Repainting question for my syntax highlighter

Question

Hello there,
I have a syntax highlighter which reuses much of the very useful code developed by Claude Dugauy, which can be found at http://www.fawcette.com/javapro/2003_07/magazine/columns/visualcomponents/default_pf.aspx
. The syntax highlighting uses regular expressions, so its easily extendable to meet your needs.
However, there is one problem: whenever the user presses a key, the whole of the TextPane containing the highlighted text, is repainted in its entirety. This is fine for small amounts of text to be highlighted, but is very slow when it comes to 1000+ lines.
Please could someone be so excellent as to tell me how to go about addressing this problem, so that only a small amount of text is repainted whenever the user types something into the TextPane e.g. that inside the current viewport, or just the last typed word - thus removing this problem of inefficiency.
Thanks in advance,
Edd.

Answer 1

I don't think it's going to be that easy. Every time a change is made, the default style is applied to the whole document, then the whole document is copied into a String so it can be reparsed and have the syntax styles applied again. Even if you could limit what actually gets painted, you'd still have all that unnecessary work going on.
You could try forcing the highlighter to only reparse a portion of the document--like,say, a hundred lines before and after the point where the edit occurred--but deciding exactly where to start and stop can be pretty tricky.