Input and Interaction

The input system separates input detection (mouse, keyboard, gamepad, or legacy navigation axes) from actions (dragging, selection, context menu). This allows changing bindings without rewriting logic and supporting different input devices.

How Input Works

flowchart LR
    A["Mouse /\nKeyboard /\nGamepad"] --> B["Determine\ninput mode"]
    B --> C["Recognize\ngesture"]
    C --> D{"Which\naction?"}
    D --> E["Dragging"]
    D --> F["Context menu"]
    D --> G["Selection"]
    D --> H["Auto-transfer"]

The slot itself does not know what to do with input. It forwards raw events (press, release, hover) to InputEventRouter, which finds the appropriate binding and executes the action.

Press Phases

The system distinguishes several press types by duration and cursor movement:

flowchart TD
    A["Press"] --> B{"What happened next?"}
    B -->|"Released quickly\nand cursor did not move"| C["Quick click"]
    B -->|"Held longer than threshold\n0.35 sec"| D["Long press"]
    B -->|"Cursor moved\nbeyond 8 px"| E["Dragging"]

Phase	Condition	Typical Action
ClickShort	Pressed and released quickly, cursor did not move	Auto-transfer, selection
ClickLong	Held longer than threshold, cursor did not move	Context menu
Down	Moment of press	Start dragging
Up	Moment of release	Finish dragging

Thresholds are configured in InputEventRouter: _longClickThresholdSeconds (default 0.35 sec) and _clickMoveTolerancePixels (default 8 pixels).

Binding Profiles

Bindings are configured via the ScriptableObject InteractionBindingsProfile. It contains pointer bindings, legacy KeyCode bindings, legacy Input Manager button-name bindings, and optional Input Action bindings.

Pointer Bindings

Each binding consists of: mouse button + modifier + phase + action.

Button	Modifier	Phase	Action
LMB	---	ClickShort	Auto-transfer
LMB	---	Down	Start dragging
LMB	---	Up	Finish dragging
LMB	Ctrl	ClickShort	Toggle selection
LMB	Shift	ClickShort	Range selection
RMB	---	ClickShort	Context menu

Legacy Input Manager Bindings

Use LegacyInputActionBinding when a project still relies on the old Input Manager and you want to bind by button name instead of KeyCode. Typical names are Submit, Cancel, or any custom button configured in Project Settings > Input Manager.

Button Name	Phase	Typical Action
Submit	Down	Auto-transfer or complete drag
Cancel	Down	Cancel drag or close UI

These bindings are polled by InputEventRouter and require Legacy Input Manager support to be enabled in Player Settings. They are separate from InputActionBinding, which belongs to the new Input System package.

Input Action Bindings

For optional hotkeys and gamepad-specific setups: bind an Input System Action to an inventory action. Mixed setups are supported, but keep in mind that InputAction-driven features still expect the new input pipeline to be configured for that scene/workflow. If a scene intentionally stays on StandaloneInputModule, pointer and navigation can still work there while some InputAction features do not.

Input Mode

The system automatically determines the current input mode:

Mode	How It Activates	Behavior
Mouse	Mouse click or mouse movement	Focus via hover, standard pointer events
Navigation	Arrows, WASD, Submit/Cancel, Tab, gamepad D-pad	Focus via `EventSystem.selectedGameObject`, navigation between slots

Switching happens automatically in both legacy input and the new Input System. When Navigation mode is active, InputEventRouter maintains focus on a slot --- if the currently selected object becomes inactive, the system finds the nearest available slot.

Overriding Bindings Per Inventory

Each inventory can have its own bindings via the InventoryExtraInteractionBinder component. This is useful when a merchant and a player have different click behavior.

If an inventory does not have an InventoryExtraInteractionBinder, the default InteractionBindingsProfile from InputEventRouter is used.

Split Drop

While dragging a stack, you can drop a portion of the items into a slot without ending the drag. The remaining items stay "in hand" and the visual counter updates automatically.

This uses the built-in SplitDropAction:

Parameter	Description	Default
`_splitCount`	How many items to split off per action	1
`_dropPolicyOverride`	Drop policy override for this operation	---

Binding Setup

Add a PointerBinding to InteractionBindingsProfile:

Button	Modifier	Phase	Action
LMB	Shift	Down	`SplitDropAction`

Binding Order

The Shift + LMB binding must be placed above the default LMB binding (Start/Complete drag) so the modifier matches first.

How It Works

Player picks up a stack of 10 items (normal drag).
Holds Shift and clicks an empty slot.
1 item is transferred through the standard pipeline (transfer engine → events).
Dragging continues with 9 items, visual updates.
When only 1 item remains, Shift+Click performs a regular CompleteDrag.

If the target slot is occupied and cannot accept the item, the operation rolls back — the stack remains unchanged.

Class Reference

Class	Role
`InputEventRouter`	Singleton: routes input to bindings
`InteractionBindingsProfile`	SO profile with pointer, legacy, and Input Action bindings
`SlotInputAdapter`	Component on a slot: forwards raw events
`InputModalityTracker`	Determines the current input mode (Mouse / Navigation) for both legacy and Input System setups
`PointerBinding`	Binding: button + modifier + phase + action
`KeyBinding`	Legacy `KeyCode` binding to an action
`LegacyInputActionBinding`	Old Input Manager button-name binding to an action
`InputActionBinding`	Input System Action binding to an action
`InventoryExtraInteractionBinder`	Binding override for a specific inventory
`SplitDropAction`	Action: drop part of a stack without ending drag
`SlotInteractionAction`	Base class for actions (inherit for custom ones)