Free-Form Slot Layout

FreeFormSlotLayout shows how to build an inventory where an item appears near the drop point instead of the next grid cell.

This is a UI layout example on top of normal transfer behavior. Item transfer does not change: the inventory still decides whether it can accept the item, creates a slot, and places the stack. FreeFormSlotLayout only chooses the screen position for the created slot.

What It Does

• the player drops an item on the inventory area
• the inventory creates a dynamic slot
• the slot is placed near the drop point
• if the position is occupied, the slot is moved to the nearest free position
• on load or ReloadUI, all slots are arranged without overlap

How It Works

Drop coordinates are not passed into transfer logic. They stay in the UI layer.

The component uses two events:

Event	Purpose
UDNDEvents.OnDropAttempting	Remember the mouse position before drop processing
UniversalInventory.OnSlotCreated	Place the new slot at the remembered position

If a slot is created outside a drop flow, the component arranges it with the default layout pass.

Components

Component	Purpose
FreeFormSlotLayout	Positions dynamically created slots and resolves overlap
InventoryDropArea	Accepts drops on the inventory area
UniversalInventory	Runs in Dynamic mode and creates slots when needed

Setup

1. Configure UniversalInventory

Set:

• Slot Management = Dynamic
• Max Free Slots = 0 if slots should appear only after drop
• Max Dynamic Slots = maximum item count for this inventory

2. Remove LayoutGroup

The slot container (_slotContainer) must not have HorizontalLayoutGroup, VerticalLayoutGroup, or GridLayoutGroup.

Unity LayoutGroup overwrites child positions, so it conflicts with free-form layout.

3. Add FreeFormSlotLayout

Add the component to the same GameObject as UniversalInventory.

Settings:

Field	What it does
UI Camera	UI camera. Leave empty for Screen Space - Overlay
Slot Spacing	Minimum spacing between slots
Bounds Override	RectTransform that bounds slot positions. If empty, the slot container is used

4. Add InventoryDropArea

The standard InventoryDropArea is enough. You do not need a custom drop target for this scenario.

Saving Positions

FreeFormSlotLayout can convert positions to normalized 0..1 coordinates. These are convenient to store in your data.

// Save: local position -> normalized 0..1
Vector2 normalized = layout.GetNormalizedPosition(slot);
myModel.SavePosition(slot.Index, normalized);

// Load: normalized 0..1 -> local position
Vector2 local = layout.NormalizedToLocal(savedNormalized);
layout.SetSlotPosition(slot, local);

Normalized coordinates survive container size changes: the slot stays in roughly the same place relative to the inventory area.

Overlap Resolution

If the drop position is occupied, the component checks nearby positions around it and chooses the nearest free position inside the allowed bounds.

This behavior is suitable for the example and small inventories. If you need another algorithm, use the same events and replace the position calculation.

Building Your Own Layout

A custom layout usually follows this pattern:

1. Create a component next to UniversalInventory.
2. Subscribe to UniversalInventory.OnSlotCreated.
3. Optionally subscribe to UDNDEvents.OnDropAttempting to remember the drop position.
4. Recalculate all slot positions in ArrangeAllSlots() after load or ReloadUI.

[RequireComponent(typeof(UniversalInventory))]
public class MyCustomLayout : MonoBehaviour
{
    private UniversalInventory _inventory;

    void Awake() => _inventory = GetComponent<UniversalInventory>();

    void OnEnable()
    {
        _inventory.OnSlotCreated += HandleSlotCreated;
    }

    void OnDisable()
    {
        _inventory.OnSlotCreated -= HandleSlotCreated;
    }

    void HandleSlotCreated(BaseSlot slot)
    {
        var rectTransform = slot.Transform as RectTransform;
        rectTransform.anchoredPosition = CalculatePosition(slot);
    }

    public void ArrangeAllSlots()
    {
        foreach (var slot in _inventory.Slots)
        {
            var rectTransform = slot.Transform as RectTransform;
            rectTransform.anchoredPosition = CalculatePosition(slot);
        }
    }

    Vector2 CalculatePosition(BaseSlot slot)
    {
        return Vector2.zero;
    }
}

Ideas For Other Layouts

Option	Idea
Circular	Place slots around a circle
Snap Grid	Drop freely, but snap the final position to the nearest cell
Physics	Give slots physics behavior
Radial Menu	Place slots in a fan from the center

Reference

Class	Role
FreeFormSlotLayout	Example component for free-form slot UI layout
UniversalInventory.OnSlotCreated	Main hook for positioning a new slot
UniversalInventory.SlotContainer	Container used for coordinate calculations
InventoryDropArea	Standard inventory drop area
DynamicSlotManagementSettings	Mode that creates slots when needed