Remix properties panel now scrolls correctly when the curor is over an inputfield (#395)

Co-authored-by: Jenny Crowe <jakobwcrowe@berkeley.edu>

Assets/Scripts/LevelEditor/ChiScrollRect.cs

@@ -0,0 +1,62 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.EventSystems;
+using UnityEngine.UI;
+
+namespace HeavenStudio.Editor
+{
+    // Thank you Unity forums!
+    // https://forum.unity.com/threads/scroll-view-does-not-scroll-with-mousewheel-when-mouse-is-over-a-button-inside-the-scroll-view.848848/
+    
+    public class ChiScrollRect : ScrollRect, IPointerEnterHandler, IPointerExitHandler
+    {
+        private static string mouseScrollWheelAxis = "Mouse ScrollWheel";
+        private bool swallowMouseWheelScrolls = true;
+        private bool isMouseOver = false;
+    
+        public void OnPointerEnter(PointerEventData eventData)
+        {
+            isMouseOver = true;
+        }
+    
+        public void OnPointerExit(PointerEventData eventData)
+        {
+            isMouseOver = false;
+        }
+    
+        private void Update()
+        {
+            // Detect the mouse wheel and generate a scroll. This fixes the issue where Unity will prevent our ScrollRect
+            // from receiving any mouse wheel messages if the mouse is over a raycast target (such as a button).
+            if (isMouseOver && IsMouseWheelRolling())
+            {
+                var delta = UnityEngine.Input.GetAxis(mouseScrollWheelAxis);
+    
+                PointerEventData pointerData = new PointerEventData(EventSystem.current);
+                pointerData.scrollDelta = new Vector2(0f, delta * scrollSensitivity);
+    
+                swallowMouseWheelScrolls = false;
+                OnScroll(pointerData);
+                swallowMouseWheelScrolls = true;
+            }
+        }
+    
+        public override void OnScroll(PointerEventData data)
+        {
+            if (IsMouseWheelRolling() && swallowMouseWheelScrolls)
+            {
+                // Eat the scroll so that we don't get a double scroll when the mouse is over an image
+            }
+            else
+            {
+                base.OnScroll(data);
+            }
+        }
+    
+        private static bool IsMouseWheelRolling()
+        {
+            return UnityEngine.Input.GetAxis(mouseScrollWheelAxis) != 0;
+        }
+    }
+}