Overflow JTextPane

Question

I've got a task that I can't quite wrap my head around. I have a few thoughts on how to proceed but no sense of which idea might be better. I was hoping more experienced Swing developers might have some suggestions about these or better ways to proceed.
The task is to build a component which might look most like two stacked JTextPanes with a shared document. The top one would be editable, and would give a WYSIWYG view of their final output. The bottom one would be an overflow area. If the user types or pastes content that doesn't fit into the top one, it would automatically move to the bottom. There would be some kind of visual cue -- just the border, or a gray background area -- to distinguish for the users the content that won't show up in their final output from the content that will.
On another thread I posted the solutions I came up with for the first pass of this process: using a document that didn't let the user type or paste anything that would cause it to overflow the bounds of the JTextComponent holding it. (See http://forum.java.sun.com/thread.jsp?forum=57&thread=165787 if you are interested.) For the second pass I have to go a bit further and allow the user to actually enter this content, but give a visual clue about what portion of the content will be visible in the final format. The document will eventually be printed on a predefined area on a paper statement, so it cannot exceed certain bounds.
One approach I've considered is a filter on the StyledDocument, a class which implements the Document interface but which delegates all the adds, deletes, etc. to a StyleDocument member variable. One of these could somehow maintain its endpoint as a Position in its delegate. A second could use that same Position as its beginning. I have some sense of how this might work, but it is still a bit fuzzy.
Another approach would be to use a document for the top Textpane that, when something is added that will overflow the Textpane, removes the offending part and adds it to the beginning of the document in the bottom Textpane. Of course I would have to reverse this for deletes. I would have to do similar work when any characteristic is changed, e.g. font size. This strikes me as trickier to work than the first approach, and a lot more error-prone, but the way to do it is a little more clear in my head.
A third approach seems likely the best one, if I only knew something about how to implement it. If I understood Views and ViewFactories a bit better, I might be able to create different Views from the same document, one for the content that will fit in the required boundaries, and one for the remainder. Unfortunately, I haven't yet made much sense out of these classes. If anyone could supply a good reference, I would really appreciate it.
The final approach is outside the bounds of what I've so far done with Swing, but might actually not be that hard: Extend JTextPane in such a way that I can simply add a separator line at the bottom of the acceptable area. This just came to me now as I write this request, and I haven't had much time to consider it, but maybe this would make life much easier. Hmmm.
I would appreciate any feedback you can give about my suggested approaches or other ones I should consider.
Yours,
-- Scott Sauyet

Answer 1

I do have to get that book. Several people have recommended it. Someone on my recent project, after I sweated days over getting the first pass at this right, told me that the Topley book said that my preferred approach (I created several) was also the preferred approach given in this book. My answer was "Why didn't you tell me what was suggested in the book before I spent all this time?!"
And yes, I need to limit the real-estate occupied by the document. I don't care if it is two characters or two million, as long as it fits in a box of the right dimensions.
Thanks for the suggestion. Let me see if I can convince my boss to buy the book...
-- Scott