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Revision 1.259, Tue Sep 3 12:31:05 2019 UTC (4 years, 6 months ago) by schwarze
Branch: MAIN
Changes since 1.258: +11 -14 lines

Make html_close_paragraph() more versatile, more robust, less
dependent on individual HTML elements, and simpler: don't just close
<p>, <pre>, and <a>, but any element that establishes phrasing
context.  This doesn't change output for any OpenBSD manual page,
but it will allow using this function more safely and at more places
in the future.

/*	$Id: html.c,v 1.259 2019/09/03 12:31:05 schwarze Exp $ */
/*
 * Copyright (c) 2008-2011, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
 * Copyright (c) 2011-2015, 2017-2019 Ingo Schwarze <schwarze@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * 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.
 */
#include "config.h"

#include <sys/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <ctype.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "mandoc_aux.h"
#include "mandoc_ohash.h"
#include "mandoc.h"
#include "roff.h"
#include "out.h"
#include "html.h"
#include "manconf.h"
#include "main.h"

struct	htmldata {
	const char	 *name;
	int		  flags;
#define	HTML_INPHRASE	 (1 << 0)  /* Can appear in phrasing context. */
#define	HTML_TOPHRASE	 (1 << 1)  /* Establishes phrasing context. */
#define	HTML_NOSTACK	 (1 << 2)  /* Does not have an end tag. */
#define	HTML_NLBEFORE	 (1 << 3)  /* Output line break before opening. */
#define	HTML_NLBEGIN	 (1 << 4)  /* Output line break after opening. */
#define	HTML_NLEND	 (1 << 5)  /* Output line break before closing. */
#define	HTML_NLAFTER	 (1 << 6)  /* Output line break after closing. */
#define	HTML_NLAROUND	 (HTML_NLBEFORE | HTML_NLAFTER)
#define	HTML_NLINSIDE	 (HTML_NLBEGIN | HTML_NLEND)
#define	HTML_NLALL	 (HTML_NLAROUND | HTML_NLINSIDE)
#define	HTML_INDENT	 (1 << 7)  /* Indent content by two spaces. */
#define	HTML_NOINDENT	 (1 << 8)  /* Exception: never indent content. */
};

static	const struct htmldata htmltags[TAG_MAX] = {
	{"html",	HTML_NLALL},
	{"head",	HTML_NLALL | HTML_INDENT},
	{"meta",	HTML_NOSTACK | HTML_NLALL},
	{"link",	HTML_NOSTACK | HTML_NLALL},
	{"style",	HTML_NLALL | HTML_INDENT},
	{"title",	HTML_NLAROUND},
	{"body",	HTML_NLALL},
	{"div",		HTML_NLAROUND},
	{"section",	HTML_NLALL},
	{"table",	HTML_NLALL | HTML_INDENT},
	{"tr",		HTML_NLALL | HTML_INDENT},
	{"td",		HTML_NLAROUND},
	{"li",		HTML_NLAROUND | HTML_INDENT},
	{"ul",		HTML_NLALL | HTML_INDENT},
	{"ol",		HTML_NLALL | HTML_INDENT},
	{"dl",		HTML_NLALL | HTML_INDENT},
	{"dt",		HTML_NLAROUND},
	{"dd",		HTML_NLAROUND | HTML_INDENT},
	{"h1",		HTML_TOPHRASE | HTML_NLAROUND},
	{"h2",		HTML_TOPHRASE | HTML_NLAROUND},
	{"p",		HTML_TOPHRASE | HTML_NLAROUND | HTML_INDENT},
	{"pre",		HTML_TOPHRASE | HTML_NLALL | HTML_NOINDENT},
	{"a",		HTML_INPHRASE | HTML_TOPHRASE},
	{"b",		HTML_INPHRASE | HTML_TOPHRASE},
	{"cite",	HTML_INPHRASE | HTML_TOPHRASE},
	{"code",	HTML_INPHRASE | HTML_TOPHRASE},
	{"i",		HTML_INPHRASE | HTML_TOPHRASE},
	{"small",	HTML_INPHRASE | HTML_TOPHRASE},
	{"span",	HTML_INPHRASE | HTML_TOPHRASE},
	{"var",		HTML_INPHRASE | HTML_TOPHRASE},
	{"br",		HTML_INPHRASE | HTML_NOSTACK | HTML_NLALL},
	{"math",	HTML_INPHRASE | HTML_NLALL | HTML_INDENT},
	{"mrow",	0},
	{"mi",		0},
	{"mn",		0},
	{"mo",		0},
	{"msup",	0},
	{"msub",	0},
	{"msubsup",	0},
	{"mfrac",	0},
	{"msqrt",	0},
	{"mfenced",	0},
	{"mtable",	0},
	{"mtr",		0},
	{"mtd",		0},
	{"munderover",	0},
	{"munder",	0},
	{"mover",	0},
};

/* Avoid duplicate HTML id= attributes. */
static	struct ohash	 id_unique;

static	void	 html_reset_internal(struct html *);
static	void	 print_byte(struct html *, char);
static	void	 print_endword(struct html *);
static	void	 print_indent(struct html *);
static	void	 print_word(struct html *, const char *);

static	void	 print_ctag(struct html *, struct tag *);
static	int	 print_escape(struct html *, char);
static	int	 print_encode(struct html *, const char *, const char *, int);
static	void	 print_href(struct html *, const char *, const char *, int);
static	void	 print_metaf(struct html *);


void *
html_alloc(const struct manoutput *outopts)
{
	struct html	*h;

	h = mandoc_calloc(1, sizeof(struct html));

	h->tag = NULL;
	h->style = outopts->style;
	if ((h->base_man1 = outopts->man) == NULL)
		h->base_man2 = NULL;
	else if ((h->base_man2 = strchr(h->base_man1, ';')) != NULL)
		*h->base_man2++ = '\0';
	h->base_includes = outopts->includes;
	if (outopts->fragment)
		h->oflags |= HTML_FRAGMENT;
	if (outopts->toc)
		h->oflags |= HTML_TOC;

	mandoc_ohash_init(&id_unique, 4, 0);

	return h;
}

static void
html_reset_internal(struct html *h)
{
	struct tag	*tag;
	char		*cp;
	unsigned int	 slot;

	while ((tag = h->tag) != NULL) {
		h->tag = tag->next;
		free(tag);
	}
	cp = ohash_first(&id_unique, &slot);
	while (cp != NULL) {
		free(cp);
		cp = ohash_next(&id_unique, &slot);
	}
	ohash_delete(&id_unique);
}

void
html_reset(void *p)
{
	html_reset_internal(p);
	mandoc_ohash_init(&id_unique, 4, 0);
}

void
html_free(void *p)
{
	html_reset_internal(p);
	free(p);
}

void
print_gen_head(struct html *h)
{
	struct tag	*t;

	print_otag(h, TAG_META, "?", "charset", "utf-8");
	if (h->style != NULL) {
		print_otag(h, TAG_LINK, "?h??", "rel", "stylesheet",
		    h->style, "type", "text/css", "media", "all");
		return;
	}

	/*
	 * Print a minimal embedded style sheet.
	 */

	t = print_otag(h, TAG_STYLE, "");
	print_text(h, "table.head, table.foot { width: 100%; }");
	print_endline(h);
	print_text(h, "td.head-rtitle, td.foot-os { text-align: right; }");
	print_endline(h);
	print_text(h, "td.head-vol { text-align: center; }");
	print_endline(h);
	print_text(h, ".Nd, .Bf, .Op { display: inline; }");
	print_endline(h);
	print_text(h, ".Pa, .Ad { font-style: italic; }");
	print_endline(h);
	print_text(h, ".Ms { font-weight: bold; }");
	print_endline(h);
	print_text(h, ".Bl-diag ");
	print_byte(h, '>');
	print_text(h, " dt { font-weight: bold; }");
	print_endline(h);
	print_text(h, "code.Nm, .Fl, .Cm, .Ic, code.In, .Fd, .Fn, .Cd "
	    "{ font-weight: bold; font-family: inherit; }");
	print_tagq(h, t);
}

int
html_setfont(struct html *h, enum mandoc_esc font)
{
	switch (font) {
	case ESCAPE_FONTPREV:
		font = h->metal;
		break;
	case ESCAPE_FONTITALIC:
	case ESCAPE_FONTBOLD:
	case ESCAPE_FONTBI:
	case ESCAPE_FONTCW:
	case ESCAPE_FONTROMAN:
		break;
	case ESCAPE_FONT:
		font = ESCAPE_FONTROMAN;
		break;
	default:
		return 0;
	}
	h->metal = h->metac;
	h->metac = font;
	return 1;
}

static void
print_metaf(struct html *h)
{
	if (h->metaf) {
		print_tagq(h, h->metaf);
		h->metaf = NULL;
	}
	switch (h->metac) {
	case ESCAPE_FONTITALIC:
		h->metaf = print_otag(h, TAG_I, "");
		break;
	case ESCAPE_FONTBOLD:
		h->metaf = print_otag(h, TAG_B, "");
		break;
	case ESCAPE_FONTBI:
		h->metaf = print_otag(h, TAG_B, "");
		print_otag(h, TAG_I, "");
		break;
	case ESCAPE_FONTCW:
		h->metaf = print_otag(h, TAG_SPAN, "c", "Li");
		break;
	default:
		break;
	}
}

void
html_close_paragraph(struct html *h)
{
	struct tag	*this, *next;
	int		 flags;

	this = h->tag;
	for (;;) {
		next = this->next;
		flags = htmltags[this->tag].flags;
		if (flags & (HTML_INPHRASE | HTML_TOPHRASE))
			print_ctag(h, this);
		if ((flags & HTML_INPHRASE) == 0)
			break;
		this = next;
	}
}

/*
 * ROFF_nf switches to no-fill mode, ROFF_fi to fill mode.
 * TOKEN_NONE does not switch.  The old mode is returned.
 */
enum roff_tok
html_fillmode(struct html *h, enum roff_tok want)
{
	struct tag	*t;
	enum roff_tok	 had;

	for (t = h->tag; t != NULL; t = t->next)
		if (t->tag == TAG_PRE)
			break;

	had = t == NULL ? ROFF_fi : ROFF_nf;

	if (want != had) {
		switch (want) {
		case ROFF_fi:
			print_tagq(h, t);
			break;
		case ROFF_nf:
			html_close_paragraph(h);
			print_otag(h, TAG_PRE, "");
			break;
		case TOKEN_NONE:
			break;
		default:
			abort();
		}
	}
	return had;
}

char *
html_make_id(const struct roff_node *n, int unique)
{
	const struct roff_node	*nch;
	char			*buf, *bufs, *cp;
	unsigned int		 slot;
	int			 suffix;

	for (nch = n->child; nch != NULL; nch = nch->next)
		if (nch->type != ROFFT_TEXT)
			return NULL;

	buf = NULL;
	deroff(&buf, n);
	if (buf == NULL)
		return NULL;

	/*
	 * In ID attributes, only use ASCII characters that are
	 * permitted in URL-fragment strings according to the
	 * explicit list at:
	 * https://url.spec.whatwg.org/#url-fragment-string
	 */

	for (cp = buf; *cp != '\0'; cp++)
		if (isalnum((unsigned char)*cp) == 0 &&
		    strchr("!$&'()*+,-./:;=?@_~", *cp) == NULL)
			*cp = '_';

	if (unique == 0)
		return buf;

	/* Avoid duplicate HTML id= attributes. */

	bufs = NULL;
	suffix = 1;
	slot = ohash_qlookup(&id_unique, buf);
	cp = ohash_find(&id_unique, slot);
	if (cp != NULL) {
		while (cp != NULL) {
			free(bufs);
			if (++suffix > 127) {
				free(buf);
				return NULL;
			}
			mandoc_asprintf(&bufs, "%s_%d", buf, suffix);
			slot = ohash_qlookup(&id_unique, bufs);
			cp = ohash_find(&id_unique, slot);
		}
		free(buf);
		buf = bufs;
	}
	ohash_insert(&id_unique, slot, buf);
	return buf;
}

static int
print_escape(struct html *h, char c)
{

	switch (c) {
	case '<':
		print_word(h, "&lt;");
		break;
	case '>':
		print_word(h, "&gt;");
		break;
	case '&':
		print_word(h, "&amp;");
		break;
	case '"':
		print_word(h, "&quot;");
		break;
	case ASCII_NBRSP:
		print_word(h, "&nbsp;");
		break;
	case ASCII_HYPH:
		print_byte(h, '-');
		break;
	case ASCII_BREAK:
		break;
	default:
		return 0;
	}
	return 1;
}

static int
print_encode(struct html *h, const char *p, const char *pend, int norecurse)
{
	char		 numbuf[16];
	const char	*seq;
	size_t		 sz;
	int		 c, len, breakline, nospace;
	enum mandoc_esc	 esc;
	static const char rejs[10] = { ' ', '\\', '<', '>', '&', '"',
		ASCII_NBRSP, ASCII_HYPH, ASCII_BREAK, '\0' };

	if (pend == NULL)
		pend = strchr(p, '\0');

	breakline = 0;
	nospace = 0;

	while (p < pend) {
		if (HTML_SKIPCHAR & h->flags && '\\' != *p) {
			h->flags &= ~HTML_SKIPCHAR;
			p++;
			continue;
		}

		for (sz = strcspn(p, rejs); sz-- && p < pend; p++)
			print_byte(h, *p);

		if (breakline &&
		    (p >= pend || *p == ' ' || *p == ASCII_NBRSP)) {
			print_otag(h, TAG_BR, "");
			breakline = 0;
			while (p < pend && (*p == ' ' || *p == ASCII_NBRSP))
				p++;
			continue;
		}

		if (p >= pend)
			break;

		if (*p == ' ') {
			print_endword(h);
			p++;
			continue;
		}

		if (print_escape(h, *p++))
			continue;

		esc = mandoc_escape(&p, &seq, &len);
		switch (esc) {
		case ESCAPE_FONT:
		case ESCAPE_FONTPREV:
		case ESCAPE_FONTBOLD:
		case ESCAPE_FONTITALIC:
		case ESCAPE_FONTBI:
		case ESCAPE_FONTCW:
		case ESCAPE_FONTROMAN:
			if (0 == norecurse) {
				h->flags |= HTML_NOSPACE;
				if (html_setfont(h, esc))
					print_metaf(h);
				h->flags &= ~HTML_NOSPACE;
			}
			continue;
		case ESCAPE_SKIPCHAR:
			h->flags |= HTML_SKIPCHAR;
			continue;
		case ESCAPE_ERROR:
			continue;
		default:
			break;
		}

		if (h->flags & HTML_SKIPCHAR) {
			h->flags &= ~HTML_SKIPCHAR;
			continue;
		}

		switch (esc) {
		case ESCAPE_UNICODE:
			/* Skip past "u" header. */
			c = mchars_num2uc(seq + 1, len - 1);
			break;
		case ESCAPE_NUMBERED:
			c = mchars_num2char(seq, len);
			if (c < 0)
				continue;
			break;
		case ESCAPE_SPECIAL:
			c = mchars_spec2cp(seq, len);
			if (c <= 0)
				continue;
			break;
		case ESCAPE_UNDEF:
			c = *seq;
			break;
		case ESCAPE_DEVICE:
			print_word(h, "html");
			continue;
		case ESCAPE_BREAK:
			breakline = 1;
			continue;
		case ESCAPE_NOSPACE:
			if ('\0' == *p)
				nospace = 1;
			continue;
		case ESCAPE_OVERSTRIKE:
			if (len == 0)
				continue;
			c = seq[len - 1];
			break;
		default:
			continue;
		}
		if ((c < 0x20 && c != 0x09) ||
		    (c > 0x7E && c < 0xA0))
			c = 0xFFFD;
		if (c > 0x7E) {
			(void)snprintf(numbuf, sizeof(numbuf), "&#x%.4X;", c);
			print_word(h, numbuf);
		} else if (print_escape(h, c) == 0)
			print_byte(h, c);
	}

	return nospace;
}

static void
print_href(struct html *h, const char *name, const char *sec, int man)
{
	struct stat	 sb;
	const char	*p, *pp;
	char		*filename;

	if (man) {
		pp = h->base_man1;
		if (h->base_man2 != NULL) {
			mandoc_asprintf(&filename, "%s.%s", name, sec);
			if (stat(filename, &sb) == -1)
				pp = h->base_man2;
			free(filename);
		}
	} else
		pp = h->base_includes;

	while ((p = strchr(pp, '%')) != NULL) {
		print_encode(h, pp, p, 1);
		if (man && p[1] == 'S') {
			if (sec == NULL)
				print_byte(h, '1');
			else
				print_encode(h, sec, NULL, 1);
		} else if ((man && p[1] == 'N') ||
		    (man == 0 && p[1] == 'I'))
			print_encode(h, name, NULL, 1);
		else
			print_encode(h, p, p + 2, 1);
		pp = p + 2;
	}
	if (*pp != '\0')
		print_encode(h, pp, NULL, 1);
}

struct tag *
print_otag(struct html *h, enum htmltag tag, const char *fmt, ...)
{
	va_list		 ap;
	struct tag	*t;
	const char	*attr;
	char		*arg1, *arg2;
	int		 style_written, tflags;

	tflags = htmltags[tag].flags;

	/* Flow content is not allowed in phrasing context. */

	if ((tflags & HTML_INPHRASE) == 0) {
		for (t = h->tag; t != NULL; t = t->next) {
			if (t->closed)
				continue;
			assert((htmltags[t->tag].flags & HTML_TOPHRASE) == 0);
			break;
		}
	}

	/* Push this tag onto the stack of open scopes. */

	if ((tflags & HTML_NOSTACK) == 0) {
		t = mandoc_malloc(sizeof(struct tag));
		t->tag = tag;
		t->next = h->tag;
		t->refcnt = 0;
		t->closed = 0;
		h->tag = t;
	} else
		t = NULL;

	if (tflags & HTML_NLBEFORE)
		print_endline(h);
	if (h->col == 0)
		print_indent(h);
	else if ((h->flags & HTML_NOSPACE) == 0) {
		if (h->flags & HTML_KEEP)
			print_word(h, "&#x00A0;");
		else {
			if (h->flags & HTML_PREKEEP)
				h->flags |= HTML_KEEP;
			print_endword(h);
		}
	}

	if ( ! (h->flags & HTML_NONOSPACE))
		h->flags &= ~HTML_NOSPACE;
	else
		h->flags |= HTML_NOSPACE;

	/* Print out the tag name and attributes. */

	print_byte(h, '<');
	print_word(h, htmltags[tag].name);

	va_start(ap, fmt);

	while (*fmt != '\0' && *fmt != 's') {

		/* Parse attributes and arguments. */

		arg1 = va_arg(ap, char *);
		arg2 = NULL;
		switch (*fmt++) {
		case 'c':
			attr = "class";
			break;
		case 'h':
			attr = "href";
			break;
		case 'i':
			attr = "id";
			break;
		case '?':
			attr = arg1;
			arg1 = va_arg(ap, char *);
			break;
		default:
			abort();
		}
		if (*fmt == 'M')
			arg2 = va_arg(ap, char *);
		if (arg1 == NULL)
			continue;

		/* Print the attributes. */

		print_byte(h, ' ');
		print_word(h, attr);
		print_byte(h, '=');
		print_byte(h, '"');
		switch (*fmt) {
		case 'I':
			print_href(h, arg1, NULL, 0);
			fmt++;
			break;
		case 'M':
			print_href(h, arg1, arg2, 1);
			fmt++;
			break;
		case 'R':
			print_byte(h, '#');
			print_encode(h, arg1, NULL, 1);
			fmt++;
			break;
		default:
			print_encode(h, arg1, NULL, 1);
			break;
		}
		print_byte(h, '"');
	}

	style_written = 0;
	while (*fmt++ == 's') {
		arg1 = va_arg(ap, char *);
		arg2 = va_arg(ap, char *);
		if (arg2 == NULL)
			continue;
		print_byte(h, ' ');
		if (style_written == 0) {
			print_word(h, "style=\"");
			style_written = 1;
		}
		print_word(h, arg1);
		print_byte(h, ':');
		print_byte(h, ' ');
		print_word(h, arg2);
		print_byte(h, ';');
	}
	if (style_written)
		print_byte(h, '"');

	va_end(ap);

	/* Accommodate for "well-formed" singleton escaping. */

	if (htmltags[tag].flags & HTML_NOSTACK)
		print_byte(h, '/');

	print_byte(h, '>');

	if (tflags & HTML_NLBEGIN)
		print_endline(h);
	else
		h->flags |= HTML_NOSPACE;

	if (tflags & HTML_INDENT)
		h->indent++;
	if (tflags & HTML_NOINDENT)
		h->noindent++;

	return t;
}

static void
print_ctag(struct html *h, struct tag *tag)
{
	int	 tflags;

	if (tag->closed == 0) {
		tag->closed = 1;
		if (tag == h->metaf)
			h->metaf = NULL;
		if (tag == h->tblt)
			h->tblt = NULL;

		tflags = htmltags[tag->tag].flags;
		if (tflags & HTML_INDENT)
			h->indent--;
		if (tflags & HTML_NOINDENT)
			h->noindent--;
		if (tflags & HTML_NLEND)
			print_endline(h);
		print_indent(h);
		print_byte(h, '<');
		print_byte(h, '/');
		print_word(h, htmltags[tag->tag].name);
		print_byte(h, '>');
		if (tflags & HTML_NLAFTER)
			print_endline(h);
	}
	if (tag->refcnt == 0) {
		h->tag = tag->next;
		free(tag);
	}
}

void
print_gen_decls(struct html *h)
{
	print_word(h, "<!DOCTYPE html>");
	print_endline(h);
}

void
print_gen_comment(struct html *h, struct roff_node *n)
{
	int	 wantblank;

	print_word(h, "<!-- This is an automatically generated file."
	    "  Do not edit.");
	h->indent = 1;
	wantblank = 0;
	while (n != NULL && n->type == ROFFT_COMMENT) {
		if (strstr(n->string, "-->") == NULL &&
		    (wantblank || *n->string != '\0')) {
			print_endline(h);
			print_indent(h);
			print_word(h, n->string);
			wantblank = *n->string != '\0';
		}
		n = n->next;
	}
	if (wantblank)
		print_endline(h);
	print_word(h, " -->");
	print_endline(h);
	h->indent = 0;
}

void
print_text(struct html *h, const char *word)
{
	if (h->col && (h->flags & HTML_NOSPACE) == 0) {
		if ( ! (HTML_KEEP & h->flags)) {
			if (HTML_PREKEEP & h->flags)
				h->flags |= HTML_KEEP;
			print_endword(h);
		} else
			print_word(h, "&#x00A0;");
	}

	assert(h->metaf == NULL);
	print_metaf(h);
	print_indent(h);
	if ( ! print_encode(h, word, NULL, 0)) {
		if ( ! (h->flags & HTML_NONOSPACE))
			h->flags &= ~HTML_NOSPACE;
		h->flags &= ~HTML_NONEWLINE;
	} else
		h->flags |= HTML_NOSPACE | HTML_NONEWLINE;

	if (h->metaf != NULL) {
		print_tagq(h, h->metaf);
		h->metaf = NULL;
	}

	h->flags &= ~HTML_IGNDELIM;
}

void
print_tagq(struct html *h, const struct tag *until)
{
	struct tag	*this, *next;

	for (this = h->tag; this != NULL; this = next) {
		next = this == until ? NULL : this->next;
		print_ctag(h, this);
	}
}

/*
 * Close out all open elements up to but excluding suntil.
 * Note that a paragraph just inside stays open together with it
 * because paragraphs include subsequent phrasing content.
 */
void
print_stagq(struct html *h, const struct tag *suntil)
{
	struct tag	*this, *next;

	for (this = h->tag; this != NULL; this = next) {
		next = this->next;
		if (this == suntil || (next == suntil &&
		    (this->tag == TAG_P || this->tag == TAG_PRE)))
			break;
		print_ctag(h, this);
	}
}


/***********************************************************************
 * Low level output functions.
 * They implement line breaking using a short static buffer.
 ***********************************************************************/

/*
 * Buffer one HTML output byte.
 * If the buffer is full, flush and deactivate it and start a new line.
 * If the buffer is inactive, print directly.
 */
static void
print_byte(struct html *h, char c)
{
	if ((h->flags & HTML_BUFFER) == 0) {
		putchar(c);
		h->col++;
		return;
	}

	if (h->col + h->bufcol < sizeof(h->buf)) {
		h->buf[h->bufcol++] = c;
		return;
	}

	putchar('\n');
	h->col = 0;
	print_indent(h);
	putchar(' ');
	putchar(' ');
	fwrite(h->buf, h->bufcol, 1, stdout);
	putchar(c);
	h->col = (h->indent + 1) * 2 + h->bufcol + 1;
	h->bufcol = 0;
	h->flags &= ~HTML_BUFFER;
}

/*
 * If something was printed on the current output line, end it.
 * Not to be called right after print_indent().
 */
void
print_endline(struct html *h)
{
	if (h->col == 0)
		return;

	if (h->bufcol) {
		putchar(' ');
		fwrite(h->buf, h->bufcol, 1, stdout);
		h->bufcol = 0;
	}
	putchar('\n');
	h->col = 0;
	h->flags |= HTML_NOSPACE;
	h->flags &= ~HTML_BUFFER;
}

/*
 * Flush the HTML output buffer.
 * If it is inactive, activate it.
 */
static void
print_endword(struct html *h)
{
	if (h->noindent) {
		print_byte(h, ' ');
		return;
	}

	if ((h->flags & HTML_BUFFER) == 0) {
		h->col++;
		h->flags |= HTML_BUFFER;
	} else if (h->bufcol) {
		putchar(' ');
		fwrite(h->buf, h->bufcol, 1, stdout);
		h->col += h->bufcol + 1;
	}
	h->bufcol = 0;
}

/*
 * If at the beginning of a new output line,
 * perform indentation and mark the line as containing output.
 * Make sure to really produce some output right afterwards,
 * but do not use print_otag() for producing it.
 */
static void
print_indent(struct html *h)
{
	size_t	 i;

	if (h->col)
		return;

	if (h->noindent == 0) {
		h->col = h->indent * 2;
		for (i = 0; i < h->col; i++)
			putchar(' ');
	}
	h->flags &= ~HTML_NOSPACE;
}

/*
 * Print or buffer some characters
 * depending on the current HTML output buffer state.
 */
static void
print_word(struct html *h, const char *cp)
{
	while (*cp != '\0')
		print_byte(h, *cp++);
}