code: public int getSeqPos(int aligSeq, Point p) {
  
  		int x = p.x - DEFAULT_X_SPACE - DEFAULT_LEGEND_SIZE;
  		int y = p.y - DEFAULT_Y_SPACE ;
  
  		y -=  (DEFAULT_LINE_SEPARATION * aligSeq) - DEFAULT_CHAR_SIZE;
  
  		int lineNr = y / DEFAULT_Y_STEP;
  		int linePos = x / DEFAULT_CHAR_SIZE;
  		return lineNr * DEFAULT_LINE_LENGTH + linePos ;
  
  	}
docs: Convert from an X position in the JPanel to the position
  in the sequence alignment.
  
  @param aligSeq sequence number
  @param p point on panel
  @return the sequence position for a point on the Panel