Implement the roff(7) .nop (no operation) request.

Examples of manual pages (ab)using it
include groff(7), chem(1), groff_mom(7), and groff_hdtbl(7).

3 files changed, 18 insertions, 8 deletions

diff --git a/TODO b/TODO
index 2ba832c2..90815dff 100644
--- a/TODO
+++ b/TODO
@@ -38,9 +38,6 @@ are mere guesses, and some may be wrong.
 
 --- missing roff features ----------------------------------------------
 
-- .nop prints its arguments as text,
-  see groff(7) for an example
-
 - .ft CB selects constant-width bold font
   see groff_out(7) for examples
 
diff --git a/roff.7 b/roff.7
index b7f499d9..f7036ef4 100644
--- a/roff.7
+++ b/roff.7
@@ -206,7 +206,7 @@ Unescaped trailing spaces are stripped from text line input unless in a
 literal context.
 In general, trailing whitespace on any input line is discouraged for
 reasons of portability.
-In the rare case that a blank character is needed at the end of an
+In the rare case that a space character is needed at the end of an
 input line, it may be forced by
 .Sq \e\ \e& .
 .Pp
@@ -665,7 +665,7 @@ produces
 .Pp
 in the input stream, and thus in the output: \fI\^XtFree\^\fP.
 Each occurrence of \e\e$* is replaced with all the arguments,
-joined together with single blank characters.
+joined together with single space characters.
 .Pp
 Since macros and user-defined strings share a common string table,
 defining a macro
@@ -1346,8 +1346,11 @@ Currently unsupported.
 Temporarily turn off line numbering.
 Currently unsupported.
 .It Ic \&nop Ar body
-Execute the rest of the input line as a request or macro line.
-Currently unsupported.
+Execute the rest of the input line as a request, macro, or text line,
+skipping the
+.Ic \&nop
+request and any space characters immediately following it.
+This is mostly used to indent text lines inside macro definitions.
 .It Ic \&nr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression Op Ar stepsize
 Define or change a register.
 A register is an arbitrary string value that defines some sort of state,
diff --git a/roff.c b/roff.c
index c6d7dad1..dde46486 100644
--- a/roff.c
+++ b/roff.c
@@ -197,6 +197,7 @@ static	enum rofferr	 roff_line_ignore(ROFF_ARGS);
 static	void		 roff_man_alloc1(struct roff_man *);
 static	void		 roff_man_free1(struct roff_man *);
 static	enum rofferr	 roff_manyarg(ROFF_ARGS);
+static	enum rofferr	 roff_nop(ROFF_ARGS);
 static	enum rofferr	 roff_nr(ROFF_ARGS);
 static	enum rofferr	 roff_onearg(ROFF_ARGS);
 static	enum roff_tok	 roff_parse(struct roff *, char *, int *,
@@ -490,7 +491,7 @@ static	struct roffmac	 roffs[TOKEN_NONE] = {
 	{ roff_line_ignore, NULL, NULL, 0 },  /* nhychar */
 	{ roff_unsupp, NULL, NULL, 0 },  /* nm */
 	{ roff_unsupp, NULL, NULL, 0 },  /* nn */
-	{ roff_unsupp, NULL, NULL, 0 },  /* nop */
+	{ roff_nop, NULL, NULL, 0 },  /* nop */
 	{ roff_nr, NULL, NULL, 0 },  /* nr */
 	{ roff_unsupp, NULL, NULL, 0 },  /* nrf */
 	{ roff_line_ignore, NULL, NULL, 0 },  /* nroff */
@@ -3161,6 +3162,15 @@ roff_eo(ROFF_ARGS)
 }
 
 static enum rofferr
+roff_nop(ROFF_ARGS)
+{
+	while (buf->buf[pos] == ' ')
+		pos++;
+	*offs = pos;
+	return ROFF_RERUN;
+}
+
+static enum rofferr
 roff_tr(ROFF_ARGS)
 {
 	const char	*p, *first, *second;