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# QAccessible Class Reference
[com.trolltech.qt.gui module]

The `QAccessible` class provides enums and static functions relating to accessibility. More...

Inherited by `QAccessibleInterface`.

## Detailed Description

The `QAccessible` class provides enums and static functions relating to accessibility.

Accessible applications can be used by people who are not able to use applications by conventional means.

The functions in this class are used for communication between accessible applications (also called AT Servers) and accessibility tools (AT Clients), such as screen readers and braille displays. Clients and servers communicate in the following way:

- AT Servers notify the clients about events through calls to the `updateAccessibility` function.
- AT Clients request information about the objects in the server. The `QAccessibleInterface` class is the core interface, and encapsulates this information in a pure virtual API. Implementations of the interface are provided by Qt through the `queryAccessibleInterface` API.

The communication between servers and clients is initialized by the `setRootObject` function. Function pointers can be installed to replace or extend the default behavior of the static functions in `QAccessible`.

Qt supports Microsoft Active Accessibility (MSAA), Mac OS X Accessibility, and the Unix/X11 AT-SPI standard. Other backends can be supported using `QAccessibleBridge`.

In addition to `QAccessible`'s static functions, Qt offers one generic interface, `QAccessibleInterface`, that can be used to wrap all widgets and objects (e.g., `QPushButton`). This single interface provides all the metadata necessary for the assistive technologies. Qt provides implementations of this interface for its built-in widgets as plugins.

When you develop custom widgets, you can create custom subclasses of `QAccessibleInterface` and distribute them as plugins (using QAccessiblePlugin) or compile them into the application. Likewise, Qt's predefined accessibility support can be built as plugin (the default) or directly into the Qt library. The main advantage of using plugins is that the accessibility classes are only loaded into memory if they are actually used; they don't slow down the common case where no assistive technology is being used.

Qt also includes two convenience classes, `QAccessibleObject` and `QAccessibleWidget`, that inherit from `QAccessibleInterface` and provide the lowest common denominator of metadata (e.g., widget geometry, window title, basic help text). You can use them as base classes when wrapping your custom `QObject` or `QWidget` subclasses.

See also `QAccessibleInterface`.