Hi,
It might be a useful syntax highlighting feature to be able to have a different background color based on the level of nesting. IE, normal background may be white, a class definition may be light grey, a public function in that class might be a darker grey, an if statement in that might... etc etc
The only example I can think of where this can be seen is Xcode.
I had a look at some of the lexing code myself, but I fear it's over my head..
This is difficult in the current Scintilla design.
There was a project called SinkWorld for looking at these sorts of features but it became too complex so was dropped:
http://www.scintilla.org/TentacleW.png