How do I resize a GtkText Widget based on line length?

["R. Bernstein" <rocky panix com>]

I have command output that I accumulate in a GtkText buffer; afterwards
I'd like to resize the lines to maybe the maximum line seen up to 
some limit.

The problem is figuring out from a line of text what size it occupies,
and then resizing the widget. How do I do?

In order to make the task precise, see gnopstree from
http://gnopstree.sourceforge.net or download via
http://sourceforge.net/project/showfiles.php?group_id=21133 build, and
click on a process and look at the popup window in that.