Break long programlisting lines without spaces?

[Peter Desjardins <peter.desjardins.us@gmail.com>]

Hi. I'm producing PDF and XHTML from DocBook using Saxon 6.5.5 and FOP 1.0.

Some of my programlistings include long lines of code or sample
output. I configured my customization layer to break long lines at
spaces as described here. It works wonderfully.

http://www.sagehill.net/docbookxsl/FittingText.html#BreakLongLines

The remaining long lines occur at unbroken strings of characters. I
have some that are long enough to spill off the paper in PDF. Is there
any way to break lines at spaces where they exist and then set a
maximum line length at which the line must be forcibly broken?

Has anyone developed a customization that will do this?

Thanks for your help.

Peter Desjardins