Well, if there are no line-breaks it is just one line - even if it is displayed in more then 1 line on your screen (which just means that it is not wide enough

)
Or in other words: It is not possible to determine which text length is "one line", as this depends on screen width.
The only way would to specify what "one line" shold be is to specify that it should be max. xx characters.
But one has to keep in mind that if this is based on a 1024x768 resolution, it will be much less then "one line" for somebody using 1600x1200 for example.