code: function onHover( evt ) {
  								evt = evt.data.$;
  								if ( textRng ) {
  									// Read the current cursor.
  									var rngEnd = body.$.createTextRange();
  
  									moveRangeToPoint( rngEnd, evt.clientX, evt.clientY );
  
  									// Handle drag directions.
  									textRng.setEndPoint(
  										startRng.compareEndPoints( 'StartToStart', rngEnd ) < 0 ?
  										'EndToEnd' : 'StartToStart', rngEnd );
  
  									// Update selection with new range.
  									textRng.select();
  								}
  							}
docs: Expand the text range along with mouse move.