Accessibility of HTML5 and Rich Internet Applications (Part 2)

Accessibility of HTML5 and Rich Internet Applications (Part 2)

Hans Hillen (TPG)Steve Faulkner (TPG)

02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 1

In This Part:

Keyboard and Focus Management Labeling and Describing Live Regions Form Validation Mode Conflicts Fallback Solutions


Keyboard and Focus Management


Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 4

The Problem with Custom ControlsProblem: Images, divs, spans etc. are not standard controls with

defined behaviorso Not focusable with keyboardo Have a default tab ordero Behavior is unknown

Solution: Ideally: Use native focusable HTML controls

o <a>, <input type=“image” />, <button>, etc. Or manually define keyboard focus and behavior needs

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Keyboard Issues in a Nutshell Reachability: Moving keyboard focus to a

widget o Through tab order

• Native focusable controls or tabindex=“0”o Through globally defined shortcuto By activating another widget

Operability: Interacting with a widgeto All functionally should be performable through

keyboard and mouse input02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 5

Focus & Keyboard Accessibility To be accessible, ARIA input widgets need focus

o Use natively focusable elements, such as <a>, <input />, etc

o Add ‘tabindex’ attribute for non focusable elements, such as <span>, <div>, etc.• Tabindex=“0”: Element becomes part of the tab order• Tabindex=“-1” (Element is not in tab order, but focusable)

o For composite widgets (menus, trees, grids, etc.):• Every widget should only have 1 stop in the tab order.• Keep track where your widget’s current tab stop is:

o Alternative for tabindex: ‘aria-activedescendant=“<idref>”• Focus remains on outer container• AT perceives element with the specified ID as being

focused.• You must manually highlight this active element, e.g. With

CSS



Keyboard Handling Every widget needs to be operable by keyboard.

common keystrokes are:o Arrow keyso Home, end, page up, page downo Enter, spaceo ESC

Mimic the navigate in the desktop environmento DHML Style Guide: http://dev.aol.com/dhtml_style_guide o ARIA Best Practices:

http://www.w3.org/TR/wai-aria-practices/

02 / 27 / 12

http://dev.aol.com/dhtml_style_guide

http://dev.aol.com/dhtml_style_guide

http://www.w3.org/TR/wai-aria-practices/

Skipping Mechanisms The ability to skip content is crucial for both screen

reader and keyboard users Skip links are out of date, out of fashion and often

misusedo But keyboard users still need to be able to skip

Other alternatives for skipping:o Collapsible sectionso Consistent shortcuts (e.g. a shortcut that moves focus

between panes and dialogs)o Custom focus manager that allows the user to move focus

into a container to skip its contents 02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 8

Popup Dialogs and Windows More and more web apps use HTML based popup dialogs rather than actual

browser windows/dialogso Get a screen reader to perceive it properly using role="dialog"

Dialogs should have their own tab ordero Focus should "wrap"

For modal dialogs, it should not be possible to interact with the main page o Prevent keyboard accesso Virtual mode access can't be prevented

For non modal dialogs, provide shortcut to switch between dialog and main page

If dialog supports moving or resizing, these features must be keyboard accessible

Support closing dialogs using Enter (OK) or Escape (Cancel) keyso Focus should be placed back on a logical element, e.g. the button that triggered the

dialog.


Selection & Editing

Trees, Lists, Grids can support single or multiple selectionoMultiple selection must be keyboard accessible,

for example: • Shift + arrow keys: contiguous selection• Ctrl + arrow keys: move focus without selection• Ctrl + space: Toggle focused item in selection

(discontiguous selection) Editable grids need to support switching to

edit mode by keyboard02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 10

Labeling and Describing


Labeling in a Nutshell All of these must have an accessible name:

o Every interactive widgeto Composite widgets (menu(bar), toolbar, tablist, tree, grid)o Groups, regions and landmarks

Browsers determines an element’s accessible name by checking the following :1. aria-labelledby2. aria-label3. Associated label (<label for=“myControl”>) or alt attribute4. Text contents5. Title attribute

Optionally, add an accessible description for additional info02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 12


Label, Labelledby & Describedby Aria-labelledby=“elemID”

o Points to element ID that identifies the widget.o Can also use regular label element / title attribute

Aria-describedby=“elemID”o Optional, provides additional info besides identity o Useful for additional info, instructions, hints

Aria-label=“text”o Only use when no on-screen text

Title attribute will also work

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<h2 id=“treeLbl”>My Folders</h2><p id=“treeDesc” class=“hidden”>Each tree item has a context menu with more options</p><div role=“tree” aria-labelledby=“treeLbl” aria-describedby=“treeDesc”>

Labeling And Describing Widgets (2) Aria-labelledby=“IDREFS”

o Value is one or more IDs of elements that identifiy the widget.o The elements ‘aria-labelledby’ targets can be any kind of text based element,

anywhere in the document.o Add multiple Ids to concatinate label text:

• Multiple elements can label one widget, and one element can label multiple widgets. (example)

Aria-describedby=“IDREFS”o Similar to labelledby, except used for additional description, e.g. Form hints,

instructions, etc. Aria-label

o Simply takes a string to be used as label.o Quick and dirty way of making the screen reader say what you want.o Very easy to use, but only supported in Firefox at the moment.

<h2 id=“treeLbl”>My Folders</h2><p class=“hidden”>Each tree item has a context menu with more options</p><div role=“tree” aria-labelledby=“treeLbl” aria-describedby=“treeDesc”>...02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 14

Labeling containers Containers such as toolbars, dialogs, and regions

provide context for their contents When the user moves focus into the container,

the screen reader should first announce the container before announcing the focused control

<div role="dialog" aria-labelledby="dialogTitle" aria-describedby="dialogDescription">

<h2 id="dialogTitle">Confirm</h2><p id="dialogDescription">

Are you sure you want to do that?</p><button>Yes</button> <button>No</button>

</div>


Labeling Tables

<caption> still alive and kickingo In HTML5 it’s allowed to nest headings

Summary attribute obsolete in HTML5


Live Regions



ARIA Live Regions Problem: content is updated dynamically on screen may not be apparent to screen

reader userso No page refresh, no screen reader announcemento Change is only announced by stealing focuso Users miss relevant informationo Users have to ‘search’ for updated page content

Solution: live regions indicate page updates without losing focuso Screen readers announce change based on type of live region

Challenge: When should users be informed of the change? o Ignore trivial changes: changing seconds in a clocko Announce important changes immediately / as convenient

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“Built In” Live Regions Role=“alert” for one-time, high-priority notifications

o Shown for a period of time, or until the cause of the alert is solvedo Basic message, no complex contento The element with the alert role does not need to be focused to be

announced Role=“alertdialog” is similar to alert, but for actual

(DHTML) dialogs.o May contain other widgets, such as buttons or other form fieldso Does require a sub-element (such as a ‘confirm’ button) to receive

focus Live regions ‘built into ‘ roles’

• role="timer", "log", "marquee" or "status“ get default live behavior• Role=“alert” implicitly sets live to assertive

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How to Use Live Regions1. Identify which part (containing HTML element) is expected to be

updated2. To make it live, add ‘aria-live’ attribute with a politeness value:

o Off (default): Do not speak this region o Polite: Speak this region when the user is idleo Assertive: Speak this region as soon as possible

3. Choose whether entire region should be announced or just the part that changed:o ‘aria-atomic': true (all) or false (part)

4. Add other attributes as necessary:o aria-relevant: choose what to announce:

• Combination of ‘Additions’, ‘removals’, ‘text’, ‘all’o aria-busy: indicate content is still updatingo aria-labelledby, aria-describedby: label and describe regions

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Forms & Validation


Forms & ARIA You can used ARIA to make your form validation easier to manage.

o aria-required & aria-invalid stateso Role="alert" to flag validation errors immediately

Use validation summaries invalid entries easier to findo Use role=“group” or Role="alertdialog" to mark up the summaryo Link to corresponding invalid controls from summary itemso Use different scope levels if necessary

Visual tooltips: Useful for validation messages and formatting instructionso Tooltips must be keyboard accessible o Tooltip text must be associated with the form control using aria-

describedby Live Regions: Use for concise feedback messages02 / 27 / 12 Accessibility of HTML5 and Rich Internet Applications - CSUN 2012 22

Mode Conflicts



Role = Application Screen readers normally browse in ‘virtual mode’

o Navigates a virtual copy of the web pageo Intercepts all keystrokes for its own navigation (e.g. ‘H’ for heading

navigation) For dynamic Web apps, virtual mode may need to be

turned offo Interactive widgets need to define the keystrokes themselveso Content needs to be live, not a virtual copyo Automatically switches between virtual and non-virtual mode

role=“application”o Screen reader switches to non-virtual for these elementso Must provide all keyboard navigation when in role=“application” modeo Screen readers don’t intercept keystrokes then, so typical functions will

not work

02 / 27 / 12


Role = Document For apps with ‘reading’ or ‘editing’ sections

o A reading pane in an email cliento Screen reader switches back to virtual mode,

standard ‘web page reading’ shortcuts work againo Read / edit documents in a web application

Banner, complementary, contentinfo, main, navigation, search & form

When applied to a container inside an application role, the screen reader switches to virtual mode.

02 / 27 / 12

Fall Back Solutions



Role = Presentation Role=“presentation” overrides existing role

o Useful to ‘hide’ default HTML roles from AT For example:

o Hide layout tables by adding the role to the <table> elemento Textual content read by the screen reader but table is ignored

02 / 27 / 12

Fall back solution for dialogs In IE, JAWS currently does not properly announce dialogs when

moving focus into them It's possible to provide a fallback solution for IE to fix this,

using hidden fieldsets to apply the ARIA dialog markup to o Hide fieldset's padding, margin, and bordero Move legend off-screen

<fieldset role="dialog" aria-labelledby="dialogTitle" aria-describedby="dialogDescription">

<legend id="dialogTitle">Confirm</legend><p id="dialogDescription">

Are you sure you want to do that?</p><button>Yes</button> <button>No</button>

</fieldset>


Fallback solutions for link buttons Developers often use links as (icon) buttons

o Side effect: screen reader will announce them as a link, not a button

This can be made accessible by setting role="button"o Screen reader announces link as button now, but also provides

hint for using a button ("press" space to activate)• You lie! Links work through the Enter key, Space will scroll down the page

o To make sure JAWS is not lying, you'll have to manually add a key event handler for the Space key.

<a role="button" onkeypress="handleKeyPress(event);">refresh</a>


Hiding Content

Three types of hiding:1. Hiding content visually and from AT:2. Hiding content visually, but not from AT3. Hiding content from AT, but not visually


1. Hiding Content from All Display: none;

o Hides content both visually and from AT products

oOnly works when CSS is supported (by user agent, user, or AT product)

oOnly use to hide content that still ‘makes sense’• E.g. contents of a collapsible section

o Do not use for content that provides incorrect information• E.g. preloaded error messages that are not applicable

at the moment, or stale content • Instead, this content should be removed from the DOM

completely


2. Hiding Content Visually Hiding content off-screen will still make it available for screen

readers, without it being visible Useful to provide extra information to screen reader users or

users that do not support CSSo E.g. add hidden headings, screen reader instructions, role & state info

for older technology/* Old */.offscreen { position: absolute; left: -999em;}

/* New */.ui-helper-hidden-accessible {

position: absolute !important; clip: rect(1px 1px 1px 1px); clip: rect(1px,1px,1px,1px);

}


3. Hiding Content From AT Only Sometimes developers want to hide content from screen

readers, e.g.:o Duplicate controlso Redundant information that was already provided through

semantic markup. Difficult to achieve:

o Role=“presentation” will remove native role, but content is still visible for AT products

o Aria-hidden=“true” would be ideal, but:• The spec did not intend for aria-hidden to be used this way• Browsers handle aria-hidden differently

• IE does nothing • FF exposes content but marks it as hidden• Chrome does not expose content (i.e. truly hides it)


Grids and Tables


Fixing Incorrect Grid Structure (1) Some developers will use multiple HTML <table>

elements to create one single grid. For example:o One <table> for the header row, one <table> for the body

rowso One <table> for every single row

Why? Because this is easier to manage, style, position, drag & drop, etc.

Screen reader does not perceive one single table, but it sees two ore more separate tableso Association between column headers and cells is brokeno Screen reader's table navigation is broken


Fixing Incorrect Grid Structure (2) If using a single table is not feasible, use

ARIA to fix the grid structure as perceived by the screen reader o Use role="presentation" to hide the original

table elements form the screen readerso Use a combination of "grid", "row", "gridcell",

"columnheader" roles to make the screen reader see one big grid.


Fixing Incorrect Grid Structure (3) Using ARIA to create a correct grid

structure <div role="grid">

<table role="presentation"><tr role="row">

<th role="columnheader">Dog Names</th><th role="columnheader">Cat Names</th><th role="columnheader">Cow names</th>

</tr></table><table role="presentation">

<tr role="row"><td role="gridcell">Fido</td><td role="gridcell">Whiskers</td><td role="gridcell">Clarabella</td>

</tr></table>

</div>


Anything Else?

Questions? Additional Topics? Course Material:

http://www.paciellogroup.com/training/CSUN2012




Documents

Accessibility of HTML5 and Rich Internet Applications (Part 2)