Unity UI Share a Drag UI and keep in screen script which is compatible with any canvas render mode.

and want to know is there any situation has not considered.

Edit: bug on different resolutions , fixed on #2

Code (CSharp):

1. /*
2. * add this script on the UI you want to drag
3. *this component should have a <Canvas> in any parents
4. * <Canvas> render mods does not matter
5. * <Canvas>should have a <Canvas Scaler> with  setting:
6. * UI scale mode: scale with screen size
7. * screen match mode : expand
8. * other settings is not tested
9. */
10.  
11. using UnityEngine;
12. using UnityEngine.EventSystems;
13.  
14.  
15.  
16.  
17. public class DragUI : MonoBehaviour, IDragHandler
18. {
19.     private RectTransform rt;
20.  
21.     private Vector3 pos;
22.  
23.     public Camera eventCamera;
24.     private Rect canvasRect;
25.     private Rect screenRect;
26.     private Vector2 thisUISize;
27.  
28.  
29.  
30.  
31.     private void Start()
32.     {
33.         rt = GetComponent<RectTransform>();
34.         eventCamera = GetComponentInParent<Canvas>().worldCamera;
35.         canvasRect = GetComponentInParent<Canvas>().GetComponent<RectTransform>().rect;
36.     }
37.  
38.     private void OnValidate()
39.     {
40.         if (!GetComponent<RectTransform>())
41.             Debug.LogWarning("DragUI needs <RectTransform> on itself");
42.         if (!GetComponentInParent<Canvas>())
43.             Debug.LogWarning("DragUI needs a <Canvas> in any parents");
44.     }
45.  
46.     public void OnDrag(PointerEventData eventData)
47.     {
48.         SetPosition_KeepInScreen(eventData);
49.     }
50.  
51.     private void SetPosition_KeepInScreen(PointerEventData eventData)
52.     {
53.         if (GetComponentInParent<Canvas>().renderMode is RenderMode.ScreenSpaceOverlay)
54.         {
55.             pos = eventData.position;
56.             screenRect = new Rect(0, 0, Screen.width, Screen.height); //screen size
57.             thisUISize = rt.sizeDelta * (Screen.width / canvasRect.width); //fix scaled size
58.         }
59.         else
60.         {
61.             var screenPoint = Input.mousePosition;
62.             //distance of the plane from the camera
63.             screenPoint.z = Mathf.Abs(eventCamera.transform.position.z - rt.position.z);
64.             pos = eventCamera!.ScreenToWorldPoint(screenPoint);
65.  
66.             screenRect = canvasRect; //canvas size for
67.             thisUISize = new Vector2(rt.rect.width, rt.rect.height);
68.         }
69.  
70.         var leftBorder = thisUISize.x * rt.pivot.x;
71.         var rightBorder = screenRect.width - thisUISize.x * (1 - rt.pivot.x);
72.         var topBorder = screenRect.height - thisUISize.y * (1 - rt.pivot.y);
73.         var bottomBorder = thisUISize.y * (rt.pivot.y);
74.         pos.x = Mathf.Clamp(pos.x, leftBorder, rightBorder); //limit x
75.         pos.y = Mathf.Clamp(pos.y, bottomBorder, topBorder); //limit y
76.  
77.         //final position
78.         transform.position = pos;
79.     }
80. }
81.  

 

version 2.0 fix bug on different resolutions
don't know why shoud do it this way.
I tried to move the ui to the each edges, recorded the positions, found out this way worked

Code (CSharp):

1. /*
2. * this component should have a <Canvas> in any parents
3. * <Canvas> render mods does not matter
4. * <Canvas>should have a <Canvas Scaler> with  setting:
5. * UI scale mode: scale with screen size
6. * screen match mode : expand
7. * other settings is not tested
8. */
9.  
10. using System;
11. using System.Linq;
12. using UnityEngine;
13. using UnityEngine.EventSystems;
14. using UnityEngine.UI;
15.  
16.  
17.  
18.  
19. public class DragUI : MonoBehaviour, IDragHandler
20. {
21.     private RectTransform rt;
22.  
23.     private Vector3 pos;
24.  
25.     public Camera eventCamera;
26.  
27.     //private Rect canvasRect => GetComponentInParent<Canvas>().GetComponent<RectTransform>().rect;
28.     //private Rect screenRect;
29.     private Vector2 thisUISize;
30.     private Canvas canvas;
31.     private CanvasScaler canvasScaler;
32.  
33.  
34.  
35.  
36.     private void Start()
37.     {
38.         rt = GetComponent<RectTransform>();
39.         eventCamera = GetComponentInParent<Canvas>().worldCamera;
40.         canvas = GetComponentsInParent<Canvas>().Last();
41.         canvasScaler = canvas.GetComponent<CanvasScaler>();
42.         if (canvasScaler && canvasScaler.screenMatchMode is not CanvasScaler.ScreenMatchMode.Expand)
43.             Debug.LogWarning("matchMode of canvasScaler of canvas of DragUI must be expand", canvasScaler);
44.     }
45.  
46.     private void OnValidate()
47.     {
48.         if (gameObject.activeInHierarchy)
49.         {
50.             if (!GetComponent<RectTransform>())
51.                 Debug.LogWarning("DragUI needs <RectTransform> on itself", gameObject);
52.  
53.             canvas = GetComponentsInParent<Canvas>().LastOrDefault();
54.             if (!canvas)
55.             {
56.                 Debug.LogWarning("DragUI needs a <Canvas> in any parents", gameObject);
57.                 return;
58.             }
59.  
60.             canvasScaler = canvas!.GetComponent<CanvasScaler>();
61.             if (canvasScaler && canvasScaler.screenMatchMode is not CanvasScaler.ScreenMatchMode.Expand)
62.                 Debug.LogWarning("canvasScaler matchMode must be expand", canvasScaler);
63.         }
64.     }
65.  
66.     public void OnDrag(PointerEventData eventData)
67.     {
68.         SetPosition_KeepInScreen(eventData);
69.         //Tooltips.HideTooltips();//限制位置时 可能让鼠标指向 自身上某些物品
70.     }
71.  
72.     private void SetPosition_KeepInScreen(PointerEventData eventData)
73.     {
74.         if (GetComponentInParent<Canvas>().renderMode is RenderMode.ScreenSpaceOverlay)
75.         {
76.             pos = eventData.position;
77.         }
78.         else
79.         {
80.             var screenPoint = Input.mousePosition;
81.             //distance of the plane from the camera
82.             screenPoint.z = GetComponentsInParent<Canvas>().Last().planeDistance;
83.             pos = eventCamera!.ScreenToWorldPoint(screenPoint);
84.         }
85.  
86.         thisUISize = new Vector2(rt.rect.width, rt.rect.height);
87.  
88.         //不同分辨率 还要调整
89.         var yDelta = Screen.height / canvas.GetComponent<RectTransform>().rect.height;
90.         var xDelta = Screen.width / canvas.GetComponent<RectTransform>().rect.width;
91.         var scale = Math.Min(xDelta, yDelta);
92.         print(scale);
93.         //final position
94.         transform.position = pos;
95.         var left = Screen.width / 2f / scale;
96.         var leftDelta = thisUISize.x * rt.pivot.x;
97.         left = Math.Clamp(rt.anchoredPosition.x, -(left - leftDelta), left - thisUISize.x * (1 - rt.pivot.x));
98.         var top = Screen.height / 2f / scale;
99.         var topDelta = thisUISize.y * rt.pivot.y;
100.         top = Math.Clamp(rt.anchoredPosition.y, -(top - topDelta), top - thisUISize.y * (1 - rt.pivot.y));
101.         rt.anchoredPosition = new Vector2(left, top);
102.     }
103. }
104.