<summary>
Get a block of text starting at the specified text position.
Returning NULL indicates the end of text - the position is after
the last character. This function is called iteratively for
each consecutive block, tying together several fragmented blocks
in the backing store into a virtual contiguous string.
</summary>
<param name="textPosition">First position of the piece to obtain. All
positions are in UTF16 code-units, not whole characters, which
matters when supplementary characters are used.</param>
<param name="textString">Address that receives a pointer to the text block
at the specified position.</param>
<param name="textLength">Number of UTF16 units of the retrieved chunk.
The returned length is not the length of the block, but the length
remaining in the block, from the given position until its end.
So querying for a position that is 75 positions into a 100
position block would return 25.</param>
<returns>Pointer to the first character at the given text position.
NULL indicates no chunk available at the specified position, either
because textPosition >= the entire text content length or because the
queried position is not mapped into the app's backing store.</returns>
<remarks>
Although apps can implement sparse textual content that only maps part of
the backing store, the app must map any text that is in the range passed
to any analysis functions.
</remarks>
<summary> Get a block of text starting at the specified text position. Returning NULL indicates the end of text - the position is after the last character. This function is called iteratively for each consecutive block, tying together several fragmented blocks in the backing store into a virtual contiguous string. </summary> <param name="textPosition">First position of the piece to obtain. All positions are in UTF16 code-units, not whole characters, which matters when supplementary characters are used.</param> <param name="textString">Address that receives a pointer to the text block at the specified position.</param> <param name="textLength">Number of UTF16 units of the retrieved chunk. The returned length is not the length of the block, but the length remaining in the block, from the given position until its end. So querying for a position that is 75 positions into a 100 position block would return 25.</param> <returns>Pointer to the first character at the given text position. NULL indicates no chunk available at the specified position, either because textPosition >= the entire text content length or because the queried position is not mapped into the app's backing store.</returns> <remarks> Although apps can implement sparse textual content that only maps part of the backing store, the app must map any text that is in the range passed to any analysis functions. </remarks>