Re: cal: add option to highlight the current day

2026-07-05T10:38:19+0000 Johannes Thyssen Tishman <[email protected]>:
> 2026-07-04T09:41:36+0000 Job Snijders <[email protected]>:
> > Hi Johannes,
> > 
> > Thanks! I've longed for this functionality for some time now. Some
> > comments below.
> 
> Thanks for the feedback Job. I've answered a couple of your comments
> inline and addressed all of them in the patch below. Is this better?
> 
> > On Fri, Jul 03, 2026 at 04:37:29PM +0000, Johannes Thyssen Tishman wrote:
> > > Please find below a patch to add an option (-h) to cal to allow
> > > highlighting the current day.
> > > 
> > > For testing purposes, the -h flag takes an optional argument specifying
> > > the date to highlight, e.g., cal -h2026-10-10 oct. I intend to remove
> > > this before committing if the patch is accepted.
> > 
> > Since the program tests whether standout highlighting can be used, to
> > me it would make most sense to highlight the current day by default.
> > Highlighting of arbitrary days seems less useful. I suggest remove '-h'
> > (bonus: it reduces the size of patch).
> 
> The optional argument of the -h flag was mostly so testers could check
> that the highlight was working for other days other than the current one
> without having to change the system date. As mentioned above, my
> intention was to drop this before committing.
> 
> I've now updated the patch to highlight the current day by default.
> However, this now conflicts with what Patrick wants. Can we find a
> compromise here? I'm not sure I like an option to *disable* the
> highlight. I'd prefer an option to *enable* it or make it the default
> and have no option at all.
> 
> > [...]
> 
> > >  void
> > > +highlight_day(char *p, int day, int *hl_len)
> > > +{
> > > +	const char *term_so, *term_se;
> > > +	char cbuf[512];
> > > +	char tbuf[1024], *b;
> > > +
> > > +	term_se = term_so = NULL;
> > > +
> > > +	/*
> > > +	 * why NULL as name here?
> > > +	 * termcap(3) doesn't seem document this
> > > +	 */
> 
> > From termcap(3):
> > 
> >      The tgetstr routine returns the string entry for id, or zero if it is not
> >      available.  Use tputs to output the returned string.  The area parameter
> >      is used as follows:
> > 
> >         * It is assumed to be the address of a pointer to a buffer managed
> >             by the calling application.
> > 
> >         * However, ncurses checks to ensure that area is not NULL, and also
> >             that the resulting buffer pointer is not NULL.  If either check
> >             fails, the area parameter is ignored.
> > 
> >         * If the checks succeed, ncurses also copies the return value to the
> >             buffer pointed to by area, and the area value will be updated to
> >             point past the null ending this value.
> > 
> >         * The return value itself is an address in the terminal description
> >             which is loaded into memory.
> 
> Right, this is why I'm asking about the use of cbuf and b, which are not
> used here or in the FreeBSD implementation, instead of just setting area
> to NULL for tgetstr (I've now done this in the revised patch below).
> However, I still don't understand why NULL for the second parameter of
> tgetent. AFAIC, that is not described in termcap(3).
> 
> > > +	if (tgetent(tbuf, NULL) == 1) {
> > > +		b = cbuf;
> > > +
> > > +		/*
> > > +		 * why not NULL here for area instead of &b?
> > > +		 * cbuf is never used
> > > +		 */
> > > +		term_so = tgetstr("so", &b);
> > > +		term_se = tgetstr("se", &b);
> > > +	}

ping

Index: Makefile
===================================================================
RCS file: /cvs/src/usr.bin/cal/Makefile,v
diff -u -p -r1.3 Makefile
--- Makefile	21 Sep 1997 11:48:29 -0000	1.3
+++ Makefile	31 Jul 2026 20:47:00 -0000
@@ -1,5 +1,6 @@
 #	$OpenBSD: Makefile,v 1.3 1997/09/21 11:48:29 deraadt Exp $
 
-PROG=	cal
+PROG=		cal
+LDADD+=		-lcurses
 
 .include <bsd.prog.mk>
Index: cal.c
===================================================================
RCS file: /cvs/src/usr.bin/cal/cal.c,v
diff -u -p -r1.36 cal.c
--- cal.c	2 Jul 2026 20:40:53 -0000	1.36
+++ cal.c	31 Jul 2026 20:47:00 -0000
@@ -42,6 +42,8 @@
 #include <string.h>
 #include <time.h>
 #include <unistd.h>
+#include <curses.h>
+#include <term.h>
 
 #define	THURSDAY		4		/* for reformation */
 #define	SATURDAY		6		/* 1 Jan 1 was a Saturday */
@@ -127,8 +129,14 @@ const char	*day_headings = NULL;
 int julian;
 int mflag = 0;
 int wflag = 0;
+int highlight = 0;
+int highlight_len = 0;
+const char *term_so = NULL;
+const char *term_se = NULL;
+struct tm *lt;
 
 void	ascii_day(char *, int);
+void	highlight_day(char *, int);
 void	center(const char *, int, int);
 void	day_array(int, int, int *);
 int	day_in_week(int, int, int);
@@ -141,15 +149,18 @@ void	trim_trailing_spaces(char *);
 void	usage(void);
 void	yearly(int);
 int	parsemonth(const char *);
+int	is_today(int, int, int);
+int	can_highlight(void);
 
 int
 main(int argc, char *argv[])
 {
-	struct tm *local_time;
 	time_t now;
 	int ch, month, year, yflag;
 	const char *errstr;
 
+	highlight = can_highlight();
+
 	if (pledge("stdio", NULL) == -1)
 		err(1, "pledge");
 
@@ -190,6 +201,13 @@ main(int argc, char *argv[])
 		day_headings = DAY_HEADINGS_JS;
 	}
 
+	(void)time(&now);
+	lt = localtime(&now);
+	if (lt == NULL) {
+		perror("localtime");
+		exit(1);
+	}
+
 	month = 0;
 	switch(argc) {
 	case 2:
@@ -202,9 +220,7 @@ main(int argc, char *argv[])
 			if (yflag)
 				errx(1, "specifying a month conflicts with -y");
 			month = parsemonth(*argv);
-			(void)time(&now);
-			local_time = localtime(&now);
-			year = local_time->tm_year + 1900;
+			year = lt->tm_year + 1900;
 		} else {
 			year = strtonum(*argv, 1, 9999, &errstr);
 			if (errstr)
@@ -212,11 +228,9 @@ main(int argc, char *argv[])
 		}
 		break;
 	case 0:
-		(void)time(&now);
-		local_time = localtime(&now);
-		year = local_time->tm_year + 1900;
+		year = lt->tm_year + 1900;
 		if (!yflag)
-			month = local_time->tm_mon + 1;
+			month = lt->tm_mon + 1;
 		break;
 	default:
 		usage();
@@ -298,8 +312,13 @@ isoweek(int day, int month, int year)
 void
 monthly(int month, int year)
 {
-	int col, row, len, days[MAXDAYS], firstday;
-	char *p, lineout[30];
+	int col, row, len, hl_len, d, days[MAXDAYS], firstday;
+
+	/*
+	 * At least 9 bytes for standout mode escape sequence. What is a safe
+	 * size for this? Could this differ from terminal to terminal?
+	 */
+	char *p, lineout[48];
 
 	day_array(month, year, days);
 	(void)snprintf(lineout, sizeof(lineout), "%s %d",
@@ -310,15 +329,22 @@ monthly(int month, int year)
 	    lineout, day_headings);
 	for (row = 0; row < 6; row++) {
 		firstday = SPACE;
+		hl_len = 0;
 		for (col = 0, p = lineout; col < 7; col++,
 		    p += julian ? J_DAY_LEN : DAY_LEN) {
-			if (firstday == SPACE && days[row * 7 + col] != SPACE)
-				firstday = days[row * 7 + col];
-			ascii_day(p, days[row * 7 + col]);
+			d = days[row * 7 + col];
+			if (firstday == SPACE && d != SPACE)
+				firstday = d;
+			if (is_today(d, month, year) && highlight) {
+				highlight_day(p, d);
+				hl_len = highlight_len;
+				p += hl_len;
+			} else
+				ascii_day(p, d);
 		}
 		*p = '\0';
 		trim_trailing_spaces(lineout);
-		(void)printf("%-20s", lineout);
+		(void)printf("%-*s", 20 + hl_len, lineout);
 		if (wflag && firstday != SPACE)
 			printf(" [%2d]", week(firstday, month, year));
 		printf("\n");
@@ -328,8 +354,13 @@ monthly(int month, int year)
 void
 j_yearly(int year)
 {
-	int col, *dp, i, month, row, which_cal;
+	int col, *dp, i, month, row, which_cal, hl_len;
 	int days[12][MAXDAYS];
+
+	/*
+	 * At least 9 bytes for standout mode escape sequence. What is a safe
+	 * size for this? Could this differ from terminal to terminal?
+	 */
 	char *p, lineout[80];
 
 	(void)snprintf(lineout, sizeof(lineout), "%d", year);
@@ -346,15 +377,32 @@ j_yearly(int year)
 		    J_HEAD_SEP, "", day_headings);
 
 		for (row = 0; row < 6; row++) {
+			hl_len = 0;
 			for (which_cal = 0; which_cal < 2; which_cal++) {
 				p = lineout + which_cal * (J_WEEK_LEN + 2);
+				p += hl_len;
 				dp = &days[month + which_cal][row * 7];
-				for (col = 0; col < 7; col++, p += J_DAY_LEN)
-					ascii_day(p, *dp++);
+				for (col = 0; col < 7; col++, p += J_DAY_LEN) {
+					if (is_today(*dp, month + which_cal + 1,
+					    year) && highlight) {
+						highlight_day(p, *dp++);
+						hl_len = highlight_len;
+						p += hl_len;
+					} else
+						ascii_day(p, *dp++);
+				}
 			}
 			*p = '\0';
 			trim_trailing_spaces(lineout);
 			(void)printf("%s\n", lineout);
+
+			/*
+			 * Highlighting a day causes escape sequences to
+			 * misalign the rows. Rather than tracking offsets to
+			 * overwrite rows day-by-day, clear the row.
+			 */
+			if (highlight)
+				(void)memset(lineout, ' ', sizeof(lineout) - 1);
 		}
 	}
 	(void)printf("\n");
@@ -363,9 +411,14 @@ j_yearly(int year)
 void
 yearly(int year)
 {
-	int col, *dp, i, month, row, which_cal, week_len, wn, firstday;
+	int col, *dp, i, month, row, which_cal, week_len, hl_len, wn, firstday;
 	int days[12][MAXDAYS];
-	char *p, lineout[81];
+
+	/*
+	 * At least 9 bytes for standout mode escape sequence. What is a safe
+	 * size for this? Could this differ from terminal to terminal?
+	 */
+	char *p, lineout[96];
 
 	week_len = WEEK_LEN;
 	if (wflag)
@@ -386,15 +439,23 @@ yearly(int year)
 		    HEAD_SEP + (wflag ? WEEKNUMBER_LEN : 0), "", day_headings);
 
 		for (row = 0; row < 6; row++) {
+			hl_len = 0;
 			for (which_cal = 0; which_cal < 3; which_cal++) {
 				p = lineout + which_cal * (week_len + 2);
+				p += hl_len;
 
 				dp = &days[month + which_cal][row * 7];
 				firstday = SPACE;
 				for (col = 0; col < 7; col++, p += DAY_LEN) {
 					if (firstday == SPACE && *dp != SPACE)
 						firstday = *dp;
-					ascii_day(p, *dp++);
+					if (is_today(*dp, month + which_cal + 1,
+					    year) && highlight) {
+						highlight_day(p, *dp++);
+						hl_len = highlight_len;
+						p += hl_len;
+					} else
+						ascii_day(p, *dp++);
 				}
 				if (wflag && firstday != SPACE) {
 					wn = week(firstday,
@@ -408,6 +469,14 @@ yearly(int year)
 			*p = '\0';
 			trim_trailing_spaces(lineout);
 			(void)printf("%s\n", lineout);
+
+			/*
+			 * Highlighting a day causes escape sequences to
+			 * misalign the rows. Rather than tracking offsets to
+			 * overwrite rows day-by-day, clear the row.
+			 */
+			if (highlight)
+				(void)memset(lineout, ' ', sizeof(lineout) - 1);
 		}
 	}
 	(void)printf("\n");
@@ -514,6 +583,23 @@ ascii_day(char *p, int day)
 }
 
 void
+highlight_day(char *p, int day)
+{
+	/* highlight on */
+	memcpy(p, term_so, strlen(term_so));
+	p += strlen(term_so);
+
+	/* the actual text */
+	ascii_day(p, day);
+	p += (julian ? J_DAY_LEN : DAY_LEN) - 1;
+
+	/* highlight off */
+	memcpy(p, term_se, strlen(term_se));
+	p += strlen(term_se);
+	*p = ' ';
+}
+
+void
 trim_trailing_spaces(char *s)
 {
 	char *p;
@@ -560,4 +646,29 @@ parsemonth(const char *s)
 	if (v <= 0 || v > 12)
 		errx(1, "invalid month: use 1-12 or a name");
 	return (v);
+}
+
+int
+is_today(int day, int month, int year)
+{
+	return (year == lt->tm_year + 1900 && month == lt->tm_mon + 1 &&
+		day == (julian ? lt->tm_yday + 1 : lt->tm_mday));
+}
+
+int
+can_highlight(void)
+{
+	char tbuf[1024];
+
+	if (!isatty(STDOUT_FILENO))
+		return 0;
+	if (tgetent(tbuf, NULL) == 1) {
+		term_so = tgetstr("so", NULL);
+		term_se = tgetstr("se", NULL);
+	}
+	if (term_so != NULL && term_se != NULL) {
+		highlight_len = strlen(term_so) + strlen(term_se);
+		return 1;
+	}
+	return 0;
 }