[Groff] Macro to detect end of line

[smoore]

 I have a consistently appearing extra line happening when line text
 ends right at the end of the line, and groff inserts a newline, and where
 I happen to insert a newline, I end of with two blank lines. 

 I am wondering how I might check for this ?

 I note the hp register as provided by Werner in a previous post, and I am
 sure I can get a read on the hp of my current line length and a little math 
 and Ive got a trap that I can call upon to determine whether the last line
 has triggered a new line, in which case hp will be near 0 or the page offset. 

 Hmmmm ..... 

 Seems to me there is a better and easier way to do this.