HotBarHUD

HUDElement that displays the player's inventory hotbar slots. Subscribes to the possessed character's CharacterInventory to reflect item changes and selection state in real time.

Definition

Namespace: Paragon.Townskeep.HUD Assembly: Townskeep.dll

public class HotBarHUD : HUDElement

Inheritance: SerializedMonoBehaviour → ParagonBehaviour → ParagonUIBehaviour → HUDElement → HotBarHUD

Remarks

HotBarHUD bridges the inventory data model and the UI slot display. It discovers HotBarSlotUI children in Awake() and auto-selects slot 0 in Start().

Activation Flow

When the HUD is activated (OnActivated()), the component:

1. Gets the current player's possessed Character via Player.Current.TryGetPossession<Character>()

2. Subscribes to character.Inventory.Inventory.OnInventoryChanged for item add/remove/change events

3. Subscribes to character.Inventory.CurrentSelectionChanged for selection highlight changes

Item Display

When the inventory fires OnInventoryChanged(index, item, amount):

• If item is not null → slots[index].SetItem(item, amount) (shows the item icon)

• If item is null → slots[index].Clear() (hides the icon)

Selection

SetSelection(int) deactivates the previous slot's highlight and activates the new one. Each HotBarSlotUI swaps between its Normal and Active background sprites.

Quick Lookup

Goal	How
Get current selection index	hotbar.CurrentSelection
Set selection programmatically	hotbar.SetSelection(index)
Access from HUD	hud.TryGetHUDElement<HotBarHUD>(out var hotbar)

Properties

Property	Type	Description
CurrentSelection	int	Index of the currently selected hotbar slot

Methods

OnActivated (override)

Subscribes to the possessed character's inventory change and selection change events.

public override void OnActivated()

Behavior:

1. Calls Player.Current.TryGetPossession<Character>() to get the current character

2. Subscribes to character.Inventory.Inventory.OnInventoryChanged

3. Subscribes to character.Inventory.CurrentSelectionChanged

SetSelection

Switches the visual selection highlight from the current slot to the new one.

public void SetSelection(int selection)

Parameter	Type	Description
selection	int	Index of the slot to select

Behavior:

1. Calls OnDeactivated() on the previously selected HotBarSlotUI

2. Updates currentSelection to the new index

3. Calls OnActivated() on the newly selected HotBarSlotUI

Common Pitfalls

No bounds checking on slot index SetSelection() and OnInventoryChanged() index directly into the slots array without bounds checking. If the inventory has more slots than HotBarSlotUI children in the hierarchy, an IndexOutOfRangeException will occur.

OnActivated assumes a possessed Character exists OnActivated() calls Player.Current.TryGetPossession<Character>(). If the player does not currently possess a character (returns false), the subscriptions are silently skipped — but no existing slot state is cleared either.

No unsubscription on deactivation OnActivated() subscribes to inventory events but there is no corresponding OnDisabled() override to unsubscribe. If the HUD is deactivated and reactivated, or the possessed character changes, event handlers may accumulate or reference stale characters.

Start() sets selection to 0 The initial selection is set in Start() via SetSelection(0). If OnActivated() runs before Start() and a selection change event fires, the selection may briefly flicker to the correct index and then snap back to 0.

Examples

Accessing the Hotbar from Game Code

if (hud.TryGetHUDElement<HotBarHUD>(out var hotbar))
{
    int selected = hotbar.CurrentSelection;
    hotbar.SetSelection(2); // Select third slot
}

Hierarchy Setup

HUD
└── Hotbar (HotBarHUD component)
    ├── Slot 0 (HotBarSlotUI)
    ├── Slot 1 (HotBarSlotUI)
    ├── Slot 2 (HotBarSlotUI)
    ├── ...
    └── Slot N (HotBarSlotUI)

See Also

• HotBarSlotUI — individual slot element

• HUDElement — abstract base class

• HUD — parent container

• Hotbar Overview — subsystem architecture