Why is my pointerEventData.position always Vector2.zero?

Question

I'm writing on a script using a PointerEventData for passing pointer events like e.g. pointerDownHandler, pointerUpHandler, dragHandler etc. events to raycasted objects using ExecuteEvents.Execute e.g. like

ExecuteEvents.Execute(sometargetGameObject, _pointerEventData, ExecuteEvents.pointerDownHandler);

Basically everything worked fine for e.g. Buttons but currently I'm stuck at dragging ScrollRect with a strange behaviour. I need to pass in the PointerEventData.position so what I tried

in Update among others I have the lines

pointerPosition3D = _laser.transform.position + _laser.transform.forward * dist / 2f;
pointerPosition2D = _camera.WorldToScreenPoint(pointerPosition3D);
_pointerEventData.position = pointerPosition2D;
_lastPointerPosition = _pointerEventData.position;

but the _pointerEventData.position always keeps being (0.0, 0.0).

When debugging line by line I can clearly see that e.g.

pointerPosition3D = (-0.177, 0.304, 0.9999)
pointerPosition2D = (74.28255, 153.9007)

however already in the next line

_lastPointerPosition = _pointerEventData.position;

_pointerEventData.position = (0.0, 0.0)

How is this possible? What am I doing wrong?

---

Further background:

I'm saw the idea of SteamVR Laser Pointer Menus and created a LaserPointer class based on their idea with steamvr_laserpointer.cs and VRUIItem. Here is the full class I have so far and as said for Button and usual 3D Colliders this already works great (for debugging I currently set isPressed via the Inspector):

#define USE_CUSTOM_EDITOR

using System.Linq;
using UnityEngine;
using UnityEngine.EventSystems;
#if UNITY_EDITOR && USE_CUSTOM_EDITOR
using UnityEditor;
#endif

public class LaserPointerController : MonoBehaviour
{
    #region Inspector

    [Header("Pointer Settings")]
    [Tooltip("Should the LaserPointer origin have an offset to the controller position (in local coordinates)?")]
    [SerializeField] private bool useOffset;
    [SerializeField] private Vector3 offset = Vector3.zero;

    [Tooltip("The maximal distance of the laser pointer (in Unity Units)")]
    [SerializeField] private float maxPointerDistance = 5f;

    [Tooltip("Should the laser have a Collider attached?\nUseful for e.g. directly using OnTriggerEnter\n\nNote: This will use Physics.RaycastAll which is less efficient.")]
    [SerializeField] private bool useCollider;
    [Tooltip("Should the laser Collider be a trigger?\nHas to be disabled to e.g. use OnCollisionEnter")]
    [SerializeField] private bool colliderIsTrigger;
    [Tooltip("Should the laser additionally have a RigidBody?\nRequired for some types of collisions.")]
    [SerializeField] private bool useRigidBody;

    [Header("Style Settings")]
    [Tooltip("Should the laser change its Color when pressed")]
    [SerializeField] private bool changeColor;
    [Tooltip("Should the laser change its thickness when pressed")]
    [SerializeField] private bool changeThickness;
    [Tooltip("Color of the Laser in idle")]
    [SerializeField] private Color idleColor = Color.red;
    [Tooltip("Color of the beam when pressed")]
    [SerializeField] private Color pressedColor = Color.green;
    [Tooltip("Thickness of the laser beam")]
    [SerializeField] private float idleThickness = 0.005f;
    [Tooltip("Thickness of the laser beam when pressed")]
    [SerializeField] private float pressedThickness = 0.007f;

    [Header("Debug")]
    [SerializeField] private bool isPressed;
    [SerializeField] private Vector3 pointerPosition3D;
    [SerializeField] private Vector2 pointerPosition2D;

#if UNITY_EDITOR && USE_CUSTOM_EDITOR
    [CustomEditor(typeof(LaserPointerController))]
    private class LaserPointerControllerEditor : Editor
    {
        private SerializedProperty useOffset;
        private SerializedProperty offset;

        private SerializedProperty maxPointerDistance;

        private SerializedProperty useCollider;
        private SerializedProperty colliderIsTrigger;
        private SerializedProperty useRigidBody;

        private SerializedProperty changeColor;
        private SerializedProperty changeThickness;
        private SerializedProperty idleColor;
        private SerializedProperty pressedColor;
        private SerializedProperty idleThickness;
        private SerializedProperty pressedThickness;

        private SerializedProperty _isPressed;
        private SerializedProperty pointerPosition3D;
        private SerializedProperty pointerPosition2D;

        private void OnEnable()
        {
            useOffset = serializedObject.FindProperty("useOffset");
            offset = serializedObject.FindProperty("offset");

            maxPointerDistance = serializedObject.FindProperty("maxPointerDistance");
            useCollider = serializedObject.FindProperty("useCollider");
            colliderIsTrigger = serializedObject.FindProperty("colliderIsTrigger");
            useRigidBody = serializedObject.FindProperty("useRigidBody");

            changeColor = serializedObject.FindProperty("changeColor");
            changeThickness = serializedObject.FindProperty("changeThickness");
            idleColor = serializedObject.FindProperty("idleColor");
            pressedColor = serializedObject.FindProperty("pressedColor");
            idleThickness = serializedObject.FindProperty("idleThickness");
            pressedThickness = serializedObject.FindProperty("pressedThickness");

            _isPressed = serializedObject.FindProperty("isPressed");
            pointerPosition3D = serializedObject.FindProperty("pointerPosition3D");
            pointerPosition2D = serializedObject.FindProperty("pointerPosition2D");
        }

        public override void OnInspectorGUI()
        {
            serializedObject.Update();

            DrawScriptField();

            EditorGUILayout.PropertyField(useOffset);
            if (useOffset.boolValue)
            {
                EditorGUILayout.PropertyField(offset);
                EditorGUILayout.Space();
            }

            EditorGUILayout.PropertyField(maxPointerDistance);

            EditorGUILayout.PropertyField(useCollider);
            if (useCollider.boolValue)
            {
                EditorGUILayout.PropertyField(colliderIsTrigger);
                EditorGUILayout.PropertyField(useRigidBody);
            }
            else
            {
                colliderIsTrigger.boolValue = true;
                useRigidBody.boolValue = false;
            }

            EditorGUILayout.PropertyField(changeColor);
            EditorGUILayout.PropertyField(changeThickness);

            EditorGUILayout.PropertyField(idleColor);
            if (changeColor.boolValue) EditorGUILayout.PropertyField(pressedColor);

            EditorGUILayout.PropertyField(idleThickness);
            if (changeThickness.boolValue) EditorGUILayout.PropertyField(pressedThickness);

            if (EditorApplication.isPlayingOrWillChangePlaymode)
            {
                EditorGUILayout.PropertyField(_isPressed);

                EditorGUI.BeginDisabledGroup(true);
                {
                    EditorGUILayout.PropertyField(pointerPosition3D);
                    EditorGUILayout.PropertyField(pointerPosition2D);
                }
                EditorGUI.EndDisabledGroup();
            }

            serializedObject.ApplyModifiedProperties();
        }

        private void DrawScriptField()
        {
            EditorGUI.BeginDisabledGroup(true);
            {
                EditorGUILayout.ObjectField("Script", MonoScript.FromMonoBehaviour((LaserPointerController)target), typeof(LaserPointerController), false);
            }
            EditorGUI.EndDisabledGroup();

            EditorGUILayout.Space();
        }
    }
#endif

    #endregion Inspector


    #region Public Members

    public Vector3 PointerPosition3D
    {
        get { return pointerPosition3D; }
    }

    public Vector2 PointerPosition2D
    {
        get { return pointerPosition2D; }
    }

    public bool IsPressed
    {
        get { return isPressed; }
    }

    public Transform CurrentlyHoveredTransform
    {
        get { return _currentlyHovered; }
    }

    #endregion Public Members


    #region Private Members

    private Transform _holder;
    private Transform _laser;
    private Transform _currentlyHovered;
    private Material _laserMaterial;

    private PointerEventData _pointerEventData
    {
        get
        {
            return new PointerEventData(EventSystem.current)
            {
                // most Unity comonents e.g. the ScrollRect expect this to be Left
                // otherwise they ignore pointer input
                button = PointerEventData.InputButton.Left
            };
        }
    }
    private Vector2 _lastPointerPosition;
    private bool _isDragging;
    private bool _lastPressed;
    private Camera _camera;

    #endregion Private Members


    #region MonoBehaviour Messages
    private void Awake()
    {
        _holder = new GameObject("LaserHolder").transform;
        _holder.parent = transform;
        _holder.localScale = Vector3.one;
        _holder.localPosition = useOffset ? offset : Vector3.zero;
        _holder.localRotation = Quaternion.identity;

        _laser = GameObject.CreatePrimitive(PrimitiveType.Cube).transform;
        var collider = _laser.GetComponent<Collider>();

        if (!useCollider)
        {
            Destroy(_laser.GetComponent<Collider>());
        }
        else
        {
            collider.isTrigger = colliderIsTrigger;
        }

        if (useRigidBody)
        {
            var rigidBody = _laser.gameObject.AddComponent<Rigidbody>();
            rigidBody.useGravity = false;
            rigidBody.isKinematic = true;
        }

        _laser.name = "LaserPointer";
        _laser.transform.parent = _holder;
        _laser.transform.localScale = new Vector3(idleThickness, idleThickness, maxPointerDistance);
        _laser.transform.localPosition = new Vector3(0f, 0f, maxPointerDistance / 2f);
        _laser.transform.localRotation = Quaternion.identity;

        _laserMaterial = new Material(Shader.Find("Unlit/Color")) { color = idleColor };
        _laser.GetComponent<MeshRenderer>().material = _laserMaterial;

        _camera = Camera.main;
    }

    private void OnEnable()
    {
        _holder.gameObject.SetActive(true);
    }

    private void OnDisable()
    {
        _holder.gameObject.SetActive(false);
    }

    // Update is called once per frame
    private void Update()
    {
        //TODO uncomment this in order to get the isPressed from the according controller
        //TODO for example like
        //isPressed = OVRInput.Get(OVRInput.Button.PrimaryIndexTrigger);
        // or
        //isPressed = MLInput.GetController(MLInput.Hand.Left).State.ButtonState[(int)MLInputControllerButton.Bumper] == 1;

        // Initially the dist is the maximum pointer distance
        var dist = maxPointerDistance;

        // create the ray from the laserpointer origin
        var ray = new Ray(_holder.position, _holder.forward);

        var hit = new RaycastHit();

        // If using a Collider we have to ignore the Collider of the LaserPointer itself
        if (useCollider)
        {
            var hits = Physics.RaycastAll(ray, maxPointerDistance);
            hit = hits.FirstOrDefault(h => h.transform != _laser.transform);
        }
        else
        {
            Physics.Raycast(ray, out hit, maxPointerDistance);
        }

        // Are we hitting something?
        if (hit.transform)
        {
            // ignore if still pressing the trigger
            if (!isPressed)
            {
                // Are we hitting something different to what we hit before?
                if (_currentlyHovered && _currentlyHovered != hit.transform)
                {
                    ExecuteEvents.Execute(_currentlyHovered.gameObject, _pointerEventData, ExecuteEvents.pointerExitHandler);

                    _currentlyHovered = null;
                }

                // Are we hitting something new?
                if (_currentlyHovered != hit.transform)
                {
                    ExecuteEvents.Execute(hit.transform.gameObject, _pointerEventData, ExecuteEvents.pointerEnterHandler);

                    _currentlyHovered = hit.transform;
                }
            }

            if (_currentlyHovered == hit.transform)
            {
                // If we are hitting something correct the dist value
                if (hit.distance < maxPointerDistance)
                {
                    dist = hit.distance;
                }

                if (isPressed)
                {
                    HandlePointerDown(hit.transform);
                }
                else
                {
                    HandlePointerUp(hit.transform);
                }
            }
        }
        else
        {
            if (!isPressed && _currentlyHovered)
            {
                HandlePointerUp(_currentlyHovered, true);

                ExecuteEvents.Execute(_currentlyHovered.gameObject, _pointerEventData, ExecuteEvents.pointerExitHandler);

                _currentlyHovered = null;
            }
        }

        // Apply changes in the thickness and set the laser dimensions using the dist
        var thickness = !changeThickness || !isPressed ? idleThickness : pressedThickness;
        _laser.transform.localScale = new Vector3(thickness, thickness, dist);
        _laser.transform.localPosition = new Vector3(0f, 0f, dist / 2f);

        // Apply color changes
        if (changeColor) _laserMaterial.color = isPressed ? pressedColor : idleColor;

        // Update the pointerEventData
        pointerPosition3D = _laser.transform.position + _laser.transform.forward * dist / 2f;
        pointerPosition2D = _camera.WorldToScreenPoint(pointerPosition3D);
        _pointerEventData.position = pointerPosition2D;
        _pointerEventData.delta = _pointerEventData.position - _lastPointerPosition;
        _lastPointerPosition = _pointerEventData.position;

        _lastPressed = isPressed;
    }

    #endregion MonoBehaviour Messages


    #region Private Methods

    private void HandlePointerDown(Component target)
    {
        if (!target) return;

        // only call once if IsPressed changed its value this frame
        if (_lastPressed != isPressed)
        {
            // Try pointerClickHandler, only use submitHandler as fallback
            // e.g. UI.Button implements both ... would lead to duplicate clicks
            var done = ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.pointerClickHandler);
            if (!done) ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.submitHandler);

            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.pointerDownHandler);
            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.selectHandler);
            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.initializePotentialDrag);
        }
        else
        {
            if (!_isDragging)
            {
                // in the first frame use beginDragHandler
                ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.beginDragHandler);
                _isDragging = true;
            }
            else
            {
                // later use dragHandler
                ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.dragHandler);
            }
        }
    }

    private void HandlePointerUp(Component target, bool forceInvoke = false)
    {
        if (!target) return;

        // only call once if IsPressed changed its value this frame
        // or forceInvoke is set
        if (_lastPressed != isPressed || forceInvoke)
        {
            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.pointerUpHandler);
            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.deselectHandler);
            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.endDragHandler);
            ExecuteEvents.Execute(target.gameObject, _pointerEventData, ExecuteEvents.dropHandler);

            _isDragging = false;
        }
    }

    #endregion Private Methods
}

Answer 1

Your problem lies in your _pointerEventData property; You are always returning a new instance of PointerEventData via that property, thus losing any data that you've set on the previous one.

I would suggest caching it at first like:

var pointerData = _pointerEventData;
pointerData.position = pointerPosition2D;
_lastPointerPosition = pointerData.position;