Merge OpenBSD mdoc.7 rev. 1.56 and 1.57:

Define the terms "callable" and "parsed" with more precision.
Be more specific about what .Xo can be used for.
Be more specific about what "historic groff" refers to.
Explicitely mention the nine argument limit below COMPATIBILITY.
feedback and ok jmc@

1 files changed, 25 insertions, 15 deletions

diff --git a/mdoc.7 b/mdoc.7
index 8f58cdd3..7b5bae25 100644
--- a/mdoc.7
+++ b/mdoc.7
@@ -1,4 +1,4 @@
-.\"	$Id$
+.\"	$OpenBSD: mdoc.7,v 1.56 2010/11/28 15:45:26 schwarze Exp $
 .\"
 .\" Copyright (c) 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
 .\" Copyright (c) 2010 Ingo Schwarze <schwarze@openbsd.org>
@@ -604,20 +604,21 @@ closes it out.
 .Pp
 The
 .Em Callable
-column indicates that the macro may be called subsequent to the initial
-line-macro.
-If a macro is not callable, then its invocation after the initial line
-macro is interpreted as opaque text, such that
+column indicates that the macro may also be called by passing its name
+as an argument to another macro.
+If a macro is not callable but its name appears as an argument
+to another macro, it is interpreted as opaque text.
+For example,
 .Sq \&.Fl \&Sh
 produces
 .Sq Fl \&Sh .
 .Pp
 The
 .Em Parsed
-column indicates whether the macro may be followed by further
-(ostensibly callable) macros.
-If a macro is not parsed, subsequent macro invocations on the line
-will be interpreted as opaque text.
+column indicates whether the macro may call other macros by receiving
+their names as arguments.
+If a macro is not parsed but the name of another macro appears
+as an argument, it is interpreted as opaque text.
 .Pp
 The
 .Em Scope
@@ -2665,9 +2666,13 @@ and
 Close a scope opened by
 .Sx \&Xo .
 .Ss \&Xo
-Open an extension scope.
-This macro originally existed to extend the 9-argument limit of troff;
-since this limit has been lifted, the macro has been deprecated.
+Extend the header of an
+.Sx \&It
+macro or the body of a partial-implicit block macro
+beyond the end of the input line.
+This macro originally existed to work around the 9-argument limit
+of historic
+.Xr roff 7 .
 .Ss \&Xr
 Link to another manual
 .Pq Qq cross-reference .
@@ -2721,10 +2726,10 @@ troff implementations, at this time limited to GNU troff
 .Pq Qq groff .
 The term
 .Qq historic groff
-refers to groff versions before the
+refers to groff versions before 1.17,
+which featured a significant update of the
 .Pa doc.tmac
-file re-write
-.Pq somewhere between 1.15 and 1.19 .
+file.
 .Pp
 Heirloom troff, the other significant troff implementation accepting
 \-mdoc, is similar to historic groff.
@@ -2815,6 +2820,11 @@ can only be called by other macros, but not at the beginning of a line.
 .Sx \&%C
 is not implemented.
 .It
+Historic groff only allows up to eight or nine arguments per macro input
+line, depending on the exact situation.
+Providing more arguments causes garbled output.
+The number of arguments on one input line is not limited with mandoc.
+.It
 Historic groff has many un-callable macros.
 Most of these (excluding some block-level macros) are callable
 in new groff and mandoc.