IAccessible2 is an accessibility

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

for

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applications. Initially developed by

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under the codename Project Missouri, IAccessible2 has been placed under the aegis of the

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, now part of the

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. It has been positioned as an alternative to Microsoft's new UI Automation API. While UI Automation is trumpeted as "royalty-free", IAccessible2 claims to be an "open standard".

Goals

Whereas UI Automation marks a radical break from Microsoft Active Accessibility (MSAA) to create a more flexible accessibility API, IAccessible2 fills in perceived omissions in MSAA to match the Java Accessibility API and Assistive Technology Service Provider Interface (AT-SPI). By extending the MSAA interface, rather than replacing it, IAccessible2 allows "application developers to leverage their investment in MSAA while also providing an Assistive Technology (AT) access to rich document applications." It is also advantageous for Microsoft's commercial competitors, Sun and IBM, to promote an alternative accessibility interface to the Windows platform standard, which explains both their focus on developing non-MSAA/UIA interfaces and their promotion of cross-platform support despite the lack of any AT that is cross-platform that might use it. Project Missouri was started when the

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, in the process of adopting the OpenDocument format for its public records, required that the format be made accessible. Increasing the accessibility of dynamic web applications, for example by exposing custom controls for use with

assistive technology Assistive technology (AT) is a term for assistive, adaptive, and rehabilitative devices for Disability, people with disabilities and the elderly. Disabled people often have difficulty performing activities of daily living (ADLs) independently, ...

and by filtering streams of new information by type and importance, became a second major focus for the project.

Support

Support for IAccessible is present in

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as of version 4.2. It is in development for

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NonVisual Desktop Access NonVisual Desktop Access (NVDA) is a free and open-source, portable screen reader for Microsoft Windows. The project was started by Michael Curran in 2006. NVDA is programmed in Python. It utilizes accessibility APIs such as UI Automation, ...

and the

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web browser. Although IAccessible2 was introduced as a Windows accessibility API, Qt Development Frameworks is treating IAccessible2 as a potential alternative to AT-SPI on Linux too, and planning to add preliminary support to Qt 4.3. As of 2019, Qt uses MSAA and IAccessible2 on Windows, and continues to use AT-SPI for Unix/X11 systems.Qt documentation
(2019), accessed 2020-11-08.

References

Accessibility API Windows APIs