From 93a372a4463b0756ab50791669b2d6f695ab7220 Mon Sep 17 00:00:00 2001
From: Ingo Schwarze <schwarze@openbsd.org>
Date: Tue, 8 Nov 2016 16:23:58 +0000
Subject: implement tag priority 0, which will tag only keys that appear as tag
 candidates exactly once, and use it for .Em and .Sy; written on the TGV
 Toulouse-Paris

---
 mdoc_term.c | 28 +++++++++++++++++++++++++---
 tag.c       | 16 ++++++++++++----
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/mdoc_term.c b/mdoc_term.c
index a05e3859..429dca6a 100644
--- a/mdoc_term.c
+++ b/mdoc_term.c
@@ -1,4 +1,4 @@
-/*	$Id: mdoc_term.c,v 1.333 2016/11/08 16:04:57 schwarze Exp $ */
+/*	$Id: mdoc_term.c,v 1.334 2016/11/08 16:23:58 schwarze Exp $ */
 /*
  * Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010, 2012-2016 Ingo Schwarze <schwarze@openbsd.org>
@@ -95,6 +95,7 @@ static	int	  termp_bx_pre(DECL_ARGS);
 static	int	  termp_cd_pre(DECL_ARGS);
 static	int	  termp_d1_pre(DECL_ARGS);
 static	int	  termp_eo_pre(DECL_ARGS);
+static	int	  termp_em_pre(DECL_ARGS);
 static	int	  termp_er_pre(DECL_ARGS);
 static	int	  termp_ex_pre(DECL_ARGS);
 static	int	  termp_fa_pre(DECL_ARGS);
@@ -119,6 +120,7 @@ static	int	  termp_skip_pre(DECL_ARGS);
 static	int	  termp_sm_pre(DECL_ARGS);
 static	int	  termp_sp_pre(DECL_ARGS);
 static	int	  termp_ss_pre(DECL_ARGS);
+static	int	  termp_sy_pre(DECL_ARGS);
 static	int	  termp_tag_pre(DECL_ARGS);
 static	int	  termp_under_pre(DECL_ARGS);
 static	int	  termp_ud_pre(DECL_ARGS);
@@ -195,7 +197,7 @@ static	const struct termact termacts[MDOC_MAX] = {
 	{ termp_quote_pre, termp_quote_post }, /* Dq */
 	{ NULL, NULL }, /* Ec */ /* FIXME: no space */
 	{ NULL, NULL }, /* Ef */
-	{ termp_under_pre, NULL }, /* Em */
+	{ termp_em_pre, NULL }, /* Em */
 	{ termp_eo_pre, termp_eo_post }, /* Eo */
 	{ termp_xx_pre, NULL }, /* Fx */
 	{ termp_bold_pre, NULL }, /* Ms */
@@ -218,7 +220,7 @@ static	const struct termact termacts[MDOC_MAX] = {
 	{ termp_quote_pre, termp_quote_post }, /* Sq */
 	{ termp_sm_pre, NULL }, /* Sm */
 	{ termp_under_pre, NULL }, /* Sx */
-	{ termp_bold_pre, NULL }, /* Sy */
+	{ termp_sy_pre, NULL }, /* Sy */
 	{ NULL, NULL }, /* Tn */
 	{ termp_xx_pre, NULL }, /* Ux */
 	{ NULL, NULL }, /* Xc */
@@ -2217,6 +2219,26 @@ termp_under_pre(DECL_ARGS)
 	return 1;
 }
 
+static int
+termp_em_pre(DECL_ARGS)
+{
+	if (n->child != NULL &&
+	    n->child->type == ROFFT_TEXT)
+		tag_put(n->child->string, 0, p->line);
+	term_fontpush(p, TERMFONT_UNDER);
+	return 1;
+}
+
+static int
+termp_sy_pre(DECL_ARGS)
+{
+	if (n->child != NULL &&
+	    n->child->type == ROFFT_TEXT)
+		tag_put(n->child->string, 0, p->line);
+	term_fontpush(p, TERMFONT_BOLD);
+	return 1;
+}
+
 static int
 termp_er_pre(DECL_ARGS)
 {
diff --git a/tag.c b/tag.c
index fd9f2a11..a618c4a0 100644
--- a/tag.c
+++ b/tag.c
@@ -1,4 +1,4 @@
-/*	$Id: tag.c,v 1.15 2016/11/08 15:57:28 schwarze Exp $ */
+/*	$Id: tag.c,v 1.16 2016/11/08 16:23:58 schwarze Exp $ */
 /*
  * Copyright (c) 2015, 2016 Ingo Schwarze <schwarze@openbsd.org>
  *
@@ -155,14 +155,22 @@ tag_put(const char *s, int prio, size_t line)
 
 	} else {
 
+		/* Handle priority 0 entries. */
+
+		if (prio == 0) {
+			if (entry->prio == 0)
+				entry->prio = -1;
+			return;
+		}
+
 		/* A better entry is already present, ignore the new one. */
 
-		if (entry->prio < prio)
+		if (entry->prio > 0 && entry->prio < prio)
 			return;
 
 		/* The existing entry is worse, clear it. */
 
-		if (entry->prio > prio)
+		if (entry->prio < 1 || entry->prio > prio)
 			entry->nlines = 0;
 	}
 
@@ -194,7 +202,7 @@ tag_write(void)
 	stream = fdopen(tag_files.tfd, "w");
 	entry = ohash_first(&tag_data, &slot);
 	while (entry != NULL) {
-		if (stream != NULL)
+		if (stream != NULL && entry->prio >= 0)
 			for (i = 0; i < entry->nlines; i++)
 				fprintf(stream, "%s %s %zu\n",
 				    entry->s, tag_files.ofn, entry->lines[i]);
-- 
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