mg: allow to change the tab width

This makes the tab width customizable per-buffer.  The new function
`set-tab-width' changes it for the current buffer or the default value
for new buffers if called with a prefix argument (or from the startup
file.)

The default tab width is still 8 column.

Together with the newly resurrected no-tab-mode, allows to use mg for a
variety of programming languages and coding styles.

Note that it's not possible to call set-tab-width with auto-execute in
the startup file due to limitations in how auto-execute and the parser
work.

ok tb@

10 files changed, 130 insertions, 71 deletions

diff --git a/usr.bin/mg/basic.c b/usr.bin/mg/basic.c
index ed7d475c494..d5f8ecb1796 100644
--- a/usr.bin/mg/basic.c
+++ b/usr.bin/mg/basic.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: basic.c,v 1.53 2023/04/17 09:49:04 op Exp $	*/
+/*	$OpenBSD: basic.c,v 1.54 2023/04/21 13:39:36 op Exp $	*/
 
 /* This file is in the public domain */
 
@@ -277,8 +277,7 @@ getgoal(struct line *dlp)
 	for (i = 0; i < llength(dlp); i++) {
 		c = lgetc(dlp, i);
 		if (c == '\t') {
-			col |= 0x07;
-			col++;
+			col = ntabstop(col, curbp->b_tabw);
 		} else if (ISCTRL(c) != FALSE) {
 			col += 2;
 		} else if (isprint(c))
diff --git a/usr.bin/mg/buffer.c b/usr.bin/mg/buffer.c
index e6605000475..8c8aab40a86 100644
--- a/usr.bin/mg/buffer.c
+++ b/usr.bin/mg/buffer.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: buffer.c,v 1.113 2023/03/08 04:43:11 guenther Exp $ */
+/* $OpenBSD: buffer.c,v 1.114 2023/04/21 13:39:36 op Exp $ */
 
 /* This file is in the public domain. */
 
@@ -26,9 +26,42 @@ static struct buffer *bnew(const char *);
 
 static int usebufname(const char *);
 
+/* Default tab width */
+int	 defb_tabw = 8;
+
 /* Flag for global working dir */
 extern int globalwd;
 
+/*
+ * Set the tab width for the current buffer, or the default for new
+ * buffers if called with a prefix argument.
+ */
+int
+settabw(int f, int n)
+{
+	char	buf[8], *bufp;
+	const char *errstr;
+
+	if (f & FFARG) {
+		if (n <= 0 || n > 16)
+			return (FALSE);
+		defb_tabw = n;
+		return (TRUE);
+	}
+
+	if ((bufp = eread("Tab Width: ", buf, sizeof(buf),
+	    EFNUL | EFNEW | EFCR)) == NULL)
+		return (ABORT);
+	if (bufp[0] == '\0')
+		return (ABORT);
+	n = strtonum(buf, 1, 16, &errstr);
+	if (errstr)
+		return (dobeep_msgs("Tab width", errstr));
+	curbp->b_tabw = n;
+	curwp->w_rflag |= WFFRAME;
+	return (TRUE);
+}
+
 int
 togglereadonlyall(int f, int n)
 {
@@ -588,6 +621,7 @@ bnew(const char *bname)
 	bp->b_lines = 1;
 	bp->b_nlseq = "\n";		/* use unix default */
 	bp->b_nlchr = bp->b_nlseq;
+	bp->b_tabw = defb_tabw;
 	if ((bp->b_bname = strdup(bname)) == NULL) {
 		dobeep();
 		ewprintf("Can't get %d bytes", strlen(bname) + 1);
diff --git a/usr.bin/mg/cmode.c b/usr.bin/mg/cmode.c
index e5442a2b6ed..2a2a1090003 100644
--- a/usr.bin/mg/cmode.c
+++ b/usr.bin/mg/cmode.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cmode.c,v 1.21 2023/04/17 09:49:04 op Exp $ */
+/* $OpenBSD: cmode.c,v 1.22 2023/04/21 13:39:37 op Exp $ */
 /*
  * This file is in the public domain.
  *
@@ -245,10 +245,10 @@ getindent(const struct line *lp, int *curi)
 	for (lo = 0; lo < llength(lp); lo++) {
 		if (!isspace(c = lgetc(lp, lo)))
 			break;
-		if (c == '\t') {
-			nicol |= 0x07;
-		}
-		nicol++;
+		if (c == '\t')
+			nicol = ntabstop(nicol, curbp->b_tabw);
+		else
+			nicol++;
 	}
 
 	/* If last line was blank, choose 0 */
@@ -411,8 +411,7 @@ findcolpos(const struct buffer *bp, const struct line *lp, int lo)
 	for (i = 0; i < lo; ++i) {
 		c = lgetc(lp, i);
 		if (c == '\t') {
-			col |= 0x07;
-			col++;
+			col = ntabstop(col, curbp->b_tabw);
 		} else if (ISCTRL(c) != FALSE)
 			col += 2;
 		else if (isprint(c)) {
diff --git a/usr.bin/mg/def.h b/usr.bin/mg/def.h
index 8cfaada0300..65ae2b43c06 100644
--- a/usr.bin/mg/def.h
+++ b/usr.bin/mg/def.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: def.h,v 1.179 2023/04/17 09:49:04 op Exp $	*/
+/*	$OpenBSD: def.h,v 1.180 2023/04/21 13:39:37 op Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -269,6 +269,7 @@ struct buffer {
 	char		 b_cwd[NFILEN]; /* working directory		 */
 	char		*b_nlseq;	/* Newline sequence of chars	 */
 	char		*b_nlchr;	/* 1st newline character	 */
+	int		 b_tabw;	/* Width of a tab character	 */
 	struct fileinfo	 b_fi;		/* File attributes		 */
 	struct undoq	 b_undo;	/* Undo actions list		 */
 	struct undo_rec *b_undoptr;
@@ -430,6 +431,7 @@ int		 shrinkwind(int, int);
 int		 delwind(int, int);
 
 /* buffer.c */
+int		 settabw(int, int);
 int		 togglereadonly(int, int);
 int		 togglereadonlyall(int, int);
 struct buffer   *bfind(const char *, int);
@@ -542,6 +544,7 @@ int		 gotoline(int, int);
 int		 setlineno(int);
 
 /* util.c X */
+int		 ntabstop(int, int);
 int		 showcpos(int, int);
 int		 getcolpos(struct mgwin *);
 int		 twiddle(int, int);
diff --git a/usr.bin/mg/display.c b/usr.bin/mg/display.c
index 3814a0bd29b..ab923d4fb9d 100644
--- a/usr.bin/mg/display.c
+++ b/usr.bin/mg/display.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: display.c,v 1.51 2023/04/17 09:49:04 op Exp $	*/
+/*	$OpenBSD: display.c,v 1.52 2023/04/21 13:39:37 op Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -52,9 +52,9 @@ struct score {
 };
 
 void	vtmove(int, int);
-void	vtputc(int);
-void	vtpute(int);
-int	vtputs(const char *);
+void	vtputc(int, struct mgwin *);
+void	vtpute(int, struct mgwin *);
+int	vtputs(const char *, struct mgwin *);
 void	vteeol(void);
 void	updext(int, int);
 void	modeline(struct mgwin *, int);
@@ -308,9 +308,10 @@ vtmove(int row, int col)
  * Three guesses how we found this.
  */
 void
-vtputc(int c)
+vtputc(int c, struct mgwin *wp)
 {
 	struct video	*vp;
+	int		 target;
 
 	c &= 0xff;
 
@@ -318,19 +319,20 @@ vtputc(int c)
 	if (vtcol >= ncol)
 		vp->v_text[ncol - 1] = '$';
 	else if (c == '\t') {
+		target = ntabstop(vtcol, wp->w_bufp->b_tabw);
 		do {
-			vtputc(' ');
-		} while (vtcol < ncol && (vtcol & 0x07) != 0);
+			vtputc(' ', wp);
+		} while (vtcol < ncol && vtcol < target);
 	} else if (ISCTRL(c)) {
-		vtputc('^');
-		vtputc(CCHR(c));
+		vtputc('^', wp);
+		vtputc(CCHR(c), wp);
 	} else if (isprint(c))
 		vp->v_text[vtcol++] = c;
 	else {
 		char bf[5];
 
 		snprintf(bf, sizeof(bf), "\\%o", c);
-		vtputs(bf);
+		vtputs(bf, wp);
 	}
 }
 
@@ -340,9 +342,10 @@ vtputc(int c)
  * margin.
  */
 void
-vtpute(int c)
+vtpute(int c, struct mgwin *wp)
 {
 	struct video *vp;
+	int target;
 
 	c &= 0xff;
 
@@ -350,12 +353,13 @@ vtpute(int c)
 	if (vtcol >= ncol)
 		vp->v_text[ncol - 1] = '$';
 	else if (c == '\t') {
+		target = ntabstop(vtcol + lbound, wp->w_bufp->b_tabw);
 		do {
-			vtpute(' ');
-		} while (((vtcol + lbound) & 0x07) != 0 && vtcol < ncol);
+			vtpute(' ', wp);
+		} while (((vtcol + lbound) < target) && vtcol < ncol);
 	} else if (ISCTRL(c) != FALSE) {
-		vtpute('^');
-		vtpute(CCHR(c));
+		vtpute('^', wp);
+		vtpute(CCHR(c), wp);
 	} else if (isprint(c)) {
 		if (vtcol >= 0)
 			vp->v_text[vtcol] = c;
@@ -365,7 +369,7 @@ vtpute(int c)
 
 		snprintf(bf, sizeof(bf), "\\%o", c);
 		for (cp = bf; *cp != '\0'; cp++)
-			vtpute(*cp);
+			vtpute(*cp, wp);
 	}
 }
 
@@ -476,7 +480,7 @@ update(int modelinecolor)
 			vscreen[i]->v_flag |= (VFCHG | VFHBAD);
 			vtmove(i, 0);
 			for (j = 0; j < llength(lp); ++j)
-				vtputc(lgetc(lp, j));
+				vtputc(lgetc(lp, j), wp);
 			vteeol();
 		} else if ((wp->w_rflag & (WFEDIT | WFFULL)) != 0) {
 			hflag = TRUE;
@@ -486,7 +490,7 @@ update(int modelinecolor)
 				vtmove(i, 0);
 				if (lp != wp->w_bufp->b_headp) {
 					for (j = 0; j < llength(lp); ++j)
-						vtputc(lgetc(lp, j));
+						vtputc(lgetc(lp, j), wp);
 					lp = lforw(lp);
 				}
 				vteeol();
@@ -509,8 +513,7 @@ update(int modelinecolor)
 	while (i < curwp->w_doto) {
 		c = lgetc(lp, i++);
 		if (c == '\t') {
-			curcol |= 0x07;
-			curcol++;
+			curcol = ntabstop(curcol, curwp->w_bufp->b_tabw);
 		} else if (ISCTRL(c) != FALSE)
 			curcol += 2;
 		else if (isprint(c))
@@ -545,7 +548,7 @@ update(int modelinecolor)
 				    (curcol < ncol - 1)) {
 					vtmove(i, 0);
 					for (j = 0; j < llength(lp); ++j)
-						vtputc(lgetc(lp, j));
+						vtputc(lgetc(lp, j), wp);
 					vteeol();
 					/* this line no longer is extended */
 					vscreen[i]->v_flag &= ~VFEXT;
@@ -677,7 +680,7 @@ updext(int currow, int curcol)
 	vtmove(currow, -lbound);		/* start scanning offscreen */
 	lp = curwp->w_dotp;			/* line to output */
 	for (j = 0; j < llength(lp); ++j)	/* until the end-of-line */
-		vtpute(lgetc(lp, j));
+		vtpute(lgetc(lp, j), curwp);
 	vteeol();				/* truncate the virtual line */
 	vscreen[currow]->v_text[0] = '$';	/* and put a '$' in column 1 */
 }
@@ -793,45 +796,45 @@ modeline(struct mgwin *wp, int modelinecolor)
 	vscreen[n]->v_flag |= (VFCHG | VFHBAD);	/* Recompute, display.	 */
 	vtmove(n, 0);				/* Seek to right line.	 */
 	bp = wp->w_bufp;
-	vtputc('-');
-	vtputc('-');
+	vtputc('-', wp);
+	vtputc('-', wp);
 	if ((bp->b_flag & BFREADONLY) != 0) {
-		vtputc('%');
+		vtputc('%', wp);
 		if ((bp->b_flag & BFCHG) != 0)
-			vtputc('*');
+			vtputc('*', wp);
 		else
-			vtputc('%');
+			vtputc('%', wp);
 	} else if ((bp->b_flag & BFCHG) != 0) {	/* "*" if changed.	 */
-		vtputc('*');
-		vtputc('*');
+		vtputc('*', wp);
+		vtputc('*', wp);
 	} else {
-		vtputc('-');
-		vtputc('-');
+		vtputc('-', wp);
+		vtputc('-', wp);
 	}
-	vtputc('-');
+	vtputc('-', wp);
 	n = 5;
-	n += vtputs("Mg: ");
+	n += vtputs("Mg: ", wp);
 	if (bp->b_bname[0] != '\0')
-		n += vtputs(&(bp->b_bname[0]));
+		n += vtputs(&(bp->b_bname[0]), wp);
 	while (n < 42) {			/* Pad out with blanks.	 */
-		vtputc(' ');
+		vtputc(' ', wp);
 		++n;
 	}
-	vtputc('(');
+	vtputc('(', wp);
 	++n;
 	for (md = 0; ; ) {
-		n += vtputs(bp->b_modes[md]->p_name);
+		n += vtputs(bp->b_modes[md]->p_name, wp);
 		if (++md > bp->b_nmodes)
 			break;
-		vtputc('-');
+		vtputc('-', wp);
 		++n;
 	}
 	/* XXX These should eventually move to a real mode */
 	if (macrodef == TRUE)
-		n += vtputs("-def");
+		n += vtputs("-def", wp);
 	if (globalwd == TRUE)
-		n += vtputs("-gwd");
-	vtputc(')');
+		n += vtputs("-gwd", wp);
+	vtputc(')', wp);
 	++n;
 
 	if (linenos && colnos)
@@ -842,10 +845,10 @@ modeline(struct mgwin *wp, int modelinecolor)
 	else if (colnos)
 		len = snprintf(sl, sizeof(sl), "--C%d", getcolpos(wp));
 	if ((linenos || colnos) && len < sizeof(sl) && len != -1)
-		n += vtputs(sl);
+		n += vtputs(sl, wp);
 
 	while (n < ncol) {			/* Pad out.		 */
-		vtputc('-');
+		vtputc('-', wp);
 		++n;
 	}
 }
@@ -854,12 +857,12 @@ modeline(struct mgwin *wp, int modelinecolor)
  * Output a string to the mode line, report how long it was.
  */
 int
-vtputs(const char *s)
+vtputs(const char *s, struct mgwin *wp)
 {
 	int n = 0;
 
 	while (*s != '\0') {
-		vtputc(*s++);
+		vtputc(*s++, wp);
 		++n;
 	}
 	return (n);
diff --git a/usr.bin/mg/funmap.c b/usr.bin/mg/funmap.c
index fbf41217328..ae1c455edff 100644
--- a/usr.bin/mg/funmap.c
+++ b/usr.bin/mg/funmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: funmap.c,v 1.66 2023/04/17 09:49:04 op Exp $	*/
+/*	$OpenBSD: funmap.c,v 1.67 2023/04/21 13:39:37 op Exp $	*/
 
 /* This file is in the public domain */
 
@@ -199,6 +199,7 @@ static struct funmap functnames[] = {
 	{ask_selfinsert, "self-insert-char", 1},
 	{selfinsert, "self-insert-command", 1},		/* startup only */
 	{sentencespace, "sentence-end-double-space", 0},
+	{settabw, "set-tab-width", 1},
 #ifdef REGEX
 	{setcasefold, "set-case-fold-search", 0},
 #endif /* REGEX */
diff --git a/usr.bin/mg/match.c b/usr.bin/mg/match.c
index acb814e3b9d..9481985ee57 100644
--- a/usr.bin/mg/match.c
+++ b/usr.bin/mg/match.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: match.c,v 1.24 2023/04/17 15:18:25 op Exp $	*/
+/*	$OpenBSD: match.c,v 1.25 2023/04/21 13:39:37 op Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -136,6 +136,7 @@ displaymatch(struct line *clp, int cbo)
 	int	 cp;
 	int	 bufo;
 	int	 c;
+	int	 col;
 	int	 inwindow;
 	char	 buf[NLINE];
 
@@ -181,9 +182,9 @@ displaymatch(struct line *clp, int cbo)
 				} else
 					buf[bufo++] = c;
 			} else {
-				do {
+				col = ntabstop(bufo, curbp->b_tabw);
+				while (bufo < col && bufo < sizeof(buf) - 1)
 					buf[bufo++] = ' ';
-				} while ((bufo & 7) && bufo < sizeof(buf) - 1);
 			}
 		}
 		buf[bufo++] = '\0';
diff --git a/usr.bin/mg/mg.1 b/usr.bin/mg/mg.1
index d2edd289cc5..0b677e9c4ca 100644
--- a/usr.bin/mg/mg.1
+++ b/usr.bin/mg/mg.1
@@ -1,7 +1,7 @@
-.\"	$OpenBSD: mg.1,v 1.129 2023/04/17 09:49:04 op Exp $
+.\"	$OpenBSD: mg.1,v 1.130 2023/04/21 13:39:37 op Exp $
 .\" This file is in the public domain.
 .\"
-.Dd $Mdocdate: April 17 2023 $
+.Dd $Mdocdate: April 21 2023 $
 .Dt MG 1
 .Os
 .Sh NAME
@@ -896,6 +896,9 @@ Used by auto-fill-mode.
 Sets the mark in the current window to the current dot location.
 .It set-prefix-string
 Sets the prefix string to be used by the 'prefix-region' command.
+.It set-tab-width
+Set the tab width for the current buffer, or the default for new buffers
+if called with a prefix argument or from the startup file.
 .It shell-command
 Execute external command from mini-buffer.
 .It shell-command-on-region
diff --git a/usr.bin/mg/paragraph.c b/usr.bin/mg/paragraph.c
index 1455295f90d..4e35770e65f 100644
--- a/usr.bin/mg/paragraph.c
+++ b/usr.bin/mg/paragraph.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: paragraph.c,v 1.48 2023/04/17 09:49:04 op Exp $	*/
+/*	$OpenBSD: paragraph.c,v 1.49 2023/04/21 13:39:37 op Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -413,7 +413,7 @@ fillword(int f, int n)
 			return selfinsert(f, n);
 		c = lgetc(curwp->w_dotp, i);
 		if (c == '\t')
-			col |= 0x07;
+			col = ntabstop(col, curwp->w_bufp->b_tabw);
 		else if (ISCTRL(c) != FALSE)
 			++col;
 	}
diff --git a/usr.bin/mg/util.c b/usr.bin/mg/util.c
index 05fd84f91c8..6168f51144b 100644
--- a/usr.bin/mg/util.c
+++ b/usr.bin/mg/util.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: util.c,v 1.47 2023/04/17 09:53:08 op Exp $	*/
+/*	$OpenBSD: util.c,v 1.48 2023/04/21 13:39:37 op Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -19,6 +19,16 @@
 int	doindent(int);
 
 /*
+ * Compute next tab stop, with `col' being the a column number and
+ * `tabw' the tab width.
+ */
+int
+ntabstop(int col, int tabw)
+{
+	return (((col + tabw) / tabw) * tabw);
+}
+
+/*
  * Display a bunch of useful information about the current location of dot.
  * The character under the cursor (in octal), the current line, row, and
  * column, and approximate position of the cursor in the file (as a
@@ -103,8 +113,7 @@ getcolpos(struct mgwin *wp)
 	for (i = 0; i < wp->w_doto; ++i) {
 		c = lgetc(wp->w_dotp, i);
 		if (c == '\t') {
-			col |= 0x07;
-			col++;
+			col = ntabstop(col, wp->w_bufp->b_tabw);
 		} else if (ISCTRL(c) != FALSE)
 			col += 2;
 		else if (isprint(c)) {
@@ -377,8 +386,9 @@ lfindent(int f, int n)
 			if (c != ' ' && c != '\t')
 				break;
 			if (c == '\t')
-				nicol |= 0x07;
-			++nicol;
+				nicol = ntabstop(nicol, curwp->w_bufp->b_tabw);
+			else
+				++nicol;
 		}
 		(void)delwhite(FFRAND, 1);
 
@@ -472,11 +482,17 @@ backdel(int f, int n)
 int
 space_to_tabstop(int f, int n)
 {
+	int	c;
+
 	if (n < 0)
 		return (FALSE);
 	if (n == 0)
 		return (TRUE);
-	return (linsert((n << 3) - (curwp->w_doto & 7), ' '));
+
+	c = curwp->w_doto;
+	while (n-- > 0)
+		c = ntabstop(c, curbp->b_tabw);
+	return (linsert(c - curwp->w_doto, ' '));
 }
 
 /*