Gtk::Label, how can I calculate what would be the actual length, if given a specific string?

[ming deng <mingd oeone com>]

I use Gtk Label object in my program. I want to do some adjustments to
the string characters, like line wrapping by my own(not by default). So
I need a program to calculate the final display length(in dot) of the
string before I get them showed.

Thanks,

Ming