Current File : /home/vacivi36/ava/lib/amd/src/menu_navigation.js
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Keyboard initialization for a given html node.
*
* @module core/menu_navigation
* @copyright 2021 Moodle
* @author Mathew May <mathew.solutions>
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
const SELECTORS = {
'menuitem': '[role="menuitem"]',
'tab': '[role="tab"]',
'dropdowntoggle': '[data-toggle="dropdown"]',
};
let openDropdownNode = null;
/**
* Small helper function to check if a given node is null or not.
*
* @param {HTMLElement|null} item The node that we want to compare.
* @param {HTMLElement} fallback Either the first node or final node that can be focused on.
* @return {HTMLElement}
*/
const clickErrorHandler = (item, fallback) => {
if (item !== null) {
return item;
} else {
return fallback;
}
};
/**
* Control classes etc of the selected dropdown item and its' parent <a>
*
* @param {HTMLElement} src The node within the dropdown the user selected.
*/
const menuItemHelper = src => {
let parent;
// Do not apply any actions if the selected dropdown item is explicitly instructing to not display an active state.
if (src.dataset.disableactive) {
return;
}
// Handling for dropdown escapes.
// A bulk of the handling is already done by aria.js just add polish.
if (src.classList.contains('dropdown-item')) {
parent = src.closest('.dropdown-menu');
const dropDownToggle = document.getElementById(parent.getAttribute('aria-labelledby'));
dropDownToggle.classList.add('active');
dropDownToggle.setAttribute('tabindex', 0);
} else if (src.matches(`${SELECTORS.tab},${SELECTORS.menuitem}`) && !src.matches(SELECTORS.dropdowntoggle)) {
parent = src.parentElement.parentElement.querySelector('.dropdown-menu');
} else {
return;
}
// Remove active class from any other dropdown elements.
Array.prototype.forEach.call(parent.children, node => {
const menuItem = node.querySelector(SELECTORS.menuitem);
if (menuItem !== null) {
menuItem.classList.remove('active');
// Remove aria selection state.
menuItem.removeAttribute('aria-current');
}
});
// Set the applicable element's selection state.
if (src.getAttribute('role') === 'menuitem') {
src.setAttribute('aria-current', 'true');
}
};
/**
* Defined keyboard event handling so we can remove listeners on nodes on resize etc.
*
* @param {event} e The triggering element and key presses etc.
*/
const keyboardListenerEvents = e => {
const src = e.srcElement;
const firstNode = e.currentTarget.firstElementChild;
const lastNode = findUsableLastNode(e.currentTarget);
// Handling for dropdown escapes.
// A bulk of the handling is already done by aria.js just add polish.
if (src.classList.contains('dropdown-item')) {
if (e.key == 'ArrowRight' ||
e.key == 'ArrowLeft') {
e.preventDefault();
if (openDropdownNode !== null) {
openDropdownNode.parentElement.click();
}
}
if (e.key == ' ' ||
e.key == 'Enter') {
e.preventDefault();
menuItemHelper(src);
if (!src.parentElement.classList.contains('dropdown')) {
src.click();
}
}
} else {
const rtl = window.right_to_left();
const arrowNext = rtl ? 'ArrowLeft' : 'ArrowRight';
const arrowPrevious = rtl ? 'ArrowRight' : 'ArrowLeft';
if (src.getAttribute('role') === 'menuitem') {
// When not rendered within a dropdown menu, handle keyboard navigation if the element is rendered as a menu item.
if (e.key == arrowNext) {
e.preventDefault();
setFocusNext(src, firstNode);
}
if (e.key == arrowPrevious) {
e.preventDefault();
setFocusPrev(src, lastNode);
}
// Let aria.js handle the dropdowns.
if (e.key == 'ArrowUp' ||
e.key == 'ArrowDown') {
openDropdownNode = src;
e.preventDefault();
}
if (e.key == 'Home') {
e.preventDefault();
setFocusHomeEnd(firstNode);
}
if (e.key == 'End') {
e.preventDefault();
setFocusHomeEnd(lastNode);
}
}
if (e.key == ' ' ||
e.key == 'Enter') {
e.preventDefault();
// Aria.js handles dropdowns etc.
if (!src.parentElement.classList.contains('dropdown')) {
src.click();
}
}
}
};
/**
* Defined click event handling so we can remove listeners on nodes on resize etc.
*
* @param {event} e The triggering element and key presses etc.
*/
const clickListenerEvents = e => {
const src = e.srcElement;
menuItemHelper(src);
};
/**
* The initial entry point that a given module can pass a HTMLElement.
*
* @param {HTMLElement} elementRoot The menu to add handlers upon.
*/
export default elementRoot => {
// Remove any and all instances of old listeners on the passed element.
elementRoot.removeEventListener('keydown', keyboardListenerEvents);
elementRoot.removeEventListener('click', clickListenerEvents);
// (Re)apply our event listeners to the passed element.
elementRoot.addEventListener('keydown', keyboardListenerEvents);
elementRoot.addEventListener('click', clickListenerEvents);
};
/**
* Handle the focusing to the next element in the dropdown.
*
* @param {HTMLElement|null} currentNode The node that we want to take action on.
* @param {HTMLElement} firstNode The backup node to focus as a last resort.
*/
const setFocusNext = (currentNode, firstNode) => {
const listElement = currentNode.parentElement;
const nextListItem = ((el) => {
do {
el = el.nextElementSibling;
} while (el && !el.offsetHeight); // We only work with the visible tabs.
return el;
})(listElement);
const nodeToSelect = clickErrorHandler(nextListItem, firstNode);
const parent = listElement.parentElement;
const isTabList = parent.getAttribute('role') === 'tablist';
const itemSelector = isTabList ? SELECTORS.tab : SELECTORS.menuitem;
const menuItem = nodeToSelect.querySelector(itemSelector);
menuItem.focus();
};
/**
* Handle the focusing to the previous element in the dropdown.
*
* @param {HTMLElement|null} currentNode The node that we want to take action on.
* @param {HTMLElement} lastNode The backup node to focus as a last resort.
*/
const setFocusPrev = (currentNode, lastNode) => {
const listElement = currentNode.parentElement;
const nextListItem = ((el) => {
do {
el = el.previousElementSibling;
} while (el && !el.offsetHeight); // We only work with the visible tabs.
return el;
})(listElement);
const nodeToSelect = clickErrorHandler(nextListItem, lastNode);
const parent = listElement.parentElement;
const isTabList = parent.getAttribute('role') === 'tablist';
const itemSelector = isTabList ? SELECTORS.tab : SELECTORS.menuitem;
const menuItem = nodeToSelect.querySelector(itemSelector);
menuItem.focus();
};
/**
* Focus on either the start or end of a nav list.
*
* @param {HTMLElement} node The element to focus on.
*/
const setFocusHomeEnd = node => {
node.querySelector(SELECTORS.menuitem).focus();
};
/**
* We need to look within the menu to find a last node we can add focus to.
*
* @param {HTMLElement} elementRoot Menu to find a final child node within.
* @return {HTMLElement}
*/
const findUsableLastNode = elementRoot => {
const lastNode = elementRoot.lastElementChild;
// An example is the more menu existing but hidden on the page for the time being.
if (!lastNode.classList.contains('d-none')) {
return elementRoot.lastElementChild;
} else {
// Cast the HTMLCollection & reverse it.
const extractedNodes = Array.prototype.map.call(elementRoot.children, node => {
return node;
}).reverse();
// Get rid of any nodes we can not set focus on.
const nodesToUse = extractedNodes.filter((node => {
if (!node.classList.contains('d-none')) {
return node;
}
}));
// If we find no elements we can set focus on, fall back to the absolute first element.
if (nodesToUse.length !== 0) {
return nodesToUse[0];
} else {
return elementRoot.firstElementChild;
}
}
};
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