shorten menu item

Sometimes the title of a page is so long, that it cant fit into width of menu and the text of title in menu is then collapsed and unreadable. Is it possible somehow do the following thing?:

if title lenght > 20:
   title = title [:20]+"..."

I was looking for a plugin –> nothing is here. I could do it manually in menu widget, but seems to me more professional that this could be done by php itself.

Thank you