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@.

4 files changed, 57 insertions, 2 deletions

diff --git a/regress/mdoc/Fo/Makefile b/regress/mdoc/Fo/Makefile
index 09941a52..7770e9a1 100644
--- a/regress/mdoc/Fo/Makefile
+++ b/regress/mdoc/Fo/Makefile
@@ -1,7 +1,7 @@
-# $OpenBSD: Makefile,v 1.13 2015/02/16 11:39:34 schwarze Exp $
+# $OpenBSD: Makefile,v 1.17 2020/02/27 01:25:58 schwarze Exp $
 
 REGRESS_TARGETS	 = basic break eos font noarg nohead
-REGRESS_TARGETS += obsolete punct section warn
+REGRESS_TARGETS += obsolete punct section transp warn
 LINT_TARGETS	 = noarg nohead obsolete punct warn
 
 # groff-1.22.3 defects:
diff --git a/regress/mdoc/Fo/transp.in b/regress/mdoc/Fo/transp.in
new file mode 100644
index 00000000..3ca83287
--- /dev/null
+++ b/regress/mdoc/Fo/transp.in
@@ -0,0 +1,23 @@
+.\" $OpenBSD: transp.in,v 1.1 2020/02/27 01:25:58 schwarze Exp $
+.Dd $Mdocdate: February 27 2020 $
+.Dt FO-TRANSP 1
+.Os
+.Sh NAME
+.Nm Fo-transp
+.Nd transparent nodes among function argument macros
+.Sh SYNOPSIS
+.Ft type
+.Fo func
+.Fa one
+.Tg one
+.Fa two
+.Tg two
+.Fc
+.Sh DESCRIPTION
+.Ft type
+.Fo func
+.Fa one
+.Tg one
+.Fa two
+.Tg two
+.Fc
diff --git a/regress/mdoc/Fo/transp.out_ascii b/regress/mdoc/Fo/transp.out_ascii
new file mode 100644
index 00000000..fb0c37fc
--- /dev/null
+++ b/regress/mdoc/Fo/transp.out_ascii
@@ -0,0 +1,13 @@
+FO-TRANSP(1)                General Commands Manual               FO-TRANSP(1)
+
+NNAAMMEE
+     FFoo--ttrraannsspp - transparent nodes among function argument macros
+
+SSYYNNOOPPSSIISS
+     _t_y_p_e
+     ffuunncc(_o_n_e, _t_w_o);
+
+DDEESSCCRRIIPPTTIIOONN
+     _t_y_p_e ffuunncc(_o_n_e, _t_w_o)
+
+OpenBSD                        February 27, 2020                       OpenBSD
diff --git a/regress/mdoc/Fo/transp.out_markdown b/regress/mdoc/Fo/transp.out_markdown
new file mode 100644
index 00000000..237d7819
--- /dev/null
+++ b/regress/mdoc/Fo/transp.out_markdown
@@ -0,0 +1,19 @@
+FO-TRANSP(1) - General Commands Manual
+
+# NAME
+
+**Fo-transp** - transparent nodes among function argument macros
+
+# SYNOPSIS
+
+*type*  
+**func**(*one*,
+*two*);
+
+# DESCRIPTION
+
+*type*
+**func**(*one*,
+*two*)
+
+OpenBSD - February 27, 2020