Provides missing functionality from Unity's new input system for MonoBehaviour.OnMouseDown/Drag/Enter/Exit/Over/Up/UpButton events

CursorRaycaster.cs

using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.Events;

public class CursorRaycaster : MonoBehaviour
{
    public UnityEvent onClickNothing;
    private const float DragThreshold = 1.0f;
    
    private Ray ray;
    private RaycastHit hit;
    private Camera cam;
    private GameObject previousHitObject;
    private GameObject clickedObject;
    private float dragDistance;
    private bool dragging;
    
    private const string MouseDown = "OnMouseDown";
    private const string MouseDrag = "OnMouseDrag";
    private const string MouseEnter = "OnMouseEnter";
    private const string MouseExit = "OnMouseExit";
    private const string MouseOver = "OnMouseOver";
    private const string MouseUp = "OnMouseUp";
    private const string MouseUpAsButton = "OnMouseUpAsButton";

    private bool clicked;
    private bool released;
    private bool down;
    private Vector2 delta;
    private Vector2 screenspaceRayOrigin;
    
    public BindInputActions(InputAction clickAction, InputAction moveDeltaAction)
    {
        clickAction.performed += Click;
        clickAction.canceled += Release;
        move = moveDeltaAction;
        moveDeltaAction.performed += Move;
    }
    
    private void Click(InputAction.CallbackContext context)
    {
        clicked = true;
        down = true;
    }

    private void Release(InputAction.CallbackContext context)
    {
        released = true;
        down = false;
    }

    private void Move(InputAction.CallbackContext context) => delta += context.ReadValue<Vector2>();
    
    private void UpdateCursorPosition() => screenspaceRayOrigin = Mouse.current.position.ReadValue();

    private void Awake() => cam = Camera.main;

    private void ConsumeInputs()
    {
        clicked = false;
        released = false;
        delta = Vector2.zero;
    }
    
    private void OnDownNoHit()
    {
        Debug.Log("Clicked Nothing");
        onClickNothing?.Invoke();
    }
    
    private void OnDown(GameObject go) => previousHitObject.SendMessage(MouseDown, SendMessageOptions.DontRequireReceiver);

    private void OnDrag()
    {
        if (dragging)
        {
            clickedObject.SendMessage(MouseDrag, SendMessageOptions.DontRequireReceiver);
            return;
        }

        dragDistance += delta.sqrMagnitude;
        dragging = dragDistance > DragThreshold;
    }

    private void OnEnter(GameObject go)
    {
        go.SendMessage(MouseEnter, SendMessageOptions.DontRequireReceiver);
        previousHitObject = go;
    }

    private void OnExit()
    {
        previousHitObject.SendMessage(MouseExit, SendMessageOptions.DontRequireReceiver);
        previousHitObject = null;
    }

    private void OnOver() => previousHitObject.SendMessage(MouseOver, SendMessageOptions.DontRequireReceiver);
    
    private void OnUp() => previousHitObject.SendMessage(MouseUp, SendMessageOptions.DontRequireReceiver);
    
    private void OnUpButton() => previousHitObject.SendMessage(MouseUpAsButton, SendMessageOptions.DontRequireReceiver);

    public void FixedUpdate()
    {
        UpdateCursorPosition();
        
        if (down && clickedObject)
            OnDrag();
        
        ray = cam.ScreenPointToRay(screenspaceRayOrigin);
        
        if (Physics.Raycast(ray, out hit, cam.farClipPlane))
        {
            var hitObject = hit.collider.gameObject;
            
            if (clicked)
            {
                OnDown(hitObject);
                clickedObject = hitObject;
            }

            if (released)
            {
                OnUp();

                if (clickedObject && ReferenceEquals(clickedObject, hitObject))
                    OnUpButton();
                
                clickedObject = null;
                dragging = false;
                dragDistance = 0;
            }

            if (!previousHitObject)
            {
                OnEnter(hitObject);
                ConsumeInputs();
                return;
            }

            if (ReferenceEquals(previousHitObject, hitObject))
            {
                OnOver();
                ConsumeInputs();
                return;
            }
            
            OnExit();
            OnEnter(hitObject);
        }
        else if (previousHitObject)
        {
            OnExit();
        }
        
        if (clicked)
                OnDownNoHit();

        ConsumeInputs();
    }
}