Accept \0 and friends within \o.

Reported by Doug McIlroy <doug@cs.dartmouth.edu>.

* src/roff/troff/token.h (token): Add TOKEN_HORIZONTAL_SPACE
enumeration value together with `horizontal_space' member function.
Add `do_overstrike' as a friend.

* src/roff/troff/input.cpp: Use TOKEN_HORIZONTAL_SPACE for \0, \|,
\^, and \h.
Update all affected places.
(do_overstrike): Remove `static' attribute.
Accept all escapes which produce a fixed horizontal space.

2 files changed, 35 insertions, 11 deletions

diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index 98b6e58f..17d24515 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -1434,7 +1434,7 @@ static void define_color()
   skip_line();
 }
 
-static node *do_overstrike()
+node *do_overstrike()
 {
   token start;
   overstrike_node *on = new overstrike_node;
@@ -1450,11 +1450,21 @@ static node *do_overstrike()
     if (tok == start
 	&& (compatible_flag || input_stack::get_level() == start_level))
       break;
-    charinfo *ci = tok.get_char(1);
-    if (ci) {
-      node *n = curenv->make_char_node(ci);
-      if (n)
-	on->overstrike(n);
+    if (tok.horizontal_space())
+      on->overstrike(tok.nd->copy());
+    else if (tok.unstretchable_space())
+    {
+      node *n = new hmotion_node(curenv->get_space_width(),
+				 curenv->get_fill_color());
+      on->overstrike(n);
+    }
+    else {
+      charinfo *ci = tok.get_char(1);
+      if (ci) {
+	node *n = curenv->make_char_node(ci);
+	if (n)
+	  on->overstrike(n);
+      }
     }
   }
   return on;
@@ -1799,13 +1809,13 @@ void token::next()
 	goto handle_escape_char;
       case ESCAPE_BAR:
       ESCAPE_BAR:
-	type = TOKEN_NODE;
+	type = TOKEN_HORIZONTAL_SPACE;
 	nd = new hmotion_node(curenv->get_narrow_space_width(),
 			      curenv->get_fill_color());
 	return;
       case ESCAPE_CIRCUMFLEX:
       ESCAPE_CIRCUMFLEX:
-	type = TOKEN_NODE;
+	type = TOKEN_HORIZONTAL_SPACE;
 	nd = new hmotion_node(curenv->get_half_narrow_space_width(),
 			      curenv->get_fill_color());
 	return;
@@ -1926,7 +1936,7 @@ void token::next()
       case '0':
 	nd = new hmotion_node(curenv->get_digit_width(),
 			      curenv->get_fill_color());
-	type = TOKEN_NODE;
+	type = TOKEN_HORIZONTAL_SPACE;
 	return;
       case '|':
 	goto ESCAPE_BAR;
@@ -2061,7 +2071,7 @@ void token::next()
       case 'h':
 	if (!get_delim_number(&x, 'm'))
 	  break;
-	type = TOKEN_NODE;
+	type = TOKEN_HORIZONTAL_SPACE;
 	nd = new hmotion_node(x, curenv->get_fill_color());
 	return;
       case 'H':
@@ -2216,7 +2226,7 @@ void token::next()
       case 'z':
 	{
 	  next();
-	  if (type == TOKEN_NODE)
+	  if (type == TOKEN_NODE || type == TOKEN_HORIZONTAL_SPACE)
 	    nd = new zero_width_node(nd);
 	  else {
   	    charinfo *ci = get_char(1);
@@ -2346,6 +2356,7 @@ int token::delimiter(int err)
   case TOKEN_SPACE:
   case TOKEN_STRETCHABLE_SPACE:
   case TOKEN_UNSTRETCHABLE_SPACE:
+  case TOKEN_HORIZONTAL_SPACE:
   case TOKEN_TAB:
   case TOKEN_NEWLINE:
     if (err)
@@ -2402,6 +2413,8 @@ const char *token::description()
     return "`\\~'";
   case TOKEN_UNSTRETCHABLE_SPACE:
     return "`\\ '";
+  case TOKEN_HORIZONTAL_SPACE:
+    return "a horizontal space";
   case TOKEN_TAB:
     return "a tab character";
   case TOKEN_TRANSPARENT:
@@ -2951,6 +2964,7 @@ void process_input_stack()
     case token::TOKEN_EOF:
       return;
     case token::TOKEN_NODE:
+    case token::TOKEN_HORIZONTAL_SPACE:
       {
 	if (possibly_handle_first_page_transition())
 	  ;
@@ -6796,6 +6810,7 @@ int token::add_to_node_list(node **pp)
     set_number_reg(nm, curenv->get_input_line_position().to_units());
     break;
   case TOKEN_NODE:
+  case TOKEN_HORIZONTAL_SPACE:
     n = nd;
     nd = 0;
     break;
@@ -6888,6 +6903,7 @@ void token::process()
     curenv->newline();
     break;
   case TOKEN_NODE:
+  case TOKEN_HORIZONTAL_SPACE:
     curenv->add_node(nd);
     nd = 0;
     break;
diff --git a/src/roff/troff/token.h b/src/roff/troff/token.h
index 22a06aa2..19842f03 100644
--- a/src/roff/troff/token.h
+++ b/src/roff/troff/token.h
@@ -54,6 +54,7 @@ class token {
     TOKEN_SPREAD,		// \p -- break and spread output line 
     TOKEN_STRETCHABLE_SPACE,	// \~
     TOKEN_UNSTRETCHABLE_SPACE,	// `\ '
+    TOKEN_HORIZONTAL_SPACE,	// \|, \^, \0, \h
     TOKEN_TAB,			// tab
     TOKEN_TRANSPARENT,		// \!
     TOKEN_TRANSPARENT_DUMMY,	// \)
@@ -73,6 +74,7 @@ public:
   int space();			// is the current token a space?
   int stretchable_space();	// is the current token a stretchable space?
   int unstretchable_space();	// is the current token an unstretchable space?
+  int horizontal_space();	// is the current token a horizontal space?
   int white_space();		// is the current token space or tab?
   int special();		// is the current token a special character?
   int newline();		// is the current token a newline?
@@ -99,6 +101,7 @@ public:
   const char *description();
 
   friend void process_input_stack();
+  friend node *do_overstrike();
 };
 
 extern token tok;		// the current token
@@ -155,6 +158,11 @@ inline int token::unstretchable_space()
   return type == TOKEN_UNSTRETCHABLE_SPACE;
 }
 
+inline int token::horizontal_space()
+{
+  return type == TOKEN_HORIZONTAL_SPACE;
+}
+
 inline int token::special()
 { 
   return type == TOKEN_SPECIAL;