Initial, still somewhat experimental implementation to leverage

less(1) -T and :t ctags(1)-like functionality to jump to the
definitions of various terms inside manual pages.
To be polished in the tree, so bear with me and report issues.

Technically, if less(1) is used as a pager, information is collected
by the mdoc(7) terminal formatter, first stored using the ohash
library, then ultimately written to a temporary file which is passed
to less via -T.  No change intended for other output formatters or
when running without a pager.

Based on an idea from Kristaps using feedback from many, in particular
phessler@ nicm@ millert@ halex@ doug@ kspillner@ deraadt@.

1 files changed, 44 insertions, 27 deletions

diff --git a/main.c b/main.c
index c7f703a3..43a90ab8 100644
--- a/main.c
+++ b/main.c
@@ -1,4 +1,4 @@
-/*	$Id: main.c,v 1.238 2015/04/29 11:04:17 schwarze Exp $ */
+/*	$Id: main.c,v 1.239 2015/07/17 22:38:29 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2012, 2014, 2015 Ingo Schwarze <schwarze@openbsd.org>
@@ -39,6 +39,7 @@
 #include "roff.h"
 #include "mdoc.h"
 #include "man.h"
+#include "tag.h"
 #include "main.h"
 #include "manconf.h"
 #include "mansearch.h"
@@ -497,7 +498,9 @@ out:
 
 	if (pager_pid != 0 && pager_pid != 1) {
 		fclose(stdout);
+		tag_write();
 		waitpid(pager_pid, NULL, 0);
+		tag_unlink();
 	}
 
 	return((int)rc);
@@ -959,10 +962,50 @@ spawn_pager(void)
 	char		*argv[MAX_PAGER_ARGS];
 	const char	*pager;
 	char		*cp;
+	size_t		 cmdlen;
 	int		 fildes[2];
 	int		 argc;
 	pid_t		 pager_pid;
 
+	pager = getenv("MANPAGER");
+	if (pager == NULL || *pager == '\0')
+		pager = getenv("PAGER");
+	if (pager == NULL || *pager == '\0')
+		pager = "more -s";
+	cp = mandoc_strdup(pager);
+
+	/*
+	 * Parse the pager command into words.
+	 * Intentionally do not do anything fancy here.
+	 */
+
+	argc = 0;
+	while (argc + 4 < MAX_PAGER_ARGS) {
+		argv[argc++] = cp;
+		cp = strchr(cp, ' ');
+		if (cp == NULL)
+			break;
+		*cp++ = '\0';
+		while (*cp == ' ')
+			cp++;
+		if (*cp == '\0')
+			break;
+	}
+
+	/* Read all text right away and use the tag file. */
+
+	if ((cmdlen = strlen(argv[0])) >= 4) {
+		cp = argv[0] + cmdlen - 4;
+		if (strcmp(cp, "less") == 0 ||
+		    strcmp(cp, "more") == 0) {
+			tag_init();
+			argv[argc++] = mandoc_strdup("+G1G");
+			argv[argc++] = mandoc_strdup("-T");
+			argv[argc++] = tag_filename();
+		}
+	}
+	argv[argc] = NULL;
+
 	if (pipe(fildes) == -1) {
 		fprintf(stderr, "%s: pipe: %s\n",
 		    progname, strerror(errno));
@@ -998,32 +1041,6 @@ spawn_pager(void)
 	}
 	close(fildes[0]);
 
-	pager = getenv("MANPAGER");
-	if (pager == NULL || *pager == '\0')
-		pager = getenv("PAGER");
-	if (pager == NULL || *pager == '\0')
-		pager = "more -s";
-	cp = mandoc_strdup(pager);
-
-	/*
-	 * Parse the pager command into words.
-	 * Intentionally do not do anything fancy here.
-	 */
-
-	argc = 0;
-	while (argc + 1 < MAX_PAGER_ARGS) {
-		argv[argc++] = cp;
-		cp = strchr(cp, ' ');
-		if (cp == NULL)
-			break;
-		*cp++ = '\0';
-		while (*cp == ' ')
-			cp++;
-		if (*cp == '\0')
-			break;
-	}
-	argv[argc] = NULL;
-
 	/* Hand over to the pager. */
 
 	execvp(argv[0], argv);