Let's try this. It's BUGGERED.

src/cmd/troff/n6.c

@@ -0,0 +1,362 @@
+#include "tdef.h"
+#include "ext.h"
+#include "fns.h"
+#include <ctype.h>
+
+/*
+ * n6.c -- width functions, sizes and fonts
+*/
+
+n_width(Tchar j)
+{
+	int i, k;
+
+	if (iszbit(j))
+		return 0;
+	if (ismot(j)) {
+		if (isvmot(j))
+			return(0);
+		k = absmot(j);
+		if (isnmot(j))
+			k = -k;
+		return(k);
+	}
+	i = cbits(j);
+	if (i < ' ') {
+		if (i == '\b')
+			return(-widthp);
+		if (i == PRESC)
+			i = eschar;
+		else if (i == HX)
+			return(0);
+	}
+	if (i == ohc)
+		return(0);
+	i = trtab[i];
+	if (i < ' ')
+		return(0);
+	if (i >= t.tfont.nchars)	/* not on the font */
+		k = t.Char;		/* really ought to check properly */
+	else
+		k = t.tfont.wp[i].wid * t.Char;
+	widthp = k;
+	return(k);
+}
+
+
+Tchar n_setch(int c)
+{
+	return t_setch(c);
+}
+
+Tchar n_setabs(void)	/* set absolute char from \N'...' */
+{			/* for now, a no-op */
+	return t_setabs();
+}
+
+int n_findft(int i)
+{
+	int k;
+
+	if ((k = i - '0') >= 0 && k <= nfonts && k < smnt)
+		return(k);
+	for (k = 0; fontlab[k] != i; k++)
+		if (k > nfonts)
+			return(-1);
+	return(k);
+}
+
+
+
+void n_mchbits(void)
+{
+	chbits = 0;
+	setfbits(chbits, font);
+	sps = width(' ' | chbits);
+}
+
+
+void n_setps(void )
+{
+	int i, j;
+
+	i = cbits(getch());
+	if (isdigit(i)) {		/* \sd or \sdd */
+		i -= '0';
+		if (i == 0)		/* \s0 */
+			;
+		else if (i <= 3 && (ch=getch()) && isdigit(cbits(ch))) {	/* \sdd */
+			ch = 0;
+		}
+	} else if (i == '(') {		/* \s(dd */
+		getch();
+		getch();
+	} else if (i == '+' || i == '-') {	/* \s+, \s- */
+		j = cbits(getch());
+		if (isdigit(j)) {		/* \s+d, \s-d */
+			;
+		} else if (j == '(') {		/* \s+(dd, \s-(dd */
+			getch();
+			getch();
+		}
+	}
+}
+
+
+Tchar n_setht(void)		/* set character height from \H'...' */
+{
+
+	getch();
+	inumb(&apts);
+	getch();
+	return(0);
+}
+
+
+Tchar n_setslant(void)		/* set slant from \S'...' */
+{
+	int n;
+
+	getch();
+	n = 0;
+	n = inumb(&n);
+	getch();
+	return(0);
+}
+
+
+void n_caseft(void)
+{
+	skip();
+	setfont(1);
+}
+
+
+void n_setfont(int a)
+{
+	int i, j;
+
+	if (a)
+		i = getrq();
+	else 
+		i = getsn();
+	if (!i || i == 'P') {
+		j = font1;
+		goto s0;
+	}
+	if (i == 'S' || i == '0')
+		return;
+	if ((j = findft(i)) == -1)
+		return;
+s0:
+	font1 = font;
+	font = j;
+	mchbits();
+}
+
+
+void n_setwd(void)
+{
+	int base, wid;
+	Tchar i;
+	int	delim, emsz, k;
+	int	savhp, savapts, savapts1, savfont, savfont1, savpts, savpts1;
+
+	base = numtabp[ST].val = numtabp[ST].val = wid = numtabp[CT].val = 0;
+	if (ismot(i = getch()))
+		return;
+	delim = cbits(i);
+	savhp = numtabp[HP].val;
+	numtabp[HP].val = 0;
+	savapts = apts;
+	savapts1 = apts1;
+	savfont = font;
+	savfont1 = font1;
+	savpts = pts;
+	savpts1 = pts1;
+	setwdf++;
+	while (cbits(i = getch()) != delim && !nlflg) {
+		k = width(i);
+		wid += k;
+		numtabp[HP].val += k;
+		if (!ismot(i)) {
+			emsz = (INCH * pts + 36) / 72;
+		} else if (isvmot(i)) {
+			k = absmot(i);
+			if (isnmot(i))
+				k = -k;
+			base -= k;
+			emsz = 0;
+		} else 
+			continue;
+		if (base < numtabp[SB].val)
+			numtabp[SB].val = base;
+		if ((k = base + emsz) > numtabp[ST].val)
+			numtabp[ST].val = k;
+	}
+	setn1(wid, 0, (Tchar) 0);
+	numtabp[HP].val = savhp;
+	apts = savapts;
+	apts1 = savapts1;
+	font = savfont;
+	font1 = savfont1;
+	pts = savpts;
+	pts1 = savpts1;
+	mchbits();
+	setwdf = 0;
+}
+
+
+Tchar n_vmot(void)
+{
+	dfact = lss;
+	vflag++;
+	return n_mot();
+}
+
+
+Tchar n_hmot(void)
+{
+	dfact = EM;
+	return n_mot();
+}
+
+
+Tchar n_mot(void)
+{
+	int j, n;
+	Tchar i;
+
+	j = HOR;
+	getch(); /*eat delim*/
+	if (n = atoi0()) {
+		if (vflag)
+			j = VERT;
+		i = makem(quant(n, j));
+	} else
+		i = 0;
+	getch();
+	vflag = 0;
+	dfact = 1;
+	return(i);
+}
+
+
+Tchar n_sethl(int k)
+{
+	int j;
+	Tchar i;
+
+	j = t.Halfline;
+	if (k == 'u')
+		j = -j;
+	else if (k == 'r')
+		j = -2 * j;
+	vflag++;
+	i = makem(j);
+	vflag = 0;
+	return(i);
+}
+
+
+Tchar n_makem(int i)
+{
+	Tchar j;
+
+	if (i >= 0)
+		j = i;
+	else
+		j = -i;
+	j |= MOT;
+	if (i < 0)
+		j |= NMOT;
+	if (vflag)
+		j |= VMOT;
+	return(j);
+}
+
+
+void n_casefp(void)
+{
+	int i, j;
+
+	skip();
+	if ((i = cbits(getch()) - '0') < 0 || i > nfonts)
+		return;
+	if (skip() || !(j = getrq()))
+		return;
+	fontlab[i] = j;
+}
+
+
+
+void n_casebd(void)
+{
+	int i, j, k;
+
+	k = 0;
+bd0:
+	if (skip() || !(i = getrq()) || (j = findft(i)) == -1) {
+		if (k)
+			goto bd1;
+		else 
+			return;
+	}
+	if (j == smnt) {
+		k = smnt;
+		goto bd0;
+	}
+	if (k) {
+		sbold = j;
+		j = k;
+	}
+bd1:
+	skip();
+	noscale++;
+	bdtab[j] = atoi0();
+	noscale = 0;
+}
+
+
+void n_casevs(void)
+{
+	int i;
+
+	skip();
+	vflag++;
+	dfact = INCH; /*default scaling is points!*/
+	dfactd = 72;
+	res = VERT;
+	i = inumb(&lss);
+	if (nonumb)
+		i = lss1;
+	if (i < VERT)
+		i = VERT;	/* was VERT */
+	lss1 = lss;
+	lss = i;
+}
+
+
+
+
+Tchar n_xlss(void)
+{
+	/* stores \x'...' into
+	/* two successive Tchars.
+	/* the first contains HX, the second the value,
+	/* encoded as a vertical motion.
+	/* decoding is done in n2.c by pchar().
+	*/
+	int	i;
+
+	getch();
+	dfact = lss;
+	i = quant(atoi0(), VERT);
+	dfact = 1;
+	getch();
+	if (i >= 0)
+		*pbp++ = MOT | VMOT | i;
+	else
+		*pbp++ = MOT | VMOT | NMOT | -i;
+	return(HX);
+}