Drag Window Script with Window Clamped within Canvas

I spent some time working on a script that would allow me to drag a window anywhere within the canvas but not let any part of that window escape the bounds of the canvas. Simply drop this script on a window, no matter the pivot of that window and it should allow you to drag that window within the canvas but not let any part of that window escape the bounds of the canvas. Thanks to Unity for their excellent tutorial which got me started https://unity3d.com/learn/tutorials/modules/intermediate/live-training-archive/panels-panes-windows

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5. using UnityEngine.EventSystems;
6.  
7. public class DragHandler : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler {
8.  
9.     private Vector2 pointerOffset;
10.     private RectTransform canvasRectTransform;
11.     private RectTransform panelRectTransform;
12.     private bool clampedToLeft;
13.     private bool clampedToRight;
14.     private bool clampedToTop;
15.     private bool clampedToBottom;
16.  
17.     public void Start(){
18.        
19.         Canvas canvas = GetComponentInParent<Canvas> ();
20.         if(canvas != null){
21.             canvasRectTransform = canvas.transform as RectTransform;
22.             panelRectTransform = transform as RectTransform;
23.         }
24.         clampedToLeft = false;
25.         clampedToRight = false;
26.         clampedToTop = false;
27.         clampedToBottom = false;
28.     }
29.  
30.     #region IBeginDragHandler implementation
31.  
32.     public void OnBeginDrag (PointerEventData eventData)
33.     {
34.         panelRectTransform.SetAsLastSibling ();
35.         RectTransformUtility.ScreenPointToLocalPointInRectangle (panelRectTransform, eventData.position, eventData.pressEventCamera, out pointerOffset);
36.  
37.     }
38.  
39.     #endregion
40.  
41.     #region IDragHandler implementation
42.  
43.     public void OnDrag (PointerEventData eventData)
44.     {
45.         if(panelRectTransform == null){
46.             return;
47.         }
48.         Vector2 localPointerPosition;
49.         if(RectTransformUtility.ScreenPointToLocalPointInRectangle (canvasRectTransform, eventData.position, eventData.pressEventCamera, out localPointerPosition)){
50.             panelRectTransform.localPosition = localPointerPosition - pointerOffset;
51.             ClampToWindow ();
52.             Vector2 clampedPosition = panelRectTransform.localPosition;
53.             if (clampedToRight) {
54.                 clampedPosition.x = (canvasRectTransform.rect.width * 0.5f) - (panelRectTransform.rect.width * (1 - panelRectTransform.pivot.x));
55.             } else if(clampedToLeft){
56.                 clampedPosition.x = (-canvasRectTransform.rect.width * 0.5f) + (panelRectTransform.rect.width * panelRectTransform.pivot.x);
57.             }
58.  
59.             if(clampedToTop){
60.                 clampedPosition.y = (canvasRectTransform.rect.height * 0.5f) - (panelRectTransform.rect.height * (1 - panelRectTransform.pivot.y));
61.             }else if(clampedToBottom){
62.                 clampedPosition.y = (-canvasRectTransform.rect.height * 0.5f) + (panelRectTransform.rect.height * panelRectTransform.pivot.y);
63.             }
64.             panelRectTransform.localPosition = clampedPosition;
65.         }
66.     }
67.  
68.     #endregion
69.  
70.     #region IEndDragHandler implementation
71.  
72.     public void OnEndDrag (PointerEventData eventData)
73.     {
74.  
75.     }
76.  
77.     #endregion
78.  
79.     void ClampToWindow(){
80.         Vector3[] canvasCorners = new Vector3[4];
81.         Vector3[] panelRectCorners = new Vector3[4];
82.         canvasRectTransform.GetWorldCorners (canvasCorners);
83.         panelRectTransform.GetWorldCorners (panelRectCorners);
84.  
85.         if (panelRectCorners [2].x > canvasCorners [2].x) {
86.             Debug.Log ("Panel is to the right of canvas limits");
87.             if (!clampedToRight) {
88.                 clampedToRight = true;
89.             }
90.         } else if (clampedToRight) {
91.             clampedToRight = false;
92.         } else if (panelRectCorners [0].x < canvasCorners [0].x) {
93.             Debug.Log ("Panel is to the left of canvas limits");
94.             if(!clampedToLeft){
95.                 clampedToLeft = true;
96.             }
97.         }else if(clampedToLeft){
98.             clampedToLeft = false;
99.         }
100.  
101.         if (panelRectCorners [2].y > canvasCorners [2].y) {
102.             Debug.Log ("Panel is to the top of canvas limits");
103.             if (!clampedToTop) {
104.                 clampedToTop = true;
105.             }
106.         }else if(clampedToTop){
107.             clampedToTop = false;
108.         }else if(panelRectCorners[0].y < canvasCorners[0].y){
109.             Debug.Log ("Panel is to the bottom of canvas limits");
110.             if(!clampedToBottom){
111.                 clampedToBottom = true;
112.             }
113.         }else if(clampedToBottom){
114.             clampedToBottom = false;
115.         }
116.     }
117. }
118.  

 

Thanks for that, I always forget to store my version somewhere works great.

 

This is great, thanks!!

 

Thank you for uploading this

 

6 years later and you are still helping the community! Thanks a million for giving the community this awesome solution to a most common feature request!

 

Works great!
Even exposed the panel so I could put the script on a child "Window Title Bar" and it still worked fine.
Thanks a bunch.

 

This is an awsome script thanks MMOERPG