1 / 47

Accessible DOM scripting with ARIA

Accessible DOM scripting with ARIA. Léonie Watson. Overview. Anatomy of a rich internet application. Web accessibility stack. First principles. Best practices. Walkthrough examples. Anatomy of a rich internet application. Controls and widgets.

star
Télécharger la présentation

Accessible DOM scripting with ARIA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Accessible DOM scripting with ARIA Léonie Watson LJWatson.co.uk @LeonieWatson

  2. Overview • Anatomy of a rich internet application. • Web accessibility stack. • First principles. • Best practices. • Walkthrough examples. LJWatson.co.uk @LeonieWatson

  3. Anatomy of a rich internet application LJWatson.co.uk @LeonieWatson

  4. Controls and widgets • Controls are single elements, like checkboxes, buttons or input fields. • Widgets are composites of multiple elements, like sliders, accordions or modal dialogs. LJWatson.co.uk @LeonieWatson

  5. Applications • Rich internet applications are web applications with desktop characteristics. LJWatson.co.uk @LeonieWatson

  6. First principles LJWatson.co.uk @LeonieWatson

  7. Perceivable • Controls and widgets must provide information to assistive technologies. • Dynamic changes in content must be communicated to assistive technologies. LJWatson.co.uk @LeonieWatson

  8. Operable • Controls and widgets must be keyboard accessible. LJWatson.co.uk @LeonieWatson

  9. Understandable • Controls and widgets must be properly labelled and described. LJWatson.co.uk @LeonieWatson

  10. Robust • Controls and widgets must have reasonable backwards compatibility. • Controls and widgets should have good forwards compatibility. LJWatson.co.uk @LeonieWatson

  11. Web accessibility stack LJWatson.co.uk @LeonieWatson

  12. Layers in the web accessibility stack • Assistive technology. • Accessibility API. • Accessible Rich Internet Applications (ARIA). • Document Object Model (DOM). LJWatson.co.uk @LeonieWatson

  13. Understanding the web accessibility stack: DOM layer <img src="button.gif" alt="Accept" onclick="doSomething()" onkeypress="doSomething()"> LJWatson.co.uk @LeonieWatson

  14. Understanding the web accessibility stack: ARIA layer <img src="button.gif" alt="Accept" onclick="doSomething()" onkeypress="doSomething()" tabindex="0" role="button"> LJWatson.co.uk @LeonieWatson

  15. Best practices LJWatson.co.uk @LeonieWatson

  16. Use native HTML elements • Do this:<p><button>Button text</button></p> LJWatson.co.uk @LeonieWatson

  17. Don’t override native semantics • Don’t do this:<prole="button">Button text</p> • Do this:<span role="button">Button text</span> LJWatson.co.uk @LeonieWatson

  18. Managing keyboard focus LJWatson.co.uk @LeonieWatson

  19. Make controls and widgets focusable • Elements with tabindex="0" are part of the natural tab sequence. • Elements with tabindex="-1" are not, but are focusable with scripting. • Elements with tabindex=">0" are never a good idea. LJWatson.co.uk @LeonieWatson

  20. Make focus visible • Do this:a:focus, a:hover, a:active { text-decoration: underline;} • Don't do this:a {text-outline:none;} LJWatson.co.uk @LeonieWatson

  21. Providing keyboard accessibility LJWatson.co.uk @LeonieWatson

  22. Use appropriate event handlers • Do this:<span tabindex="0" role="button" onclick="doSomething()" onkeypress="doSomething()"> <img src="example.png" alt="Submit"></span> • Don't do this:<span tabindex="0" role="button" onclick="doSomething()"> <img src="example.png" alt="Submit"></span> LJWatson.co.uk @LeonieWatson

  23. Don’t cause keyboard traps • Don't do this:<input type="text" id="user" required onblur="if(this.value=='') {this.focus();}"> • Don’t do this either:onfocus = "this.blur()" LJWatson.co.uk @LeonieWatson

  24. Don’t change context on focus • Don't do this:<select onchange="document.location=‘http://google.com';"> …</select> LJWatson.co.uk @LeonieWatson

  25. Handling widget focus LJWatson.co.uk @LeonieWatson

  26. Give widgets a single tab stop • A widget represents a single tab stop, and other keys are used to interact with the widget itself. LJWatson.co.uk @LeonieWatson

  27. Using JavaScript to handle child focus • Set tabindex of current child to 0, and all other children to -1. • As the user moves to another child, update the tabindex for the previous and current children accordingly. • Use element.focus() to move focus to the child with tabindex set to 0. LJWatson.co.uk @LeonieWatson

  28. Using ARIA to handle child focus • Set the tabindex of the parent element to 0, and set its aria-activedescendant property to the id of the currently active child. • As the user moves to another child, update the aria-activedescendant property accordingly. LJWatson.co.uk @LeonieWatson

  29. Put the key handler on the parent element • Captures the keystrokes, determines which element takes focus next, and updates the aria-activedesendantproperty. LJWatson.co.uk @LeonieWatson

  30. Use the scrollIntoView() method • Or a purpose built function, to ensure the active descendant moves into view. LJWatson.co.uk @LeonieWatson

  31. Providing keyboard shortcuts LJWatson.co.uk @LeonieWatson

  32. Don’t enable keyboard shortcuts by default • Many assistive technologies are controlled with native shortcuts. • Custom shortcuts should be clearly documented. LJWatson.co.uk @LeonieWatson

  33. Cancel (or swallow) keyboard events • Prevent the key from executing an action outside of the widget or web application, unless focus is on a form field. LJWatson.co.uk @LeonieWatson

  34. Dynamically updating content LJWatson.co.uk @LeonieWatson

  35. Using CSS to show/hide content • Use CSS when the content makes sense as part of the page, not when it’s dependent on a certain action. LJWatson.co.uk @LeonieWatson

  36. Injecting content into the DOM • Do this:<div id="errors"></div><script>var errors = document.getElementById("errors");var error = document.createElement("p");error.appendChild(document.createTextNode("You must provide a username."));errors.appendChild(error);</script> LJWatson.co.uk @LeonieWatson

  37. Using innerHTML • Do this:<div id="errors"></div><script>var html = "";html = html + "<li>You must enter a username</li>";html = html + "<li>Please use at least one number in your password</li>";document.getElementById("errors").innerHTML = "<ul>" + html + "</ul>";</script> LJWatson.co.uk @LeonieWatson

  38. Walkthrough examples LJWatson.co.uk @LeonieWatson

  39. Expandable content (HTML/ARIA) <div id="collapsible"> <button id="tea" aria-controls="tea-content">Types of tea</button> <div style="display:none;" id="tea-content" aria-expanded="false"> <h2>Types of tea</h2> <ul> <li>Black tea</li> <li>Green tea</li> </ul> </div> </div> LJWatson.co.uk @LeonieWatson

  40. Expandable content (JavaScript) <script> document.getElementById("tea").onclick = function() { var tea = document.getElementById("tea-content"); var expanded; tea.style.display = (tea.style.display == "block") ? "none" : "block“; expanded = tea.getAttribute("aria-expanded") == "false" ? "true" : "false“; tea.setAttribute("aria-expanded", expanded); }; </script> LJWatson.co.uk @LeonieWatson

  41. Live region updates (HTML/ARIA) <h1>Tequila</h1> <p>Tequila makes me happy...</p> <div> <button onclick="updateItems()">Add to basket</button> </div> <h2>Basket summary</h2> <div aria-live="assertive" aria-atomic="true"> <p>Your basket contains <span id="quantity">0</span> items.</p> </div> LJWatson.co.uk @LeonieWatson

  42. Live region updates (JavaScript) <script> var items = 0; function updateItems () { items = items + 1; document.getElementById("quantity").innerHTML=items; } </script> LJWatson.co.uk @LeonieWatson

  43. Modal dialogs (HTML/ARIA) <div> <button id="launchBtn">Open modal</button> </div> <div id="modal" style="display:none;" role="alertdialog" aria-labelledby="mdlTitle" aria-describedby="mdlMsg“> <h1 id="mdlTitle">Modal title</h1> <p id="mdlMsg">Modal message.</p> <div> <button id="ok">Ok</button><button id="cancel">Cancel</button> </div> </div> LJWatson.co.uk @LeonieWatson

  44. Modal dialogs (JavaScript 1) (function(){ function openModal() { modal.style.display= 'block‘; setTimeout(function () {objFirst.focus();}, 100); } function closeModal() { modal.style.display= 'none‘; trigger.focus(); } … })(); LJWatson.co.uk @LeonieWatson

  45. Modal dialogs (JavaScript 2) (function(){ … function handleKeyboard(event) { switch (event.keyCode) { case 9: if (event.target === objLast && !event.shiftKey) {objFirst.focus();event.preventDefault(); } else if (event.target === objFirst && event.shiftKey) {objLast.focus();event.preventDefault(); } return false; break; case 27:closeModal(); return false; break; default: return true; }} … } LJWatson.co.uk @LeonieWatson

  46. Resources • WAI-ARIA 1.0 Authoring Practices:http://www.w3.org/TR/wai-aria-practices/ • Using WAI-ARIA in HTML:http://www.w3.org/TR/2013/WD-aria-in-html-20130214/ • HTML to Platform Accessibility APIs Implementation Guide:http://www.w3.org/TR/html-aapi/ • The Paciello Group Blog:http://blog.paciellogroup.com/ • Open AJAX Alliance Examples:http://www.oaa-accessibility.org/examples/ LJWatson.co.uk @LeonieWatson

  47. Thank you! LJWatson.co.uk @LeonieWatson

More Related