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ITextRangeProvider::ExpandToEnclosingUnit method

Normalizes the text range by the specified text unit. The range is expanded if it is smaller than the specified unit, or shortened if it is longer than the specified unit.


HRESULT ExpandToEnclosingUnit(
  [in] TextUnit unit


unit [in]

Type: TextUnit

The type of text units, such as character, word, paragraph, and so on.

Return value


If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.


Client applications such as screen readers use this method to retrieve the full word, sentence, or paragraph that exists at the insertion point or caret position.

Despite its name, the ITextRangeProvider::ExpandToEnclosingUnit method does not necessarily expand a text range. Instead, it "normalizes" a text range by moving the endpoints so that the range encompasses the specified text unit. The range is expanded if it is smaller than the specified unit, or shortened if it is longer than the specified unit. If the range is already an exact quantity of the specified units, it remains unchanged. It is critical that the ExpandToEnclosingUnit method always normalizes text ranges in a consistent manner; otherwise, other aspects of text range manipulation by text unit would be unpredictable. The following diagram shows how ExpandToEnclosingUnit normalizes a text range by moving the endpoints of the range.

Diagram showing endpoint positions before and after a call to ExpandToEnclosingUnit

ExpandToEnclosingUnit defaults to the next largest text unit supported if the specified text unit is not supported by the control. The order, from smallest unit to largest, is as follows:

  • Character
  • Format
  • Word
  • Line
  • Paragraph
  • Page
  • Document

ExpandToEnclosingUnit respects both visible and hidden text.

Range behavior when unit is TextUnit::Format

TextUnit::Format as a unit value positions the boundary of a text range to expand or move the range based on shared text attributes (format) of the text within the range. However, using the format text unit should not move or expand a text range across the boundary of an embedded object, such as an image or hyperlink. For more info, see UI Automation Text Units or Text and TextRange Control Patterns.


Minimum supported client

Windows XP [desktop apps | Windows Store apps]

Minimum supported server

Windows Server 2003 [desktop apps | Windows Store apps]


UIAutomationCore.h (include UIAutomation.h)



See also

UI Automation Providers Overview
Text and TextRange Control Patterns



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