<page xmlns="http://projectmallard.org/1.0/"
      xmlns:its="http://www.w3.org/2005/11/its"
      type="topic"
      id="tech-atk">

  <info>
    <link type="guide" xref="tech" group="atk"/>

    <revision pkgversion="3.0" date="2011-04-05" status="candidate"/>

    <credit type="author copyright">
      <name>Shaun McCance</name>
      <email its:translate="no">shaunm@gnome.org</email>
      <years>2011–2012</years>
    </credit>

    <include href="cc-by-sa-3-0.xml" xmlns="http://www.w3.org/2001/XInclude"/>

    <desc>Accessibility toolkit to implement support for screen readers and
    other tools</desc>
  </info>

<title>ATK</title>

<p>Accessibility is the process of ensuring your application can be
used by people with various disabilities.  Disabilities come in many forms:
visual impairments, movement impairments, hearing impairments, cognitive
and language impairments, and seizure disorders.  Many people have some
sort of disability, and making your application accessible will allow
more people to use it effectively, even if they are not disabled.</p>

<p>GNOME provides support for accessibility devices using the ATK framework,
which stands for Accessibility Tool Kit.  This framework defines a set of
interfaces to which graphical interface components adhere.  This allows, for
instance, screen readers to read the text of an interface and interact with its
controls.  ATK support is built into GTK and the rest of the GNOME platform,
so any application using GTK will have reasonable accessibility support for
free.</p>

<p>ATK solves the problem of plugging many different kinds of widgets (text
entries, text areas, buttons, menus) with many different types of accessibility
technologies (screen readers, braille displays, sip-and-puff control devices).
Instead of writing N×M interfaces, from each widget to each accessibility
device, one just has to expose a widget through ATK's interfaces.
Accessibility devices will in turn use these interfaces to query accessible
widgets.  For example, an aural screen reader and a braille display will both
use a standard "get the text contents" interface in ATK for all widgets with
textual information.</p>

<p>Nonetheless, you should be aware of accessibility issues when
developing your applications.  Although GTK interfaces provide
reasonable accessibility by default, you can often improve how well
your program behaves with accessibility tools by providing additional
information to ATK.  If you develop custom widgets, you should ensure
that they expose their properties to ATK.  You should also avoid using
sound, graphics, or color as the sole means of conveying information
to the user; have redundant ways of providing this information instead of
relying on the user being able to perceive a particular medium.</p>

<p>The GNOME desktop ships with a number of accessibility tools which enable
users with disabilities to take full advantage of their desktop and
applications.  Applications that fully implement ATK will be able to work with
the accessibility tools.  These include a screen reader, a screen magnifier, an
on-screen keyboard, and <app>Dasher</app>, an innovative predictive text entry
tool.</p>

<list style="compact">
  <item><p><link href="http://developer.gnome.org/accessibility-devel-guide/">GNOME Accessibility for Developers</link></p></item>
  <item><p><link href="https://developer.gnome.org/atk/stable/">ATK Reference</link></p></item>
</list>
</page>
