[gui-talk] Theoretical Question

Tue Dec 23 15:56:54 UTC 2014

Ideally all information spoken would come from the same application programming interface.  For example for a button you have name, the name of the button, the role, "it's a button", which defines how you interact with it, and the state and/or value of the button, which could be on or off, pushed or unpushed, or focusable or not focusable.  However, beyond this applications like browsers and Word processors also use something called a document object model, (DOM), which is a representation of the information in the web page or document being presented or worked on.  Screen readers have to be able to inspect the DOM to provide you access to the information, and access to such information is sometimes done via standard means, and sometimes extraordinary measures and "backdoors" are developed by screen reader producers to resolve challenges.  Finally, sometimes even the information in the pictorial graphics system is "inspected" through backdoor roundabout mechanisms to figure out what's happening because easy to get information was not provided by the developer.  So, generally when one screen reader works better with an app over others they have either created scripting to deduce information, built backdoors to do workarounds, or have implement4ed support for a new interface that others haven't developed support for yet.

I hope this helps.

Allen Hoffman
Deputy Executive Director
The Office of Accessible Systems & Technology
Department of Homeland Security
202-447-0503 (voice)
allen.hoffman at hq.dhs.gov

DHS Accessibility Helpdesk
202-447-0440 (voice)
202-447-0582 (fax)
202-447-5857 (TTY)
accessibility at dhs.gov

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-----Original Message-----
From: gui-talk [mailto:gui-talk-bounces at nfbnet.org] On Behalf Of Dave Marthouse via gui-talk
Sent: Tuesday, December 23, 2014 10:48 AM
To: GUI Talk List
Subject: [gui-talk] Theoretical Question

As I under stand it screen readers use hooks in the operating system to 
render the material on the screen readable with speech.  Knowing that, 
why do some screen readers work better than others with identical apps.  
Is it a matter of scripting or is there an inherent basic difference on 
how different readers work as far as their interface with the software 
used.  I'm academically curious.

Dave Marthouse
dmarthouse at gmail.com

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