Hello Michael,
I am the author of tkrevdiff (see
http://ptktools.sourceforge.net/#tkrevdiff ) which is a Perl/Tk based
diff programm, but with another aim as Tk::DiffText, namely generating
quick diffs between revisions of a file.
I find it very helpful, especially in large files, if some kind of
indication of the diff regions is shown. In tkrevdiff, there is a small
bar beside the scrollbar (newer Tk versions) or even inside the
scrollbar (older Tk versions under X11, which had still -tile support)
which shows the diff regions (see link or attached image). Maybe you can
implement something similar?
Regards,
Slaven