diff options
Diffstat (limited to 'devtools/server/actors/accessibility/audit/text-label.js')
-rw-r--r-- | devtools/server/actors/accessibility/audit/text-label.js | 439 |
1 files changed, 439 insertions, 0 deletions
diff --git a/devtools/server/actors/accessibility/audit/text-label.js b/devtools/server/actors/accessibility/audit/text-label.js new file mode 100644 index 0000000000..f90146e684 --- /dev/null +++ b/devtools/server/actors/accessibility/audit/text-label.js @@ -0,0 +1,439 @@ +/* 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"; + +const { + accessibility: { + AUDIT_TYPE: { TEXT_LABEL }, + ISSUE_TYPE, + SCORES: { BEST_PRACTICES, FAIL, WARNING }, + }, +} = require("resource://devtools/shared/constants.js"); + +const { + AREA_NO_NAME_FROM_ALT, + DIALOG_NO_NAME, + DOCUMENT_NO_TITLE, + EMBED_NO_NAME, + FIGURE_NO_NAME, + FORM_FIELDSET_NO_NAME, + FORM_FIELDSET_NO_NAME_FROM_LEGEND, + FORM_NO_NAME, + FORM_NO_VISIBLE_NAME, + FORM_OPTGROUP_NO_NAME_FROM_LABEL, + FRAME_NO_NAME, + HEADING_NO_CONTENT, + HEADING_NO_NAME, + IFRAME_NO_NAME_FROM_TITLE, + IMAGE_NO_NAME, + INTERACTIVE_NO_NAME, + MATHML_GLYPH_NO_NAME, + TOOLBAR_NO_NAME, +} = ISSUE_TYPE[TEXT_LABEL]; + +/** + * Check if the accessible is visible to the assistive technology. + * @param {nsIAccessible} accessible + * Accessible object to be tested for visibility. + * + * @returns {Boolean} + * True if accessible object is visible to assistive technology. + */ +function isVisible(accessible) { + const state = {}; + accessible.getState(state, {}); + return !(state.value & Ci.nsIAccessibleStates.STATE_INVISIBLE); +} + +/** + * 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)]; +} + +/** + * Get a trimmed name of the accessible object. + * + * @param {nsIAccessible} accessible + * Accessible objects to get a name for. + * + * @returns {null|String} + * Trimmed name of the accessible object if available. + */ +function getAccessibleName(accessible) { + return accessible.name && accessible.name.trim(); +} + +/** + * A text label rule for accessible objects that must have a non empty + * accessible name. + * + * @returns {null|Object} + * Failure audit report if accessible object has no or empty name, null + * otherwise. + */ +const mustHaveNonEmptyNameRule = function(issue, accessible) { + const name = getAccessibleName(accessible); + return name ? null : { score: FAIL, issue }; +}; + +/** + * A text label rule for accessible objects that should have a non empty + * accessible name as a best practice. + * + * @returns {null|Object} + * Best practices audit report if accessible object has no or empty + * name, null otherwise. + */ +const shouldHaveNonEmptyNameRule = function(issue, accessible) { + const name = getAccessibleName(accessible); + return name ? null : { score: BEST_PRACTICES, issue }; +}; + +/** + * A text label rule for accessible objects that can be activated via user + * action and must have a non-empty name. + * + * @returns {null|Object} + * Failure audit report if interactive accessible object has no or + * empty name, null otherwise. + */ +const interactiveRule = mustHaveNonEmptyNameRule.bind( + null, + INTERACTIVE_NO_NAME +); + +/** + * A text label rule for accessible objects that correspond to dialogs and thus + * should have a non-empty name. + * + * @returns {null|Object} + * Best practices audit report if dialog accessible object has no or + * empty name, null otherwise. + */ +const dialogRule = shouldHaveNonEmptyNameRule.bind(null, DIALOG_NO_NAME); + +/** + * A text label rule for accessible objects that provide visual information + * (images, canvas, etc.) and must have a defined name (that can be empty, e.g. + * ""). + * + * @returns {null|Object} + * Failure audit report if interactive accessible object has no name, + * null otherwise. + */ +const imageRule = function(accessible) { + const name = getAccessibleName(accessible); + return name != null ? null : { score: FAIL, issue: IMAGE_NO_NAME }; +}; + +/** + * A text label rule for accessible objects that correspond to form elements. + * These objects must have a non-empty name and must have a visible label. + * + * @returns {null|Object} + * Failure audit report if form element accessible object has no name, + * warning if the name does not come from a visible label, null + * otherwise. + */ +const formRule = function(accessible) { + const name = getAccessibleName(accessible); + if (!name) { + return { score: FAIL, issue: FORM_NO_NAME }; + } + + const labels = getLabels(accessible); + const hasNameFromVisibleLabel = labels.some(label => isVisible(label)); + + return hasNameFromVisibleLabel + ? null + : { score: WARNING, issue: FORM_NO_VISIBLE_NAME }; +}; + +/** + * A text label rule for elements that map to ROLE_GROUPING: + * * <OPTGROUP> must have a non-empty name and must be provided via the + * "label" attribute. + * * <FIELDSET> must have a non-empty name and must be provided via the + * corresponding <LEGEND> element. + * + * @returns {null|Object} + * Failure audit report if form grouping accessible object has no name, + * or has a name that is not derived from a required location, null + * otherwise. + */ +const formGroupingRule = function(accessible) { + const name = getAccessibleName(accessible); + const { DOMNode } = accessible; + + switch (DOMNode.nodeName) { + case "OPTGROUP": + return name && DOMNode.label && DOMNode.label.trim() === name + ? null + : { + score: FAIL, + issue: FORM_OPTGROUP_NO_NAME_FROM_LABEL, + }; + case "FIELDSET": + if (!name) { + return { score: FAIL, issue: FORM_FIELDSET_NO_NAME }; + } + + const labels = getLabels(accessible); + const hasNameFromLegend = labels.some( + label => + label.DOMNode.nodeName === "LEGEND" && + label.name && + label.name.trim() === name && + isVisible(label) + ); + + return hasNameFromLegend + ? null + : { + score: WARNING, + issue: FORM_FIELDSET_NO_NAME_FROM_LEGEND, + }; + default: + return null; + } +}; + +/** + * A text label rule for elements that map to ROLE_TEXT_CONTAINER: + * * <METER> mapps to ROLE_TEXT_CONTAINER and must have a name provided via + * the visible label. Note: Will only work when bug 559770 is resolved (right + * now, unlabelled meters are not mapped to an accessible object). + * + * @returns {null|Object} + * Failure audit report depending on requirements for dialogs or form + * meter element, null otherwise. + */ +const textContainerRule = function(accessible) { + const { DOMNode } = accessible; + + switch (DOMNode.nodeName) { + case "DIALOG": + return dialogRule(accessible); + case "METER": + return formRule(accessible); + default: + return null; + } +}; + +/** + * A text label rule for elements that map to ROLE_INTERNAL_FRAME: + * * <OBJECT> maps to ROLE_INTERNAL_FRAME. Check the type attribute and whether + * it includes "image/" (e.g. image/jpeg, image/png, image/gif). If so, audit + * it the same way other image roles are audited. + * * <EMBED> maps to ROLE_INTERNAL_FRAME and must have a non-empty name. + * * <FRAME> and <IFRAME> map to ROLE_INTERNAL_FRAME and must have a non-empty + * title attribute. + * + * @returns {null|Object} + * Failure audit report if the internal frame accessible object name is + * not provided or if it is not derived from a required location, null + * otherwise. + */ +const internalFrameRule = function(accessible) { + const { DOMNode } = accessible; + switch (DOMNode.nodeName) { + case "FRAME": + return mustHaveNonEmptyNameRule(FRAME_NO_NAME, accessible); + case "IFRAME": + const name = getAccessibleName(accessible); + const title = DOMNode.title && DOMNode.title.trim(); + + return title && title === name + ? null + : { score: FAIL, issue: IFRAME_NO_NAME_FROM_TITLE }; + case "OBJECT": { + const type = DOMNode.getAttribute("type"); + if (!type || !type.startsWith("image/")) { + return null; + } + + return imageRule(accessible); + } + case "EMBED": { + const type = DOMNode.getAttribute("type"); + if (!type || !type.startsWith("image/")) { + return mustHaveNonEmptyNameRule(EMBED_NO_NAME, accessible); + } + return imageRule(accessible); + } + default: + return null; + } +}; + +/** + * A text label rule for accessible objects that represent documents and should + * have title element provided. + * + * @returns {null|Object} + * Failure audit report if document accessible object has no or empty + * title, null otherwise. + */ +const documentRule = function(accessible) { + const title = accessible.DOMNode.title && accessible.DOMNode.title.trim(); + return title ? null : { score: FAIL, issue: DOCUMENT_NO_TITLE }; +}; + +/** + * A text label rule for accessible objects that correspond to headings and thus + * must be non-empty. + * + * @returns {null|Object} + * Failure audit report if heading accessible object has no or + * empty name or if its text content is empty, null otherwise. + */ +const headingRule = function(accessible) { + const name = getAccessibleName(accessible); + if (!name) { + return { score: FAIL, issue: HEADING_NO_NAME }; + } + + const content = + accessible.DOMNode.textContent && accessible.DOMNode.textContent.trim(); + return content ? null : { score: WARNING, issue: HEADING_NO_CONTENT }; +}; + +/** + * A text label rule for accessible objects that represent toolbars and must + * have a non-empty name if there is more than one toolbar present. + * + * @returns {null|Object} + * Failure audit report if toolbar accessible object is not the only + * toolbar in the document and has no or empty title, null otherwise. + */ +const toolbarRule = function(accessible) { + const toolbars = accessible.DOMNode.ownerDocument.querySelectorAll( + `[role="toolbar"]` + ); + + return toolbars.length > 1 + ? mustHaveNonEmptyNameRule(TOOLBAR_NO_NAME, accessible) + : null; +}; + +/** + * A text label rule for accessible objects that represent link (anchors, areas) + * and must have a non-empty name. + * + * @returns {null|Object} + * Failure audit report if link accessible object has no or empty name, + * or in case when it's an <area> element with href attribute the name + * is not specified by an alt attribute, null otherwise. + */ +const linkRule = function(accessible) { + const { DOMNode } = accessible; + if (DOMNode.nodeName === "AREA" && DOMNode.hasAttribute("href")) { + const alt = DOMNode.getAttribute("alt"); + const name = getAccessibleName(accessible); + return alt && alt.trim() === name + ? null + : { score: FAIL, issue: AREA_NO_NAME_FROM_ALT }; + } + + return interactiveRule(accessible); +}; + +/** + * A text label rule for accessible objects that are used to display + * non-standard symbols where existing Unicode characters are not available and + * must have a non-empty name. + * + * @returns {null|Object} + * Failure audit report if mglyph accessible object has no or empty + * name, and no or empty alt attribute, null otherwise. + */ +const mathmlGlyphRule = function(accessible) { + const name = getAccessibleName(accessible); + if (name) { + return null; + } + + const { DOMNode } = accessible; + const alt = DOMNode.getAttribute("alt"); + return alt && alt.trim() + ? null + : { score: FAIL, issue: MATHML_GLYPH_NO_NAME }; +}; + +const RULES = { + [Ci.nsIAccessibleRole.ROLE_BUTTONMENU]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_CANVAS]: imageRule, + [Ci.nsIAccessibleRole.ROLE_CHECKBUTTON]: formRule, + [Ci.nsIAccessibleRole.ROLE_CHECK_MENU_ITEM]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_CHECK_RICH_OPTION]: formRule, + [Ci.nsIAccessibleRole.ROLE_COLUMNHEADER]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_COMBOBOX]: formRule, + [Ci.nsIAccessibleRole.ROLE_COMBOBOX_OPTION]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_DIAGRAM]: imageRule, + [Ci.nsIAccessibleRole.ROLE_DIALOG]: dialogRule, + [Ci.nsIAccessibleRole.ROLE_DOCUMENT]: documentRule, + [Ci.nsIAccessibleRole.ROLE_EDITCOMBOBOX]: formRule, + [Ci.nsIAccessibleRole.ROLE_ENTRY]: formRule, + [Ci.nsIAccessibleRole.ROLE_FIGURE]: shouldHaveNonEmptyNameRule.bind( + null, + FIGURE_NO_NAME + ), + [Ci.nsIAccessibleRole.ROLE_GRAPHIC]: imageRule, + [Ci.nsIAccessibleRole.ROLE_GROUPING]: formGroupingRule, + [Ci.nsIAccessibleRole.ROLE_HEADING]: headingRule, + [Ci.nsIAccessibleRole.ROLE_IMAGE_MAP]: imageRule, + [Ci.nsIAccessibleRole.ROLE_INTERNAL_FRAME]: internalFrameRule, + [Ci.nsIAccessibleRole.ROLE_LINK]: linkRule, + [Ci.nsIAccessibleRole.ROLE_LISTBOX]: formRule, + [Ci.nsIAccessibleRole.ROLE_MATHML_GLYPH]: mathmlGlyphRule, + [Ci.nsIAccessibleRole.ROLE_MENUITEM]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_OPTION]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_OUTLINEITEM]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_PAGETAB]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_PASSWORD_TEXT]: formRule, + [Ci.nsIAccessibleRole.ROLE_PROGRESSBAR]: formRule, + [Ci.nsIAccessibleRole.ROLE_PUSHBUTTON]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_RADIOBUTTON]: formRule, + [Ci.nsIAccessibleRole.ROLE_RADIO_MENU_ITEM]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_ROWHEADER]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_SLIDER]: formRule, + [Ci.nsIAccessibleRole.ROLE_SPINBUTTON]: formRule, + [Ci.nsIAccessibleRole.ROLE_SWITCH]: formRule, + [Ci.nsIAccessibleRole.ROLE_TEXT_CONTAINER]: textContainerRule, + [Ci.nsIAccessibleRole.ROLE_TOGGLE_BUTTON]: interactiveRule, + [Ci.nsIAccessibleRole.ROLE_TOOLBAR]: toolbarRule, +}; + +/** + * Perform audit for WCAG 1.1 criteria related to providing alternative text + * depending on the type of content. + * @param {nsIAccessible} accessible + * Accessible object to be tested to determine if it requires and has + * an appropriate text alternative. + * + * @return {null|Object} + * Null if accessible does not need or has the right text alternative, + * audit data otherwise. This data is used in the accessibility panel + * for its audit filters, audit badges, sidebar checks section and + * highlighter. + */ +function auditTextLabel(accessible) { + const rule = RULES[accessible.role]; + return rule ? rule(accessible) : null; +} + +module.exports.auditTextLabel = auditTextLabel; |