control where snapping is performed.
 <p>
 The implementation handles empty geometry and empty snap vertex sets.
<P>

<P>
<DL>
<DT><B>Version:</B></DT>
  <DD>1.7</DD>
<DT><B>Author:</B></DT>
  <DD>Martin Davis</DD>
</DL>
<HR>

<P>

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