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, 112 insertions, 2 deletions

diff --git a/regress/mdoc/Fl/Makefile b/regress/mdoc/Fl/Makefile
index f2b2a9aa..e4e4a6bc 100644
--- a/regress/mdoc/Fl/Makefile
+++ b/regress/mdoc/Fl/Makefile
@@ -1,6 +1,6 @@
-# $OpenBSD: Makefile,v 1.8 2014/08/21 12:56:24 schwarze Exp $
+# $OpenBSD: Makefile,v 1.13 2020/02/27 01:25:58 schwarze Exp $
 
-REGRESS_TARGETS = noarg multiarg parsed punct font
+REGRESS_TARGETS = font multiarg noarg parsed punct spacing
 LINT_TARGETS	= punct
 
 .include <bsd.regress.mk>
diff --git a/regress/mdoc/Fl/spacing.in b/regress/mdoc/Fl/spacing.in
new file mode 100644
index 00000000..8613e6b4
--- /dev/null
+++ b/regress/mdoc/Fl/spacing.in
@@ -0,0 +1,42 @@
+.\" $OpenBSD: spacing.in,v 1.1 2020/02/27 01:25:58 schwarze Exp $
+.Dd $Mdocdate$
+.Dt FL-SPACING 1
+.Os
+.Sh NAME
+.Nm Fl-spacing
+.Nd horizontal spacing after flag macros
+.Sh DESCRIPTION
+with argument:
+.Fl a
+.Pp
+no next node:
+.Xo Fl Xc suffix
+.Pp
+transparent next node only:
+.Xo Fl
+.Tg transparent1
+.Xc suffix
+.Pp
+following text:
+.Fl
+text
+.Pp
+text after transparent node on the same line:
+.Fl Es < >
+text
+.Pp
+following macro on the same line:
+.Fl Em word
+.Pp
+following macro on the next line:
+.Fl
+.Em word
+.Pp
+following macro on the next line after transparent node on the same line:
+.Fl Es < >
+.Em word
+.Pp
+following macro after transparent node on the next line:
+.Fl
+.Tg transparent3
+.Em word
diff --git a/regress/mdoc/Fl/spacing.out_ascii b/regress/mdoc/Fl/spacing.out_ascii
new file mode 100644
index 00000000..c96c3923
--- /dev/null
+++ b/regress/mdoc/Fl/spacing.out_ascii
@@ -0,0 +1,26 @@
+FL-SPACING(1)               General Commands Manual              FL-SPACING(1)
+
+NNAAMMEE
+     FFll--ssppaacciinngg - horizontal spacing after flag macros
+
+DDEESSCCRRIIPPTTIIOONN
+     with argument: --aa
+
+     no next node: -- suffix
+
+     transparent next node only: -- suffix
+
+     following text: -- text
+
+     text after transparent node on the same line: -- text
+
+     following macro on the same line: --_w_o_r_d
+
+     following macro on the next line: -- _w_o_r_d
+
+     following macro on the next line after transparent node on the same line:
+     -- _w_o_r_d
+
+     following macro after transparent node on the next line: -- _w_o_r_d
+
+OpenBSD                        February 27, 2020                       OpenBSD
diff --git a/regress/mdoc/Fl/spacing.out_markdown b/regress/mdoc/Fl/spacing.out_markdown
new file mode 100644
index 00000000..a46a44e3
--- /dev/null
+++ b/regress/mdoc/Fl/spacing.out_markdown
@@ -0,0 +1,42 @@
+FL-SPACING(1) - General Commands Manual
+
+# NAME
+
+**Fl-spacing** - horizontal spacing after flag macros
+
+# DESCRIPTION
+
+with argument:
+**-a**
+
+no next node:
+**-** suffix
+
+transparent next node only:
+**-**
+suffix
+
+following text:
+**-**
+text
+
+text after transparent node on the same line:
+**-**
+text
+
+following macro on the same line:
+**-**&zwnj;*word*
+
+following macro on the next line:
+**-**
+*word*
+
+following macro on the next line after transparent node on the same line:
+**-**
+*word*
+
+following macro after transparent node on the next line:
+**-**
+*word*
+
+OpenBSD - February 27, 2020