Supported MSAA Interfaces

Introduction

To use MSAA with Gecko, you'll need the tools and docs that come with the Active Accessibility 2.0 SDK Tools. The method AccessibleObjectFromWindow() will get you the root IAccessible corresponding to the top level window. Hold on to this root IAccessible, and use it to walk through the entire tree of IAccessible's.

IAccessible Overview

Refer to original specification to get more information about IAccessible interface.

MSAA	Description	Gecko
accDoDefaultAction	Performs the specified object's default action	`nsIAccessible.doAction()`
accHitTest	Retrieves the child element or child object at a given point on the screen	`nsIAccessible.getChildAtPoint()`
accLocation	Retrieves the specified object's current screen location	`nsIAccessible.getBounds()`
accNavigate	Traverses to another user interface (UI) element within a container and retrieves the object	complex mapping
accSelect	Modifies the selection or moves the keyboard focus of the specified object	complex mapping
get_accChild	Retrieves an `IDispatch` interface pointer for the specified child, if one exists	`nsIAccessible.getChildAt()`
get_accChildCount	Retrieves the number of children that belong to this object. All objects must support this property	nsIAccessible.childCount
get_accDefaultAction	Retrieves a string that describes the object's default action.	`nsIAccessible.getActionName()`
get_accDescription	retrieves a string that describes the visual appearance of the specified object.	nsIAccessible.description
get_accFocus	Returns the localized extended role	nsIAccessible.focusedChild
get_accHelp	Retrieves an object's Help property string.	not supported
get_accHelpTopic	Retrieves the full path of the WinHelp file associated with the specified object and the identifier of the appropriate topic within that file.	not supported
get_accKeyboardShortcut	Retrieves the specified object's shortcut key or access key, also known as the mnemonic.	nsIAccessible.keyboardShortcut
get_accName	Retrieves the name of the specified object. All objects support this property.	nsIAccessible.name
get_accParent	Retrieves the IDispatch interface of the object's parent.	nsIAccessible.parent
get_accRole	Retrieves information that describes the role of the specified object.	nsIAccessible.role
get_accSelection	Retrieves the selected children of this object.	`nsIAccessibleSelectable.getSelectedChildren()`
get_accState	Retrieves the current state of the specified object.	`nsIAccessible.getStates()`
get_accValue	Retrieves the value of the specified object.	nsIAccessible.value

IAccessible Details

accNavigate

Summary

Traverses to another user interface (UI) element within a container and retrieves the object (see MSDN: IAccessible::accNavigate).

HRESULT accNavigate(
  long navDir,
  VARIANT varStart,
  VARIANT* pvarEnd
);

The traversed object depends on the given constant navDir. Refer to the supported constants.

accSelect

Summary

Modifies the selection or moves the keyboard focus of the specified object (see MSDN: IAccessible::accSelect).

HRESULT accSelect(
  long flagsSelect,
  VARIANT varID
);

Implementation

Depending on flagsSelect argument (see MSDN: SELFLAG) the method is mapped to Gecko methods by the following way:

`flagsSelect`	Description	Gecko
`SELFLAG_TAKEFOCUS`	Sets the focus to the object	`nsIAccessible.takeFocus()`
`SELFLAG_TAKESELECTION`	Selects the object and removes the selection from all other objects in the container.	`nsIAccessible.takeSelection()`
`SELFLAG_ADDSELECTION`	Adds the object to the current selection	`nsIAccessible.setSelected()`
`SELFLAG_REMOVESELECTION`	Removes the object from the current selection	`nsIAccessible.setSelected()`
`SELFLAG_EXTENDSELECTION`	Alters the selection so that all objects between the selection anchor and this object take on the anchor object's selection state.	`nsIAccessible.extendSelection()`

get_accName

Summary

Retrieves the name of the specified object (see MSDN: IAccessible::get_accName).

HRESULT get_accName(
  VARIANT varID,
  BSTR* pszName
);

Return values

If there is not name: S_OK and *pszName == NULL; For example, when alt attribute isn't presented and title or ARIA attributes aren't specified or empty on html:img element.

If there is a name (possibly empty): S_OK and *pszName != NULL; The empty name means we allocate the string by SysAllocStringLen("", 0) method. You can get empty name, when, for example, html:img has only alt attribute with empty value (<img alt = "" >).

If error occured: E_FAIL

Introduction

IAccessible Overview

IAccessible Details

accNavigate

Summary

accSelect

Summary

Implementation

get_accName

Summary

Return values

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