Announcing AxTk - an accessibility toolkit for wxWidgets

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Announcing AxTk - an accessibility toolkit for wxWidgets

Julian Smart
Announcing AxTk - an accessibility toolkit for wxWidgets
7th May 2009

* What is AxTk?

AxTk (pronounced Ay Ex Tee Kay) is an open source, C++ add-on for
wxWidgets that helps developers create highly accessible, talking
applications for users with impaired vision. It may also be useful for
other impairments that benefit from a simplified user interface.

AxTk features a new menu-based system that is easy to learn and use, in
addition to providing adaptation for some existing GUI controls and
dialogs. The developer can choose whether to use the menu system, or to
adapt an existing application UI, or use a combination of methods.

AxTk is cross-platform (tested so far on Windows XP, Linux and Mac OS X
10.5), and includes text-to-speech classes with the ability to drive
SAPI 5, Apple Speech Synthesis Manager, eSpeak, and Cepstral. Other
speech engines can be driven by writing additional handlers.

Note that AxTk is a work in progress and the API is subject to change.

* What else is AxTk?

There is an additional, higher-level layer for building applications
that help the user maintain 'resource libraries' for all kinds of files
and services. The motivation is to provided simplified access to many
resources and activities that are currently spread amongst many
applications and web sites. By making this part of AxTk, we increase the
chances of providing a really useful, accessible application platform
that can be customised in interesting ways for individuals or government
sectors. However, this is currently a less well-developed aspect of AxTk
and one which you can ignore fo now. The resource demo shows playing of
audio albums and reading Epub books (having converted the XHTML content
to plain text first).

* What about Braille output?

Although nothing is specifically coded yet for Braille devices, they
could be supported relatively easily by adding handlers to the
wxTextToSpeech system, to output to the device instead of a speech engine.

* Why not just use a screen reader?

Screen readers don't have an in-depth knowledge of the application; in
theory, an AxTk application can make use of knowledge of its own
structure to make speech more helpful and less verbose. Also, an
application's custom controls are not accessible to screen readers. In
additon, AxTk provides an alternative, menu-based user interface that is
not so prone to the problems of accessing conventional layouts via a
screen reader. Finally, an AxTk application provides support for
application-wide colour and text size changes that are harder to achieve
in an ad-hoc way.

* Is this anything to do with MSAA (Microsoft Active Accessibility)?

No; a different approach is used. Although wxWidgets has some basic MSAA
support, other ports have no similar support and it may be hard to
create a comprehensive cross-platform solution to accessibility based on
OS-level accessibility support. It would still leave applications and
users at the mercy of particular screen readers and it would not solve
other problems that AxTk sets out to solve: visual adaptation, fine
control over speech (such as content voicing), customisable shortcut
support, and more.

Having said that, work on integrating MSAA equivalents for other
platforms would be very welcome, either as part of AxTk or built into

* How hard is it to use?

Apart from some housekeeping that you can pinch from the sample, the
amount of extra code can be small if you're just adapting existing UIs.
For example, to make a dialog self-voicing and responsive to visual
appearance changes (assuming the dialog's controls are in the set of
controls currently handled by AxTk):

#include "ax/ax_ui_adaptation.h"


class MyDialog: public wxDialog
    AxSelfVoicing m_adapter;


If you have controls that are not currently handled by AxTk, you can
write adapter classes and also handler classes that detect the
appropriate controls and create their adapters.

Using the new menu system is also pretty straightforward as you can see
from the sample (mainframe.cpp). There are some new concepts such as
AxActivator, which handles menu item activation, but there's plenty in
common with conventional wxWidgets programming.

* Where and how do I get it?

AxTk is hosted at Google Code and is available via SVN or as a source
tarball or zip file.

The discussion group is [hidden email].

The documentation is available here:

* Are there demos?

Yes; you can download axsample binaries for Windows, Linux and Mac from:

You can ignore axresourcesample unless you're interested in the
higher-level resource library layer mentioned previously.

* Can I contribute?

Please do! See docs/todo.txt for some of the things left to do. You'll
probably find things to do yourself. You can supply patches in the
AxTk's Issue Tracker, or you can ask to be added to the list of project
members in order to make changes in SVN.

* What's the build system?

None to speak of. This would make a good contribution. Currently you can
use DialogBlocks to generate projects and makefiles for the two samples,
which simply include all the AxTk code.

* What is the license?

The license is the New BSD License, which is very brief, easy to
understand, and industry-friendly. Please see license.txt in the source
tarball for details.

I hope you find AxTk useful - or at least, fun to play with.

Julian Smart, Anthemion Software

Julian Smart, Anthemion Software Ltd.
28/5 Gillespie Crescent, Edinburgh, Midlothian, EH10 4HU | +44 (0)131 229 5306
Tools for writers:
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