ButtonHitZone

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;

//based on a script by: booferei
//https://answers.unity.com/questions/844524/ugui-how-to-increase-hitzone-click-area-button-rec.html?page=1&pageSize=5&sort=votes
public class ButtonHitZone : MonoBehaviour
{
    [Header("Size")]
    [SerializeField]
    private float m_Width;
    [SerializeField]
    private float m_Height;

    [Header("Gizmo")]
    [SerializeField]
    private Color m_GizmoColor = Color.white;
    [SerializeField]
    private float m_GizmoFillOpacity = 0.5f;

    public class EmptyGraphic : Graphic
    {
        protected override void OnPopulateMesh(VertexHelper vh)
        {
            vh.Clear();
        }
    }

    void OnValidate()
    {
        RectTransform rectTransform = GetComponent<RectTransform>();

        if (rectTransform != null)
        {
            m_Width = Mathf.Max(m_Width, rectTransform.sizeDelta.x);
            m_Height = Mathf.Max(m_Height, rectTransform.sizeDelta.y);
        }
    }

    void OnDrawGizmosSelected()
    {
        RectTransform rectTransform = GetComponent<RectTransform>();

        if (rectTransform != null)
        {
            float gizmoWidth = m_Width * rectTransform.lossyScale.x;
            float gizmoHeight = m_Height * rectTransform.lossyScale.y;

            Gizmos.color = m_GizmoColor;
            Gizmos.DrawWireCube(rectTransform.position, new Vector3(gizmoWidth, gizmoHeight, 0.0001f));

            if (m_GizmoFillOpacity > 0)
            {
                Gizmos.color = new Color(m_GizmoColor.r, m_GizmoColor.g, m_GizmoColor.b, m_GizmoFillOpacity);
                Gizmos.DrawCube(rectTransform.position, new Vector3(gizmoWidth, gizmoHeight, 0.0001f));
            }
        }
    }

    void Awake()
    {
        CreateHitZone();
    }

    void CreateHitZone()
    {
        // create child object
        GameObject gobj = new GameObject("Button Hit Zone");

        RectTransform hitzoneRectTransform = gobj.AddComponent<RectTransform>();
        {
            hitzoneRectTransform.SetParent(transform);
            hitzoneRectTransform.localPosition = Vector3.zero;
            hitzoneRectTransform.localScale = Vector3.one;
            hitzoneRectTransform.sizeDelta = new Vector2(m_Width, m_Height);
        }

        // create transparent graphic
        // Image image = gobj.AddComponent<Image>();
        // image.color = new Color(0, 0, 0, 0);
        gobj.AddComponent<EmptyGraphic>();

        // delegate events
        EventTrigger eventTrigger = gobj.AddComponent<EventTrigger>();
        // pointer up
        AddEventTriggerListener(eventTrigger, EventTriggerType.PointerDown,
            (BaseEventData data) =>
            {
                ExecuteEvents.Execute(gameObject, data,
                   ExecuteEvents.pointerDownHandler);
            });
        // pointer down
        AddEventTriggerListener(eventTrigger, EventTriggerType.PointerUp,
            (BaseEventData data) =>
            {
                ExecuteEvents.Execute(gameObject, data,
                   ExecuteEvents.pointerUpHandler);
            });
        // pointer click
        AddEventTriggerListener(eventTrigger, EventTriggerType.PointerClick,
            (BaseEventData data) =>
            {
                ExecuteEvents.Execute(gameObject, data,
                   ExecuteEvents.pointerClickHandler);
            });
    }

    static void AddEventTriggerListener(EventTrigger trigger, EventTriggerType eventType, System.Action<BaseEventData> method)
    {
        EventTrigger.Entry entry = new EventTrigger.Entry();
        {
            entry.eventID = eventType;
            entry.callback = new EventTrigger.TriggerEvent();
            entry.callback.AddListener(new UnityEngine.Events.UnityAction<BaseEventData>(method));
        }

        trigger.triggers.Add(entry);
    }
}