🚀 go-pugleaf

In article <8172@xenna.Xylogics.COM>, loverso@Xylogics.COM (John Robert LoVerso) writes:
> I haven't tracked down in the code the bug, but I have found it.  Feed
> the following to psroff/ptroff/ditroff with -me:
> 
> 	.ce
> 	this is a test
> 	.(c
> 	this is a test
> 	.)c
> 
> The bug is that the line centered by .ce will be correctly center,
> while the block centered by .(c .)c will be off center!  I tracked
> this down to the line following line from the .)c macro in tmac.e:
> 
> 	.in (\\n(.lu-\\n(.iu-\\n(dlu)/2u
> 
> If you replace the .l with $l, as thus:
> 
> 	.in (\\n($lu-\\n(.iu-\\n(dlu)/2u
> 
> then both of the two lines above get centered correctly!  However,
> prior to the .in, .l and $l have identical values.

The problem is that the indentation computation line shown above
is done in environment 1, in which the line length has (at least
in the default case) a value different from that in environment 0,
whereas the value of the number register $l is global to both
environments, so its use produces the correct centering.
Prior to use of the macros, $l and .l have the same values
because the test is made in environment 0.

I guess we must call this a bug in the -me macros for failing to use
the "correct" line length when computing the indentation for centering
in the )c macro.  It is NOT a bug in troff.
-- 
Walt Brainerd  Unicomp, Inc.           brainerd@unmvax.cs.unm.edu
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