Web checklist

Checkpoint 2.1d: No keyboard trap

If focus can be moved to a component of the page using a keyboard interface, then focus can be moved away from that component using only a keyboard interface, and, if it requires more than unmodified arrow or tab keys, the user is advised of the method for moving focus away.


Rationale

The intent of this checkpoint is to ensure that content does not "trap" keyboard focus within subsections of content on a Web page. This is a common problem when multiple formats are combined within a page and rendered using plug-ins or embedded applications.

Required development and unit test techniques


To comply with this checkpoint, you must meet all of the following techniques. These techniques are defined in WCAG 2.0 Level A Success Criterion 2.1.2 (link resides outside of ibm.com).

  1. No trap: Ensure that users are not trapped in content.

General examples

  1. No trap: Ensure that users are not trapped in content.

    To comply with this technique, you must implement all of the following examples .

    General example 1

    Make sure that any applets launch in their own browser window. This helps ensure that a user can exit or enter an applet or plug-in using only the keyboard.

    General example 2

    Develop plug-ins so that users can enter and exit a plug-in, such as an Adobe® Flash® object, using only a keyboard. Plug-ins should not launch in a separate window.

    For additional information, refer to the WCAG 2.0 examples for ensuring that users are not trapped in content (link resides outside of ibm.com).

    General example 3

    Where audio or video content is implemented with an HTML5 audio or video element, ensure that users can enter and exit the content using only a keyboard.

    Note for iOS platform: Apple recommends using the HTML5 audio and video elements for audio and video content on mobile Safari. However, these elements use the browsers' native players, and the controls on the players are not keyboard accessible. Therefore, developers must use the HTML5 audio/video API, JavaScript and CSS to implement keyboard focusable controls. An example implementation of an accessible HTML5 video/audio player can be found in chapter 6 of Pro HTML5 Accessibility: Building an Inclusive Web. (link resides outside of ibm.com).

    Required unit tests for general development technique 1

    Perform the following unit test.

    • Use available tools to identify any HTML5 video elements, HTML5 audio elements, applets, plug-ins or embedded applications on the page. Then manually verify that a keyboard mechanism is provided to enter and exit the plug-ins or embedded content.

Adobe® Flash® examples

  1. No trap: Ensure that users are not trapped in content.

    To comply with this technique, you must implement the following example .

    Flash example 1

    Control the tab order and reading order and ensure that both are logical. The tab order determines the objects that will receive focus when the Tab key is pressed. The reading order is the order in which the screen reader reads information about the object. Use the tabIndex property in ActionScript® to set both the tab order and reading order.

    For more information about the tabIndex property, visit the Adobe LiveDocs Website (link resides outside of ibm.com).

    Although it is not recommended, you can use the Tab Index text box in the Accessibility Panel (Adobe® Flash CS3 Professional only) to set the tab order. If you choose to set the tab order using the Tab Index text box, you will still need to use ActionScript to set a tabIndex property, which creates a clean reading order for the screen reader. In other words, you can set a tab order with the Accessibility Panel, but you can set both the tab order and reading order with the more powerful ActionScript.

    Accessibility X

    Visit the Adobe Flash Accessibility Design Guidelines Web site for more information about the Reading Order (link resides outside of ibm.com).

    Required unit tests for Flash development technique 1

    Use available tools to identify any Flash content on the page and verify that a keyboard mechanism is provided to enter and exit the Flash content.

    Note for iOS platform: Mobile Safari does not support Java applets, Flash or other third party plugins. Therefore, equivalent content must be presented in a manner that is accessible on iOS devices. Apple recommends using the HTML5 audio and video elements for audio and video content. However, these elements use the browsers' native players, and the controls on the players are not keyboard accessible. Therefore, developers must use the HTML5 audio/video API, JavaScript and CSS to implement keyboard focusable controls. An example implementation of an accessible HTML5 video/audio player can be found in chapter 6 of Pro HTML5 Accessibility: Building an Inclusive Web. (link resides outside of ibm.com).


IBM® Lotus® Domino® examples

  1. No trap: Ensure that users are not trapped in content.

    To comply with this technique, you must implement the following example .

    Domino example 1

    There is a known bug in Lotus Domino Designer 7 and 8 that prevents users from accessing content within sections. Until this problem is fixed, do not use sections to group and organize elements on a page or form.

    • This technique does not apply to Flash content that is added using Domino Designer. If Flash content is added to your Domino application, it must be developed in a way that allows a keyboard user to navigate in and out of the content.

    Required unit tests for Domino development technique 1

    Perform the following unit test:

    • Verify that no sections have been used in the content.
    • For any Flash content, verify that a keyboard mechanism is provided to enter and exit the Flash content.

Copyright 2011, 2013 IBM Corporation

Last updated May 1, 2011.

W3C Recommendation 11 December 2008: http://www.w3.org/TR/WCAG20/ (link resides outside of ibm.com)
Copyright 1994-2009 W3C (Massachusetts Institute of Technology, European Research Consortium for Informatics and Mathematics, Keio University), All Rights Reserved.