Re: [Groff] Odd adjusting behavior

[Deri James]

On Saturday 03 July 2010 00:31:20 brian m. carlson wrote:
> I'm working on autogenerating some troff input for a project of mine,
> but I found some very odd behavior with the ad request.  My testcase is
> attached.  If you run groff with -rTC=1, my name is properly centered
> and in italics (as desired).  However, if you do not, my name is left
> adjusted.
> 

I believe groff does not "action" the .ad request until it is about to output 
the line (makes sense since it needs to know total width of text before 
centreing).

I can think of 3 circumstances when groff can output a line:-

a) while adding words to the output line and the current line length is 
exceeded.

b) a specific .br or .fl is executed.

c) another command is executed which implies a break (EXCEPT when introduced 
by apostrophe instead of period)

As all the commands after "brian m. carlson" are introduced with apostrophes 
no breaks occur until the final .br (at which time .ad b is in effect rather 
than the earlier .ad c).

If you replace all the apostrophes with periods all works as you desire 
because the .ft  R causes an implied break (at which point .ad c is in 
effect).

> It seems a little odd to me that a break *after* the text, but *before*
> another change of adjustment is required to make this work.  Is this
> behavior intentional?

Normally .ad implies a break (so line would be flushed out with previous 
justification before switching to new justification for following text),  but 
using 'ad suppresses the implied break so becomes the new justification for  
the current line when it eventually gets flushed out and justification is 
applied.

Cheers

Deri