Accessibility Architecture

The design is based on Microsoft UI Automation which helps provide us a low overhead path to implementation on Windows. This design scales well to NSAccessibility protocol on Mac platform too.

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Overview

AccessibleStage initializes and maintains a graph of all accessible implementation of UI controls. Every node in the scene graph can support accessibility by returning a corresponding object that implements accessibility, using the method getAccessible().

The super class of all components supporting accessibility is AccessibleNode. AccessibleNode implements AccessibleProvider. AccessibleNode maintains a reference to the Glass accessible object which in turn creates/maintains a reference to the native accessible object..

AccessibleStage is responsible for creating the native object and associating it with the AccessibleNode.

Each control defines its accessible providers by super class AccessibleNode or subclassed implementation for control specific providers.

Example AccessibleButton, AccessibleList, and AccessibleMenu.

Accessible providers

Accessible providers are a package of interfaces which define the accessible behavior of controls. A control may have one or more providers it may implement. AccessibleProvider is the base provider for any control to support accessibility. Multiple providers implemented by controls define its accessible behavior.

See package com.sun.javafx.accessible.providers for a list of providers.

AccessibleProvider

AccessibleStageProvider

ExpandCollapseProvider

GridItemProvider

GridProvider

InvokeProvider

RangeValueProvider

SelectionItemProvider

SelectionProvider

ToggleProvider

ValueProvider

<TODO:> Add short description of the features of the various providers.

 

Accessible utils

Accessible utils define static identifierts used by accessible providers applicable to various controls.

See package com.sun.javafx.accessible.utils for list of values.

ControlTypeIds

EventIds

ExpandCollapseState

NavigateDirection

OrientationType

PatternIds

PropertyIds

ProviderOptions

Rect

ToggleState

 

Accessibility Initialization

Accessibility is initialized, using the following flow of events:

On Windows / Mac:

(WM_GETOBJECT / accessibilityAttributeNames) → Bridge calls up into glass to Window → notifyInitAccessibility()

This call passes through quantum → StagePeerListener → which instantiates AccessibleStage.

AccessibleStage

AccessibleStage : initAccessibleHierarchy ()

  • On instantiation it initializes the corresponding accessible hierarchy for FX scene graph

  • For native object handle it makes a down call to bridge to create its associated native accessible component and saves its value in the AccessibleNode.

  • Attaches a listener for any new nodes being added to the scene graph.

  • Attaches a listener for any new Stage, Scene added to the window, which in return will add a listener to Scene for new node additions.

  • Attaches a Focus listener for tracking change of Focus.

 

AccessibleStage : updateAccessibleHierarchy ()

  • When a node is added or removed, make a down call to notify native bridge to add or remove the native accessible component.

  • Update AccessibleHierarchy

 

AccessibleStage : FocusChangeListener ()

  • Down call to Bridge to notify focus change

 

AccessibleNode

  • AccessibleNode is the super class implementation of the accessible behavior for all node

  • Implements common accessibility behavior for a node

  • Implements AccessibleProvider

  • Common accessible behavior that apply to nodes are:

    • Name, Description, State, Selection, Parent, Child, ScreenLocation, Height, Width, HitTest, Focus, Help, Keyboard Shortcut

 

AccessibleText

  • extends AccessibleNode

 

AccessibleControl

  • AccessibleControl is the super class implementation of the accessible behavior for all controls

  • Implements common accessibility behavior for any control in JavaFX.

  • extends AccessibleNode

  • Common accessible behavior that apply to controls are:

    • Name, Description, State, Selection, Parent, Child, ScreenLocation, Height, Width, HitTest, Focus, Help, Keyboard Shortcut

All controls extends from AccessibleControl

AccessibleButton

  • Extends AccessibleControl

  • Listener for change of properties that are not focus driven

  • Button specific Accessible behavior such as:

    • Name, Role, Value, DefaultAction, DoDefaultAction

AccessibleRadioButton

  • extends AccessibleControl

  • implements provider SelectionItemProvider

  • Listener for control specific property changes

 

AccessibleList

  • extends AccessibleControl

  • implements provider SelectionProvider and GridProvider

     

AccessibleListItem

  • extends AccessibleControl

  • implements provider SelectionItemProvider and GridItemProvider

 

AccessibleCheckBox

  • extends AccessibleControl

  • implements provider ToggleProvider

     

AccessibleSlider

  • extends AccessibleControl

  • implements RangeValueProvider

 

<TODO:Add other Controls>

 

 

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