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name: unity-input-ui description: | Unity new Input System and UI — InputAction, InputActionAsset, PlayerInput, rebinding, multi-device, plus UI Toolkit (UXML/USS, runtime + editor) and uGUI Canvas optimization.

USE WHEN: wiring input bindings, supporting gamepads/keyboard/touch, building menus/HUD with UI Toolkit or uGUI, optimizing Canvas batches, runtime rebinding, on-screen control overlays.

DO NOT USE FOR: legacy Input.GetKey API (deprecated — migrate to new Input System); 3D world-space UI specifics (use unity-rendering). allowed-tools: Read, Grep, Glob, Write, Edit

Unity Input System & UI

New Input System — basics

public class PlayerInput : MonoBehaviour {
    [SerializeField] private InputActionAsset inputActions;
    private InputAction _move, _jump, _attack;

    private void OnEnable() {
        var gameplay = inputActions.FindActionMap("Gameplay", true);
        gameplay.Enable();
        _move   = gameplay.FindAction("Move", true);
        _jump   = gameplay.FindAction("Jump", true);
        _attack = gameplay.FindAction("Attack", true);

        _jump.performed   += OnJump;
        _attack.performed += OnAttack;
    }

    private void OnDisable() {
        _jump.performed   -= OnJump;
        _attack.performed -= OnAttack;
    }

    private void Update() {
        Vector2 dir = _move.ReadValue<Vector2>();
        // movement using dir
    }

    private void OnJump(InputAction.CallbackContext ctx)   => /* jump */;
    private void OnAttack(InputAction.CallbackContext ctx) => /* attack */;
}

PlayerInput component variant: use when designer wants a UI to wire callbacks; manual binding (above) is better for systems code.

Action types

• Button — pressed/released; works for any binding kind.
• Value — continuous (e.g. stick).
• PassThrough — unfiltered, for raw streams (gestures).

Composite bindings (WASD + arrows + stick)

In InputActionAsset: action Move (Value/Vector2), 2D Vector composite with W/A/S/D + arrows; second binding from <Gamepad>/leftStick.

Runtime rebinding

var rebind = action.PerformInteractiveRebindingOperation()
    .WithControlsExcluding("<Mouse>/position")
    .WithCancelingThrough("<Keyboard>/escape")
    .OnComplete(op => {
        op.Dispose();
        SaveBindings(inputActions);
    })
    .Start();

Save with inputActions.SaveBindingOverridesAsJson() → PlayerPrefs/file. Load on startup with LoadBindingOverridesFromJson(json).

On-screen controls

Use the Input System's On-Screen Button/On-Screen Stick components on UI elements; they emit input through the same action — no separate touch path.

UI Toolkit (UXML/USS)

<!-- HUD.uxml -->
<ui:UXML xmlns:ui="UnityEngine.UIElements">
  <ui:VisualElement class="hud-root">
    <ui:Label name="health" class="hud-label" text="HP: 100" />
    <ui:ProgressBar name="hpBar" low-value="0" high-value="100" value="100" />
  </ui:VisualElement>
</ui:UXML>

/* HUD.uss */
.hud-root { position: absolute; top: 16px; left: 16px; }
.hud-label { color: white; font-size: 18px; -unity-font-style: bold; }

public class HUD : MonoBehaviour {
    [SerializeField] private UIDocument doc;
    private Label _health;
    private ProgressBar _hpBar;

    private void OnEnable() {
        var root = doc.rootVisualElement;
        _health = root.Q<Label>("health");
        _hpBar  = root.Q<ProgressBar>("hpBar");
    }

    public void SetHealth(int hp) {
        _health.text  = quot;HP: {hp}";
        _hpBar.value  = hp;
    }
}

UI Toolkit is the default for new in-game UI in Unity 6 — better batching, retained-mode tree, USS hot reload.

uGUI optimization (when you must use uGUI)

Issue	Fix
Whole canvas redraws on any change	Split canvas: static elements on one, dynamic on another
Many Image with different sprites	Sprite Atlas v2 → identical material → batched
Per-frame text.text = …	Only assign when value actually changes
LayoutGroup rebuilds	Cache results; prefer fixed sizes when possible

Anti-patterns

Anti-pattern	Fix
Input.GetKey legacy API	Use new Input System actions
Polling _jump.WasPressedThisFrame() everywhere	Subscribe to .performed events once
One huge canvas with HUD + menus	Multiple canvases; only the one being interacted redraws
GameObject.Find("HpBar")	[SerializeField] reference or UIDocument.rootVisualElement.Q

Production checklist

• InputActionAsset committed; bindings cover keyboard + gamepad + touch
• Rebinding UI persists overrides
• UI Toolkit used for new UI; uGUI only for legacy reasons
• All sprites in Sprite Atlases
• Canvas split static vs dynamic
• EventSystem present and configured for chosen UI module