[bug #61710] $v and $V are in the wrong namespace

[Dave]

URL:
  <https://savannah.gnu.org/bugs/?61710>

                 Summary: $v and $V are in the wrong namespace
                 Project: GNU troff
            Submitted by: barx
            Submitted on: Mon 20 Dec 2021 07:13:58 PM CST
                Category: Macro - me
                Severity: 2 - Minor
              Item Group: Documentation
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

(This bug is sort of a counterpart to bug #61683 and a cousin to bug #61314.)

The "me Reference Manual" says, "Registers and strings with names of the form
$x may be used in expressions and text but should not be changed."  For most
of them, this makes sense: they store values that are set by invoking specific
-me macros.

However, $v and $V (and seemingly $r and $R, the undocumented registers of bug
#61683) are exceptions to this: the macro package provides no way* to set the
line spacing other than by changing those registers directly.  Indeed, e.tmac
initializes $v and $V to default values but otherwise never sets them (aside
from the special case quoted in #61683 where $r or $R is set), meaning it is
up to the user to change them if she cares to.  So they violate the manual's
general edict concerning $-named registers.

It probably doesn't make much sense to rename them at this stage, so maybe
that sentence in the reference manual needs to carve out a $v/$V exception. 
Alternately (and more complicatedly), new registers in the correct namespace
could be defined for new -me documents, keeping $v and $V around only for back
compatibility.

* No sanctioned way, that is.  The user can call the low-level roff request
.vs, but this request is not on -me's "use with impunity" list" -- which makes
sense, because any line spacing the user set this way would get clobbered next
time -me set it from $v or $V.




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