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QAccessible Class

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

Header: #include <QAccessible>
CMake: find_package(Qt6 REQUIRED COMPONENTS Gui)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: QT += gui

Public Types

struct State
enum Event { AcceleratorChanged, ActionChanged, ActiveDescendantChanged, Alert, AttributeChanged, …, VisibleDataChanged }
enum InterfaceType { TextInterface, ValueInterface, ActionInterface, TableInterface, TableCellInterface, HyperlinkInterface }
flags Relation
enum RelationFlag { Label, Labelled, Controller, Controlled, AllRelations }
enum Role { AlertMessage, Animation, Application, Assistant, Border, …, Window }
enum Text { Name, Description, Value, Help, Accelerator, UserText }
enum TextBoundaryType { CharBoundary, WordBoundary, SentenceBoundary, ParagraphBoundary, LineBoundary, NoBoundary }

Static Public Members

QAccessibleInterface * accessibleInterface(QAccessible::Id id)
void deleteAccessibleInterface(QAccessible::Id id)
void installFactory(QAccessible::InterfaceFactory factory)
bool isActive()
QAccessibleInterface * queryAccessibleInterface(QObject *object)
QAccessible::Id registerAccessibleInterface(QAccessibleInterface *iface)
void removeFactory(QAccessible::InterfaceFactory factory)
void setRootObject(QObject *object)
QAccessible::Id uniqueId(QAccessibleInterface *iface)
void updateAccessibility(QAccessibleEvent *event)

Detailed Description

This class is part of Accessibility for QWidget Applications.

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), macOS Accessibility, and the Unix/X11 AT-SPI standard. Other backends can be supported using QAccessibleBridge.

In the Unix/X11 AT-SPI implementation, applications become accessible when two conditions are met:

  • org.a11y.Status.IsEnabled DBus property is true
  • org.a11y.Status.ScreenReaderEnabled DBus property is true

An alternative to setting the DBus AT-SPI properties is to set the QT_LINUX_ACCESSIBILITY_ALWAYS_ON environment variable.

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.

Member Type Documentation

enum QAccessible::Event

This enum type defines accessible event types.

Constant Value Description
QAccessible::AcceleratorChanged 0x80C0 The keyboard accelerator for an action has been changed.
QAccessible::ActionChanged 0x0101 An action has been changed.
QAccessible::ActiveDescendantChanged 0x0102  
QAccessible::Alert 0x0002 A system alert (e.g., a message from a QMessageBox)
QAccessible::AttributeChanged 0x0103  
QAccessible::ContextHelpEnd 0x000D Context help (QWhatsThis) for an object is finished.
QAccessible::ContextHelpStart 0x000C Context help (QWhatsThis) for an object is initiated.
QAccessible::DefaultActionChanged 0x80B0 The default QAccessible::Action for the accessible object has changed.
QAccessible::DescriptionChanged 0x800D The object's QAccessible::Description changed.
QAccessible::DialogEnd 0x0011 A dialog (QDialog) has been hidden
QAccessible::DialogStart 0x0010 A dialog (QDialog) has been set visible.
QAccessible::DocumentContentChanged 0x0104 The contents of a text document have changed.
QAccessible::DocumentLoadComplete 0x0105 A document has been loaded.
QAccessible::DocumentLoadStopped 0x0106 A document load has been stopped.
QAccessible::DocumentReload 0x0107 A document reload has been initiated.
QAccessible::DragDropEnd 0x000F A drag and drop operation is about to finished.
QAccessible::DragDropStart 0x000E A drag and drop operation is about to be initiated.
QAccessible::Focus 0x8005 An object has gained keyboard focus.
QAccessible::ForegroundChanged 0x0003 A window has been activated (i.e., a new window has gained focus on the desktop).
QAccessible::HelpChanged 0x80A0 The QAccessible::Help text property of an object has changed.
QAccessible::HyperlinkEndIndexChanged 0x0108 The end position of the display text for a hypertext link has changed.
QAccessible::HyperlinkNumberOfAnchorsChanged 0x0109 The number of anchors in a hypertext link has changed, perhaps because the display text has been split to provide more than one link.
QAccessible::HyperlinkSelectedLinkChanged 0x010A The link for the selected hypertext link has changed.
QAccessible::HyperlinkStartIndexChanged 0x010D The start position of the display text for a hypertext link has changed.
QAccessible::HypertextChanged 0x010E The display text for a hypertext link has changed.
QAccessible::HypertextLinkActivated 0x010B A hypertext link has been activated, perhaps by being clicked or via a key press.
QAccessible::HypertextLinkSelected 0x010C A hypertext link has been selected.
QAccessible::HypertextNLinksChanged 0x010F  
QAccessible::LocationChanged 0x800B An object's location on the screen has changed.
QAccessible::MenuCommand 0x0018 A menu item is triggered.
QAccessible::MenuEnd 0x0005 A menu has been closed (Qt uses PopupMenuEnd for all menus).
QAccessible::MenuStart 0x0004 A menu has been opened on the menubar (Qt uses PopupMenuStart for all menus).
QAccessible::NameChanged 0x800C The QAccessible::Name property of an object has changed.
QAccessible::ObjectAttributeChanged 0x0110  
QAccessible::ObjectCreated 0x8000 A new object is created.
QAccessible::ObjectDestroyed 0x8001 An object is deleted.
QAccessible::ObjectHide 0x8003 An object is hidden; for example, with QWidget::hide(). Any children the object that is hidden has do not send this event. It is not sent when an object is hidden as it is being obcured by others.
QAccessible::ObjectReorder 0x8004 A layout or item view has added, removed, or moved an object (Qt does not use this event).
QAccessible::ObjectShow 0x8002 An object is displayed; for example, with QWidget::show().
QAccessible::PageChanged 0x0111  
QAccessible::ParentChanged 0x800F An object's parent object changed.
QAccessible::PopupMenuEnd 0x0007 A pop-up menu has closed.
QAccessible::PopupMenuStart 0x0006 A pop-up menu has opened.
QAccessible::ScrollingEnd 0x0013 A scrollbar scroll operation has ended (the mouse has released the slider handle).
QAccessible::ScrollingStart 0x0012 A scrollbar scroll operation is about to start; this may be caused by a mouse press on the slider handle, for example.
QAccessible::SectionChanged 0x0112  
QAccessible::SelectionAdd 0x8007 An item has been added to the selection in an item view.
QAccessible::SelectionRemove 0x8008 An item has been removed from an item view selection.
QAccessible::Selection 0x8006 The selection has changed in a menu or item view.
QAccessible::SelectionWithin 0x8009 Several changes to a selection has occurred in an item view.
QAccessible::SoundPlayed 0x0001 A sound has been played by an object
QAccessible::TableCaptionChanged 0x0113 A table caption has been changed.
QAccessible::TableColumnDescriptionChanged 0x0114 The description of a table column, typically found in the column's header, has been changed.
QAccessible::TableColumnHeaderChanged 0x0115 A table column header has been changed.
QAccessible::TableRowDescriptionChanged 0x0117 The description of a table row, typically found in the row's header, has been changed.
QAccessible::TableRowHeaderChanged 0x0118 A table row header has been changed.
QAccessible::TableSummaryChanged 0x0119 The summary of a table has been changed.
QAccessible::TextColumnChanged 0x011D A text column has been changed.
QAccessible::VisibleDataChanged 0x0122  

The values for this enum are defined to be the same as those defined in the IAccessible2 and MSAA specifications.


Synonym for unsigned, used by the QAccessibleInterface cache.


This is a typedef for a pointer to a function with the following signature:

typedef QAccessibleInterface *myFactoryFunction(const QString &key, QObject *);

The function receives a QString and a QObject pointer, where the QString is the key identifying the interface. The QObject is used to pass on to the QAccessibleInterface so that it can hold a reference to it.

If the key and the QObject does not have a corresponding QAccessibleInterface, nullptr will be returned.

Installed factories are called by queryAccessibilityInterface() until one provides an interface.

enum QAccessible::InterfaceType

QAccessibleInterface supports several sub interfaces. In order to provide more information about some objects, their accessible representation should implement one or more of these interfaces.

Note: When subclassing one of these interfaces, QAccessibleInterface::interface_cast() needs to be implemented.

Constant Value Description
QAccessible::TextInterface 0 For text that supports selections or is more than one line. Simple labels do not need to implement this interface.
QAccessible::ValueInterface 2 For objects that are used to manipulate a value, for example slider or scroll bar.
QAccessible::ActionInterface 3 For interactive objects that allow the user to trigger an action. Basically everything that allows for example mouse interaction.
QAccessible::TableInterface 5 For lists, tables and trees.
QAccessible::TableCellInterface 6 For cells in a TableInterface object.
QAccessible::HyperlinkInterface 7 For hyperlink nodes (usually embedded as children of text nodes)

See also QAccessibleInterface::interface_cast(), QAccessibleTextInterface, QAccessibleValueInterface, QAccessibleActionInterface, QAccessibleTableInterface, and QAccessibleTableCellInterface.

enum QAccessible::RelationFlag
flags QAccessible::Relation

This enum type defines bit flags that can be combined to indicate the relationship between two accessible objects.

Constant Value Description
QAccessible::Label 0x00000001 The first object is the label of the second object.
QAccessible::Labelled 0x00000002 The first object is labelled by the second object.
QAccessible::Controller 0x00000004 The first object controls the second object.
QAccessible::Controlled 0x00000008 The first object is controlled by the second object.
QAccessible::AllRelations 0xffffffff Used as a mask to specify that we are interesting in information about all relations

Implementations of relations() return a combination of these flags. Some values are mutually exclusive.

The Relation type is a typedef for QFlags<RelationFlag>. It stores an OR combination of RelationFlag values.

enum QAccessible::Role

This enum defines the role of an accessible object. The roles are:

Constant Value Description
QAccessible::AlertMessage 0x00000008 An object that is used to alert the user.
QAccessible::Animation 0x00000036 An object that displays an animation.
QAccessible::Application 0x0000000E The application's main window.
QAccessible::Assistant 0x00000020 An object that provides interactive help.
QAccessible::Border 0x00000013 An object that represents a border.
QAccessible::ButtonDropDown 0x00000038 A button that drops down a list of items.
QAccessible::ButtonDropGrid 0x0000003A A button that drops down a grid.
QAccessible::ButtonMenu 0x00000039 A button that drops down a menu.
QAccessible::Canvas 0x00000035 An object that displays graphics that the user can interact with.
QAccessible::Caret 0x00000007 An object that represents the system caret (text cursor).
QAccessible::Cell 0x0000001D A cell in a table.
QAccessible::Chart 0x00000011 An object that displays a graphical representation of data.
QAccessible::CheckBox 0x0000002C An object that represents an option that can be checked or unchecked. Some options provide a "mixed" state, e.g. neither checked nor unchecked.
QAccessible::Client 0x0000000A The client area in a window.
QAccessible::Clock 0x0000003D A clock displaying time.
QAccessible::ColorChooser 0x404 A dialog that lets the user choose a color.
QAccessible::Column 0x0000001B A column of cells, usually within a table.
QAccessible::ColumnHeader 0x00000019 A header for a column of data.
QAccessible::ComboBox 0x0000002E A list of choices that the user can select from.
QAccessible::ComplementaryContent 0x42C A part of the document or web page that is complementary to the main content, usually a landmark (see WAI-ARIA).
QAccessible::Cursor 0x00000006 An object that represents the mouse cursor.
QAccessible::Desktop 0x00000082 The object represents the desktop or workspace.
QAccessible::Dial 0x00000031 An object that represents a dial or knob.
QAccessible::Dialog 0x00000012 A dialog box.
QAccessible::Document 0x0000000F A document, for example in an office application.
QAccessible::EditableText 0x0000002A Editable text such as a line or text edit.
QAccessible::Equation 0x00000037 An object that represents a mathematical equation.
QAccessible::Footer 0x40E A footer in a page (usually in documents).
QAccessible::Form 0x410 A web form containing controls.
QAccessible::Graphic 0x00000028 A graphic or picture, e.g. an icon.
QAccessible::Grip 0x00000004 A grip that the user can drag to change the size of widgets.
QAccessible::Grouping 0x00000014 An object that represents a logical grouping of other objects.
QAccessible::Heading 0x414 A heading in a document.
QAccessible::HelpBalloon 0x0000001F An object that displays help in a separate, short lived window.
QAccessible::HotkeyField 0x00000032 A hotkey field that allows the user to enter a key sequence.
QAccessible::Indicator 0x00000027 An indicator that represents a current value or item.
QAccessible::LayeredPane 0x00000080 An object that can contain layered children, e.g. in a stack.
QAccessible::Link 0x0000001E A link to something else.
QAccessible::List 0x00000021 A list of items, from which the user can select one or more items.
QAccessible::ListItem 0x00000022 An item in a list of items.
QAccessible::MenuBar 0x00000002 A menu bar from which menus are opened by the user.
QAccessible::MenuItem 0x0000000C An item in a menu or menu bar.
QAccessible::NoRole 0x00000000 The object has no role. This usually indicates an invalid object.
QAccessible::Note 0x41B A section whose content is parenthetic or ancillary to the main content of the resource.
QAccessible::Notification 0x00000086 An object that represents a notification (e.g. in the system tray). This role only has an effect on Linux.
QAccessible::PageTab 0x00000025 A page tab that the user can select to switch to a different page in a dialog.
QAccessible::PageTabList 0x0000003C A list of page tabs.
QAccessible::Paragraph 0x00000083 A paragraph of text (usually found in documents).
QAccessible::Pane 0x00000010 A generic container.
QAccessible::PopupMenu 0x0000000B A menu which lists options that the user can select to perform an action.
QAccessible::ProgressBar 0x00000030 The object displays the progress of an operation in progress.
QAccessible::PropertyPage 0x00000026 A property page where the user can change options and settings.
QAccessible::Button 0x0000002B A button.
QAccessible::RadioButton 0x0000002D An object that represents an option that is mutually exclusive with other options.
QAccessible::Row 0x0000001C A row of cells, usually within a table.
QAccessible::RowHeader 0x0000001A A header for a row of data.
QAccessible::ScrollBar 0x00000003 A scroll bar, which allows the user to scroll the visible area.
QAccessible::Section 0x00000085 A section (in a document).
QAccessible::Separator 0x00000015 A separator that divides space into logical areas.
QAccessible::Slider 0x00000033 A slider that allows the user to select a value within a given range.
QAccessible::Sound 0x00000005 An object that represents a sound.
QAccessible::SpinBox 0x00000034 A spin box widget that allows the user to enter a value within a given range.
QAccessible::Splitter 0x0000003E A splitter distributing available space between its child widgets.
QAccessible::StaticText 0x00000029 Static text, such as labels for other widgets.
QAccessible::StatusBar 0x00000017 A status bar.
QAccessible::Table 0x00000018 A table representing data in a grid of rows and columns.
QAccessible::Terminal 0x00000081 A terminal or command line interface.
QAccessible::TitleBar 0x00000001 The title bar caption of a window.
QAccessible::ToolBar 0x00000016 A tool bar, which groups widgets that the user accesses frequently.
QAccessible::ToolTip 0x0000000D A tool tip which provides information about other objects.
QAccessible::Tree 0x00000023 A list of items in a tree structure.
QAccessible::TreeItem 0x00000024 An item in a tree structure.
QAccessible::UserRole 0x0000ffff The first value to be used for user defined roles.
QAccessible::WebDocument 0x00000084 HTML document, usually in a browser.
QAccessible::Whitespace 0x0000003B Blank space between other objects.
QAccessible::Window 0x00000009 A top level window.

enum QAccessible::Text

This enum specifies string information that an accessible object returns.

Constant Value Description
QAccessible::Name 0 The name of the object. This can be used both as an identifier or a short description by accessible clients.
QAccessible::Description 1 A short text describing the object.
QAccessible::Value 2 The value of the object.
QAccessible::Help 3 A longer text giving information about how to use the object.
QAccessible::Accelerator 4 The keyboard shortcut that executes the object's default action.
QAccessible::UserText 0x0000ffff The first value to be used for user defined text.

enum QAccessible::TextBoundaryType

This enum describes different types of text boundaries. It follows the IAccessible2 API and is used in the QAccessibleTextInterface.

Constant Value Description
QAccessible::CharBoundary 0 Use individual characters as boundary.
QAccessible::WordBoundary 1 Use words as boundaries.
QAccessible::SentenceBoundary 2 Use sentences as boundary.
QAccessible::ParagraphBoundary 3 Use paragraphs as boundary.
QAccessible::LineBoundary 4 Use newlines as boundary.
QAccessible::NoBoundary 5 No boundary (use the whole text).

See also QAccessibleTextInterface.

Member Function Documentation

[static] QAccessibleInterface *QAccessible::accessibleInterface(QAccessible::Id id)

Returns the QAccessibleInterface belonging to the id.

Returns nullptr if the id is invalid.

[static] void QAccessible::deleteAccessibleInterface(QAccessible::Id id)

Removes the interface belonging to this id from the cache and deletes it. The id becomes invalid an may be re-used by the cache.

[static] void QAccessible::installFactory(QAccessible::InterfaceFactory factory)

Installs the InterfaceFactory factory. The last factory added is the first one used by queryAccessibleInterface().

[static] bool QAccessible::isActive()

Returns true if the platform requested accessibility information.

This function will return false until a tool such as a screen reader accessed the accessibility framework. It is still possible to use QAccessible::queryAccessibleInterface() even if accessibility is not active. But there will be no notifications sent to the platform.

It is recommended to use this function to prevent expensive notifications via updateAccessibility() when they are not needed.

[static] QAccessibleInterface *QAccessible::queryAccessibleInterface(QObject *object)

If a QAccessibleInterface implementation exists for the given object, this function returns a pointer to the implementation; otherwise it returns nullptr.

The function calls all installed factory functions (from most recently installed to least recently installed) until one is found that provides an interface for the class of object. If no factory can provide an accessibility implementation for the class the function loads installed accessibility plugins, and tests if any of the plugins can provide the implementation.

If no implementation for the object's class is available, the function tries to find an implementation for the object's parent class, using the above strategy.

All interfaces are managed by an internal cache and should not be deleted.

[static] QAccessible::Id QAccessible::registerAccessibleInterface(QAccessibleInterface *iface)

Call this function to ensure that manually created interfaces are properly memory managed.

Must only be called exactly once per interface iface. This is implicitly called when calling queryAccessibleInterface, calling this function is only required when QAccessibleInterfaces are instantiated with the "new" operator. This is not recommended, whenever possible use the default functions and let queryAccessibleInterface() take care of this.

When it is necessary to reimplement the QAccessibleInterface::child() function and returning the child after constructing it, this function needs to be called.

[static] void QAccessible::removeFactory(QAccessible::InterfaceFactory factory)

Removes factory from the list of installed InterfaceFactories.

[static] void QAccessible::setRootObject(QObject *object)

Sets the root object of the accessible objects of this application to object. All other accessible objects are reachable using object navigation from the root object.

Normally, it isn't necessary to call this function, because Qt sets the QApplication object as the root object immediately before the event loop is entered in QApplication::exec().

Use QAccessible::installRootObjectHandler() to redirect the function call to a customized handler function.

See also queryAccessibleInterface().

[static] QAccessible::Id QAccessible::uniqueId(QAccessibleInterface *iface)

Returns the unique ID for the QAccessibleInterface iface.

[static] void QAccessible::updateAccessibility(QAccessibleEvent *event)

Notifies about a change that might be relevant for accessibility clients.

event provides details about the change. These include the source of the change and the nature of the change. The event should contain enough information give meaningful notifications.

For example, the type ValueChange indicates that the position of a slider has been changed.

Call this function whenever the state of your accessible object or one of its sub-elements has been changed either programmatically (e.g. by calling QLabel::setText()) or by user interaction.

If there are no accessibility tools listening to this event, the performance penalty for calling this function is small, but if determining the parameters of the call is expensive you can test QAccessible::isActive() to avoid unnecessary computation.

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