Make ST-style buttons keyboard selectable

- Make ST-style buttons keyboard selectable
- Allow custom classes/selectors to be set as buttons too, with the same functionality (CSS selector-based)
- Observer to automatically add functionality to any button added to the DOM
- Allow buttons to not be selectable via 'disabled' or 'not_focusable'

public/scripts/keyboard.js

@@ -0,0 +1,165 @@
+/* All selectors that should act as keyboard buttons by default */
+const buttonSelectors = ['.menu_button', '.right_menu_button', '.clickable'];
+
+const CUSTOM_CLICKABLE_BUTTON_CLASS = 'clickable';
+
+const NOT_FOCUSABLE_CLASS = 'not_focusable';
+const DISABLED_CLASS = 'disabled';
+
+/**
+ * An observer that will check if any new buttons are added to the body
+ * @type {MutationObserver}
+ */
+const observer = new MutationObserver(mutations => {
+    mutations.forEach(mutation => {
+        if (mutation.type === 'childList') {
+            mutation.addedNodes.forEach(node => {
+                if (node.nodeType === Node.ELEMENT_NODE && node instanceof Element) {
+                    // Check if the node itself is a button
+                    if (isKeyboardButton(node)) {
+                        enableKeyboardButton(node);
+                    }
+                    // Check for any descendants that might be buttons
+                    const newButtons = getAllButtons(node);
+                    enableKeyboardButton(...newButtons);
+                }
+            });
+        } else if (mutation.type === 'attributes') {
+            const target = mutation.target;
+            if (mutation.attributeName === 'class' && target instanceof Element) {
+                if (isKeyboardButton(target)) {
+                    enableKeyboardButton(target);
+                }
+            }
+        }
+    });
+});
+
+/**
+ * Registers a button class (for example for an exatension) and makes it keyboard-selectable.
+ * Optionally apply the 'not_focusable' and 'disabled' classes if needed.
+ *
+ * @param {string} buttonSelector - The CSS selector for the button (Supports class combinations, chained via dots like <c>tag.actionable</c>, and sub selectors)
+ * @param {object} [options={}] - Optional settings for the button class
+ * @param {boolean} [options.disabledByDefault=false] - Whether buttons of this class should be disabled by default
+ * @param {boolean} [options.notFocusableByDefault=false] - Whether buttons of this class should not be focusable by default
+ */
+export function registerKeyboardButtonClass(buttonSelector, { disabledByDefault = false, notFocusableByDefault = false } = {}) {
+    buttonSelectors.push(buttonSelector);
+
+    const buttons = document.querySelectorAll(buttonSelector);
+
+    if (disabledByDefault || notFocusableByDefault) {
+        buttons.forEach(button => {
+            if (disabledByDefault) button.classList.add(DISABLED_CLASS);
+            if (notFocusableByDefault) button.classList.add(NOT_FOCUSABLE_CLASS);
+        });
+    }
+
+    enableKeyboardButton(...buttons);
+}
+
+/**
+ * Checks if the given button is a keyboard-enabled button.
+ *
+ * @param {Element} button - The button element to check
+ * @returns {boolean} Returns true if the button is a keyboard button, false otherwise
+ */
+export function isKeyboardButton(button) {
+    // Check if this button matches any of the selectors
+    return buttonSelectors.some(selector => button.matches(selector));
+}
+
+/**
+ * Sets a
+ * Adds the 'tabindex' attribute to buttons that are not marked as 'not_focusable' or 'disabled'
+ *
+ * @param {Element[]} buttons - The buttons to add the 'tabindex' attribute to
+ */
+export function enableKeyboardButton(...buttons) {
+    buttons.forEach(button => {
+        // If this button doesn't have any of the classes, lets say the caller knows this and wants this to be a custom-enabled keyboard button.
+        if (!isKeyboardButton(button)) {
+            button.classList.add(CUSTOM_CLICKABLE_BUTTON_CLASS);
+        }
+
+        // Set/remove the tabindex accordingly to the classes. Remembering if it had a custom value.
+        if (!button.classList.contains(NOT_FOCUSABLE_CLASS) && !button.classList.contains(DISABLED_CLASS)) {
+            if (!button.hasAttribute('tabindex')) {
+                const tabIndex = button.getAttribute('data-original-tabindex') ?? '0';
+                button.setAttribute('tabindex', tabIndex);
+            }
+        } else {
+            button.setAttribute('data-original-tabindex', button.getAttribute('tabindex'));
+            button.removeAttribute('tabindex');
+        }
+    });
+}
+
+/**
+ * Initializes the focusability of buttons on the given element or the document
+ *
+ * @param {Element|Document} [element=document] - The element on which to initialize the button focus. Defaults to the document
+ */
+function initializeButtonFocus(element = document) {
+    const buttons = getAllButtons(element);
+    enableKeyboardButton(...buttons);
+}
+
+/**
+ * Queries all buttons within the given element based on the button selectors and returns them as an array
+ *
+ * @param {Element|Document} element - The element within which to query the buttons
+ * @returns {HTMLElement[]} An array containing all the buttons that match the button selectors
+ */
+function getAllButtons(element) {
+    // Query each selecter individually and combine all to a big array to return
+    return [].concat(...buttonSelectors.map(selector => Array.from(element.querySelectorAll(`${selector}`))));
+}
+
+/**
+ * Handles keydown events on the document to trigger click on Enter key press for buttons
+ *
+ * @param {KeyboardEvent} event - The keyboard event
+ */
+function handleGlobalKeyDown(event) {
+    if (event.key === 'Enter') {
+        if (!(event.target instanceof HTMLElement))
+            return;
+
+        // Only count enter on this button if no modifier key is pressed
+        if (event.altKey || event.ctrlKey || event.shiftKey)
+            return;
+
+        // Traverse up the DOM tree to find the actual button element
+        let target = event.target;
+        while (target && !isKeyboardButton(target)) {
+            target = target.parentElement;
+        }
+
+        // Trigger click if a valid button is found and it's not disabled
+        if (target && !target.classList.contains(DISABLED_CLASS)) {
+            console.debug('Triggering click on keyboard-focused button via Enter', target);
+            target.click();
+        }
+    }
+}
+
+/**
+ * Initializes severial keyboard functionalities for ST
+ */
+export function initKeyboard() {
+    // Start observing the body for added elements and attribute changes
+    observer.observe(document.body, {
+        childList: true,
+        subtree: true,
+        attributes: true,
+        attributeFilter: ['class']
+    });
+
+    // Initialize tabindex for existing buttons
+    initializeButtonFocus();
+
+    // Add a global keydown listener
+    document.addEventListener('keydown', handleGlobalKeyDown);
+}