Inventory UI

A complete, controller-first inventory UI: a player inventory screen with an equipment paper doll, a two-pane container screen, a loot window for multi-item pickups, a split-stack dialog, per-item-type tooltips, a HUD capacity / currency strip, and a toast feed. Every widget is a Blueprintable C++ base under Source/CrimsonCore/Public/UserInterface/Inventory/, and every base has a shipped Blueprint under /CrimsonCore/UserInterface/Inventory/ that you can use as-is or duplicate.

What ships

Architecture: MVVM on the CrimsonUI bases

Widgets never touch the inventory directly. Each screen owns view models built on the CrimsonUI bases (UCrimsonScreenViewModelBase, UCrimsonViewModelBase, UCrimsonEntryViewModelBase); widgets subscribe to FieldNotify properties with FCrimsonFieldBindingTracker in C++ and expose a single BlueprintImplementableEvent (On Appearance Changed, On Group Rebuilt, On Currencies Changed, ...) for visual reactions. Every mutation is a Request* call on a view model that forwards to UCrimsonInventoryRoutingComponent on the owning PlayerController, which owns the Server RPCs.

Controller-first interaction

UCrimsonCoreInventoryScreenBase is the interaction controller every screen shares. Focus drives everything: the focused slot owns the tooltip, the action-bar prompts are re-evaluated on every focus change, and a drop preview is drawn on the slot under focus while you carry an item. Mouse users get the same results through drag and drop; both paths end in PlaceCarried / EquipCarried.

The ten verbs are FCrimsonCoreUIAction properties on the screen (SortAction, SplitAction, RotateAction, LockAction, DropAction, ContextMenuAction (opens the focused item's context menu, where Use lives), TakeAllAction, MarkAction, NextPanelAction, PreviousPanelAction). Each holds an InputAction, an optional CommonUI ActionTag (UI.Action.*) used for the prompt when no Input Action is set, and a DisplayName override. The screen registers each verb as a CommonUI action-bar prompt, and that binding is what executes it: a key press, a completed hold, and a click on the bar button all run the same delegate. Nothing is bound on the Enhanced Input component - CommonUI's action router sees every key before the player controller does and consumes it, so a second binding ran every verb twice. The prompt only shows while the verb is allowed (CanSort, CanSplit, ... are re-checked per focus change).

Setup

These steps assume CrimsonCore is installed per Integration. Add each action below to the UCrimsonExperienceActionSet - or the UCrimsonExperienceDefinition Actions array - that your project's experience loads.

1. Give the player an inventory, routing, and equipment

2. Open the inventory screen

3. Put the HUD strip and toasts on screen

4. Review the settings

UCrimsonCoreInventoryUISettings ships with working defaults in Plugins/CrimsonCore/Config/DefaultCrimsonCore.ini. Project Settings -> Crimson -> Crimson Inventory UI edits the same values.

[/Script/CrimsonCore.CrimsonCoreInventoryUISettings]
DefaultTooltipWidgetClass=/CrimsonCore/UserInterface/Inventory/Tooltips/W_ItemTooltip.W_ItemTooltip_C
TooltipClassByItemType=(((TagName="Item.Type.Consumable"),"/CrimsonCore/UserInterface/Inventory/Tooltips/W_ItemTooltip_Consumable.W_ItemTooltip_Consumable_C"),((TagName="Item.Type.Weapon"),"/CrimsonCore/UserInterface/Inventory/Tooltips/W_ItemTooltip_Equipment.W_ItemTooltip_Equipment_C"),((TagName="Item.Type.Armor"),"/CrimsonCore/UserInterface/Inventory/Tooltips/W_ItemTooltip_Equipment.W_ItemTooltip_Equipment_C"),((TagName="Item.Type.Bag"),"/CrimsonCore/UserInterface/Inventory/Tooltips/W_ItemTooltip_Bag.W_ItemTooltip_Bag_C"))
SplitStackDialogClass=/CrimsonCore/UserInterface/Inventory/Dialogs/W_SplitStack_Dialog.W_SplitStack_Dialog_C

Slot widget contract

UCrimsonCoreInventorySlotWidget (on UCrimsonButtonBase) computes one ECrimsonCoreInventorySlotState per refresh and applies it in C++: Empty, Occupied, Filtered (search / category mismatch; FilteredOpacity), CarrySource (the item you are holding; CarrySourceOpacity), DropValid, DropInvalid. The rim material instance receives RimColor (FocusRimColor, DropValidRimColor, DropInvalidRimColor, EmptyRimColor) and InsetBandPx (DropPreviewInsetBand). Everything below is BindWidgetOptional - bind what your design needs; W_Inventory_Slot binds all of them.

Grid groups place one W_Inventory_Slot per cell in Grid_Cells and one W_Inventory_SlotOverlay (bIsGridItemOverlay = true) per item in Canvas_Items, sized by footprint and rotation. UCrimsonCoreInventoryGroupPanel exposes CellSize, FlatSlotGap, GridCellGap, FlatColumns, SlotWidgetClass, GridItemWidgetClass, and bWeightListTrailingEmptyRow; its optional widgets are Text_Title, Meter_Capacity, Switcher_Content, Widget_GridContent, Grid_Cells, Canvas_Items, Box_List.

UCrimsonCoreEquipmentSlotWidget mirrors the slot: Image_Icon, Image_Rarity, Image_EmptyGlyph, Text_Label (from GetTagLabel(SlotTag)), Bar_Durability, Image_Focus, the same rim colors, and On Appearance Changed (ViewModel, bDropHighlighted).

Tooltip resolution

UCrimsonCoreItemTooltipWidget::ResolveTooltipClass(Item) picks, in order: the item definition's UCrimsonInventoryItemFragment_Tooltip widget class (CrimsonInventory), then TooltipClassByItemType for the item's Item.Type.* tag (walking up parent tags), then DefaultTooltipWidgetClass. The screen creates one instance, parents it to Canvas_Tooltip when that optional canvas is bound (otherwise the viewport), and calls SetEntry / SetEquipmentSlot on focus. Optional widgets on the base: Text_Name, Text_Type, Text_Description, Text_Count, Text_Weight, Image_Icon, Image_RarityBar, Bar_Durability; _Equipment adds Text_Slot, Text_CurrentlyEquipped, Widget_CompareRow; _Bag adds Text_Capacity, Text_Rules. On Tooltip Refreshed (Item) is the Blueprint hook.

Blueprint hooks

Multiplayer

• Server: UCrimsonInventoryManagerComponent on the PlayerState owns the items and replicates them; every Request* ends in a Server RPC on UCrimsonInventoryRoutingComponent, which validates and applies. The UI never mutates state.
• Owning client: the screens, carry mode, drag-drop, tooltips, HUD strip, and toasts. PreviewDrop is a client-side dry run for highlighting only; the server still decides.
• All clients: nothing - inventory UI is never pushed on simulated proxies.
• Late join / respawn: view models rebuild from replicated state on bind, and the HUD widget rebinds on RebindInterval until it finds the player's inventory.

See also

• Pickup Actor & Loot Window
• Inventory Showcases
• Context Menu
• GameFeatureActions
• CrimsonInventory -> Overview
• CrimsonUI -> Overview