Flex TextArea Track Changes, highlight

Last week I was given an assignment to provide highlight effect on certain text ranges in a flex text area. The purpose of this was to first allow a highlighting certain words as spelling mistakes and second to allow highlighting added and deleted text ranges. The spelling checker. The idea of highlighting a text range is not new, its basically finding the position of the first and last character in a range. Getting their boundary rectangles and the reset is just graphics. I developed three basic highlighting effects
1. The normal text background highlight
2. The strike-through highlight
3. The spelling mistake highlight like that of Microsoft word