[gtkmm] Wrapping a label when it exceeds width of parent?

[Maurizio Colucci <seguso forever tin it>]

hello,

for the project   http://segusoland.sourceforge.net (see screenshots), I have 
the following widget hierarchy:

scrolled window
--viewport
----vbox1
------hbox1
--------togglebutton1
----------hbox2
------------image1
------------vbox2
--------------label_name
--------------label_dir
--------------label_size
--------------label_date
--------button1
     ....

Unfortunately, the scrolledwindow (and therefore also the viewport and vbox1) 
has a very low width, and the filenames are very long.

So I need to wrap the filenames: I need to add newlines to label_name and 
label_dir so they don't cross the right boundary of the scrolledwindow.

(Of course I tried to set the wrap flag of gtk labels, but it wraps at a fixed 
width, hard-coded. Why on earth?)

In order to wrap correctly, I must take into account:
1) the width of image1
2) the width of button1 (which can also be hidden!)
3) the current font width, and the width in pixels of a string with a given 
font
4) the width of the scrolledwindow//viewport/vbox1 in pixels

But I don't know how. I am totally clueless. I really need help about the 
techinque... I need to use pango? How? I also couldn't figure out how to get 
the pixel width of a widget, not mention the pixel width of the text redered 
so far...

I beg your help,

Maurizio