From 70410dfcfd38b668debf911095b28861d93134f1 Mon Sep 17 00:00:00 2001
From: Ingo Schwarze <schwarze@openbsd.org>
Date: Thu, 1 Jun 2017 19:05:37 +0000
Subject: Minimal implementation of the \h (horizontal motion) escape sequence.
 Good enough to cope with the average DocBook insanity.

---
 mandoc.c              |  2 +-
 mandoc.h              |  1 +
 mdoc_term.c           |  3 ++-
 regress/roff/esc/h.in |  4 ++--
 roff.7                |  7 ++++---
 term.c                | 22 ++++++++++++++++++++++
 6 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/mandoc.c b/mandoc.c
index 4bfe4c36..03c25e0d 100644
--- a/mandoc.c
+++ b/mandoc.c
@@ -175,7 +175,7 @@ mandoc_escape(const char **end, const char **start, int *sz)
 				++*end;
 			return ESCAPE_ERROR;
 		}
-		gly = ESCAPE_IGNORE;
+		gly = (*start)[-1] == 'h' ? ESCAPE_HORIZ : ESCAPE_IGNORE;
 		term = **start;
 		*start = ++*end;
 		break;
diff --git a/mandoc.h b/mandoc.h
index 37baee40..51290770 100644
--- a/mandoc.h
+++ b/mandoc.h
@@ -411,6 +411,7 @@ enum	mandoc_esc {
 	ESCAPE_NUMBERED, /* a numbered glyph */
 	ESCAPE_UNICODE, /* a unicode codepoint */
 	ESCAPE_NOSPACE, /* suppress space if the last on a line */
+	ESCAPE_HORIZ, /* horizontal movement */
 	ESCAPE_SKIPCHAR, /* skip the next character */
 	ESCAPE_OVERSTRIKE /* overstrike all chars in the argument */
 };
diff --git a/mdoc_term.c b/mdoc_term.c
index 585b507a..751f3702 100644
--- a/mdoc_term.c
+++ b/mdoc_term.c
@@ -407,7 +407,8 @@ print_mdoc_node(DECL_ARGS)
 	if (NODE_EOS & n->flags)
 		p->flags |= TERMP_SENTENCE;
 
-	p->offset = offset;
+	if (n->type != ROFFT_TEXT)
+		p->offset = offset;
 	p->rmargin = rmargin;
 }
 
diff --git a/regress/roff/esc/h.in b/regress/roff/esc/h.in
index 31fbb4e2..4bc1953e 100644
--- a/regress/roff/esc/h.in
+++ b/regress/roff/esc/h.in
@@ -7,11 +7,11 @@
 .Sh DESCRIPTION
 simple: >\h'0'<
 .br
-escape only: >\h'\w'\&''<
+escape only: >\h'\w'\&'M'<
 .br
 escape at the end: >\h'0+\w'\&''<
 .br
-escape at the beginning: >\h'\w'\&'+0'<
+escape at the beginning: >\h'\w'\&'M+0'<
 .br
 escape in the middle: >\h'0+\w'\&'+0'<
 .br
diff --git a/roff.7 b/roff.7
index 6dc1c1de..464ee2ad 100644
--- a/roff.7
+++ b/roff.7
@@ -1925,9 +1925,10 @@ and
 .Ss \eH\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
 Set the height of the current font; ignored by
 .Xr mandoc 1 .
-.Ss \eh\(aq Ns Ar number Ns \(aq
-Horizontal motion; ignored by
-.Xr mandoc 1 .
+.Ss \eh\(aq Ns Ar width Ns \(aq
+Horizontal motion relative to the current position.
+The default scaling unit is
+.Cm m .
 .Ss \ek[ Ns Ar name ]
 Mark horizontal input place in register; ignored by
 .Xr mandoc 1 .
diff --git a/term.c b/term.c
index e52ba40c..2c8aa7c6 100644
--- a/term.c
+++ b/term.c
@@ -400,6 +400,7 @@ term_fontpop(struct termp *p)
 void
 term_word(struct termp *p, const char *word)
 {
+	struct roffsu	 su;
 	const char	 nbrsp[2] = { ASCII_NBRSP, 0 };
 	const char	*seq, *cp;
 	int		 sz, uc;
@@ -488,6 +489,27 @@ term_word(struct termp *p, const char *word)
 			else if (*word == '\0')
 				p->flags |= (TERMP_NOSPACE | TERMP_NONEWLINE);
 			continue;
+		case ESCAPE_HORIZ:
+			if (a2roffsu(seq, &su, SCALE_EM) == 0)
+				continue;
+			uc = term_hspan(p, &su) / 24;
+			if (uc > 0)
+				while (uc-- > 0)
+					bufferc(p, ASCII_NBRSP);
+			else if (p->col > (size_t)(-uc))
+				p->col += uc;
+			else {
+				uc += p->col;
+				p->col = 0;
+				if (p->offset > (size_t)(-uc)) {
+					p->ti += uc;
+					p->offset += uc;
+				} else {
+					p->ti -= p->offset;
+					p->offset = 0;
+				}
+			}
+			continue;
 		case ESCAPE_SKIPCHAR:
 			p->flags |= TERMP_BACKAFTER;
 			continue;
-- 
cgit