ScreenCameraController.cs

namespace PaintCraft.Controllers{    
	[RequireComponent(typeof(Camera))]
    public class ScreenCameraController : InputController, IPointerDownHandler, IPointerUpHandler, IPointerClickHandler {		        
        ...
	      void Update()
        {
            UpdateDragIfNeeded();
          ...
        }
        ...     

        HashSet<PointerEventData> _activeDragIds = new HashSet<PointerEventData>();
       
        public void OnPointerDown(PointerEventData eventData)
        {
            var worldPosition = eventData.pointerCurrentRaycast.worldPosition;
            if (!Canvas.IsWithinInputRect(worldPosition))
            {
                return;
            }

            _activeDragIds.Add(eventData);
            BeginLine(LineConfig, eventData.pointerId, worldPosition, true);
            eventData.selectedObject = gameObject;
            eventData.Use();
            _deactivateRaycasterOnDrawing.ForEach(raycaster => raycaster.enabled = false);
            Debug.Log("FrameNumber[down] = "+Time.frameCount);
        }


        public void OnPointerUp(PointerEventData eventData)
        {
            EndLine(eventData.pointerId, eventData.pointerCurrentRaycast.worldPosition);
            eventData.selectedObject = null;
            eventData.Use();
            _deactivateRaycasterOnDrawing.ForEach(raycaster => raycaster.enabled = true);
            _activeDragIds.Remove(eventData);
            Debug.Log("FrameNumber[up] = "+Time.frameCount);
        }


        private void UpdateDragIfNeeded()
        {            
            foreach (var eventData in _activeDragIds)
            {
                if (!eventData.used)
                {
                    Debug.Log("FrameNumber[update] = "+Time.frameCount);
                    ContinueLine(eventData.pointerId, eventData.pointerCurrentRaycast.worldPosition);                    
                }
            }
        }       
        
        public void OnPointerClick(PointerEventData eventData)
        {
            if (eventData.used || eventData.selectedObject != null)
            {
                return;
            }
            var worldPosition = eventData.pointerCurrentRaycast.worldPosition;
            if (!Canvas.IsWithinInputRect(worldPosition))
            {
                return;
            }            
            MakeSingleDot(LineConfig, eventData.pointerId, worldPosition, true);            
        }        
    }
}