Sticker.cs

using UnityEngine;
using UnityEngine.UI;

[Script(ScriptRole.View)]
public abstract class Sticker : MonoBehaviour
{
    public Transform Target;
    public GameObject Prefab;
    public string Tag;
    public float Padding = 60;
    public Vector3 Offset;
    public bool ClampAnchor;
    public bool PointAtTarget;
    public bool ShowInBounds;
    public bool Shown;
    public bool LockScreenPosition;
    public Vector2 LockPoint;

    protected GameObject _guiObject;
    protected bool _initialized;

    public bool IsVisible
    {
        get { return (ShowInBounds || !InBounds) && Shown; }
    }

    Vector3 WorldPoint
    {
        get { return Camera.main.WorldToScreenPoint(Target.position) + Offset; }
    }

    bool InBounds
    {
        get
        {
            if (Target == null)
                return false;

            Vector3 point = WorldPoint - Offset;
            if (point.x > 0 && point.x < Screen.width && point.y > 0 && point.y < Screen.height)
                return true;
            return false;
        }
    }

    protected virtual void OnEnable()
    {
        if (_guiObject != null)
            _guiObject.SetActive(true);
    }

    protected virtual void OnDisable()
    {
        if (_guiObject != null)
            _guiObject.SetActive(false);
    }

    protected virtual void Awake()
    {
        if (Target == null)
            Target = transform;
    }

    protected virtual void OnSpawn()
    {
        StickerManager.RegisterSticker(this);
        _guiObject = Sync.SpawnLocal(Prefab, WorldPoint);
        _guiObject.transform.SetParent(StickerManager.Canvas, false);

        if (LockScreenPosition)
        {
            Target = null;
            _guiObject.GetComponent<RectTransform>().anchoredPosition = LockPoint;
        }

        _initialized = true;
    }

    protected virtual void Update()
    {
        // If the Sticker was disabled when a viewing player joined the server, it won't have OnSpawn Called
        // This makes sure OnSpawn is called at least once.
        if (!_initialized)
            OnSpawn();

        if (Target != null)
        {
            Vector3 newPosition = WorldPoint;

            if (ClampAnchor)
            {
                newPosition = new Vector3(Mathf.Clamp(newPosition.x + Offset.x, Padding, Screen.width - Padding),
                                          Mathf.Clamp(newPosition.y + Offset.y, Padding, Screen.height - Padding));
            }

            _guiObject.transform.position = newPosition;

            if (PointAtTarget)
            {
                // Points at the actual target position without the applied offset.
                Vector3 targetPoint = WorldPoint - Offset;
                float angle = Mathf.Atan2(targetPoint.y - _guiObject.transform.position.y, targetPoint.x - _guiObject.transform.position.x) * Mathf.Rad2Deg;
                _guiObject.transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);
            }
        }
    }

    protected virtual void OnDestroy()
    {
        if (Game.IsClient)
            StickerManager.UnregisterSticker(this);
    }
}