Rounding rules for horizontal scaling widths are more complicated.

There is a first rounding to basic units on the input side.
After that, rounding rules differ between requests and macros.
Requests round to the nearest possible character position.
Macros round to the next character position to the left.

Implement that by changing the return value of term_hspan()
to basic units and leaving the second scaling and rounding stage
to the formatters instead of doing it in the terminal handler.

Improves for example argtable2(3).

6 files changed, 38 insertions, 44 deletions

diff --git a/man_term.c b/man_term.c
index d0dd4263..e1f37d99 100644
--- a/man_term.c
+++ b/man_term.c
@@ -427,7 +427,7 @@ pre_in(DECL_ARGS)
 	if ( ! a2roffsu(++cp, &su, SCALE_EN))
 		return(0);
 
-	v = term_hspan(p, &su);
+	v = (term_hspan(p, &su) + 11) / 24;
 
 	if (less < 0)
 		p->offset -= p->offset > v ? v : p->offset;
@@ -512,7 +512,7 @@ pre_HP(DECL_ARGS)
 
 	if ((nn = n->parent->head->child) != NULL &&
 	    a2roffsu(nn->string, &su, SCALE_EN)) {
-		len = term_hspan(p, &su);
+		len = term_hspan(p, &su) / 24;
 		if (len < 0 && (size_t)(-len) > mt->offset)
 			len = -mt->offset;
 		else if (len > SHRT_MAX)
@@ -597,7 +597,7 @@ pre_IP(DECL_ARGS)
 	if ((nn = n->parent->head->child) != NULL &&
 	    (nn = nn->next) != NULL &&
 	    a2roffsu(nn->string, &su, SCALE_EN)) {
-		len = term_hspan(p, &su);
+		len = term_hspan(p, &su) / 24;
 		if (len < 0 && (size_t)(-len) > mt->offset)
 			len = -mt->offset;
 		else if (len > SHRT_MAX)
@@ -679,7 +679,7 @@ pre_TP(DECL_ARGS)
 	if ((nn = n->parent->head->child) != NULL &&
 	    nn->string != NULL && ! (MAN_LINE & nn->flags) &&
 	    a2roffsu(nn->string, &su, SCALE_EN)) {
-		len = term_hspan(p, &su);
+		len = term_hspan(p, &su) / 24;
 		if (len < 0 && (size_t)(-len) > mt->offset)
 			len = -mt->offset;
 		else if (len > SHRT_MAX)
@@ -868,7 +868,7 @@ pre_RS(DECL_ARGS)
 	n = n->parent->head;
 	n->aux = SHRT_MAX + 1;
 	if (n->child != NULL && a2roffsu(n->child->string, &su, SCALE_EN))
-		n->aux = term_hspan(p, &su);
+		n->aux = term_hspan(p, &su) / 24;
 	if (n->aux < 0 && (size_t)(-n->aux) > mt->offset)
 		n->aux = -mt->offset;
 	else if (n->aux > SHRT_MAX)
diff --git a/mdoc_term.c b/mdoc_term.c
index 55598c4f..c4745c29 100644
--- a/mdoc_term.c
+++ b/mdoc_term.c
@@ -533,7 +533,7 @@ a2width(const struct termp *p, const char *v)
 		SCALE_HS_INIT(&su, term_strlen(p, v));
 		su.scale /= term_strlen(p, "0");
 	}
-	return(term_hspan(p, &su));
+	return(term_hspan(p, &su) / 24);
 }
 
 /*
diff --git a/term.c b/term.c
index b1360388..b46659bd 100644
--- a/term.c
+++ b/term.c
@@ -619,8 +619,7 @@ void
 term_setwidth(struct termp *p, const char *wstr)
 {
 	struct roffsu	 su;
-	size_t		 width;
-	int		 iop;
+	int		 iop, width;
 
 	iop = 0;
 	width = 0;
@@ -831,11 +830,12 @@ term_vspan(const struct termp *p, const struct roffsu *su)
 	return(ri < 66 ? ri : 1);
 }
 
+/*
+ * Convert a scaling width to basic units, rounding down.
+ */
 int
 term_hspan(const struct termp *p, const struct roffsu *su)
 {
-	double		 v;
 
-	v = (*p->hspan)(p, su);
-	return(v > 0.0 ? v + 0.0005 : v - 0.0005);
+	return((*p->hspan)(p, su));
 }
diff --git a/term.h b/term.h
index b6bd13bf..5b5fcc95 100644
--- a/term.h
+++ b/term.h
@@ -95,9 +95,9 @@ struct	termp {
 	void		(*end)(struct termp *);
 	void		(*endline)(struct termp *);
 	void		(*advance)(struct termp *, size_t);
-	void		(*setwidth)(struct termp *, int, size_t);
+	void		(*setwidth)(struct termp *, int, int);
 	size_t		(*width)(const struct termp *, int);
-	double		(*hspan)(const struct termp *,
+	int		(*hspan)(const struct termp *,
 				const struct roffsu *);
 	const void	 *argf;		/* arg for headf/footf */
 	struct termp_ps	 *ps;
diff --git a/term_ascii.c b/term_ascii.c
index cbc9c9ea..908f3182 100644
--- a/term_ascii.c
+++ b/term_ascii.c
@@ -40,7 +40,7 @@
 
 static	struct termp	 *ascii_init(enum termenc, const struct mchars *,
 				const struct manoutput *);
-static	double		  ascii_hspan(const struct termp *,
+static	int		  ascii_hspan(const struct termp *,
 				const struct roffsu *);
 static	size_t		  ascii_width(const struct termp *, int);
 static	void		  ascii_advance(struct termp *, size_t);
@@ -48,7 +48,7 @@ static	void		  ascii_begin(struct termp *);
 static	void		  ascii_end(struct termp *);
 static	void		  ascii_endline(struct termp *);
 static	void		  ascii_letter(struct termp *, int);
-static	void		  ascii_setwidth(struct termp *, int, size_t);
+static	void		  ascii_setwidth(struct termp *, int, int);
 
 #if HAVE_WCHAR
 static	void		  locale_advance(struct termp *, size_t);
@@ -137,15 +137,16 @@ locale_alloc(const struct mchars *mchars, const struct manoutput *outopts)
 }
 
 static void
-ascii_setwidth(struct termp *p, int iop, size_t width)
+ascii_setwidth(struct termp *p, int iop, int width)
 {
 
+	width /= 24;
 	p->rmargin = p->defrmargin;
 	if (iop > 0)
 		p->defrmargin += width;
 	else if (iop == 0)
-		p->defrmargin = width ? width : p->lastrmargin;
-	else if (p->defrmargin > width)
+		p->defrmargin = width ? (size_t)width : p->lastrmargin;
+	else if (p->defrmargin > (size_t)width)
 		p->defrmargin -= width;
 	else
 		p->defrmargin = 0;
@@ -218,52 +219,45 @@ ascii_advance(struct termp *p, size_t len)
 		putchar(' ');
 }
 
-static double
+static int
 ascii_hspan(const struct termp *p, const struct roffsu *su)
 {
 	double		 r;
 
-	/*
-	 * Approximate based on character width.
-	 * None of these will be actually correct given that an inch on
-	 * the screen depends on character size, terminal, etc., etc.
-	 */
 	switch (su->unit) {
 	case SCALE_BU:
-		r = su->scale * 10.0 / 240.0;
+		r = su->scale;
 		break;
 	case SCALE_CM:
-		r = su->scale * 10.0 / 2.54;
+		r = su->scale * 240.0 / 2.54;
 		break;
 	case SCALE_FS:
-		r = su->scale * 2730.666;
+		r = su->scale * 65536.0;
 		break;
 	case SCALE_IN:
-		r = su->scale * 10.0;
+		r = su->scale * 240.0;
 		break;
 	case SCALE_MM:
-		r = su->scale / 100.0;
+		r = su->scale * 0.24;
 		break;
+	case SCALE_VS:
+		/* FALLTHROUGH */
 	case SCALE_PC:
-		r = su->scale * 10.0 / 6.0;
+		r = su->scale * 40.0;
 		break;
 	case SCALE_PT:
-		r = su->scale * 10.0 / 72.0;
-		break;
-	case SCALE_VS:
-		r = su->scale * 2.0 - 1.0;
+		r = su->scale * 10.0 / 3.0;
 		break;
 	case SCALE_EN:
 		/* FALLTHROUGH */
 	case SCALE_EM:
-		r = su->scale;
+		r = su->scale * 24.0;
 		break;
 	default:
 		abort();
 		/* NOTREACHED */
 	}
-
-	return(r);
+	return(r > 0.0 ? r + 0.01 : r - 0.01);
 }
 
 const char *
diff --git a/term_ps.c b/term_ps.c
index c819b55f..726af23f 100644
--- a/term_ps.c
+++ b/term_ps.c
@@ -87,7 +87,7 @@ struct	termp_ps {
 	size_t		  pdfobjsz;	/* size of pdfobjs */
 };
 
-static	double		  ps_hspan(const struct termp *,
+static	int		  ps_hspan(const struct termp *,
 				const struct roffsu *);
 static	size_t		  ps_width(const struct termp *, int);
 static	void		  ps_advance(struct termp *, size_t);
@@ -106,7 +106,7 @@ __attribute__((__format__ (__printf__, 2, 3)))
 static	void		  ps_printf(struct termp *, const char *, ...);
 static	void		  ps_putchar(struct termp *, char);
 static	void		  ps_setfont(struct termp *, enum termfont);
-static	void		  ps_setwidth(struct termp *, int, size_t);
+static	void		  ps_setwidth(struct termp *, int, int);
 static	struct termp	 *pspdf_alloc(const struct mchars *,
 				const struct manoutput *);
 static	void		  pdf_obj(struct termp *, size_t);
@@ -620,7 +620,7 @@ pspdf_alloc(const struct mchars *mchars, const struct manoutput *outopts)
 }
 
 static void
-ps_setwidth(struct termp *p, int iop, size_t width)
+ps_setwidth(struct termp *p, int iop, int width)
 {
 	size_t	 lastwidth;
 
@@ -628,8 +628,8 @@ ps_setwidth(struct termp *p, int iop, size_t width)
 	if (iop > 0)
 		p->ps->width += width;
 	else if (iop == 0)
-		p->ps->width = width ? width : p->ps->lastwidth;
-	else if (p->ps->width > width)
+		p->ps->width = width ? (size_t)width : p->ps->lastwidth;
+	else if (p->ps->width > (size_t)width)
 		p->ps->width -= width;
 	else
 		p->ps->width = 0;
@@ -1273,7 +1273,7 @@ ps_width(const struct termp *p, int c)
 	return((size_t)fonts[(int)TERMFONT_NONE].gly[c].wx);
 }
 
-static double
+static int
 ps_hspan(const struct termp *p, const struct roffsu *su)
 {
 	double		 r;
@@ -1325,7 +1325,7 @@ ps_hspan(const struct termp *p, const struct roffsu *su)
 		break;
 	}
 
-	return(r);
+	return(r * 24.0);
 }
 
 static void