Unity UI [SOLVED] EventSystem input, scale with screen size, and different resolutions

I'm working on a unit selection system for an RTS based on Kiwasi's tutorial on the subject and I've run into an annoying problem. I'm using "Scale with screen size" and a screen space camera to keep my UI properly scaled on different resolutions with a default setting of 1920x1080. When the game is set in 1080p mode, everything works perfectly fine. If I change the resolution to, say, 720p however, the cursor position is completely offset in the wrong place.

Working as intended:


Super busted:


Here's the modified code I'm using. I tried setting up a manual offset based on information from the canvas scaler and the camera resolution, but I couldn't get that to work at all.

Code (CSharp):

1. using System;
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.EventSystems;
6. using UnityEngine.UI;
7.  
8. public class DragHandler : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler, IPointerClickHandler
9. {
10.     [SerializeField]
11.     CanvasScaler canvasScaler;
12.  
13.     [SerializeField]
14.     Image selectionBoxImage;
15.     [SerializeField]
16.     Image selectionManager;
17.  
18.     Vector2 startPosition;
19.     Rect selectionRect;
20.  
21.     PointerEventData mainEventData;
22.  
23.     public void OnBeginDrag(PointerEventData eventData)
24.     {
25.         selectionBoxImage.gameObject.SetActive(true);
26.         startPosition = eventData.position;
27.         selectionRect = new Rect();
28.     }
29.  
30.     public void OnDrag(PointerEventData eventData)
31.     {
32.         if (eventData.position.x < startPosition.x)
33.         {
34.             selectionRect.xMin = eventData.position.x;
35.             selectionRect.xMax = startPosition.x;
36.         }
37.         else
38.         {
39.             selectionRect.xMin = startPosition.x;
40.             selectionRect.xMax = eventData.position.x;
41.         }
42.  
43.         if (eventData.position.y < startPosition.y)
44.         {
45.             selectionRect.yMin = eventData.position.y;
46.             selectionRect.yMax = startPosition.y;
47.         }
48.         else
49.         {
50.             selectionRect.yMin = startPosition.y;
51.             selectionRect.yMax = eventData.position.y;
52.         }
53.  
54.         if (eventData.position.x < 0)
55.         {
56.             selectionRect.x = 0;
57.             selectionRect.width = startPosition.x;
58.         }
59.  
60.         if (eventData.position.x > selectionManager.rectTransform.rect.width)
61.         {
62.             selectionRect.width = selectionManager.rectTransform.rect.width - selectionRect.x;
63.         }
64.  
65.         if (eventData.position.y < 0)
66.         {
67.             selectionRect.y = 0;
68.             selectionRect.height = startPosition.y;
69.         }
70.  
71.         if (eventData.position.y > selectionManager.rectTransform.rect.height)
72.         {
73.             selectionRect.height = selectionManager.rectTransform.rect.height - selectionRect.y;
74.         }
75.  
76.         selectionBoxImage.rectTransform.offsetMin = selectionRect.min;
77.         selectionBoxImage.rectTransform.offsetMax = selectionRect.max;
78.     }
79.  
80.     public void OnEndDrag(PointerEventData eventData)
81.     {
82.         selectionBoxImage.gameObject.SetActive(false);
83.         foreach(Selectable selectable in Selectable.allSelectables)
84.         {
85.             if (selectionRect.Contains(Camera.main.WorldToScreenPoint(selectable.transform.position)))
86.             {
87.                 selectable.OnSelect(eventData);
88.             }
89.         }
90.     }
91.  
92.     public void OnPointerClick(PointerEventData eventData)
93.     {
94.         Selectable.DeselectAll(eventData);
95.  
96.         List<RaycastResult> results = new List<RaycastResult>();
97.         EventSystem.current.RaycastAll(eventData, results);
98.  
99.         float distance = 0f;
100.  
101.         foreach (RaycastResult result in results)
102.         {
103.             if (result.gameObject == gameObject)
104.             {
105.                 distance = result.distance;
106.                 break;
107.             }
108.         }
109.  
110.         GameObject nextObject = null;
111.         float maxDistance = Mathf.Infinity;
112.  
113.         foreach (RaycastResult result in results)
114.         {
115.             if (result.distance > distance && result.distance < maxDistance)
116.             {
117.                 nextObject = result.gameObject;
118.                 maxDistance = result.distance;
119.             }
120.         }
121.  
122.         if (nextObject)
123.         {
124.             ExecuteEvents.Execute<IPointerClickHandler>(nextObject, eventData, (x, y) => { x.OnPointerClick((PointerEventData)y); });
125.         }
126.     }
127. }
128.  

 

After some amount of digging, I came across Canvas.scaleFactor, which seems to do exactly what I was trying to do, only correctly.