Two functional improvements to filling in terminal output.

1. Fully support no-fill mode in mdoc(7), even when invoked with
low-level roff(7) .nf requests.  As a side effect, this substantially
simplifies the implementation of .Bd -unfilled and .Bd -literal.

2. Let .Bd -centered fill its text, using the new TERMP_CENTER flag.
That finally fixes the long-standing bug that it used to operate in
no-fill mode, which was known to be wrong for at least five years.
This also simplifies the implementation of .Bd -centered considerably.

2 files changed, 43 insertions, 70 deletions

diff --git a/TODO b/TODO
index 8f05cb9a..d191bea0 100644
--- a/TODO
+++ b/TODO
@@ -90,13 +90,6 @@ are mere guesses, and some may be wrong.
   from jmc@  Wed, 14 Jul 2010 18:10:32 +0100
   loc *  exist ***  algo ***  size **  imp **
 
-- .Bd -centered implies -filled, not -unfilled, which is not
-  easy to implement; it requires code similar to .ce, which
-  we don't have either.
-  Besides, groff has bug causing text right *before* .Bd -centered
-  to be centered as well.
-  loc ***  exist ***  algo **  size **  imp **  (parser reorg would help)
-
 - .Bd -filled should not be the same as .Bd -ragged, but align both
   the left and right margin.  In groff, it is implemented in terms
   of .ad b, which we don't have either.  Found in cksum(1).
diff --git a/mdoc_term.c b/mdoc_term.c
index e520ac6f..6ef49375 100644
--- a/mdoc_term.c
+++ b/mdoc_term.c
@@ -1,7 +1,7 @@
 /*	$Id$ */
 /*
  * Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
- * Copyright (c) 2010, 2012-2018 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2010, 2012-2019 Ingo Schwarze <schwarze@openbsd.org>
  * Copyright (c) 2013 Franco Fichtner <franco@lastsummer.de>
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -312,6 +312,19 @@ print_mdoc_node(DECL_ARGS)
 	size_t		 offset, rmargin;
 	int		 chld;
 
+	/*
+	 * In no-fill mode, break the output line at the beginning
+	 * of new input lines except after \c, and nowhere else.
+	 */
+
+	if (n->flags & NODE_NOFILL) {
+		if (n->flags & NODE_LINE &&
+		    (p->flags & TERMP_NONEWLINE) == 0)
+			term_newln(p);
+		p->flags |= TERMP_BRNEVER;
+	} else
+		p->flags &= ~TERMP_BRNEVER;
+
 	if (n->type == ROFFT_COMMENT || n->flags & NODE_NOPRT)
 		return;
 
@@ -341,9 +354,22 @@ print_mdoc_node(DECL_ARGS)
 
 	switch (n->type) {
 	case ROFFT_TEXT:
-		if (*n->string == ' ' && n->flags & NODE_LINE &&
-		    (p->flags & TERMP_NONEWLINE) == 0)
-			term_newln(p);
+		if (n->flags & NODE_LINE) {
+			switch (*n->string) {
+			case '\0':
+				if (p->flags & TERMP_NONEWLINE)
+					term_newln(p);
+				else
+					term_vspace(p);
+				return;
+			case ' ':
+				if ((p->flags & TERMP_NONEWLINE) == 0)
+					term_newln(p);
+				break;
+			default:
+				break;
+			}
+		}
 		if (NODE_DELIMC & n->flags)
 			p->flags |= TERMP_NOSPACE;
 		term_word(p, n->string);
@@ -1418,8 +1444,6 @@ termp_fa_pre(DECL_ARGS)
 static int
 termp_bd_pre(DECL_ARGS)
 {
-	size_t			 lm, len;
-	struct roff_node	*nn;
 	int			 offset;
 
 	if (n->type == ROFFT_BLOCK) {
@@ -1445,65 +1469,19 @@ termp_bd_pre(DECL_ARGS)
 			p->tcol->offset += offset;
 	}
 
-	/*
-	 * If -ragged or -filled are specified, the block does nothing
-	 * but change the indentation.  If -unfilled or -literal are
-	 * specified, text is printed exactly as entered in the display:
-	 * for macro lines, a newline is appended to the line.  Blank
-	 * lines are allowed.
-	 */
-
-	if (n->norm->Bd.type != DISP_literal &&
-	    n->norm->Bd.type != DISP_unfilled &&
-	    n->norm->Bd.type != DISP_centered)
-		return 1;
-
-	if (n->norm->Bd.type == DISP_literal) {
+	switch (n->norm->Bd.type) {
+	case DISP_literal:
 		term_tab_set(p, NULL);
 		term_tab_set(p, "T");
 		term_tab_set(p, "8n");
+		break;
+	case DISP_centered:
+		p->flags |= TERMP_CENTER;
+		break;
+	default:
+		break;
 	}
-
-	lm = p->tcol->offset;
-	p->flags |= TERMP_BRNEVER;
-	for (nn = n->child; nn != NULL; nn = nn->next) {
-		if (n->norm->Bd.type == DISP_centered) {
-			if (nn->type == ROFFT_TEXT) {
-				len = term_strlen(p, nn->string);
-				p->tcol->offset = len >= p->tcol->rmargin ?
-				    0 : lm + len >= p->tcol->rmargin ?
-				    p->tcol->rmargin - len :
-				    (lm + p->tcol->rmargin - len) / 2;
-			} else
-				p->tcol->offset = lm;
-		}
-		print_mdoc_node(p, pair, meta, nn);
-		/*
-		 * If the printed node flushes its own line, then we
-		 * needn't do it here as well.  This is hacky, but the
-		 * notion of selective eoln whitespace is pretty dumb
-		 * anyway, so don't sweat it.
-		 */
-		if (nn->tok < ROFF_MAX)
-			continue;
-		switch (nn->tok) {
-		case MDOC_Sm:
-		case MDOC_Bl:
-		case MDOC_D1:
-		case MDOC_Dl:
-		case MDOC_Pp:
-			continue;
-		default:
-			break;
-		}
-		if (p->flags & TERMP_NONEWLINE ||
-		    (nn->next && ! (nn->next->flags & NODE_LINE)))
-			continue;
-		term_flushln(p);
-		p->flags |= TERMP_NOSPACE;
-	}
-	p->flags &= ~TERMP_BRNEVER;
-	return 0;
+	return 1;
 }
 
 static void
@@ -1511,12 +1489,14 @@ termp_bd_post(DECL_ARGS)
 {
 	if (n->type != ROFFT_BODY)
 		return;
-	if (DISP_literal == n->norm->Bd.type ||
-	    DISP_unfilled == n->norm->Bd.type)
+	if (n->norm->Bd.type == DISP_unfilled ||
+	    n->norm->Bd.type == DISP_literal)
 		p->flags |= TERMP_BRNEVER;
 	p->flags |= TERMP_NOSPACE;
 	term_newln(p);
 	p->flags &= ~TERMP_BRNEVER;
+	if (n->norm->Bd.type == DISP_centered)
+		p->flags &= ~TERMP_CENTER;
 }
 
 static int