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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Accessible states used to check node's state from the accessiblity API
+ * perspective.
+ *
+ * Note: if gecko is built with --disable-accessibility, the interfaces
+ * are not defined. This is why we use getters instead to be able to use
+ * these statically.
+ */
+
+this.AccessibilityUtils = (function() {
+ const FORCE_DISABLE_ACCESSIBILITY_PREF = "accessibility.force_disabled";
+
+ // Accessible states.
+ const {
+ STATE_FOCUSABLE,
+ STATE_INVISIBLE,
+ STATE_LINKED,
+ STATE_UNAVAILABLE,
+ } = Ci.nsIAccessibleStates;
+
+ // Accessible action for showing long description.
+ const CLICK_ACTION = "click";
+
+ // Roles that are considered focusable with the keyboard.
+ const KEYBOARD_FOCUSABLE_ROLES = new Set([
+ Ci.nsIAccessibleRole.ROLE_BUTTONMENU,
+ Ci.nsIAccessibleRole.ROLE_CHECKBUTTON,
+ Ci.nsIAccessibleRole.ROLE_COMBOBOX,
+ Ci.nsIAccessibleRole.ROLE_EDITCOMBOBOX,
+ Ci.nsIAccessibleRole.ROLE_ENTRY,
+ Ci.nsIAccessibleRole.ROLE_LINK,
+ Ci.nsIAccessibleRole.ROLE_LISTBOX,
+ Ci.nsIAccessibleRole.ROLE_PASSWORD_TEXT,
+ Ci.nsIAccessibleRole.ROLE_PUSHBUTTON,
+ Ci.nsIAccessibleRole.ROLE_RADIOBUTTON,
+ Ci.nsIAccessibleRole.ROLE_SLIDER,
+ Ci.nsIAccessibleRole.ROLE_SPINBUTTON,
+ Ci.nsIAccessibleRole.ROLE_SUMMARY,
+ Ci.nsIAccessibleRole.ROLE_SWITCH,
+ Ci.nsIAccessibleRole.ROLE_TOGGLE_BUTTON,
+ ]);
+
+ // Roles that are user interactive.
+ const INTERACTIVE_ROLES = new Set([
+ ...KEYBOARD_FOCUSABLE_ROLES,
+ Ci.nsIAccessibleRole.ROLE_CHECK_MENU_ITEM,
+ Ci.nsIAccessibleRole.ROLE_CHECK_RICH_OPTION,
+ Ci.nsIAccessibleRole.ROLE_COMBOBOX_OPTION,
+ Ci.nsIAccessibleRole.ROLE_MENUITEM,
+ Ci.nsIAccessibleRole.ROLE_OPTION,
+ Ci.nsIAccessibleRole.ROLE_OUTLINE,
+ Ci.nsIAccessibleRole.ROLE_OUTLINEITEM,
+ Ci.nsIAccessibleRole.ROLE_PAGETAB,
+ Ci.nsIAccessibleRole.ROLE_PARENT_MENUITEM,
+ Ci.nsIAccessibleRole.ROLE_RADIO_MENU_ITEM,
+ Ci.nsIAccessibleRole.ROLE_RICH_OPTION,
+ ]);
+
+ // Roles that are considered interactive when they are focusable.
+ const INTERACTIVE_IF_FOCUSABLE_ROLES = new Set([
+ // If article is focusable, we can assume it is inside a feed.
+ Ci.nsIAccessibleRole.ROLE_ARTICLE,
+ // Column header can be focusable.
+ Ci.nsIAccessibleRole.ROLE_COLUMNHEADER,
+ Ci.nsIAccessibleRole.ROLE_GRID_CELL,
+ Ci.nsIAccessibleRole.ROLE_MENUBAR,
+ Ci.nsIAccessibleRole.ROLE_MENUPOPUP,
+ Ci.nsIAccessibleRole.ROLE_PAGETABLIST,
+ // Row header can be focusable.
+ Ci.nsIAccessibleRole.ROLE_ROWHEADER,
+ Ci.nsIAccessibleRole.ROLE_SCROLLBAR,
+ Ci.nsIAccessibleRole.ROLE_SEPARATOR,
+ Ci.nsIAccessibleRole.ROLE_TOOLBAR,
+ ]);
+
+ // Roles that are considered form controls.
+ const FORM_ROLES = new Set([
+ Ci.nsIAccessibleRole.ROLE_CHECKBUTTON,
+ Ci.nsIAccessibleRole.ROLE_CHECK_RICH_OPTION,
+ Ci.nsIAccessibleRole.ROLE_COMBOBOX,
+ Ci.nsIAccessibleRole.ROLE_EDITCOMBOBOX,
+ Ci.nsIAccessibleRole.ROLE_ENTRY,
+ Ci.nsIAccessibleRole.ROLE_LISTBOX,
+ Ci.nsIAccessibleRole.ROLE_PASSWORD_TEXT,
+ Ci.nsIAccessibleRole.ROLE_PROGRESSBAR,
+ Ci.nsIAccessibleRole.ROLE_RADIOBUTTON,
+ Ci.nsIAccessibleRole.ROLE_SLIDER,
+ Ci.nsIAccessibleRole.ROLE_SPINBUTTON,
+ Ci.nsIAccessibleRole.ROLE_SWITCH,
+ ]);
+
+ const DEFAULT_ENV = Object.freeze({
+ // Checks that accessible object has at least one accessible action.
+ actionCountRule: true,
+ // Checks that accessible object (and its corresponding node) is focusable
+ // (has focusable state and its node's tabindex is not set to -1).
+ focusableRule: true,
+ // Checks that clickable accessible object (and its corresponding node) has
+ // appropriate interactive semantics.
+ ifClickableThenInteractiveRule: true,
+ // Checks that accessible object has a role that is considered to be
+ // interactive.
+ interactiveRule: true,
+ // Checks that accessible object has a non-empty label.
+ labelRule: true,
+ // Checks that a node has a corresponging accessible object.
+ mustHaveAccessibleRule: true,
+ // Checks that accessible object (and its corresponding node) have a non-
+ // negative tabindex. Platform accessibility API still sets focusable state
+ // on tabindex=-1 nodes.
+ nonNegativeTabIndexRule: true,
+ });
+
+ let gA11YChecks = false;
+
+ let gEnv = {
+ ...DEFAULT_ENV,
+ };
+
+ /**
+ * Get role attribute for an accessible object if specified for its
+ * corresponding {@code DOMNode}.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible for which to determine its role attribute value.
+ *
+ * @returns {String}
+ * Role attribute value if specified.
+ */
+ function getAriaRoles(accessible) {
+ try {
+ return accessible.attributes.getStringProperty("xml-roles");
+ } catch (e) {
+ // No xml-roles. nsPersistentProperties throws if the attribute for a key
+ // is not found.
+ }
+
+ return "";
+ }
+
+ /**
+ * Get related accessible objects that are targets of labelled by relation e.g.
+ * labels.
+ * @param {nsIAccessible} accessible
+ * Accessible objects to get labels for.
+ *
+ * @returns {Array}
+ * A list of accessible objects that are labels for a given accessible.
+ */
+ function getLabels(accessible) {
+ const relation = accessible.getRelationByType(
+ Ci.nsIAccessibleRelation.RELATION_LABELLED_BY
+ );
+ return [...relation.getTargets().enumerate(Ci.nsIAccessible)];
+ }
+
+ /**
+ * Test if an accessible has a {@code hidden} attribute.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object.
+ *
+ * @return {boolean}
+ * True if the accessible object has a {@code hidden} attribute, false
+ * otherwise.
+ */
+ function hasHiddenAttribute(accessible) {
+ let hidden = false;
+ try {
+ hidden = accessible.attributes.getStringProperty("hidden");
+ } catch (e) {}
+ // If the property is missing, error will be thrown
+ return hidden && hidden === "true";
+ }
+
+ /**
+ * Test if an accessible is hidden from the user.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object.
+ *
+ * @return {boolean}
+ * True if accessible is hidden from user, false otherwise.
+ */
+ function isHidden(accessible) {
+ if (!accessible) {
+ return true;
+ }
+
+ while (accessible) {
+ if (hasHiddenAttribute(accessible)) {
+ return true;
+ }
+
+ accessible = accessible.parent;
+ }
+
+ return false;
+ }
+
+ /**
+ * Check if an accessible has a given state.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object to test.
+ * @param {number} stateToMatch
+ * State to match.
+ *
+ * @return {boolean}
+ * True if |accessible| has |stateToMatch|, false otherwise.
+ */
+ function matchState(accessible, stateToMatch) {
+ const state = {};
+ accessible.getState(state, {});
+
+ return !!(state.value & stateToMatch);
+ }
+
+ /**
+ * Determine if accessible is focusable with the keyboard.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible for which to determine if it is keyboard focusable.
+ *
+ * @returns {Boolean}
+ * True if focusable with the keyboard.
+ */
+ function isKeyboardFocusable(accessible) {
+ // State will be focusable even if the tabindex is negative.
+ return (
+ matchState(accessible, STATE_FOCUSABLE) &&
+ // Platform accessibility will still report STATE_FOCUSABLE even with the
+ // tabindex="-1" so we need to check that it is >= 0 to be considered
+ // keyboard focusable.
+ (!gEnv.nonNegativeTabIndexRule || accessible.DOMNode.tabIndex > -1)
+ );
+ }
+
+ function buildMessage(message, DOMNode) {
+ if (DOMNode) {
+ const { id, tagName, className } = DOMNode;
+ message += `: id: ${id}, tagName: ${tagName}, className: ${className}`;
+ }
+
+ return message;
+ }
+
+ /**
+ * Fail a test with a given message because of an issue with a given
+ * accessible object. This is used for cases where there's an actual
+ * accessibility failure that prevents UI from being accessible to keyboard/AT
+ * users.
+ *
+ * @param {String} message
+ * @param {nsIAccessible} accessible
+ * Accessible to log along with the failure message.
+ */
+ function a11yFail(message, { DOMNode }) {
+ SpecialPowers.SimpleTest.ok(false, buildMessage(message, DOMNode));
+ }
+
+ /**
+ * Log a todo statement with a given message because of an issue with a given
+ * accessible object. This is used for cases where accessibility best
+ * practices are not followed or for something that is not as severe to be
+ * considered a failure.
+ * @param {String} message
+ * @param {nsIAccessible} accessible
+ * Accessible to log along with the todo message.
+ */
+ function a11yWarn(message, { DOMNode }) {
+ SpecialPowers.SimpleTest.todo(false, buildMessage(message, DOMNode));
+ }
+
+ /**
+ * Test if the node's unavailable via the accessibility API.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object.
+ */
+ function assertEnabled(accessible) {
+ if (matchState(accessible, STATE_UNAVAILABLE)) {
+ a11yFail(
+ "Node is enabled but disabled via the accessibility API",
+ accessible
+ );
+ }
+ }
+
+ /**
+ * Test if it is possible to focus on a node with the keyboard. This method
+ * also checks for additional keyboard focus issues that might arise.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object for a node.
+ */
+ function assertFocusable(accessible) {
+ if (gEnv.focusableRule && !isKeyboardFocusable(accessible)) {
+ const ariaRoles = getAriaRoles(accessible);
+ // Do not force ARIA combobox or listbox to be focusable.
+ if (!ariaRoles.includes("combobox") && !ariaRoles.includes("listbox")) {
+ a11yFail("Node is not focusable via the accessibility API", accessible);
+ }
+
+ return;
+ }
+
+ if (!INTERACTIVE_IF_FOCUSABLE_ROLES.has(accessible.role)) {
+ // ROLE_TABLE is used for grids too which are considered interactive.
+ if (
+ accessible.role === Ci.nsIAccessibleRole.ROLE_TABLE &&
+ !getAriaRoles(accessible).includes("grid")
+ ) {
+ a11yWarn(
+ "Focusable nodes should have interactive semantics",
+ accessible
+ );
+
+ return;
+ }
+ }
+
+ if (accessible.DOMNode.tabIndex > 0) {
+ a11yWarn("Avoid using tabindex attribute greater than zero", accessible);
+ }
+ }
+
+ /**
+ * Test if it is possible to interact with a node via the accessibility API.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object for a node.
+ */
+ function assertInteractive(accessible) {
+ if (gEnv.actionCountRule && accessible.actionCount === 0) {
+ a11yFail("Node does not support any accessible actions", accessible);
+
+ return;
+ }
+
+ if (gEnv.interactiveRule && !INTERACTIVE_ROLES.has(accessible.role)) {
+ if (
+ // Labels that have a label for relation with their target are clickable.
+ (accessible.role !== Ci.nsIAccessibleRole.ROLE_LABEL ||
+ accessible.getRelationByType(
+ Ci.nsIAccessibleRelation.RELATION_LABEL_FOR
+ ).targetsCount === 0) &&
+ // Images that are inside an anchor (have linked state).
+ (accessible.role !== Ci.nsIAccessibleRole.ROLE_GRAPHIC ||
+ !matchState(accessible, STATE_LINKED))
+ ) {
+ // Look for click action in the list of actions.
+ for (let i = 0; i < accessible.actionCount; i++) {
+ if (
+ gEnv.ifClickableThenInteractiveRule &&
+ accessible.getActionName(i) === CLICK_ACTION
+ ) {
+ a11yFail(
+ "Clickable nodes must have interactive semantics",
+ accessible
+ );
+ }
+ }
+ }
+
+ a11yFail(
+ "Node does not have a correct interactive role and may not be " +
+ "manipulated via the accessibility API",
+ accessible
+ );
+ }
+ }
+
+ /**
+ * Test if the node is labelled appropriately for accessibility API.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object for a node.
+ */
+ function assertLabelled(accessible) {
+ const name = accessible.name && accessible.name.trim();
+ if (gEnv.labelRule && !name) {
+ a11yFail("Interactive elements must be labeled", accessible);
+
+ return;
+ }
+
+ const { DOMNode } = accessible;
+ if (FORM_ROLES.has(accessible.role)) {
+ const labels = getLabels(accessible);
+ const hasNameFromVisibleLabel = labels.some(
+ label => !matchState(label, STATE_INVISIBLE)
+ );
+
+ if (!hasNameFromVisibleLabel) {
+ a11yWarn("Form elements should have a visible text label", accessible);
+ }
+ } else if (
+ accessible.role === Ci.nsIAccessibleRole.ROLE_LINK &&
+ DOMNode.nodeName === "AREA" &&
+ DOMNode.hasAttribute("href")
+ ) {
+ const alt = DOMNode.getAttribute("alt");
+ if (alt && alt.trim() !== name) {
+ a11yFail(
+ "Use alt attribute to label area elements that have the href attribute",
+ accessible
+ );
+ }
+ }
+ }
+
+ /**
+ * Test if the node's visible via accessibility API.
+ *
+ * @param {nsIAccessible} accessible
+ * Accessible object for a node.
+ */
+ function assertVisible(accessible) {
+ if (isHidden(accessible)) {
+ a11yFail(
+ "Node is not currently visible via the accessibility API and may not " +
+ "be manipulated by it",
+ accessible
+ );
+ }
+ }
+
+ /**
+ * Walk node ancestry and force refresh driver tick in every document.
+ * @param {DOMNode} node
+ * Node for traversing the ancestry.
+ */
+ function forceRefreshDriverTick(node) {
+ const wins = [];
+ let bc = BrowsingContext.getFromWindow(node.ownerDocument.defaultView); // eslint-disable-line
+ while (bc) {
+ wins.push(bc.associatedWindow);
+ bc = bc.embedderWindowGlobal?.browsingContext;
+ }
+
+ let win = wins.pop();
+ while (win) {
+ // Stop the refresh driver from doing its regular ticks and force two
+ // refresh driver ticks: first to let layout update and notify a11y, and
+ // the second to let a11y process updates.
+ win.windowUtils.advanceTimeAndRefresh(100);
+ win.windowUtils.advanceTimeAndRefresh(100);
+ // Go back to normal refresh driver ticks.
+ win.windowUtils.restoreNormalRefresh();
+ win = wins.pop();
+ }
+ }
+
+ /**
+ * Get an accessible object for a node.
+ * Note: this method will not resolve if accessible object does not become
+ * available for a given node.
+ *
+ * @param {DOMNode} node
+ * Node to get the accessible object for.
+ *
+ * @return {nsIAccessible}
+ * Accessibility object for a given node.
+ */
+ function getAccessible(node) {
+ const accessibilityService = Cc[
+ "@mozilla.org/accessibilityService;1"
+ ].getService(Ci.nsIAccessibilityService);
+ if (!accessibilityService) {
+ // This is likely a build with --disable-accessibility
+ return null;
+ }
+
+ let acc = accessibilityService.getAccessibleFor(node);
+ if (acc) {
+ return acc;
+ }
+
+ // Force refresh tick throughout document hierarchy
+ forceRefreshDriverTick(node);
+ return accessibilityService.getAccessibleFor(node);
+ }
+
+ function runIfA11YChecks(task) {
+ return (...args) => (gA11YChecks ? task(...args) : null);
+ }
+
+ /**
+ * AccessibilityUtils provides utility methods for retrieving accessible objects
+ * and performing accessibility related checks.
+ * Current methods:
+ * assertCanBeClicked
+ * setEnv
+ * resetEnv
+ *
+ */
+ const AccessibilityUtils = {
+ assertCanBeClicked(node) {
+ const acc = getAccessible(node);
+ if (!acc) {
+ if (gEnv.mustHaveAccessibleRule) {
+ a11yFail("Node is not accessible via accessibility API", {
+ DOMNode: node,
+ });
+ }
+
+ return;
+ }
+
+ assertInteractive(acc);
+ assertFocusable(acc);
+ assertVisible(acc);
+ assertEnabled(acc);
+ assertLabelled(acc);
+ },
+
+ setEnv(env = DEFAULT_ENV) {
+ gEnv = {
+ ...DEFAULT_ENV,
+ ...env,
+ };
+ },
+
+ resetEnv() {
+ gEnv = { ...DEFAULT_ENV };
+ },
+
+ reset(a11yChecks = false) {
+ gA11YChecks = a11yChecks;
+
+ const { Services } = SpecialPowers;
+ // Disable accessibility service if it is running and if a11y checks are
+ // disabled.
+ if (!gA11YChecks && Services.appinfo.accessibilityEnabled) {
+ Services.prefs.setIntPref(FORCE_DISABLE_ACCESSIBILITY_PREF, 1);
+ Services.prefs.clearUserPref(FORCE_DISABLE_ACCESSIBILITY_PREF);
+ }
+
+ // Reset accessibility environment flags that might've been set within the
+ // test.
+ this.resetEnv();
+ },
+ };
+
+ AccessibilityUtils.assertCanBeClicked = runIfA11YChecks(
+ AccessibilityUtils.assertCanBeClicked.bind(AccessibilityUtils)
+ );
+
+ AccessibilityUtils.setEnv = runIfA11YChecks(
+ AccessibilityUtils.setEnv.bind(AccessibilityUtils)
+ );
+
+ AccessibilityUtils.resetEnv = runIfA11YChecks(
+ AccessibilityUtils.resetEnv.bind(AccessibilityUtils)
+ );
+
+ return AccessibilityUtils;
+})();