https://www.univ-ubs.fr/plugins/cms/resources/js/AmetysFront/Accessibility.js

1/*
2 *  Copyright 2024 Anyware Services
3 *
4 *  Licensed under the Apache License, Version 2.0 (the "License");
5 *  you may not use this file except in compliance with the License.
6 *  You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 *  Unless required by applicable law or agreed to in writing, software
11 *  distributed under the License is distributed on an "AS IS" BASIS,
12 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 *  See the License for the specific language governing permissions and
14 *  limitations under the License.
15 */
16AmetysFront.Accessibility = {
17    
18    _FOCUSABLE_ELEMENTS_SELECTOR: 'a[href]:not([disabled]), summary, button:not([disabled]), textarea:not([disabled]), input[type="text"]:not([disabled]), input[type="radio"]:not([disabled]), input[type="checkbox"]:not([disabled]), select:not([disabled]), [tabindex]:not([tabindex="-1"]), iframe:not([disabled])',
19    
20    _KEYCODE_TAB: 9,
21    
22    _firstFocusableEl: null,
23    _lastFocusableEl: null,
24    
25    _handleTabKeyPress: function(event) 
26    {
27      var isTabPressed = (event.key === 'Tab' || event.keyCode === AmetysFront.Accessibility._KEYCODE_TAB);
28	  if (!isTabPressed) { 
29	      return; 
30	  }
31      
32      if (event.shiftKey && document.activeElement === AmetysFront.Accessibility._firstFocusableEl) 
33      {
34        event.preventDefault();

35        AmetysFront.Accessibility._lastFocusableEl.focus();
36      } 
37      else if (!event.shiftKey && document.activeElement === AmetysFront.Accessibility._lastFocusableEl) 
38      {
39        event.preventDefault();
40        AmetysFront.Accessibility._firstFocusableEl.focus();
41      }
42	},
43    
44    /**
45     * Trap focus into the given modal. Assume that this modal and any other modals into this modal have a "role='dialog"" attribute
46     * @param modal the modal with role='dialog' attribute
47     * @param focusFirstElmt set to true to focus the first focusable element
48     */
49    trapFocus: function(modalEl, focusFirstElmt)
50    {
51        // Reinit event
52        AmetysFront.Accessibility.untrapFocus(modalEl);
53        
54        var focusableEls = modalEl.querySelectorAll(AmetysFront.Accessibility._FOCUSABLE_ELEMENTS_SELECTOR);
55  
56        // Remove not visible elements and elements from sub-modal
57        var $focusableEls = $j(focusableEls).filter(":visible").filter(function (i, elmt){
58            let $elmt = $j(elmt); 
59            return $elmt.css('visibility') != 'hidden'
60                && ($elmt.closest("[role='dialog']").length === 0 || $elmt.closest("[role='dialog']").get(0) == modalEl);
61        });
62        
63        if ($focusableEls.length)
64        {
65	        AmetysFront.Accessibility._firstFocusableEl = $focusableEls.get(0);  
66	        AmetysFront.Accessibility._lastFocusableEl = $focusableEls.get($focusableEls.length - 1);
67            
68            if (focusFirstElmt)
69            {
70		        // Put focus on first focusable element
71		        $j(AmetysFront.Accessibility._firstFocusableEl).trigger('focus');
72            }
73            
74	        modalEl.addEventListener('keydown', AmetysFront.Accessibility._handleTabKeyPress);
75        }
76    },
77    
78    untrapFocus: function(modalEl)
79    {
80        modalEl.removeEventListener('keydown', AmetysFront.Accessibility._handleTabKeyPress);
81        AmetysFront.Accessibility._firstFocusableEl = null;
82        AmetysFront.Accessibility._lastFocusableEl = null;
83    }
84}