Split tagging into a validation part including prioritization

in tag.{h,c} and {mdoc,man}_validate.c
and into a formatting part including command line argument checking
in term_tag.{h,c}, html.c, and {mdoc|man}_{term|html}.c.

Immediate functional benefits include:
* Improved prioritization of automatic tags for .Em and .Sy.
* Avoiding bogus automatic tags when .Em, .Fn, or .Sy are explicitly tagged.
* Explicit tagging of .Er and .Fl now works in HTML output.
* Automatic tagging of .IP and .TP now works in HTML output.
But mainly, this patch provides clean earth to build further improvements on.

Technical changes:
* Main program: Write a tag file for ASCII and UTF-8 output only.
* All formatters: There is no more need to delay writing the tags.
* mdoc(7)+man(7) formatters: No more need for elaborate syntax tree inspection.
* HTML formatter: If available, use the "string" attribute as the tag.
* HTML formatter: New function to write permalinks, to reduce code duplication.

Style cleanup in the vicinity while here:
* mdoc(7) terminal formatter: To set up bold font for children,
defer to termp_bold_pre() rather than calling term_fontpush() manually.
* mdoc(7) terminal formatter: Garbage collect some duplicate functions.
* mdoc(7) HTML formatter: Unify <code> handling, delete redundant functions.
* Where possible, use switch statements rather than if cascades.
* Get rid of some more Yoda notation.

The necessity for such changes was first discussed with kn@, but i didn't
bother him with a request to review the resulting -673/+782 line patch.

1 files changed, 15 insertions, 14 deletions

diff --git a/tag.h b/tag.h
index c1d917c8..dda0ec68 100644
--- a/tag.h
+++ b/tag.h
@@ -1,4 +1,4 @@
-/*      $Id$    */
+/* $Id$ */
 /*
  * Copyright (c) 2015, 2018, 2019, 2020 Ingo Schwarze <schwarze@openbsd.org>
  *
@@ -13,6 +13,9 @@
  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Internal interfaces to tag syntax tree nodes.
+ * For use by mandoc(1) validation modules only.
  */
 
 /*
@@ -25,19 +28,17 @@
 #define	TAG_FALLBACK	(INT_MAX - 1)	/* Tag only used if unique. */
 #define	TAG_DELETE	(INT_MAX)	/* Tag not used at all. */
 
-
-struct	tag_files {
-	char	 ofn[20];
-	char	 tfn[20];
-	char	*tagname;
-	int	 ofd;
-	int	 tfd;
-	pid_t	 tcpgid;
-	pid_t	 pager_pid;
+/*
+ * Return values of tag_check().
+ */
+enum tag_result {
+	TAG_OK,		/* Argument exists as a tag. */
+	TAG_MISS,	/* Argument not found. */
+	TAG_EMPTY	/* No tag exists at all. */
 };
 
 
-struct tag_files *tag_init(char *);
-void	 tag_put(const char *, int, size_t);
-void	 tag_write(void);
-void	 tag_unlink(void);
+void		 tag_alloc(void);
+void		 tag_put(const char *, int, struct roff_node *);
+enum tag_result	 tag_check(const char *);
+void		 tag_free(void);