Ok, nice. So it can be done...

I see you have exactly the same problem I have.
I am using a QTabWidget, I seem to have an orrible space on the right side, which means the right scrollbar is not on the "infinite-right". I have looked into Qt-Assistant code for some ideas about how they did it, and I "borrowed" that code, but still the internal editor is way from from the sides of the window.

Again, a few questions if you do not mind:
1) "display tab as X spaces", did you implement it? If so how? if not, how are you planning?
2) The syntax highlighter. It's based on the examples from the trolls? See notes bellow.
3) Current line and match brackets. Planned...? Implemented...?

I am toying with this issue myself, and I already implemented a hack of a system for displaying and loading SL. I am currently loading parts of GtkSourceView SH definitions, and I can display in a rather good quality C/C++/C# syntaxes. I will fix the implementation I have to display DIFF and other goodies (I am still messing the implementation...). I used as a base the SH example supplied by the trolls with some spin ups.

If found that using RegEx for for the painting is extreamly painfull, as in big files (~1000 lines) text will take about 5 seconds to load. I will try to see if the code for settign the QSyntaxHighliter can be put in a QTimer::singleShot() to make this call asynchroneous and improove usability, as hack for a good SH system.

Did you write the SH yourself (as the example on Qt4.0 showed), or are you deriving QSyntaxHihlighter. In any case, how is the drawing made? (hard coded contexts or something like Kate?)