Draw Abstract Instances in Editor

[AccessTransformers]
Friend = (Class="AFGBuildable", FriendClass="UKBFLEditorSubsystem")

#pragma once

#include "CoreMinimal.h"
#include "EditorSubsystem.h"

#include "KBFLEditorSubsystem.generated.h"

UCLASS()
class KBFL_API UKBFLEditorSubsystem : public UEditorSubsystem {
GENERATED_BODY()
public:
    virtual void Initialize(FSubsystemCollectionBase& Collection) override;
        virtual void Deinitialize() override { Super::Deinitialize(); };

private:
    static void OnWorldPreActorTick(UWorld* World, ELevelTick TickType, float DeltaSeconds);
};

// Fill out your copyright notice in the Description page of Project Settings.
#include "Editor/KBFLEditorSubsystem.h"

#include "AbstractInstanceManager.h"
#include "Buildables/FGBuildable.h"

class AFGBuildable;

void UKBFLEditorSubsystem::Initialize(FSubsystemCollectionBase& Collection)
{
    Super::Initialize(Collection);
    
    FWorldDelegates::OnWorldPreActorTick.AddStatic(&UKBFLEditorSubsystem::OnWorldPreActorTick);
}

void UKBFLEditorSubsystem::OnWorldPreActorTick(UWorld* World, ELevelTick TickType, float DeltaSeconds)
{
    if (World->WorldType == EWorldType::EditorPreview)
    {
        for (FConstLevelIterator LevelIt = World->GetLevelIterator(); LevelIt; ++LevelIt)
        {
            for (AActor* actor : (*LevelIt)->Actors)
            {
                if (AFGBuildable* Buildable = Cast<AFGBuildable>(actor))
                {
                    if (Buildable->mCanContainLightweightInstances && IsValid(Buildable->mInstanceDataCDO) && Buildable->mInstanceHandles.IsEmpty())
                    {
                        for (FInstanceData InstanceData : Buildable->mInstanceDataCDO->GetInstanceData())
                        {
                            if (IsValid(InstanceData.StaticMesh) && !InstanceData.OverridenMaterials.Contains(nullptr))
                            {
                                FInstanceHandle* Handle;
                                AAbstractInstanceManager::SetInstanceFromDataStatic(Buildable, FTransform(), InstanceData, Handle, false);
                                Buildable->mInstanceHandles.Add(Handle);
                            }
                        }
                    }
                }
            }
        }
    }
}