Unity3D more Complex Input. Differentiate between UI clicks and world clicks, check if mouse is dragging

CInput.cs

using System.Linq;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.Experimental.LowLevel;
using UnityEngine.Experimental.PlayerLoop;
using UInput = UnityEngine.Input;

public static class CInput {

    [RuntimeInitializeOnLoadMethod]
    private static void init() {
        /// attaching this class's Update method to the PreUpdate Loop (were 'NewInputUpdate' and 'SendMouseEvents' are)
        /// so this class does not need to be a monobehaviour it'll work out of the box
        
        /// note: those classes are experimental and may change in the future.
        
        var defaultSystems = PlayerLoop.GetDefaultPlayerLoop();
        var index = defaultSystems.subSystemList.ToList().FindIndex(0, s => s.type == typeof(PreUpdate));
        var updateSubSystem = defaultSystems.subSystemList[index];

        var list = updateSubSystem.subSystemList.ToList();
        list.Add(new PlayerLoopSystem() {
            updateDelegate = Update,
            type = typeof(CInput)
        });
        updateSubSystem.subSystemList = list.ToArray();

        defaultSystems.subSystemList[index] = updateSubSystem;
        PlayerLoop.SetPlayerLoop(defaultSystems);
    }

    private static Vector3 lastMousePosition;
    private static Vector3 dragDelta;
    
    private static void Update() {
        if (Input.GetMouseButtonDown(0)) {
            lastMousePosition = Input.mousePosition;
            dragDelta = Vector3.zero;
        }
        if (Input.GetMouseButton(0)) {
            dragDelta += Input.mousePosition - lastMousePosition;
            lastMousePosition = Input.mousePosition;
        }
    }

    public static bool IsDraging() {
        if (!Input.GetMouseButton(0) && !Input.GetMouseButtonUp(0)) return false;
        return Vector3.SqrMagnitude(dragDelta) > 9;
    }

    public static bool IsUIInput() { return (EventSystem.current != null && EventSystem.current.IsPointerOverGameObject()); }
    
    public static bool GetMouseButtonUI(int index) {
        return IsUIInput() && UInput.GetMouseButton(index); 
    }
    
    public static bool GetMouseButtonWorld(int index) {
        return !IsUIInput() && UInput.GetMouseButton(index); 
    }
    
    public static bool GetMouseButtonUpWorld(int index) {
        return !IsUIInput() && UInput.GetMouseButtonUp(index); 
    }
    
    public static bool GetMouseButtonDownWorld(int index) {
        return !IsUIInput() && UInput.GetMouseButtonDown(index); 
    }
    
}
    

Example usage:

have a game object which should be "selectable", so you want to check if it was clicked but not dragged - also it should not be behind a UI window:

[RequireComponent(typeof(Collider))]
public class SelectController : MonoBehaviour {
	private bool clicked = false;
	private void OnMouseDown() { clicked = true; }
	private void OnMouseUp() {
		if(!clicked || CInput.IsUIInput() || CInput.IsDraging()) return;

		// do something
	}
}

private void Update() { // or LateUpdate
	if(! CInput.GetMouseButtonWorld(0)) clicked = false;
}