IAccessibleText Interface Reference

This interface gives read-only access to text. More...

import "AccessibleText.idl";

Inheritance diagram for IAccessibleText:

IAccessibleHypertext

List of all members.


Public Member Functions

HRESULT addSelection ([in] long startOffset,[in] long endOffset)
 Adds a text selection.
HRESULT attributes ([in] long offset,[out] long *startOffset,[out] long *endOffset,[out, retval] BSTR *textAttributes)
 Returns text attributes.
HRESULT caretOffset ([out, retval] long *offset)
 Returns the position of the caret.
HRESULT characterExtents ([in] long offset,[in] enum IA2CoordinateType coordType,[out] long *x,[out] long *y,[out] long *width,[out, retval] long *height)
 Returns the bounding box of the specified position.
HRESULT nSelections ([out, retval] long *nSelections)
 Returns the number of active non-contiguous selections.
HRESULT offsetAtPoint ([in] long x,[in] long y,[in] enum IA2CoordinateType coordType,[out, retval] long *offset)
 Returns the text position for the specified screen position.
HRESULT selection ([in] long selectionIndex,[out] long *startOffset,[out, retval] long *endOffset)
 Returns the character offsets of Nth active text selection.
HRESULT text ([in] long startOffset,[in] long endOffset,[out, retval] BSTR *text)
 Returns the substring between the two given indices.
HRESULT textBeforeOffset ([in] long offset,[in] enum IA2TextBoundaryType boundaryType,[out] long *startOffset,[out] long *endOffset,[out, retval] BSTR *text)
 Returns a text portion before the given position.
HRESULT textAfterOffset ([in] long offset,[in] enum IA2TextBoundaryType boundaryType,[out] long *startOffset,[out] long *endOffset,[out, retval] BSTR *text)
 Returns a text portion after the given position.
HRESULT textAtOffset ([in] long offset,[in] enum IA2TextBoundaryType boundaryType,[out] long *startOffset,[out] long *endOffset,[out, retval] BSTR *text)
 Returns a text portion that spans the given position.
HRESULT removeSelection ([in] long selectionIndex)
 Unselects a range of text.
HRESULT setCaretOffset ([in] long offset)
 Sets the position of the caret.
HRESULT setSelection ([in] long selectionIndex,[in] long startOffset,[in] long endOffset)
 Changes the bounds of an existing selection.
HRESULT nCharacters ([out, retval] long *nCharacters)
 Returns total number of characters.
HRESULT scrollSubstringTo ([in] long startIndex,[in] long endIndex,[in] enum IA2ScrollType scrollType)
 Makes a specific part of string visible on screen.
HRESULT scrollSubstringToPoint ([in] long startIndex,[in] long endIndex,[in] enum IA2CoordinateType coordinateType,[in] long x,[in] long y)
 Moves the top left of a substring to a specified location.
HRESULT newText ([out, retval] IA2TextSegment *newText)
 Returns any inserted text.
HRESULT oldText ([out, retval] IA2TextSegment *oldText)
 Returns any removed text.

Detailed Description

This interface gives read-only access to text.

The IAccessibleText interface should be implemented by all components that present textual information on the display like buttons, text entry fields, or text portions of the document window. The interface provides access to the text's content, attributes, and spatial location. However, text can not be modified with this interface. That is the task of the IAccessibleEditableText interface.

The text length, i.e. the number of characters in the text, is returned by IAccessibleText::nCharacters. All methods that operate on particular characters (e.g. IAccessibleText::textAtOffset) use character indices from 0 to length-1. All methods that operate on character positions (e.g. IAccessibleText::text) use indices from 0 to length.

Please note that accessible text does not necessarily support selection. In this case it should behave as if there where no selection. An empty selection is used for example to express the current cursor position.

Refer to Special Offsets for use in the IAccessibleText and IAccessibleEditableText Methods for information about special offsets that can be used in IAccessibleText methods.

E_FAIL is returned in the following cases


Member Function Documentation

HRESULT IAccessibleText::addSelection ( [in] long  startOffset,
[in] long  endOffset 
)

Adds a text selection.

Parameters:
[in] startOffset Starting offset ( 0 based).
[in] endOffset Offset of first character after new selection (0 based).
Return values:
S_OK 
E_INVALIDARG if bad [in] passed

HRESULT IAccessibleText::attributes ( [in] long  offset,
[out] long *  startOffset,
[out] long *  endOffset,
[out, retval] BSTR *  textAttributes 
) [get]

Returns text attributes.

Parameters:
[in] offset Text offset (0 based)
[out] startOffset The starting offset of the character range over which all text attributes match those of offset. (0 based)
[out] endOffset The offset of the first character past the character range over which all text attributes match those of offset. (0 based)
[out] textAttributes A string of attributes describing the text. The attributes are described in the text attributes specification on the IAccessible2 web site.
Return values:
S_OK 
S_FALSE if there is nothing to return, [out] values are 0s and NULL respectively
E_INVALIDARG if bad [in] passed, [out] values are 0s and NULL respectively

HRESULT IAccessibleText::caretOffset ( [out, retval] long *  offset  )  [get]

Returns the position of the caret.

Returns the 0-based offset of the caret within the text. If the text is implemented as a tree of text objects with embed characters in higher levels representing substrings of child text objects and the caret is in one of the child text objects, then the offset in the higher level text object would be at the embed character representing child text object that contains the caret.

For example, if the string "one two three" is implemented as a two text objects, with a top level text object containing an embed character "one ? three" and a child text object containing "two" and if the caret is in the descendant object just before the 'o' in "two", then:

  • the caretOffset for the "one ? three" object would be 4, matching the embed character
  • the caretOffset for "two" would be 2, matching the "o"
The caret position/offset is that of the character logically following it, e.g. to the right of it in a left to right language.
Parameters:
[out] offset The returned offset is relative to the text represented by this object.
Return values:
S_OK 
S_FALSE if the caret is not currently active on this object, i.e. the caret is located on some other object. The returned offset value will be -1.
Note:
S_FALSE (and an offset of -1) will not be returned if the caret is somewhere in the text object or one of its descendants.

HRESULT IAccessibleText::characterExtents ( [in] long  offset,
[in] enum IA2CoordinateType  coordType,
[out] long *  x,
[out] long *  y,
[out] long *  width,
[out, retval] long *  height 
) [get]

Returns the bounding box of the specified position.

The virtual character after the last character of the represented text, i.e. the one at position length is a special case. It represents the current input position and will therefore typically be queried by AT more often than other positions. Because it does not represent an existing character its bounding box is defined in relation to preceding characters. It should be roughly equivalent to the bounding box of some character when inserted at the end of the text. Its height typically being the maximal height of all the characters in the text or the height of the preceding character, its width being at least one pixel so that the bounding box is not degenerate.

Note that the index 'length' is not always valid. Whether it is or not is implementation dependent. It typically is when text is editable or otherwise when on the screen the caret can be placed behind the text. You can be sure that the index is valid after you have received a IA2_EVENT_TEXT_CARET_MOVED event for this index.

Parameters:
[in] offset Index of the character for which to return its bounding box. The valid range is 0..length.
[in] coordType Specifies if the coordinates are relative to the screen or to the parent window.
[out] x X coordinate of the top left corner of the bounding box of the referenced character.
[out] y Y coordinate of the top left corner of the bounding box of the referenced character.
[out] width Width of the bounding box of the referenced character.
[out] height Height of the bounding box of the referenced character.
Return values:
S_OK 
E_INVALIDARG if bad [in] passed, [out] values are 0s

HRESULT IAccessibleText::nCharacters ( [out, retval] long *  nCharacters  )  [get]

Returns total number of characters.

Note that this may be different than the total number of bytes required to store the text, if the text contains multi-byte characters.

Parameters:
[out] nCharacters 
Return values:
S_OK 

HRESULT IAccessibleText::newText ( [out, retval] IA2TextSegment newText  )  [get]

Returns any inserted text.

Provided for use by the IA2_EVENT_TEXT_INSERTED and IA2_EVENT_TEXT_UPDATED event handlers.

This data is only guaranteed to be valid while the thread notifying the event continues. Once the handler has returned, the validity of the data depends on how the server manages the life cycle of its objects. Also, note that the server may have different life cycle management strategies for controls depending on whether or not a control manages its children. Lists, trees, and tables can have a large number of children and thus it's possible that the child objects for those controls would only be created as needed. Servers should document their life cycle strategy as this will be of interest to assistive technology or script engines accessing data out of process or from other threads. Servers only need to save the last inserted block of text and a scope of the entire application is adequate.

Parameters:
[out] newText The text that was just inserted.
Return values:
S_OK 
S_FALSE if there is nothing to return, [out] value is NULL

HRESULT IAccessibleText::nSelections ( [out, retval] long *  nSelections  )  [get]

Returns the number of active non-contiguous selections.

Parameters:
[out] nSelections 
Return values:
S_OK 

HRESULT IAccessibleText::offsetAtPoint ( [in] long  x,
[in] long  y,
[in] enum IA2CoordinateType  coordType,
[out, retval] long *  offset 
) [get]

Returns the text position for the specified screen position.

Given a point return the zero-based index of the character under that point. The same functionality could be achieved by using the bounding boxes for each character as returned by IAccessibleText::characterExtents. The method IAccessibleText::offsetAtPoint, however, can be implemented more efficiently.

Parameters:
[in] x The position's x value for which to look up the index of the character that is rendered on to the display at that point.
[in] y The position's y value for which to look up the index of the character that is rendered on to the display at that point.
[in] coordType Screen coordinates or window coordinates.
[out] offset Index of the character under the given point or -1 if the point is invalid or there is no character under the point.
Return values:
S_OK 
E_INVALIDARG if bad [in] passed, [out] value is 0

HRESULT IAccessibleText::oldText ( [out, retval] IA2TextSegment oldText  )  [get]

Returns any removed text.

Provided for use by the IA2_EVENT_TEXT_REMOVED/UPDATED event handlers.

This data is only guaranteed to be valid while the thread notifying the event continues. Once the handler has returned, the validity of the data depends on how the server manages the life cycle of its objects. Also, note that the server may have different life cycle management strategies for controls depending on whether or not a control manages its children. Lists, trees, and tables can have a large number of children and thus it's possible that the child objects for those controls would only be created as needed. Servers should document their life cycle strategy as this will be of interest to assistive technology or script engines accessing data out of process or from other threads. Servers only need to save the last removed block of text and a scope of the entire application is adequate.

Parameters:
[out] oldText The text that was just removed.
Return values:
S_OK 
S_FALSE if there is nothing to return, [out] value is NULL

HRESULT IAccessibleText::removeSelection ( [in] long  selectionIndex  ) 

Unselects a range of text.

Parameters:
[in] selectionIndex Index of selection to remove (0 based).
Return values:
S_OK 
E_INVALIDARG if bad [in] passed

HRESULT IAccessibleText::scrollSubstringTo ( [in] long  startIndex,
[in] long  endIndex,
[in] enum IA2ScrollType  scrollType 
)

Makes a specific part of string visible on screen.

Parameters:
[in] startIndex 0 based character offset.
[in] endIndex 0 based character offset - the offset of the character just past the last character of the string.
[in] scrollType Defines where the object should be placed on the screen.
Return values:
S_OK 
E_INVALIDARG if bad [in] passed

HRESULT IAccessibleText::scrollSubstringToPoint ( [in] long  startIndex,
[in] long  endIndex,
[in] enum IA2CoordinateType  coordinateType,
[in] long  x,
[in] long  y 
)

Moves the top left of a substring to a specified location.

Parameters:
[in] startIndex 0 based character offset.
[in] endIndex 0 based character offset - the offset of the character just past the last character of the string.
[in] coordinateType Specifies whether the coordinates are relative to the screen or the parent object.
[in] x Defines the x coordinate.
[in] y Defines the y coordinate.
Return values:
S_OK 
S_FALSE if the object is already at the specified location.
E_INVALIDARG if bad [in] passed

HRESULT IAccessibleText::selection ( [in] long  selectionIndex,
[out] long *  startOffset,
[out, retval] long *  endOffset 
) [get]

Returns the character offsets of Nth active text selection.

Parameters:
[in] selectionIndex Index of selection (0 based).
[out] startOffset 0 based offset of first selected character
[out] endOffset 0 based offset of one past the last selected character.
Return values:
S_OK 
S_FALSE if there is nothing to return, [out] values are 0s
E_INVALIDARG if bad [in] passed, [out] values are 0s

HRESULT IAccessibleText::setCaretOffset ( [in] long  offset  ) 

Sets the position of the caret.

The caret position/offset is that of the character logically following it, e.g. to the right of it in a left to right language.

Setting the caret position may or may not alter the current selection. A change of the selection is notified to the accessibility event listeners with an IA2_EVENT_TEXT_SELECTION_CHANGED event.

When the new caret position differs from the old one (which, of course, is the standard case) this is notified to the accessibility event listeners with an IA2_EVENT_TEXT_CARET_MOVED event.

Parameters:
[in] offset The new index of the caret. This caret is actually placed to the left side of the character with that index. An index of 0 places the caret so that the next insertion goes before the first character. An index of IAccessibleText::nCharacters leads to insertion after the last character.
Return values:
S_OK 
E_FAIL if the caret cannot be set
E_INVALIDARG if bad [in] passed

HRESULT IAccessibleText::setSelection ( [in] long  selectionIndex,
[in] long  startOffset,
[in] long  endOffset 
)

Changes the bounds of an existing selection.

Parameters:
[in] selectionIndex Index of selection to change (0 based)
[in] startOffset New starting offset (0 based)
[in] endOffset New ending offset (0 based) - the offset of the character just past the last character of the selection.
Return values:
S_OK 
E_INVALIDARG if bad [in] passed

HRESULT IAccessibleText::text ( [in] long  startOffset,
[in] long  endOffset,
[out, retval] BSTR *  text 
) [get]

Returns the substring between the two given indices.

The substring starts with the character at startOffset (inclusive) and up to the character at endOffset (exclusive), if startOffset is less or equal endOffste. If endOffset is lower than startOffset, the result is the same as a call with the two arguments being exchanged.

The whole text can be requested by passing the indices zero and IAccessibleText::nCharacters. If both indices have the same value, an empty string is returned.

Parameters:
[in] startOffset Index of the first character to include in the returned string. The valid range is 0..length.
[in] endOffset Index of the last character to exclude in the returned string. The valid range is 0..length.
[out] text Returns the substring starting with the character at startOffset (inclusive) and up to the character at endOffset (exclusive), if startOffset is less than or equal to endOffset.
Return values:
S_OK 
E_INVALIDARG if bad [in] passed, [out] value is NULL
Note:
The returned string may be longer than endOffset-startOffset bytes if text contains multi-byte characters.

HRESULT IAccessibleText::textAfterOffset ( [in] long  offset,
[in] enum IA2TextBoundaryType  boundaryType,
[out] long *  startOffset,
[out] long *  endOffset,
[out, retval] BSTR *  text 
) [get]

Returns a text portion after the given position.

Returns the substring of the specified text type that is located after the given character and does not include it. The result of this method should be same as a result for IAccessibleText::textAtOffset with a suitably increased index value.

For example, if text type is IA2_TEXT_BOUNDARY_WORD, then the complete word that is closest to and located after offset is returned.

If the index is valid, but no suitable word (or other text type) is found, a NULL pointer is returned.

Parameters:
[in] offset Index of the character for which to return the text part before it. The index character will not be part of the returned string. The valid range is 0..length.
[in] boundaryType The type of the text portion to return. See IA2TextBoundaryType for the complete list.
[out] startOffset 0 based offset of first character.
[out] endOffset 0 based offset of one past the last character.
[out] text Returns the requested text portion. This portion may be empty or invalid when no appropriate text portion is found or text type is invalid.
Return values:
S_OK 
S_FALSE if the requested boundary type is not implemented, such as IA2_TEXT_BOUNDARY_SENTENCE, or if there is nothing to return; [out] values are 0s and NULL respectively
E_INVALIDARG if bad [in] passed, [out] values are 0s and NULL respectively

HRESULT IAccessibleText::textAtOffset ( [in] long  offset,
[in] enum IA2TextBoundaryType  boundaryType,
[out] long *  startOffset,
[out] long *  endOffset,
[out, retval] BSTR *  text 
) [get]

Returns a text portion that spans the given position.

Returns the substring of the specified text type at the specified offset.

If the index is valid, but no suitable word (or other text type) is found, a NULL pointer is returned.

Parameters:
[in] offset Index of the character for which to return the text part before it. The index character will not be part of the returned string. The valid range is 0..length.
[in] boundaryType The type of the text portion to return. See IA2TextBoundaryType for the complete list.
[out] startOffset 0 based offset of first character.
[out] endOffset 0 based offset of one past the last character.
[out] text Returns the requested text portion. This portion may be empty or invalid when no appropriate text portion is found or text type is invalid.
Return values:
S_OK 
S_FALSE if the requested boundary type is not implemented, such as IA2_TEXT_BOUNDARY_SENTENCE, or if there is nothing to return; [out] values are 0s and NULL respectively
E_INVALIDARG if bad [in] passed, [out] values are 0s and NULL respectively

HRESULT IAccessibleText::textBeforeOffset ( [in] long  offset,
[in] enum IA2TextBoundaryType  boundaryType,
[out] long *  startOffset,
[out] long *  endOffset,
[out, retval] BSTR *  text 
) [get]

Returns a text portion before the given position.

Returns the substring of the specified text type that is located before the given character and does not include it. The result of this method should be same as a result for IAccessibleText::textAtOffset with a suitably decreased index value.

For example, if text type is IA2_TEXT_BOUNDARY_WORD, then the complete word that is closest to and located before offset is returned.

If the index is valid, but no suitable word (or other boundary type) is found, a NULL pointer is returned.

Parameters:
[in] offset Index of the character for which to return the text part before it. The index character will not be part of the returned string. The valid range is 0..length.
[in] boundaryType The type of the text portion to return. See IA2TextBoundaryType for the complete list.
[out] startOffset 0 based offset of first character.
[out] endOffset 0 based offset of one past the last character.
[out] text Returns the requested text portion. This portion may be empty or invalid when no appropriate text portion is found or text type is invalid.
Return values:
S_OK 
S_FALSE if the requested boundary type is not implemented, such as IA2_TEXT_BOUNDARY_SENTENCE, or if there is nothing to return; [out] values are 0s and NULL respectively
E_INVALIDARG if bad [in] passed, [out] values are 0s and NULL respectively


The documentation for this interface was generated from the following file:

To submit feedback on IAccessible2 API Version 1.2, please use the Bugzilla interface located at: http://bugs.linuxfoundation.org/. When using Bugzilla please be sure to select IAccessible2 from the list of components. Bugzilla is the preferred method for receiving feedback because it automatically logs one's feedback in the IAccessible2 tracking system without additional human intervention. One may also, however, send email to accessibility-rfc@a11y.org, a publicly archived emailing list. Please address any technical problems you encounter with this document or the resources to which it links, to the Open A11y Webmaster <webmaster@a11y.org>

A stable online reference version of the documentation for IAccessible2 API Version 1.2, is available at: http://a11y.org/ia2-spec. A list of known and reported errors in the documentation for IAccessible2 API Version 1.2 can be found at: http://a11y.org/ia2-errata


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