Introduce the concept of nodes that are semantically transparent:

they are skipped when looking for previous or following high-level
macros.  Examples include roff(7) .ft, .ll, and .ta, mdoc(7) .Sm
and .Tg, and man(7) .DT and .PD.  Use this concept for a variety
of improved decisions in various validators and formatters.

While here,
* remove a few const qualifiers on struct arguments that caused trouble;
* get rid of some more Yoda notation in the vicinity;
* and apply some other stylistic improvements in the vicinity.

I found this class of issues while considering .Tg patches from kn@.

1 files changed, 54 insertions, 1 deletions

diff --git a/roff.c b/roff.c
index 84f2b7cc..017f28f9 100644
--- a/roff.c
+++ b/roff.c
@@ -1,4 +1,4 @@
-/*	$Id: roff.c,v 1.369 2020/01/19 18:02:00 schwarze Exp $ */
+/*	$Id: roff.c,v 1.370 2020/02/27 01:43:52 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2015, 2017-2020 Ingo Schwarze <schwarze@openbsd.org>
@@ -1114,6 +1114,59 @@ roff_node_delete(struct roff_man *man, struct roff_node *n)
 	roff_node_free(n);
 }
 
+int
+roff_node_transparent(struct roff_node *n)
+{
+	if (n == NULL)
+		return 0;
+	if (n->type == ROFFT_COMMENT || n->flags & NODE_NOPRT)
+		return 1;
+	switch (n->tok) {
+	case ROFF_ft:
+	case ROFF_ll:
+	case ROFF_mc:
+	case ROFF_po:
+	case ROFF_ta:
+	case MDOC_Db:
+	case MDOC_Es:
+	case MDOC_Sm:
+	case MDOC_Tg:
+	case MAN_DT:
+	case MAN_UC:
+	case MAN_PD:
+	case MAN_AT:
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+struct roff_node *
+roff_node_child(struct roff_node *n)
+{
+	for (n = n->child; roff_node_transparent(n); n = n->next)
+		continue;
+	return n;
+}
+
+struct roff_node *
+roff_node_prev(struct roff_node *n)
+{
+	do {
+		n = n->prev;
+	} while (roff_node_transparent(n));
+	return n;
+}
+
+struct roff_node *
+roff_node_next(struct roff_node *n)
+{
+	do {
+		n = n->next;
+	} while (roff_node_transparent(n));
+	return n;
+}
+
 void
 deroff(char **dest, const struct roff_node *n)
 {