Inventory System Plugin for Unreal Engine 5

A production-ready, multiplayer-compatible grid-based inventory system for Unreal Engine 5.6+ featuring fragment-based item composition, spatial grid UI with drag-drop functionality, equipment management, and full network replication.

Features

Core Inventory System

• Fragment-Based Item Architecture - Modular item composition using FInv_ItemFragment system allowing flexible item definitions without class inheritance
• Spatial Grid Layout - Multi-slot items with configurable dimensions and grid padding
• GameplayTag Identification - Tag-based item identification and querying instead of hard-coded IDs
• Stack Management - Configurable max stack sizes with automatic stack merging
• Item Categories - Automatic categorization (Equippable, Consumable, Craftable) with category-specific grids
• Weight System - Automatic player movement speed adjustment based on total inventory weight
• Server-Authoritative - All inventory operations validated on server with FastArray replication

Equipment System

• Equipment Slots - Support for multiple equipment slots (weapons, cloaks, masks, etc.)
• Stat Modifiers - Equipment items can apply stat bonuses via FInv_EquipModifier
• Actor Spawning - Equipment automatically spawns and attaches AInv_EquipActor to skeletal mesh sockets
• Visual Feedback - Equipment slots show currently equipped items in UI

Consumable System

• Consumable Effects - Health/Mana potions with configurable restoration amounts
• Consume Modifiers - Extensible modifier system via FInv_ConsumeModifier
• Stacking Support - Consumables can be stackable with configurable limits

UI System

• Spatial Grid Widget - Visual grid representation with multi-slot item support
• Drag-Drop System - Full drag-drop between inventory slots, equipment slots, and world
• Item Hover Tooltips - Detailed item information on mouse hover via UInv_HoverItem
• Item Description Panel - Stat display and item details via composite pattern widgets
• Context Menus - Right-click popup menus for split, drop, consume actions
• HUD Integration - Pickup notifications and status messages via UInv_HUDWidget
• Composite Widget System - Flexible UI composition using UInv_CompositeBase pattern

Interaction System

• Line Trace Pickup - Configurable distance-based item detection
• Highlight System - Visual highlighting via IInv_Highlightable interface
• Interactable Interface - Generic interaction system via IInv_Interactable
• Pickup Animations - Optional pickup montages and sounds

Network Features

• Multiplayer Ready - Full server-client replication using FFastArraySerializer
• Optimized Serialization - Efficient network bandwidth usage
• RPC Support - Server/client RPCs for all inventory operations
• Delegate Events - Comprehensive event system for UI updates (OnItemAdded, OnItemRemoved, OnStackChange, etc.)

Installation

Requirements

• Unreal Engine 5.6 or higher
• C++17 compiler (MSVC 2022 or later)
• Git (for version control)

Step-by-Step Installation

1. Clone or download this repository into your project's Plugins folder:

   cd YourProject/Plugins
   git clone https://github.com/alessandrobelli/InventoryPluginUE5.git Inventory

2. Add the plugin to your project's .uproject file:

   {
     "Plugins": [
       {
         "Name": "Inventory",
         "Enabled": true
       }
     ]
   }

3. Add module dependency to your game's Build.cs file:

   PublicDependencyModuleNames.AddRange(new string[] {
       "Core", "CoreUObject", "Engine", "InputCore",
       "Inventory"  // Add this line
   });

4. Regenerate project files and compile:

   # Right-click .uproject → Generate Visual Studio project files
   # Open solution and build

5. Enable the plugin in Unreal Editor:

   • Edit → Plugins → Search "Inventory" → Enable → Restart Editor

Usage

Quick Start: Adding Inventory to Your Character

// YourCharacter.h
#include "InventoryManagement/Components/Inv_InventoryComponent.h"
#include "EquipmentManagement/Components/Inv_EquipmentComponent.h"

UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Inventory")
UInv_InventoryComponent* InventoryComponent;

UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = "Equipment")
UInv_EquipmentComponent* EquipmentComponent;

// YourCharacter.cpp (Constructor)
InventoryComponent = CreateDefaultSubobject<UInv_InventoryComponent>(TEXT("InventoryComponent"));
InventoryComponent->SetIsReplicatedByDefault(true);

EquipmentComponent = CreateDefaultSubobject<UInv_EquipmentComponent>(TEXT("EquipmentComponent"));
EquipmentComponent->SetOwningSkeletalMesh(GetMesh());

Creating a Pickup Item

1. Create a Blueprint Actor inheriting from AActor
2. Add Components:
   • StaticMeshComponent for visuals
   • UInv_ItemComponent for inventory data
3. Configure the Item Manifest on UInv_ItemComponent:

   // In Blueprint or C++
   ItemManifest.ItemCategory = EInv_ItemCategory::Equippable;
   ItemManifest.ItemType = FGameplayTag::RequestGameplayTag(FName("GameItems.Weapons.Sword"));
   
   // Add required fragments
   FInv_GridFragment GridFragment;
   GridFragment.GridSize = FIntPoint(2, 3);  // 2 wide, 3 tall
   GridFragment.GridPadding = 5.0f;
   ItemManifest.AddFragment(GridFragment);
   
   FInv_ImageFragment ImageFragment;
   ImageFragment.Icon = SwordIconTexture;
   ItemManifest.AddFragment(ImageFragment);
   
   FInv_TextFragment TextFragment;
   TextFragment.FragmentText = FText::FromString("Iron Sword");
   ItemManifest.AddFragment(TextFragment);
   
   FInv_WeightFragment WeightFragment;
   WeightFragment.Weight = 15;
   ItemManifest.AddFragment(WeightFragment);

Creating an Equippable Weapon

1. Create Equipment Actor inheriting from AInv_EquipActor
2. Add visual components (StaticMesh or SkeletalMesh)
3. Configure Equipment Fragment:

   FInv_EquipmentFragment EquipFragment;
   EquipFragment.EquipActorClass = AMyWeaponActor::StaticClass();
   EquipFragment.SocketAttachPoint = FName("hand_rSocket");
   EquipFragment.EquipmentType = FGameplayTag::RequestGameplayTag(FName("Equipment.Weapon"));
   
   // Add stat modifiers
   FInv_StrengthModifier StrengthMod;
   StrengthMod.StrengthBonus = 10;
   EquipFragment.EquipModifiers.Add(FInstancedStruct::Make(StrengthMod));
   
   ItemManifest.AddFragment(EquipFragment);

Querying Inventory in C++

// Find item by GameplayTag
FGameplayTag KeyTag = FGameplayTag::RequestGameplayTag(FName("GameItems.Keys.GoldenKey"));
UInv_InventoryItem* Item = InventoryComponent->FindItemByTag(KeyTag);

if (Item != nullptr)
{
    UE_LOG(LogTemp, Log, TEXT("Player has the golden key!"));
}

// Get inventory weight
int32 TotalWeight = InventoryComponent->GetInventoryWeight();

// Listen to inventory events
InventoryComponent->OnItemAdded.AddDynamic(this, &AMyCharacter::OnInventoryItemAdded);
InventoryComponent->OnItemEquipped.AddDynamic(this, &AMyCharacter::OnItemEquipped);

Setting Up UI

1. Create Blueprint Widget inheriting from UInv_InventoryBase

   • Or use provided WBP_Inv_SpatialInventory or WBP_Inv_SpatialInventoryFullScreen

2. Assign to Inventory Component:

   • In Blueprint: Set InventoryMenuClass on BP_Inv_InventoryComponent

3. Toggle Inventory via Input Action:

   • Use IA_ToggleInventory (default: "I" key)
   • Or call ToggleInventory() on AInv_PlayerController

Architecture

Core Components

Component	Purpose	Replication
UInv_InventoryComponent	Main inventory storage and management	✅ Server-authoritative
UInv_EquipmentComponent	Equipment slot management and actor spawning	✅ Replicated
UInv_ItemComponent	Attached to world pickups	❌ No replication needed
AInv_PlayerController	Handles pickup interaction and weight management	✅ Replicated

Data Structures

Type	Purpose
FInv_ItemManifest	Item definition with fragment composition
UInv_InventoryItem	Runtime inventory item instance
FInv_InventoryFastArray	Replicated inventory storage
FInv_ItemFragment	Base class for all item fragments

Available Item Fragments

Fragment	Purpose	Properties
FInv_GridFragment	Grid size and padding	GridSize: FIntPoint, GridPadding: float
FInv_ImageFragment	Icon texture	Icon: UTexture2D*, IconDimensions: FVector2D
FInv_TextFragment	Display text	FragmentText: FText
FInv_WeightFragment	Item weight	Weight: int32
FInv_StackableFragment	Stack behavior	MaxStackSize: int32, StackCount: int32
FInv_EquipmentFragment	Equipment data	EquipActorClass, SocketAttachPoint, EquipModifiers
FInv_ConsumableFragment	Consumable effects	ConsumeModifiers: TArray<FInv_ConsumeModifier>
FInv_HealthPotionFragment	Health restoration	Inherits from FInv_ConsumableFragment
FInv_ManaPotionFragment	Mana restoration	Inherits from FInv_ConsumableFragment
FInv_LabeledNumberFragment	Stat display	Label: FText, Value: float, Min/Max: float

Widget System

Widget Class	Purpose
UInv_InventoryBase	Base inventory menu widget
UInv_InventoryGrid	Category-specific spatial grid
UInv_GridSlot	Individual grid slot widget
UInv_SlottedItem	Visual item representation in grid
UInv_HoverItem	Item tooltip on mouse hover
UInv_ItemDescription	Item stats and description panel
UInv_ItemPopUp	Right-click context menu
UInv_HUDWidget	Main HUD with pickup messages
UInv_EquippedGridSlot	Equipment slot widget
UInv_CompositeBase	Base for composite pattern widgets

Delegates & Events

The inventory system exposes comprehensive delegates for UI updates:

// UInv_InventoryComponent delegates
FInventoryItemChange OnItemAdded;              // Called when item added
FInventoryItemChange OnItemRemoved;            // Called when item removed
FNoRoomInInventory OnNoRoomInInventory;        // Called when inventory full
FStackChange OnStackChange;                    // Called when stack count changes
FItemEquippedStatusChanged OnItemEquipped;     // Called when item equipped
FItemEquippedStatusChanged OnItemUnequipped;   // Called when item unequipped
FInventoryMenuToggle OnInventoryMenuToggle;    // Called when UI opens/closes

Controls

• E / Primary Interact - Pick up item from world
• I / Toggle Inventory - Open/close inventory menu
• Left Mouse - Click to pick up item from slot
• Left Mouse Drag - Drag item to move between slots
• Right Mouse - Open context menu (split/drop/consume)
• Drop outside grid - Drop item to world

Support

For bugs, questions, or feature requests:

• GitHub Issues: https://github.com/alessandrobelli/InventoryPluginUE5/issues
• Discussions: Use GitHub Discussions for general questions

Roadmap

Future planned features:

• Container system (chests, loot boxes)
• Item durability system
• Item comparison tooltips
• Inventory sorting and filtering

Contributing

Contributions are welcome! To contribute:

1. Fork the repository
2. Create a feature branch: git checkout -b feature/YourFeature
3. Make your changes following the existing code style
4. Test thoroughly in multiplayer scenarios
5. Commit with clear messages: git commit -m "Add feature: description"
6. Push to your fork: git push origin feature/YourFeature
7. Open a Pull Request with detailed description

Development Guidelines

• Follow Unreal Engine coding standards
• Use UPROPERTY() for all replicated variables
• Add UFUNCTION() for Blueprint-exposed functions
• Test in both single-player and multiplayer (listen server + clients)
• Document public APIs with comments

License

This project is licensed under the MIT License - see the LICENSE file for details.

Project Status

Active Development - This plugin is actively maintained and used in production projects.

Recent Updates

• v1.1.0 (2025-11-16)

  • Fixed drag-drop edge highlighting issues
  • Added bIsDragging flag to prevent boundary interference
  • Improved GridSlot event handling for reliable hover detection
  • Removed canvas boundary check from HighlightSlots()

• v1.0.0 (2025)

  • Initial release
  • Core inventory system with grid layout
  • Equipment system with stat modifiers
  • Consumable system
  • Full multiplayer support
  • Drag-drop UI system