Accessibility of HTML5 and Rich Internet Applications (Part - PowerPoint Presentation

Slide1

Accessibility of HTML5 and Rich Internet Applications (Part 2)

Hans Hillen

Steve FaulknerSlide2

In This Part:

Keyboard and Focus Management

Form Validation

Screen Reader Mode Conflicts Solutions, Workarounds and Considerations

2Slide3

Keyboard and Focus Management

3Slide4

The Problem with Custom Controls

Problem:

Images, divs, spans etc. are not standard controls with defined behaviors

Not focusable with keyboardHave a default tab orderBehavior is unknownSolution:Ideally: Use native focusable HTML controls <a>, <input type=“image” />, <button>, etc.

Or manually define keyboard focus and behavior

needsSlide5

Keyboard Issues In A Nutshell

Reachability: Moving keyboard focus to a widget

Through tab order

Native focusable controls or tabindex=“0”Through globally defined shortcutBy activating another widget Operability: Interacting with a widgetAll functionally should be performable through keyboard and mouse input

5Slide6

Focus & Keyboard Accessibility

To be accessible, ARIA input widgets need focus

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

Add 'tabindex' attribute for non focusable elements, such as <span>, <div>, etc.Tabindex="0": Element becomes part of the tab orderTabindex="-1" (Element is not in tab order, but focusable)For composite widgets (menus, trees, grids, etc.), use a "roving tabindex

"

:

Every widget should only have 1 stop in the tab order.

Dynamically keep track where your widget’s current tab stop (active part) is:

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

6Slide7

Keyboard Handling

Every widget needs to be operable by keyboard. common keystrokes are:

Arrow keys

Home, end, page up, page downEnter, spaceESCMimic the navigate in the desktop environment ARIA Best Practices: http://www.w3.org/WAI/PF/aria-practices/

Always manage and keep track of your focus. Never let it get lost.

7Slide8

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Skip links are out of date, out of fashion and often misused

But keyboard users still need to be able to skip Other alternatives for skipping:Collapsible sectionsConsistent shortcuts (e.g. a shortcut that moves focus between panes and dialogs)Custom focus manager that allows the user to move focus into a container to skip its contents

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Form Validation

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ARIA & Form Validation

You can use ARIA to make your form validation easier to manage.

aria-required & aria-invalid states

Role="alert" or live regions can be used to flag validation errors immediately, but are likely to be disruptiveProvide validation feedback both in inline scope and form scopeUse validation summaries invalid entries easier to find

Use

role="group"

or Role="alertdialog" to mark up the

summary

Provide quick access to invalid

fields:

Link to corresponding invalid controls from summary

items

Nice to have: provide global shortcuts

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Solutions, Workarounds and Considerations

11Slide12

Fallback solutions for link buttons

Developers often use links as (icon) buttons

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

This can be made accessible by setting role="button"Screen reader announces link as button now, but also provides hint for using a button ("press" space to activate”)Screen reader lies: Links work through the Enter key, Space will scroll down the page To make sure JAWS is not lying, you'll have to manually add a key event handler for the Space key.Slide13

Screen Reader Mode ConflictsSlide14

VIRTUAL VS NON VIRTUAL MODE

Virtual

Mode

(a.k.a. browse / virtual PC cursor mode

)

Non-Virtual Mode (

a.k.a.

forms / application mode)

Default navigation

m

ode for navigating and reading documents, such

as PDF documents or web pages.

Default

navigation mode for desktop applications, interactive web forms, and web applications (i.e. role=“application”).

User navigates through the document with

a “virtual cursor”, allow

ing static content (e.g. plain text, images, data tables) to be traversed as well.

Only keyboard accessible content

(e.g. focusable elements) or content associated with such elements (e.g. through

aria-labelledby

)

can be accessed.

Screen reader provides special shortcuts and features

to enhance virtual navigation, e.g. heading navigation or link lists. Arrow keys are used for basic sequential navigation.

No special shortcuts

or features are available, except what’s provided by the web page’s level of keyboard accessibility (tabbing, keyboard shortcuts, and scripted movement of keyboard focus).

Screen reader will intercept user’s key strokes and break custom

keyboard behavior, e.g. a custom widget requiring arrow key

input

won’t work in this mode.

Screen

reader lets all keystrokes pass through to the web content. Custom widgets will work as intended provided they are keyboard accessible.Slide15

Role="Application"

Screen readers normally browse in ‘virtual mode’

Navigates a virtual copy of the web page

Intercepts all keystrokes for its own navigation (e.g. ‘H’ for heading navigation)For dynamic Web apps, virtual mode may need to be turned offInteractive widgets need to define the keystrokes themselvesContent needs to be live, not a virtual copyAutomatically switches between virtual and non-virtual mode

role=“application”

Screen reader switches to non-virtual for these elements

Must provide all keyboard navigation when in role=“application” mode

Screen readers don’t intercept keystrokes then, so typical functions will not workSlide16

Role="Document"

For apps with ‘reading’ or ‘editing’ sections

A reading pane in an email client

Screen reader switches back to virtual mode, standard ‘web page reading’ shortcuts work againRead / edit documents in a web applicationBanner, complementary, contentinfo, main, navigation, search & formWhen applied to a container inside an application role, the screen reader switches to virtual mode.

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Explaining to Users how Rich Internet Applications (RIA) works

People that depend on assistive technology often:

Expect to be able to tab through all interactive elements

Expect virtual mode to work Expect web content to be like it was in the late 90's:Simple page loads, no dynamic changesSimple Keyboard navigation: Tab, Enter, some times arrow keysWAI – ARIA is meant for "Application UI's"

Requires virtual mode to be disabled

Requires custom shortcuts

Content can update

dynamically

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Explaining to Users how Rich Internet Applications (RIA) works (2)

How do you convey this different navigation style to screen reader users?

Modern screen readers have "auto-forms" mode (virtual mode is automatically turned off where applicable

Screen readers will provide basic instructions for interactionsLess experienced users will likely be confusedSighted keyboard users do not get any instructions at all

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19

A tab list widget:

Web 1.0: Tab through every tab in the list

Web 2.0: Tab list takes up one tab stop, arrow keys are used for switchingWhich one is correct?

What will the end user expect?

ExampleSlide20

The Perfect Dialog

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Dialog: Roles & States

Use role="dialog", combined with:

Aria-labelledby (for dialog title)

Aria-describedby (for dialog message text)Slide22

Dialog: Focus Management

When

dialog opens, focus should move to first focusable element inside the dialog

Focus should "wrap" inside dialog and be contained by it . For modal dialogs: No keyboard access with background content should be possible When the dialog closes, focus should be placed back on a logical element, e.g. the button that triggered the dialog.For modal dialogs: prevent virtual navigation to background using aria-hidden="true"

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Dialog: Shortcuts

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

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

Support closing dialogs using buttons and Escape key23Slide24

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"WAI-ARIA provides dialog and alertdialog roles that are to be treated as special case application roles. Like application,

screen readers will leave the main job of keyboard navigation up the dialog

."

WAI-ARIA 1.0 Authoring Practices

Dialog Quote 1:Slide25

25

"When using dialog,

all static text must be associated with widgets, groups or panes using the aria-labelledby and aria-describedby properties

, otherwise it will not be read by the screen reader when the user navigates to the related widget or group. "

WAI-ARIA 1.0 Authoring Practices

Dialog Quote 2:Slide26

Dialog Pitfalls

According to the ARIA Best Practices document:

A dialog is a special type of "application window"

All content must be (associated with) keyboard accessible content. Regular static is content not allowed.Virtual navigation by screen readers is not allowedThis works for simple dialogs…But not for complex dialog content often found in real life projects, which may have a large amount of static contentTo force support for virtual navigation, role=“document” can be wrapped around the dialog

content.

Focus management

For dialogs with a large amount of (scrollable) content, the first focusable element may be too far down. Moving focus to it would cause a lot of content to be

skipped

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Code Sample Original Dialog:

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<div tabindex="-1" role="dialog" aria-labelledby="ui-id-1">

<div>

<h1 id="ui-id-1" tabindex="-1">For Your Information</h1>

<button>Close</close>

</div>

…

</div>Slide28

Code Sample Modified Dialog:

28

<div tabindex="-1" role="dialog" arialabelledby="ui-id-1">

<div role="document" aria-label="Dialog contents">

<p class=“HiddenText">Start of dialog</p>

<div>

<h1 id="ui-id-1" tabindex="-1">For Your Information</h1>

<button>Close</button>

<span class="HiddenText">Close</span></a>

</div>

<div id="dialog" class="contentWrap">

…

</div>

<p class="HiddenText">End of dialog</p>

</div>

</div>Slide29

Hiding Content

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Hiding Content

Three types of hiding:

Hiding content visually and from AT:

Hiding content visually, but not from ATHiding content from AT, but not visually Slide31

1. Hiding Content from All

Display: none;

Hides content both visually and from AT products

Only works when CSS is supported (by user agent, user, or AT product)Only use to hide content that still ‘makes sense’E.g. contents of a collapsible section Do not use for content that provides incorrect informationE.g. preloaded error messages that are not applicable at the moment, or stale content Instead, this content should be removed from the DOM completely

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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 CSS

E.g. add hidden headings, screen reader instructions, role & state info for older technology32Slide33

Styles for Visually Hidden Content As Used in Bootstrap:

33

.sr-only {

position

: absolute;

width

: 1px;

height

: 1px;

margin

: -1px;

padding

: 0;

overflow

: hidden; clip: rect(0,0,0,0); border: 0

;

}Slide34

3. Hiding Content From

Screen Readers

Only

Sometimes developers want to hide content from screen readers, e.g.:Duplicate controlsRedundant information that was already provided through semantic mark up. Difficult to achieve:Role=“presentation” will remove native role, but content is still visible for AT products

Aria-hidden=“true” provides a solution:

Not supported well in older technology

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Aria-hidden

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Supported by the latest versions of major browsers and assistive technology.

Use with care: only for redundant/decorative contentNEVER use directly on focusable elements

<a href="#">

<span aria-hidden="true">A</span>

<span class="HiddenText">Small Font</span>

</a>Slide36

Scrollable Content

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Scrollable Content

Some widgets use scrolling or animation to "slide" content into view

Example: a carousel widget: A long list of items, of which only a few are visible at a time

Example: A table that only shows a few columns at a time, and can be scrolled horizontally through "next" and "previous" buttons.Content that slides into view is often not hidden properly, but "clipped" through overflow:hidden stylesContent is visually hidden, but still part of the tab order and (unintentionally) reachable to keyboard users

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Scrollable Content - Solution

When content is scrolled out of view, ensure that it's not reachable to keyboard users

To do this, the "visibility: hidden" style is often easiest to use:

When content is scrolled out of view, set visibility: hiddenBefore content is about to be scrolled into view, set visibility: visible Use "visibility: hidden" over "display: none" to maintain the content's layout, which is often needed for the scrolling / animation to function correctly

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Tables

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Labeling Tables

<caption> still alive and kicking

In HTML5 it’s allowed to nest headings

Summary attribute obsolete in HTML540Slide41

Heading In Caption Example

41

<table>

<caption>

<h2>Animals</h2>

</caption>

<tbody>

<tr>

<th scope="col" abbr="pet name">Name

<th scope="col">Age</th>

<th scope="col">Species</th>

</tr>

...

</tbody>

</table>Slide42

Fixing Incorrect Grid Structure

Some developers will use multiple HTML <table> elements to create one single grid. For example:

One <table> for the header row, one <table> for the body rows

One <table> for every single rowWhy? 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 tablesAssociation between column headers and cells is broken

Screen reader's table navigation is broken

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Support for High Contrast Mode

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Support for High Contrast Mode

When Windows High Contrast Mode is enabled, the following will happen:

Background and foreground colors are overridden

Background images are removedCustom user style sheets often apply similar changesUI libraries often uses background images for icons, which means these icons become invisible

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High Contrast Mode – Solutions?

It's possible to detect the effects of high contrast mode or a custom stylesheet using scripting:

On page load, create an off screen div element, assign border and background styles to it, and inspect computed styles to see if they are overridden

This detection can be used to "fix" issues related to HC mode, e.g.:Unhide hidden text to replace background imagesFont icons are great for high contrast mode, but:Not supported on all devices

Break easily when custom user stylesheet overrides font-family

“Invisible font” solution is a promising workaround for this issue

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