Port ctags-style, less(1) :t internal searching from terminal output

to HTML output.  For certain macros appearing at the beginning of .It
heads, write HTML id="..." attributes such that deep linking works.
Write HTML <a> attributes such that you can easily copy out link
targets with the mouse.  Try: http://man.openbsd.org/vmctl.8#create

Feature suggested by <guettliml at Thomas dash Guettler dot de>,
some details of the design and implementation by me.

2 files changed, 85 insertions, 10 deletions

diff --git a/mandoc.css b/mandoc.css
index cd9cf056..afe34f44 100644
--- a/mandoc.css
+++ b/mandoc.css
@@ -14,6 +14,11 @@ ul, ol, dl {	margin-top: 0em;
 		margin-bottom: 0em; }
 li, dt {	margin-top: 1em; }
 
+a.selflink {	border-bottom: thin dotted;
+		color: inherit;
+		font: inherit;
+		text-decoration: inherit; }
+
 /* Search form and search results. */
 
 fieldset {	border: thin solid silver;
diff --git a/mdoc_html.c b/mdoc_html.c
index 5f427c27..b628bb56 100644
--- a/mdoc_html.c
+++ b/mdoc_html.c
@@ -48,6 +48,7 @@ struct	htmlmdoc {
 	void		(*post)(MDOC_ARGS);
 };
 
+static	char		 *cond_id(const struct roff_node *);
 static	char		 *make_id(const struct roff_node *);
 static	void		  print_mdoc_head(MDOC_ARGS);
 static	void		  print_mdoc_node(MDOC_ARGS);
@@ -498,6 +499,22 @@ make_id(const struct roff_node *n)
 	return buf;
 }
 
+static char *
+cond_id(const struct roff_node *n)
+{
+	if (n->child != NULL &&
+	    n->child->type == ROFFT_TEXT &&
+	    (n->prev == NULL ||
+	     (n->prev->type == ROFFT_TEXT &&
+	      strcmp(n->prev->string, "|") == 0)) &&
+	    (n->parent->tok == MDOC_It ||
+	     (n->parent->tok == MDOC_Xo &&
+	      n->parent->parent->prev == NULL &&
+	      n->parent->parent->parent->tok == MDOC_It)))
+		return make_id(n);
+	return NULL;
+}
+
 static int
 mdoc_sh_pre(MDOC_ARGS)
 {
@@ -507,6 +524,7 @@ mdoc_sh_pre(MDOC_ARGS)
 	case ROFFT_HEAD:
 		id = make_id(n);
 		print_otag(h, TAG_H1, "cTi", "Sh", id);
+		print_otag(h, TAG_A, "chR", "selflink", id);
 		free(id);
 		break;
 	case ROFFT_BODY:
@@ -529,6 +547,7 @@ mdoc_ss_pre(MDOC_ARGS)
 
 	id = make_id(n);
 	print_otag(h, TAG_H2, "cTi", "Ss", id);
+	print_otag(h, TAG_A, "chR", "selflink", id);
 	free(id);
 	return 1;
 }
@@ -536,9 +555,14 @@ mdoc_ss_pre(MDOC_ARGS)
 static int
 mdoc_fl_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_B, "cT", "Fl");
-	print_text(h, "\\-");
+	char	*id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_B, "cTi", "Fl", id);
+	free(id);
 
+	print_text(h, "\\-");
 	if (!(n->child == NULL &&
 	    (n->next == NULL ||
 	     n->next->type == ROFFT_TEXT ||
@@ -551,7 +575,12 @@ mdoc_fl_pre(MDOC_ARGS)
 static int
 mdoc_cm_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_B, "cT", "Cm");
+	char	*id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_B, "cTi", "Cm", id);
+	free(id);
 	return 1;
 }
 
@@ -1068,21 +1097,42 @@ mdoc_cd_pre(MDOC_ARGS)
 static int
 mdoc_dv_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_CODE, "cT", "Dv");
+	char	*id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_CODE, "cTi", "Dv", id);
+	free(id);
 	return 1;
 }
 
 static int
 mdoc_ev_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_CODE, "cT", "Ev");
+	char	*id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_CODE, "cTi", "Ev", id);
+	free(id);
 	return 1;
 }
 
 static int
 mdoc_er_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_CODE, "cT", "Er");
+	char	*id;
+
+	id = n->sec == SEC_ERRORS &&
+	    (n->parent->tok == MDOC_It ||
+	     (n->parent->tok == MDOC_Bq &&
+	      n->parent->parent->parent->tok == MDOC_It)) ?
+	    make_id(n) : NULL;
+
+	if (id != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_CODE, "cTi", "Er", id);
+	free(id);
 	return 1;
 }
 
@@ -1436,7 +1486,12 @@ mdoc_in_pre(MDOC_ARGS)
 static int
 mdoc_ic_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_B, "cT", "Ic");
+	char	*id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_B, "cTi", "Ic", id);
+	free(id);
 	return 1;
 }
 
@@ -1488,7 +1543,12 @@ mdoc_bf_pre(MDOC_ARGS)
 static int
 mdoc_ms_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_B, "cT", "Ms");
+	char *id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_B, "cTi", "Ms", id);
+	free(id);
 	return 1;
 }
 
@@ -1524,14 +1584,24 @@ mdoc_rs_pre(MDOC_ARGS)
 static int
 mdoc_no_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_SPAN, "c", "No");
+	char *id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_SPAN, "ci", "No", id);
+	free(id);
 	return 1;
 }
 
 static int
 mdoc_li_pre(MDOC_ARGS)
 {
-	print_otag(h, TAG_CODE, "c", "Li");
+	char	*id;
+
+	if ((id = cond_id(n)) != NULL)
+		print_otag(h, TAG_A, "chR", "selflink", id);
+	print_otag(h, TAG_CODE, "ci", "Li", id);
+	free(id);
 	return 1;
 }