INDEX_NONE)
+	{
+		CameraModeStack.RemoveAt(ExistingStackIndex);
+		StackSize--;
+	}
+	else
+	{
+		ExistingStackContribution = 0.0f;
+	}
+
+	// Decide what initial weight to start with.
+	const bool bShouldBlend = ((NewCameraMode->GetBlendTime() > 0.0f) && (StackSize > 0));
+	const float BlendWeight = (bShouldBlend ? ExistingStackContribution : 1.0f);
+
+	NewCameraMode->SetBlendWeight(BlendWeight);
+
+	// Add new entry to top of stack.
+	CameraModeStack.Insert(NewCameraMode, 0);
+
+	// Make sure stack bottom is always weighted 100%.
+	CameraModeStack.Last()->SetBlendWeight(1.0f);
+
+	// Let the camera mode know if it's being added to the stack.
+	if (ExistingStackIndex == INDEX_NONE)
+	{
+		NewCameraMode->OnActivation();
+	}
+}
+
+void UGCMS_CameraModeStack::PopCameraMode(TSubclassOf<UGCMS_CameraMode> CameraModeClass)
+{
+}
+
+bool UGCMS_CameraModeStack::EvaluateStack(float DeltaTime, FGCMS_CameraModeView& OutCameraModeView)
+{
+	if (!bIsActive)
+	{
+		return false;
+	}
+
+	//Update camera modes. 
+	UpdateStack(DeltaTime);
+
+	//Blend values from camera modes.
+	BlendStack(OutCameraModeView);
+
+	return true;
+}
+
+UGCMS_CameraMode* UGCMS_CameraModeStack::GetCameraModeInstance(TSubclassOf<UGCMS_CameraMode> CameraModeClass)
+{
+	check(CameraModeClass);
+
+	// First see if we already created one.
+	for (UGCMS_CameraMode* CameraMode : CameraModeInstances)
+	{
+		if ((CameraMode != nullptr) && (CameraMode->GetClass() == CameraModeClass))
+		{
+			return CameraMode;
+		}
+	}
+
+	// Not found, so we need to create it.
+	UGCMS_CameraMode* NewCameraMode = NewObject<UGCMS_CameraMode>(GetOuter(), CameraModeClass, NAME_None, RF_NoFlags);
+	check(NewCameraMode);
+
+	CameraModeInstances.Add(NewCameraMode);
+
+	return NewCameraMode;
+}
+
+void UGCMS_CameraModeStack::UpdateStack(float DeltaTime)
+{
+	const int32 StackSize = CameraModeStack.Num();
+	if (StackSize <= 0)
+	{
+		return;
+	}
+
+	int32 RemoveCount = 0;
+	int32 RemoveIndex = INDEX_NONE;
+
+	for (int32 StackIndex = 0; StackIndex < StackSize; ++StackIndex)
+	{
+		UGCMS_CameraMode* CameraMode = CameraModeStack[StackIndex];
+		check(CameraMode);
+
+		CameraMode->UpdateCameraMode(DeltaTime);
+
+		if (CameraMode->GetBlendWeight() >= 1.0f)
+		{
+			// Everything below this mode is now irrelevant and can be removed.
+			RemoveIndex = (StackIndex + 1);
+			RemoveCount = (StackSize - RemoveIndex);
+			break;
+		}
+	}
+
+	if (RemoveCount > 0)
+	{
+		// Let the camera modes know they being removed from the stack.
+		for (int32 StackIndex = RemoveIndex; StackIndex < StackSize; ++StackIndex)
+		{
+			UGCMS_CameraMode* CameraMode = CameraModeStack[StackIndex];
+			check(CameraMode);
+
+			CameraMode->OnDeactivation();
+		}
+
+		CameraModeStack.RemoveAt(RemoveIndex, RemoveCount);
+	}
+}
+
+void UGCMS_CameraModeStack::BlendStack(FGCMS_CameraModeView& OutCameraModeView) const
+{
+	const int32 StackSize = CameraModeStack.Num();
+	if (StackSize <= 0)
+	{
+		return;
+	}
+
+	// Start at the bottom and blend up the stack
+	const UGCMS_CameraMode* CameraMode = CameraModeStack[StackSize - 1];
+	check(CameraMode);
+
+	OutCameraModeView = CameraMode->GetCameraModeView();
+
+	for (int32 StackIndex = (StackSize - 2); StackIndex >= 0; --StackIndex)
+	{
+		CameraMode = CameraModeStack[StackIndex];
+		check(CameraMode);
+
+		OutCameraModeView.Blend(CameraMode->GetCameraModeView(), CameraMode->GetBlendWeight());
+	}
+}
+
+void UGCMS_CameraModeStack::DrawDebug(UCanvas* Canvas) const
+{
+	check(Canvas);
+
+	FDisplayDebugManager& DisplayDebugManager = Canvas->DisplayDebugManager;
+
+	DisplayDebugManager.SetDrawColor(FColor::Green);
+	DisplayDebugManager.DrawString(FString(TEXT("   --- Camera Modes (Begin) ---")));
+
+	for (const UGCMS_CameraMode* CameraMode : CameraModeStack)
+	{
+		check(CameraMode);
+		CameraMode->DrawDebug(Canvas);
+	}
+
+	DisplayDebugManager.SetDrawColor(FColor::Green);
+	DisplayDebugManager.DrawString(FString::Printf(TEXT("   --- Camera Modes (End) ---")));
+}
+
+void UGCMS_CameraModeStack::GetBlendInfo(float& OutWeightOfTopLayer, FGameplayTag& OutTagOfTopLayer) const
+{
+	if (CameraModeStack.Num() == 0)
+	{
+		OutWeightOfTopLayer = 1.0f;
+		OutTagOfTopLayer = FGameplayTag();
+		return;
+	}
+	else
+	{
+		UGCMS_CameraMode* TopEntry = CameraModeStack.Last();
+		check(TopEntry);
+		OutWeightOfTopLayer = TopEntry->GetBlendWeight();
+		OutTagOfTopLayer = TopEntry->GetCameraTypeTag();
+	}
+}