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Re: Accessability Interfaces

Steve Lee wrote:
Out of interest do assistive technologies (AT) get to use an API or library (similar to ATK for the server applications) or do they use direct CORBA calls?
They use CORBA bindings, which on the client side are usually fairly straightforward. For instance, the python AT-SPI bindings are just python methods on python objects. The only place where the client needs to implement any CORBA methods is in the event listener interface, which is pretty small (one method).
AT is very unlikely to use a particular GUI for any UI they present as that UI has to be accessible.
What do you mean by this statement? Most ATs are using the same mechanism for enabling the accessibility of their own APIs as other apps on the desktop; e.g. orca's GUI uses pygtk, and thus appears like any other accessible app. 

Bill


--
Steve Lee
www.oatsoft.org <http://www.oatsoft.org>
www.fullmeasure.co.uk <http://www.fullmeasure.co.uk>
On 11/8/06, *Bill Haneman* <Bill Haneman sun com <mailto:Bill Haneman sun com>> wrote: 

    Ian Pascoe wrote:
    > Hi all
    >
    > Some thoughts that have been kind of troubling me over the past.
    >
    > There have been various postings in the past about compatability
    , or lack
    > of it, with various applications.  The most notable being that
    of Firefox
    > just recently.  In my ignorance, should the community be aiming
    to get those
    > projects that run and maintain development languages to provide the
    > necessary interfaces in the output so that the wheel doesn't
    need to be
    > re-invented each time for the application development projects?
    >
    Firefox is using ATK as its accessibility interface (or, rather, it is
    including ATK as its exported accessibility interface on
    Linux/Unix/Solaris).  Because Firefox is cross-platform, and also
    needs
    to speak MSAA on the Windows platform, is uses a different
    accessibility
    interface based on something called nsiAccessible
    internally.  However,
    by design, nsiAccessible maps rather well onto ATK, and ATK has
    been a
    major influence in the evolution of the mozilla-specific nsiAccessible
    interface.

    To clarify - ATK itself is available on Windows, but it not a standard
    part of a Windows installation, so in that respect ATK is already
    "cross-platform".  However, existing Windows assistive
    technologies use
    a mixture of Microsoft's MSAA and proprietary interfaces to do their
    job, so Firefox needs handle the export of its accessibility info
    differently on the two platforms.  On Linux/Unix/Solaris, the
    information is exported via ATK.

    OpenOffice.org also uses ATK as its accessibility interface now.

    ATK is an "in process" interface, so in order for the ATK
    information to
    be available to assistive technologies it must be "exported" via some
    interprocess communication technology.  AT-SPI is the standard
    interface
    for this, and a component called "atk-bridge" takes care of the
    details
    of turning in-process ATK calls into their equivalent AT-SPI
    equivalents.
    > I am aware that this is a GNOME list, but is the basic API used
    to drive
    > accessability the same that other projects are using or is it GNOME
    > specific?
    >
    In the above sense, this technology is not Gnome specific, since the
    same technique is used for Firefox, OpenOffice.org, and some other
    components such as recent RealPlayer and (I believe) recent
    versions of
    the Acrobat PDF reader.

    However, the existing atk-bridge does rely on some "gnome
    technologies",
    i.e. it uses Gnome libraries which are present on most
    distributions but
    may be missing from some distros, for instance some KDE-centric
    distros.

    KDE 4 is planning to support AT-SPI, but they wish to do so without
    using Gnome libraries or CORBA.  This will take some effort to
    sort out,
    since it means sacrificing binary compatibility with existing AT-SPI
    implementations.  I know they wish to do this in a way that preserves
    the functionality of existing AT-SPI clients like orca, LSR, GOK,
    Dasher, gnopernicus, as much as possible, but it is not clear when
    this
    work will be readily available.
    > Lastly, are the accessability modules like Orca specific to
    GNOME or will
    > they work cross GUIs?  I ask only out of curiosity as I'd like
    to try out a
    > few of the mainstream, and some of the backwater distros that
    are out there.
    >
    In theory orca could work with any distro which provides the necessary
    dependencies, and can work with other GUIs as well; however the
    distros
    need to do the work to make sure the necessary components are bundled
    and tested.  ATK is not bound to any specific GUI toolkit - while
    it is
    a dependency of GTK+, it does not require GTK+ in order to work,
    so any
    GUI toolkit is free to implement ATK as Firefox and OpenOffice.org
    have
    done.

    Best regards,

    Bill
    > Ian
    >
    >
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