netsurf/render/html.c

/*
 * Copyright 2007 James Bursa <bursa@users.sourceforge.net>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * NetSurf is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/** \file
 * Content for text/html (implementation).
 */

#define _GNU_SOURCE /* for strndup() */

#include <assert.h>
#include <ctype.h>
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>
#include "utils/config.h"
#include "content/content.h"
#include "content/fetch.h"
#include "content/fetchcache.h"
#include "desktop/browser.h"
#include "desktop/gui.h"
#include "desktop/options.h"
#include "image/bitmap.h"
#include "render/box.h"
#include "render/favicon.h"
#include "render/font.h"
#include "render/form.h"
#include "render/html.h"
#include "render/imagemap.h"
#include "render/layout.h"
#include "utils/log.h"
#include "utils/messages.h"
#include "utils/talloc.h"
#include "utils/url.h"
#include "utils/utils.h"

#define CHUNK 4096

/* Change these to 1 to cause a dump to stderr of the frameset or box
 * when the trees have been built.
 */
#define ALWAYS_DUMP_FRAMESET 0
#define ALWAYS_DUMP_BOX 0

static void html_convert_css_callback(content_msg msg, struct content *css,
		intptr_t p1, intptr_t p2, union content_msg_data data);
static bool html_meta_refresh(struct content *c, xmlNode *head);
static bool html_head(struct content *c, xmlNode *head);
static bool html_find_stylesheets(struct content *c, xmlNode *html);
static bool html_process_style_element(struct content *c, unsigned int *index,
		xmlNode *style);
static void html_object_callback(content_msg msg, struct content *object,
		intptr_t p1, intptr_t p2, union content_msg_data data);
static void html_object_done(struct box *box, struct content *object,
			     bool background);
static void html_object_failed(struct box *box, struct content *content,
		bool background);
static bool html_object_type_permitted(const content_type type,
		const content_type *permitted_types);
static void html_object_refresh(void *p);
static void html_destroy_frameset(struct content_html_frames *frameset);
static void html_destroy_iframe(struct content_html_iframe *iframe);
#if ALWAYS_DUMP_FRAMESET
static void html_dump_frameset(struct content_html_frames *frame,
		unsigned int depth);
#endif

static const char empty_document[] =
	"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\""
	"	\"http://www.w3.org/TR/html4/strict.dtd\">"
	"<html>"
	"<head>"
	"<title>Empty document</title>"
	"</head>"
	"<body>"
	"<h1>Empty document</h1>"
	"<p>The document sent by the server is empty.</p>"
	"</body>"
	"</html>";

/**
 * Allocator
 *
 * \param ptr   Pointer to reallocate, or NULL for new allocation
 * \param size  Number of bytes requires
 * \param pw    Allocation context
 * \return Pointer to allocated block, or NULL on failure
 */
static void *myrealloc(void *ptr, size_t len, void *pw)
{
	return realloc(ptr, len);
}

/**
 * Create a CONTENT_HTML.
 *
 * The content_html_data structure is initialized and the HTML parser is
 * created.
 */

bool html_create(struct content *c, struct content *parent, 
		const char *params[])
{
	unsigned int i;
	struct content_html_data *html = &c->data.html;
	union content_msg_data msg_data;
	binding_error error;
	lwc_context *dict;
	lwc_error lerror;

	html->parser_binding = NULL;
	html->document = 0;
	html->quirks = BINDING_QUIRKS_MODE_NONE;
	html->encoding = 0;
	html->base_url = c->url;
	html->base_target = NULL;
	html->layout = 0;
	html->background_colour = NS_TRANSPARENT;
	html->stylesheet_count = 0;
	html->stylesheets = NULL;
	html->select_ctx = NULL;
	html->object_count = 0;
	html->object = 0;
	html->forms = 0;
	html->imagemaps = 0;
	html->bw = 0;
	html->frameset = 0;
	html->iframe = 0;
	html->page = 0;
	html->index = 0;
	html->box = 0;
	html->font_func = &nsfont;

	lerror = lwc_create_context(myrealloc, c, &dict);
	if (lerror != lwc_error_ok) {
		error = BINDING_NOMEM;
		goto error;
	}

	html->dict = lwc_context_ref(dict);

	for (i = 0; params[i]; i += 2) {
		if (strcasecmp(params[i], "charset") == 0) {
			html->encoding = talloc_strdup(c, params[i + 1]);
			if (!html->encoding) {
				error = BINDING_NOMEM;
				goto error;
			}
			html->encoding_source = ENCODING_SOURCE_HEADER;
			break;
		}
	}

	/* Create the parser binding */
	error = binding_create_tree(c, html->encoding, &html->parser_binding);
	if (error == BINDING_BADENCODING && html->encoding != NULL) {
		/* Ok, we don't support the declared encoding. Bailing out 
		 * isn't exactly user-friendly, so fall back to autodetect */
		talloc_free(html->encoding);
		html->encoding = NULL;

		error = binding_create_tree(c, html->encoding, 
				&html->parser_binding);
	}

	if (error != BINDING_OK)
		goto error;

	return true;

error:
	if (error == BINDING_BADENCODING) {
		LOG(("Bad encoding: %s", html->encoding ? html->encoding : ""));
		msg_data.error = messages_get("ParsingFail");
	} else
		msg_data.error = messages_get("NoMemory");

	content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
	return false;
}


/**
 * Process data for CONTENT_HTML.
 *
 * The data is parsed in chunks of size CHUNK, multitasking in between.
 */

bool html_process_data(struct content *c, char *data, unsigned int size)
{
	unsigned long x;
	binding_error err;
	const char *encoding;

	for (x = 0; x + CHUNK <= size; x += CHUNK) {
		err = binding_parse_chunk(c->data.html.parser_binding,
				(uint8_t *) data + x, CHUNK);
		if (err == BINDING_ENCODINGCHANGE) {
			goto encoding_change;
		} else if (err != BINDING_OK) {
			union content_msg_data msg_data;

			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);

			return false;
		}

		gui_multitask();
	}

	err = binding_parse_chunk(c->data.html.parser_binding,
			(uint8_t *) data + x, (size - x));
	if (err == BINDING_ENCODINGCHANGE) {
		goto encoding_change;
	} else if (err != BINDING_OK) {
		union content_msg_data msg_data;

		msg_data.error = messages_get("NoMemory");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);

		return false;
	}

	return true;

encoding_change:

	/* Retrieve new encoding */
	encoding = binding_get_encoding(
			c->data.html.parser_binding,
			&c->data.html.encoding_source);

	if (c->data.html.encoding != NULL)
		talloc_free(c->data.html.encoding);

	c->data.html.encoding = talloc_strdup(c, encoding);
	if (c->data.html.encoding == NULL) {
		union content_msg_data msg_data;

		msg_data.error = messages_get("NoMemory");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}

	/* Destroy binding */
	binding_destroy_tree(c->data.html.parser_binding);

	/* Create new binding, using the new encoding */
	err = binding_create_tree(c, c->data.html.encoding,
			&c->data.html.parser_binding);
	if (err == BINDING_BADENCODING) {
		/* Ok, we don't support the declared encoding. Bailing out 
		 * isn't exactly user-friendly, so fall back to Windows-1252 */
		talloc_free(c->data.html.encoding);
		c->data.html.encoding = talloc_strdup(c, "Windows-1252");
		if (c->data.html.encoding == NULL) {
			union content_msg_data msg_data;

			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		}

		err = binding_create_tree(c, c->data.html.encoding,
				&c->data.html.parser_binding);
	}

	if (err != BINDING_OK) {
		union content_msg_data msg_data;

		if (err == BINDING_BADENCODING) {
			LOG(("Bad encoding: %s", c->data.html.encoding 
					? c->data.html.encoding : ""));
			msg_data.error = messages_get("ParsingFail");
		} else
			msg_data.error = messages_get("NoMemory");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}

	/* Recurse to reprocess all that data.  This is safe because
	 * the encoding is now specified at parser-start which means
	 * it cannot be changed again. */
	return html_process_data(c, c->source_data, c->source_size);
}

/**
 * Convert a CONTENT_HTML for display.
 *
 * The following steps are carried out in order:
 *
 *  - parsing to an XML tree is completed
 *  - stylesheets are fetched
 *  - favicon is retrieved
 *  - the XML tree is converted to a box tree and object fetches are started
 *  - the box tree is laid out
 *
 * On exit, the content status will be either CONTENT_STATUS_DONE if the
 * document is completely loaded or CONTENT_STATUS_READY if objects are still
 * being fetched.
 */

bool html_convert(struct content *c, int width, int height)
{
	binding_error err;
	xmlNode *html, *head;
	union content_msg_data msg_data;
	unsigned int time_before, time_taken;
	struct form *f;

	/* finish parsing */
	if (c->source_size == 0) {
		/* Destroy current binding */
		binding_destroy_tree(c->data.html.parser_binding);

		/* Also, any existing encoding information, 
		 * as it's not guaranteed to match the error page.
		 */
		talloc_free(c->data.html.encoding);
		c->data.html.encoding = NULL;

		/* Create new binding, using default charset */
		err = binding_create_tree(c, NULL, 
				&c->data.html.parser_binding);
		if (err != BINDING_OK) {
			union content_msg_data msg_data;

			if (err == BINDING_BADENCODING) {
				LOG(("Bad encoding: %s", c->data.html.encoding 
						? c->data.html.encoding : ""));
				msg_data.error = messages_get("ParsingFail");
			} else
				msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		}

		/* Process the error page */
		if (html_process_data(c, (char *) empty_document, 
				SLEN(empty_document)) == false)
			return false;
	}

	err = binding_parse_completed(c->data.html.parser_binding);
	if (err != BINDING_OK) {
		union content_msg_data msg_data;

		msg_data.error = messages_get("NoMemory");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);

		return false;
	}

	c->data.html.document =
			binding_get_document(c->data.html.parser_binding,
					&c->data.html.quirks);
	/*xmlDebugDumpDocument(stderr, c->data.html.document);*/

	if (!c->data.html.document) {
		LOG(("Parsing failed"));
		msg_data.error = messages_get("ParsingFail");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}

	if (c->data.html.encoding == NULL) {
		const char *encoding = binding_get_encoding(
				c->data.html.parser_binding, 
				&c->data.html.encoding_source);

		c->data.html.encoding = talloc_strdup(c, encoding);
		if (c->data.html.encoding == NULL) {
			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		}
	}

	/* locate html and head elements */
	html = xmlDocGetRootElement(c->data.html.document);
	if (html == 0 || strcmp((const char *) html->name, "html") != 0) {
		LOG(("html element not found"));
		msg_data.error = messages_get("ParsingFail");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}
	for (head = html->children;
			head != 0 && head->type != XML_ELEMENT_NODE;
			head = head->next)
		;
	if (head && strcmp((const char *) head->name, "head") != 0) {
		head = 0;
		LOG(("head element not found"));
	}

	if (head) {
		if (!html_head(c, head)) {
			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		}

		/* handle meta refresh */
		if (!html_meta_refresh(c, head))
			return false;
	}

	/* get stylesheets */
	if (!html_find_stylesheets(c, html))
		return false;

	/* get icon */
	favicon_get_icon(c, html);
	
	/* Retrieve forms from parser */
	c->data.html.forms = binding_get_forms(c->data.html.parser_binding);
	for (f = c->data.html.forms; f != NULL; f = f->prev) {
		char *action;
		url_func_result res;

		/* Make all actions absolute */
		res = url_join(f->action, c->data.html.base_url, &action);
		if (res != URL_FUNC_OK) {
			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		}

		free(f->action);
		f->action = action;

		/* Ensure each form has a document encoding */
		if (f->document_charset == NULL) {
			f->document_charset = strdup(c->data.html.encoding);
			if (f->document_charset == NULL) {
				msg_data.error = messages_get("NoMemory");
				content_broadcast(c, CONTENT_MSG_ERROR, 
						msg_data);
				return false;
			}
		}
	}

	/* convert xml tree to box tree */
	LOG(("XML to box"));
	content_set_status(c, messages_get("Processing"));
	content_broadcast(c, CONTENT_MSG_STATUS, msg_data);
	if (!xml_to_box(html, c)) {
		msg_data.error = messages_get("NoMemory");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}
#if ALWAYS_DUMP_BOX
	box_dump(stderr, c->data.html.layout->children, 0);
#endif
#if ALWAYS_DUMP_FRAMESET
	if (c->data.html.frameset)
                html_dump_frameset(c->data.html.frameset, 0);
#endif

	/* extract image maps - can't do this sensibly in xml_to_box */
	if (!imagemap_extract(html, c)) {
		LOG(("imagemap extraction failed"));
		msg_data.error = messages_get("NoMemory");
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}
	/*imagemap_dump(c);*/

	/* layout the box tree */
	html_set_status(c, messages_get("Formatting"));
	content_broadcast(c, CONTENT_MSG_STATUS, msg_data);
	LOG(("Layout document"));
	time_before = wallclock();
	html_reformat(c, width, height);
	time_taken = wallclock() - time_before;
	LOG(("Layout took %dcs", time_taken));
	c->reformat_time = wallclock() +
		((time_taken < option_min_reflow_period ?
		option_min_reflow_period : time_taken * 1.25));
	LOG(("Scheduling relayout no sooner than %dcs",
		c->reformat_time - wallclock()));
	/*box_dump(stderr, c->data.html.layout->children, 0);*/

	/* Destroy the parser binding */
	binding_destroy_tree(c->data.html.parser_binding);
	c->data.html.parser_binding = NULL;

	c->size += lwc_context_size(c->data.html.dict);

	if (c->active == 0)
		c->status = CONTENT_STATUS_DONE;
	else
		c->status = CONTENT_STATUS_READY;
	html_set_status(c, "");

	return true;
}


/**
 * Process elements in <head>.
 *
 * \param  c     content structure
 * \param  head  xml node of head element
 * \return  true on success, false on memory exhaustion
 *
 * The title and base href are extracted if present.
 */

bool html_head(struct content *c, xmlNode *head)
{
	xmlNode *node;
	xmlChar *s;

	c->title = 0;

	for (node = head->children; node != 0; node = node->next) {
		if (node->type != XML_ELEMENT_NODE)
			continue;

		LOG(("Node: %s", node->name));
		if (!c->title && strcmp((const char *) node->name,
				"title") == 0) {
			xmlChar *title = xmlNodeGetContent(node);
			char *title2;
			if (!title)
				return false;
			title2 = squash_whitespace((const char *) title);
			xmlFree(title);
			if (!title2)
				return false;
			c->title = talloc_strdup(c, title2);
			free(title2);
			if (!c->title)
				return false;

		} else if (strcmp((const char *) node->name, "base") == 0) {
			char *href = (char *) xmlGetProp(node,
					(const xmlChar *) "href");
			if (href) {
				char *url;
				url_func_result res;
				res = url_normalize(href, &url);
				if (res == URL_FUNC_OK) {
					c->data.html.base_url =
							talloc_strdup(c, url);
					free(url);
				}
				xmlFree(href);
			}
			/* don't use the central values to ease freeing later on */
			if ((s = xmlGetProp(node, (const xmlChar *) "target"))) {
				if ((!strcasecmp((const char *) s, "_blank")) ||
						(!strcasecmp((const char *) s,
								"_top")) ||
						(!strcasecmp((const char *) s,
								"_parent")) ||
						(!strcasecmp((const char *) s,
								"_self")) ||
						('a' <= s[0] && s[0] <= 'z') ||
						('A' <= s[0] && s[0] <= 'Z')) {  /* [6.16] */
					c->data.html.base_target =
						talloc_strdup(c,
							(const char *) s);
					if (!c->data.html.base_target) {
						xmlFree(s);
						return false;
					}
				}
				xmlFree(s);
			}
		}
	}
	return true;
}


/**
 * Search for meta refresh
 *
 * http://wp.netscape.com/assist/net_sites/pushpull.html
 *
 * \param c content structure
 * \param head xml node of head element
 * \return true on success, false otherwise (error reported)
 */

bool html_meta_refresh(struct content *c, xmlNode *head)
{
	xmlNode *n;
	xmlChar *equiv, *content;
	union content_msg_data msg_data;
	char *url, *end, *refresh = NULL, quote = 0;
	url_func_result res;

	for (n = head == 0 ? 0 : head->children; n; n = n->next) {
		if (n->type != XML_ELEMENT_NODE)
			continue;

		/* Recurse into noscript elements */
		if (strcmp((const char *) n->name, "noscript") == 0) {
			if (!html_meta_refresh(c, n)) {
				/* Some error occurred */
				return false;
			} else if (c->refresh) {
				/* Meta refresh found - stop */
				return true;
			}
		}

		if (strcmp((const char *) n->name, "meta")) {
			continue;
		}

		equiv = xmlGetProp(n, (const xmlChar *) "http-equiv");
		if (!equiv)
			continue;

		if (strcasecmp((const char *) equiv, "refresh")) {
			xmlFree(equiv);
			continue;
		}

		xmlFree(equiv);

		content = xmlGetProp(n, (const xmlChar *) "content");
		if (!content)
			continue;

		end = (char *) content + strlen((const char *) content);

		/* content  := *LWS intpart fracpart? *LWS [';' *LWS *1url *LWS]
		 * intpart  := 1*DIGIT
		 * fracpart := 1*('.' | DIGIT)
		 * url      := "url" *LWS '=' *LWS (url-nq | url-sq | url-dq)
		 * url-nq   := *urlchar
		 * url-sq   := "'" *(urlchar | '"') "'"
		 * url-dq   := '"' *(urlchar | "'") '"'
		 * urlchar  := [#x9#x21#x23-#x26#x28-#x7E] | nonascii
		 * nonascii := [#x80-#xD7FF#xE000-#xFFFD#x10000-#x10FFFF]
		 */

		/* *LWS intpart */
		msg_data.delay = (int)strtol((char *) content, &url, 10);
		/* a very small delay and self-referencing URL can cause a loop
		 * that grinds machines to a halt. To prevent this we set a
		 * minimum refresh delay of 1s. */
		if (msg_data.delay < 1)
			msg_data.delay = 1;

		/* fracpart? (ignored, as delay is integer only) */
		while (url < end && (('0' <= *url && *url <= '9') || 
				*url == '.')) {
			url++;
		}

		/* *LWS */
		while (url < end && isspace(*url)) {
			url++;
		}

		/* ';' */
		if (url < end && *url == ';')
			url++;

		/* *LWS */
		while (url < end && isspace(*url)) {
			url++;
		}

		if (url == end) {
			/* Just delay specified, so refresh current page */
			xmlFree(content);

			c->refresh = talloc_strdup(c, c->url);
			if (!c->refresh) {
				msg_data.error = messages_get("NoMemory");
				content_broadcast(c,
					CONTENT_MSG_ERROR, msg_data);
				return false;
			}

			content_broadcast(c, CONTENT_MSG_REFRESH, msg_data);
			break;
		}

		/* "url" */
		if (url <= end - 3) {
			if (strncasecmp(url, "url", 3) == 0) {
				url += 3;
			} else {
				/* Unexpected input, ignore this header */
				continue;
			}
		} else {
			/* Insufficient input, ignore this header */
			continue;
		}

		/* *LWS */
		while (url < end && isspace(*url)) {
			url++;
		}

		/* '=' */
		if (url < end) {
			if (*url == '=') {
				url++;
			} else {
				/* Unexpected input, ignore this header */
				continue;
			}
		} else {
			/* Insufficient input, ignore this header */
			continue;
		}

		/* *LWS */
		while (url < end && isspace(*url)) {
			url++;
		}

		/* '"' or "'" */
		if (url < end && (*url == '"' || *url == '\'')) {
			quote = *url;
			url++;
		}

		/* Start of URL */
		refresh = url;

		if (quote != 0) {
			/* url-sq | url-dq */
			while (url < end && *url != quote)
				url++;
		} else {
			/* url-nq */
			while (url < end && !isspace(*url))
				url++;
		}

		/* '"' or "'" or *LWS (we don't care) */
		if (url < end)
			*url = '\0';

		res = url_join(refresh, c->data.html.base_url, &refresh);

		xmlFree(content);

		if (res == URL_FUNC_NOMEM) {
			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		} else if (res == URL_FUNC_FAILED) {
			/* This isn't fatal so carry on looking */
			continue;
		}

		c->refresh = talloc_strdup(c, refresh);

		free(refresh);

		if (!c->refresh) {
			msg_data.error = messages_get("NoMemory");
			content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
			return false;
		}

		content_broadcast(c, CONTENT_MSG_REFRESH, msg_data);
	}

	return true;
}


/**
 * Process inline stylesheets and fetch linked stylesheets.
 *
 * Uses STYLE and LINK elements inside and outside HEAD
 *
 * \param  c     content structure
 * \param  html  xml node of html element
 * \return  true on success, false if an error occurred
 */

bool html_find_stylesheets(struct content *c, xmlNode *html)
{
	xmlNode *node;
	char *rel, *type, *media, *href, *url, *url2;
	unsigned int i = STYLESHEET_START;
	unsigned int last_active = 0;
	union content_msg_data msg_data;
	url_func_result res;
	struct nscss_import *stylesheets;
	css_error error;

	/* stylesheet 0 is the base style sheet,
	 * stylesheet 1 is the quirks mode style sheet,
	 * stylesheet 2 is the adblocking stylesheet */
	c->data.html.stylesheets = talloc_array(c, struct nscss_import,
			STYLESHEET_START);
	if (c->data.html.stylesheets == NULL)
		goto no_memory;
	c->data.html.stylesheets[STYLESHEET_BASE].c = NULL;
	c->data.html.stylesheets[STYLESHEET_BASE].media = CSS_MEDIA_ALL;
	c->data.html.stylesheets[STYLESHEET_QUIRKS].c = NULL;
	c->data.html.stylesheets[STYLESHEET_QUIRKS].media = CSS_MEDIA_ALL;
	c->data.html.stylesheets[STYLESHEET_ADBLOCK].c = NULL;
	c->data.html.stylesheets[STYLESHEET_ADBLOCK].media = CSS_MEDIA_ALL;
	c->data.html.stylesheet_count = STYLESHEET_START;

	c->active = 0;

	c->data.html.stylesheets[STYLESHEET_BASE].c = fetchcache(
			default_stylesheet_url,
			html_convert_css_callback, (intptr_t) c,
			STYLESHEET_BASE, c->width, c->height,
			true, 0, 0, false, false);
	if (c->data.html.stylesheets[STYLESHEET_BASE].c == NULL)
		goto no_memory;
	c->active++;
	fetchcache_go(c->data.html.stylesheets[STYLESHEET_BASE].c,
			c->url, html_convert_css_callback, (intptr_t) c,
			STYLESHEET_BASE, c->width, c->height,
			0, 0, false, c);

	if (c->data.html.quirks == BINDING_QUIRKS_MODE_FULL) {
		c->data.html.stylesheets[STYLESHEET_QUIRKS].c =
				fetchcache(quirks_stylesheet_url,
				html_convert_css_callback, (intptr_t) c,
				STYLESHEET_QUIRKS, c->width, c->height,
				true, 0, 0, false, false);
		if (c->data.html.stylesheets[STYLESHEET_QUIRKS].c == NULL)
			goto no_memory;
		c->active++;
		fetchcache_go(c->data.html.stylesheets[STYLESHEET_QUIRKS].c,
				c->url, html_convert_css_callback,
				(intptr_t) c, STYLESHEET_QUIRKS, c->width,
				c->height, 0, 0, false, c);
	}

	if (option_block_ads) {
		c->data.html.stylesheets[STYLESHEET_ADBLOCK].c =
				fetchcache(adblock_stylesheet_url,
				html_convert_css_callback, (intptr_t) c,
				STYLESHEET_ADBLOCK, c->width,
				c->height, true, 0, 0, false, false);
		if (c->data.html.stylesheets[STYLESHEET_ADBLOCK].c == NULL)
			goto no_memory;
		c->active++;
		fetchcache_go(c->data.html.stylesheets[STYLESHEET_ADBLOCK].c,
				c->url, html_convert_css_callback,
				(intptr_t) c, STYLESHEET_ADBLOCK, c->width,
				c->height, 0, 0, false, c);
	}

	node = html;

	/* depth-first search the tree for link elements */
	while (node) {
		if (node->children) {  /* 1. children */
			node = node->children;
		} else if (node->next) {  /* 2. siblings */
			node = node->next;
		} else {  /* 3. ancestor siblings */
			while (node && !node->next)
				node = node->parent;
			if (!node)
				break;
			node = node->next;
		}

		assert(node);

		if (node->type != XML_ELEMENT_NODE)
			continue;

		if (strcmp((const char *) node->name, "link") == 0) {
			/* rel=<space separated list, including 'stylesheet'> */
			if ((rel = (char *) xmlGetProp(node,
					(const xmlChar *) "rel")) == NULL)
				continue;
			if (strcasestr(rel, "stylesheet") == 0) {
				xmlFree(rel);
				continue;
			} else if (strcasestr(rel, "alternate")) {
				/* Ignore alternate stylesheets */
				xmlFree(rel);
				continue;
			}
			xmlFree(rel);

			/* type='text/css' or not present */
			if ((type = (char *) xmlGetProp(node,
					(const xmlChar *) "type")) != NULL) {
				if (strcmp(type, "text/css") != 0) {
					xmlFree(type);
					continue;
				}
				xmlFree(type);
			}

			/* media contains 'screen' or 'all' or not present */
			if ((media = (char *) xmlGetProp(node,
					(const xmlChar *) "media")) != NULL) {
				if (strcasestr(media, "screen") == NULL &&
						strcasestr(media, "all") == 
						NULL) {
					xmlFree(media);
					continue;
				}
				xmlFree(media);
			}

			/* href='...' */
			if ((href = (char *) xmlGetProp(node,
					(const xmlChar *) "href")) == NULL)
				continue;

			/* TODO: only the first preferred stylesheets (ie.
			 * those with a title attribute) should be loaded
			 * (see HTML4 14.3) */

			res = url_join(href, c->data.html.base_url, &url);
			xmlFree(href);
			if (res != URL_FUNC_OK)
				continue;

			LOG(("linked stylesheet %i '%s'", i, url));

			res = url_normalize(url, &url2);

			free(url);

			if (res != URL_FUNC_OK) {
				if (res == URL_FUNC_NOMEM)
					goto no_memory;
				continue;
			}

			/* start fetch */
			stylesheets = talloc_realloc(c,
					c->data.html.stylesheets,
					struct nscss_import, i + 1);
			if (stylesheets == NULL) {
				free(url2);
				goto no_memory;
			}

			c->data.html.stylesheets = stylesheets;
			/** \todo Reflect actual media specified in link */
			c->data.html.stylesheets[i].media = CSS_MEDIA_ALL;
			c->data.html.stylesheets[i].c = fetchcache(url2,
					html_convert_css_callback,
					(intptr_t) c, i, c->width, c->height,
					true, 0, 0, false, false);
			free(url2);
			if (c->data.html.stylesheets[i].c == NULL)
				goto no_memory;

			c->active++;
			fetchcache_go(c->data.html.stylesheets[i].c,
					c->url,
					html_convert_css_callback,
					(intptr_t) c, i, c->width, c->height,
					0, 0, false, c);
			i++;
		} else if (strcmp((const char *) node->name, "style") == 0) {
			if (!html_process_style_element(c, &i, node))
				return false;
		}
	}

	c->data.html.stylesheet_count = i;

	/* complete the fetches */
	while (c->active != 0) {
		if (c->active != last_active) {
			html_set_status(c, "");
			content_broadcast(c, CONTENT_MSG_STATUS, msg_data);
			last_active = c->active;
		}
		fetch_poll();
		gui_multitask();
	}

	/* check that the base stylesheet loaded; layout fails without it */
	if (c->data.html.stylesheets[STYLESHEET_BASE].c == NULL) {
		msg_data.error = "Base stylesheet failed to load";
		content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
		return false;
	}

	/* Create selection context */
	error = css_select_ctx_create(myrealloc, c, &c->data.html.select_ctx);
	if (error != CSS_OK)
		goto no_memory;

	/* Add sheets to it */
	for (i = STYLESHEET_BASE; i != c->data.html.stylesheet_count; i++) {
		if (c->data.html.stylesheets[i].c != NULL) {
			error = css_select_ctx_append_sheet(
					c->data.html.select_ctx,
					c->data.html.stylesheets[i].c->
							data.css.sheet);
			if (error != CSS_OK)
				goto no_memory;
		}
	}

	return true;

no_memory:
	msg_data.error = messages_get("NoMemory");
	content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
	return false;
}


/**
 * Process an inline stylesheet in the document.
 *
 * \param  c      content structure
 * \param  index  Index of stylesheet in stylesheet_content array, 
 *                updated if successful
 * \param  style  xml node of style element
 * \return  true on success, false if an error occurred
 */

bool html_process_style_element(struct content *c, unsigned int *index,
		xmlNode *style)
{
	xmlNode *child;
	char *type, *media, *data;
	union content_msg_data msg_data;
	struct nscss_import *stylesheets;
	struct nscss_import *sheet;
	const char *params[] = { 0 };

	/* type='text/css', or not present (invalid but common) */
	if ((type = (char *) xmlGetProp(style, (const xmlChar *) "type"))) {
		if (strcmp(type, "text/css") != 0) {
			xmlFree(type);
			return true;
		}
		xmlFree(type);
	}

	/* media contains 'screen' or 'all' or not present */
	if ((media = (char *) xmlGetProp(style, (const xmlChar *) "media"))) {
		if (strcasestr(media, "screen") == NULL &&
				strcasestr(media, "all") == NULL) {
			xmlFree(media);
			return true;
		}
		xmlFree(media);
	}

	/* Extend array */
	stylesheets = talloc_realloc(c, c->data.html.stylesheets,
			struct nscss_import, *index + 1);
	if (stylesheets == NULL)
		goto no_memory;

	c->data.html.stylesheets = stylesheets;

	/* create stylesheet */
	sheet = &c->data.html.stylesheets[(*index)];

	/** \todo Reflect specified media */
	sheet->media = CSS_MEDIA_ALL;
	sheet->c = content_create(c->data.html.base_url);
	if (sheet->c == NULL)
		goto no_memory;

	if (content_set_type(sheet->c, 
			CONTENT_CSS, "text/css", params, c) == false) {
		/** \todo  not necessarily caused by
		 *  memory exhaustion */
		sheet->c = NULL;
		goto no_memory;
	}

	/* can't just use xmlNodeGetContent(style), because that won't
	 * give the content of comments which may be used to 'hide'
	 * the content */
	for (child = style->children; child != 0; child = child->next) {
		data = (char *) xmlNodeGetContent(child);
		if (content_process_data(sheet->c, data, strlen(data)) == 
				false) {
			xmlFree(data);
			/** \todo  not necessarily caused by
			 *  memory exhaustion */
			sheet->c = NULL;
			goto no_memory;
		}
		xmlFree(data);
	}

	/* Convert the content -- manually, as we want the result */
	if (sheet->c->source_allocated != sheet->c->source_size) {
		/* Minimise source data block */
		char *data = talloc_realloc(sheet->c, sheet->c->source_data, 
				char, sheet->c->source_size);

		if (data != NULL) {
			sheet->c->source_data = data;
			sheet->c->source_allocated = sheet->c->source_size;
		}
	}

	if (nscss_convert(sheet->c, c->width, c->height)) {
		if (content_add_user(sheet->c,
				html_convert_css_callback,
				(intptr_t) c, (*index)) == false) {
			/* no memory */
			sheet->c = NULL;
			goto no_memory;
		}
	} else {
		/* conversion failed */
		sheet->c = NULL;
	}

	/* Update index */
	(*index)++;

	return true;

no_memory:
	msg_data.error = messages_get("NoMemory");
	content_broadcast(c, CONTENT_MSG_ERROR, msg_data);
	return false;
}


/**
 * Callback for fetchcache() for linked stylesheets.
 */

void html_convert_css_callback(content_msg msg, struct content *css,
		intptr_t p1, intptr_t p2, union content_msg_data data)
{
	struct content *c = (struct content *) p1;
	unsigned int i = p2;

	switch (msg) {
	case CONTENT_MSG_LOADING:
		/* check that the stylesheet is really CSS */
		if (css->type != CONTENT_CSS) {
			c->data.html.stylesheets[i].c = NULL;
			c->active--;
			LOG(("%s is not CSS", css->url));
			content_add_error(c, "NotCSS", 0);
			html_set_status(c, messages_get("NotCSS"));
			content_broadcast(c, CONTENT_MSG_STATUS, data);
			content_remove_user(css,
					html_convert_css_callback,
					(intptr_t) c, i);
			if (css->user_list->next == NULL) {
				/* we were the only user and we
				 * don't want this content, so
				 * stop it fetching and mark it
				 * as having an error so it gets
				 * removed from the cache next time
				 * content_clean() gets called */
				fetch_abort(css->fetch);
				css->fetch = 0;
				css->status = CONTENT_STATUS_ERROR;
			}
		}
		break;

	case CONTENT_MSG_READY:
		break;

	case CONTENT_MSG_DONE:
		LOG(("got stylesheet '%s'", css->url));
		c->active--;
		break;

	case CONTENT_MSG_LAUNCH:
		/* Fall through */
	case CONTENT_MSG_ERROR:
		LOG(("stylesheet %s failed: %s", css->url, data.error));
		/* The stylesheet we were fetching may have been
		 * redirected, in that case, the object pointers
		 * will differ, so ensure that the object that's
		 * in error is still in use by us before invalidating
		 * the pointer */
		if (c->data.html.stylesheets[i].c == css) {
			c->data.html.stylesheets[i].c = NULL;
			c->active--;
			content_add_error(c, "?", 0);
		}
		break;

	case CONTENT_MSG_STATUS:
		html_set_status(c, css->status_message);
		content_broadcast(c, CONTENT_MSG_STATUS, data);
		break;

	case CONTENT_MSG_NEWPTR:
		c->data.html.stylesheets[i].c = css;
		break;

	case CONTENT_MSG_AUTH:
		c->data.html.stylesheets[i].c = NULL;
		c->active--;
		content_add_error(c, "?", 0);
		break;

	case CONTENT_MSG_SSL:
		c->data.html.stylesheets[i].c = NULL;
		c->active--;
		content_add_error(c, "?", 0);
		break;

	default:
		assert(0);
	}
}


/**
 * Start a fetch for an object required by a page.
 *
 * \param  c                 content of type CONTENT_HTML
 * \param  url               URL of object to fetch (copied)
 * \param  box               box that will contain the object
 * \param  permitted_types   array of types, terminated by CONTENT_UNKNOWN,
 *	      or 0 if all types except OTHER and UNKNOWN acceptable
 * \param  available_width   estimate of width of object
 * \param  available_height  estimate of height of object
 * \param  background        this is a background image
 * \return  true on success, false on memory exhaustion
 */

bool html_fetch_object(struct content *c, const char *url, struct box *box,
		const content_type *permitted_types,
		int available_width, int available_height,
		bool background)
{
	unsigned int i = c->data.html.object_count;
	struct content_html_object *object;
	struct content *c_fetch;
	char *url2;
	url_func_result res;

	/* Normalize the URL */
	res = url_normalize(url, &url2);
	if (res != URL_FUNC_OK) {
		LOG(("failed to normalize url '%s'", url));
		return res != URL_FUNC_NOMEM;
	}

	/* initialise fetch */
	c_fetch = fetchcache(url2, html_object_callback,
			(intptr_t) c, i, available_width, available_height,
			true, 0, 0, false, false);

	/* No longer need normalized url */
	free(url2);

	if (!c_fetch)
		return false;

	/* add to object list */
	object = talloc_realloc(c, c->data.html.object,
			struct content_html_object, i + 1);
	if (!object) {
		content_remove_user(c_fetch, html_object_callback,
				(intptr_t) c, i);
		return false;
	}
	c->data.html.object = object;
	c->data.html.object[i].box = box;
	c->data.html.object[i].permitted_types = permitted_types;
       	c->data.html.object[i].background = background;
	c->data.html.object[i].content = c_fetch;
	c->data.html.object_count++;
	c->active++;

	/* start fetch */
	fetchcache_go(c_fetch, c->url,
			html_object_callback, (intptr_t) c, i,
			available_width, available_height,
			0, 0, false, c);

	return true;
}


/**
 * Start a fetch for an object required by a page, replacing an existing object.
 *
 * \param  c               content of type CONTENT_HTML
 * \param  i               index of object to replace in c->data.html.object
 * \param  url             URL of object to fetch (copied)
 * \param  post_urlenc     url encoded post data, or 0 if none
 * \param  post_multipart  multipart post data, or 0 if none
 * \return  true on success, false on memory exhaustion
 */

bool html_replace_object(struct content *c, unsigned int i, char *url,
		char *post_urlenc,
		struct form_successful_control *post_multipart)
{
	struct content *c_fetch;
	struct content *page;
	char *url2;
	url_func_result res;

	assert(c->type == CONTENT_HTML);

	if (c->data.html.object[i].content) {
		/* remove existing object */
		if (c->data.html.object[i].content->status !=
				CONTENT_STATUS_DONE)
			c->active--;
		content_remove_user(c->data.html.object[i].content,
				html_object_callback, (intptr_t) c, i);
		c->data.html.object[i].content = 0;
		c->data.html.object[i].box->object = 0;
	}

	res = url_normalize(url, &url2);
	if (res != URL_FUNC_OK)
		return res != URL_FUNC_NOMEM;

	/* initialise fetch */
	c_fetch = fetchcache(url2, html_object_callback,
			(intptr_t) c, i,
			c->data.html.object[i].box->width,
			c->data.html.object[i].box->height,
			false, post_urlenc, post_multipart, false, false);

	free(url2);

	if (!c_fetch)
		return false;

	c->data.html.object[i].content = c_fetch;

	for (page = c; page; page = page->data.html.page) {
		assert(page->type == CONTENT_HTML);
		page->active++;
		page->status = CONTENT_STATUS_READY;
	}

	/* start fetch */
	fetchcache_go(c_fetch, c->url,
			html_object_callback, (intptr_t) c, i,
			c->data.html.object[i].box->width,
			c->data.html.object[i].box->height,
			post_urlenc, post_multipart, false, c);

	return true;
}


/**
 * Callback for fetchcache() for objects.
 */

void html_object_callback(content_msg msg, struct content *object,
		intptr_t p1, intptr_t p2, union content_msg_data data)
{
	struct content *c = (struct content *) p1;
	unsigned int i = p2;
	int x, y;
	struct box *box = c->data.html.object[i].box;

	switch (msg) {
		case CONTENT_MSG_LOADING:
			/* check if the type is acceptable for this object */
			if (html_object_type_permitted(object->type,
				c->data.html.object[i].permitted_types)) {
				if (c->data.html.bw)
					content_open(object,
							c->data.html.bw, c,
							i, box,
							box->object_params);
				break;
			}

			/* not acceptable */
			c->data.html.object[i].content = 0;
			c->active--;
			content_add_error(c, "?", 0);
			html_set_status(c, messages_get("BadObject"));
			content_broadcast(c, CONTENT_MSG_STATUS, data);
			content_remove_user(object, html_object_callback,
					(intptr_t) c, i);
			if (!object->user_list->next) {
				/* we were the only user and we
				 * don't want this content, so
				 * stop it fetching and mark it
				 * as having an error so it gets
				 * removed from the cache next time
				 * content_clean() gets called */
				fetch_abort(object->fetch);
				object->fetch = 0;
				object->status = CONTENT_STATUS_ERROR;
			}
			html_object_failed(box, c,
					c->data.html.object[i].background);
			break;

		case CONTENT_MSG_READY:
			if (object->type == CONTENT_HTML) {
				html_object_done(box, object,
					c->data.html.object[i].background);
				if (c->status == CONTENT_STATUS_READY ||
						c->status ==
						CONTENT_STATUS_DONE)
					content_reformat(c,
							c->available_width,
							c->height);
			}
			break;

		case CONTENT_MSG_DONE:
			html_object_done(box, object,
					c->data.html.object[i].background);
			c->active--;
			break;

		case CONTENT_MSG_LAUNCH:
			/* Fall through */
		case CONTENT_MSG_ERROR:
			/* The object we were fetching may have been
			 * redirected, in that case, the object pointers
			 * will differ, so ensure that the object that's
			 * in error is still in use by us before invalidating
			 * the pointer */
			if (c->data.html.object[i].content == object) {
				c->data.html.object[i].content = 0;
				c->active--;
				content_add_error(c, "?", 0);
				html_set_status(c, data.error);
				content_broadcast(c, CONTENT_MSG_STATUS,
						data);
				html_object_failed(box, c,
					c->data.html.object[i].background);
			}
			break;

		case CONTENT_MSG_STATUS:
			html_set_status(c, object->status_message);
			/* content_broadcast(c, CONTENT_MSG_STATUS, 0); */
			break;

		case CONTENT_MSG_REFORMAT:
			break;

		case CONTENT_MSG_REDRAW:
			if (!box_visible(box))
				break;
			box_coords(box, &x, &y);
			if (object == data.redraw.object) {
				data.redraw.x = data.redraw.x *
						box->width / object->width;
				data.redraw.y = data.redraw.y *
						box->height / object->height;
				data.redraw.width = data.redraw.width *
						box->width / object->width;
				data.redraw.height = data.redraw.height *
						box->height / object->height;
				data.redraw.object_width = box->width;
				data.redraw.object_height = box->height;
			}
			data.redraw.x += x + box->padding[LEFT];
			data.redraw.y += y + box->padding[TOP];
			data.redraw.object_x += x + box->padding[LEFT];
			data.redraw.object_y += y + box->padding[TOP];
			content_broadcast(c, CONTENT_MSG_REDRAW, data);
			break;

		case CONTENT_MSG_NEWPTR:
			c->data.html.object[i].content = object;
			break;

		case CONTENT_MSG_AUTH:
			c->data.html.object[i].content = 0;
			c->active--;
			content_add_error(c, "?", 0);
			break;

		case CONTENT_MSG_SSL:
			c->data.html.object[i].content = 0;
			c->active--;
			content_add_error(c, "?", 0);
			break;

		case CONTENT_MSG_REFRESH:
			if (object->type == CONTENT_HTML)
				/* only for HTML objects */
				schedule(data.delay * 100,
						html_object_refresh, object);
			break;

		default:
			assert(0);
	}

	if (c->status == CONTENT_STATUS_READY && c->active == 0 &&
			(msg == CONTENT_MSG_LOADING ||
			msg == CONTENT_MSG_DONE ||
			msg == CONTENT_MSG_ERROR ||
			msg == CONTENT_MSG_AUTH)) {
		/* all objects have arrived */
		content_reformat(c, c->available_width, c->height);
		html_set_status(c, "");
		content_set_done(c);
	}
	/* If  1) the configuration option to reflow pages while objects are
	 *        fetched is set
	 *     2) an object is newly fetched & converted,
	 *     3) the object's parent HTML is ready for reformat,
	 *     4) the time since the previous reformat is more than the
	 *        configured minimum time between reformats
	 * then reformat the page to display newly fetched objects */
	else if (option_incremental_reflow && msg == CONTENT_MSG_DONE &&
			(c->status == CONTENT_STATUS_READY ||
			 c->status == CONTENT_STATUS_DONE) &&
			(wallclock() > c->reformat_time)) {
		unsigned int time_before = wallclock(), time_taken;
		content_reformat(c, c->available_width, c->height);
		time_taken = wallclock() - time_before;
		c->reformat_time = wallclock() +
			((time_taken < option_min_reflow_period ?
			option_min_reflow_period : time_taken * 1.25));
	}
}


/**
 * Update a box whose content has completed rendering.
 */

void html_object_done(struct box *box, struct content *object,
		      bool background)
{
	struct box *b;

	if (background) {
		box->background = object;
		return;
	}

	box->object = object;

	/* invalidate parent min, max widths */
	for (b = box; b; b = b->parent)
		b->max_width = UNKNOWN_MAX_WIDTH;

	/* delete any clones of this box */
	while (box->next && box->next->clone) {
		/* box_free_box(box->next); */
		box->next = box->next->next;
	}
}


/**
 * Handle object fetching or loading failure.
 *
 * \param  box         box containing object which failed to load
 * \param  content     document of type CONTENT_HTML
 * \param  background  the object was the background image for the box
 *
 * Any fallback content for the object is made visible.
 */

void html_object_failed(struct box *box, struct content *content,
		bool background)
{
	struct box *b, *ic;

	if (background)
		return;
	if (!box->fallback)
		return;

	/* make fallback boxes into children or siblings, as appropriate */
	if (box->type != BOX_INLINE) {
		/* easy case: fallbacks become children */
		assert(box->type == BOX_BLOCK ||
				box->type == BOX_TABLE_CELL ||
				box->type == BOX_INLINE_BLOCK);
		box->children = box->fallback;
		box->last = box->children;
		while (box->last->next)
			box->last = box->last->next;
		box->fallback = 0;
		box_normalise_block(box, content);
	} else {
		assert(box->parent->type == BOX_INLINE_CONTAINER);
		if (box->fallback->type == BOX_INLINE_CONTAINER &&
				!box->fallback->next) {
			/* the fallback is a single inline container: splice
			 * it into this inline container */
			for (b = box->fallback->children; b; b = b->next)
				b->parent = box->parent;
			box->fallback->last->next = box->next;
			if (!box->next)
				box->parent->last = box->fallback->last;
			box->next = box->fallback->children;
			box->next->prev = box;
			box->fallback = 0;
		} else {
			if (box->next) {
				/* split this inline container into two inline
				 * containers */
				ic = box_create(0, 0, 0, 0, 0, content);
				if (!ic) {
					union content_msg_data msg_data;

					msg_data.error =
						messages_get("NoMemory");
					content_broadcast(content,
							CONTENT_MSG_ERROR,
							msg_data);
					return;
				}
				ic->type = BOX_INLINE_CONTAINER;
				box_insert_sibling(box->parent, ic);
				ic->children = box->next;
				ic->last = box->parent->last;
				ic->children->prev = 0;
				box->next = 0;
				box->parent->last = box;
				for (b = ic->children; b; b = b->next)
					b->parent = ic;
			}
			/* insert the fallback after the parent */
			for (b = box->fallback; b->next; b = b->next)
				b->parent = box->parent->parent;
			b->parent = box->parent->parent;
			/* [b is the last fallback box] */
			b->next = box->parent->next;
			if (b->next)
				b->next->prev = b;
			box->parent->next = box->fallback;
			box->fallback->prev = box->parent;
			box->fallback = 0;
			box_normalise_block(box->parent->parent, content);
		}
	}

	/* invalidate parent min, max widths */
	for (b = box->parent; b; b = b->parent)
		b->max_width = UNKNOWN_MAX_WIDTH;
	box->width = UNKNOWN_WIDTH;
}


/**
 * Check if a type is in a list.
 *
 * \param type the content_type to search for
 * \param permitted_types array of types, terminated by CONTENT_UNKNOWN,
 *	      or 0 if all types except OTHER and UNKNOWN acceptable
 * \return the type is in the list or acceptable
 */

bool html_object_type_permitted(const content_type type,
		const content_type *permitted_types)
{
	if (permitted_types) {
		for (; *permitted_types != CONTENT_UNKNOWN; permitted_types++)
			if (*permitted_types == type)
				return true;
	} else if (type < CONTENT_OTHER) {
		return true;
	}
	return false;
}


/**
 * schedule() callback for object refresh
 */

void html_object_refresh(void *p)
{
	struct content *c = (struct content *)p;

	assert(c->type == CONTENT_HTML);

	/* Ignore if refresh URL has gone
	 * (may happen if fetch errored) */
	if (!c->refresh)
		return;

	c->fresh = false;

	if (!html_replace_object(c->data.html.page, c->data.html.index,
			c->refresh, 0, 0)) {
		/** \todo handle memory exhaustion */
	}
}

/**
 * Stop loading a CONTENT_HTML in state READY.
 */

void html_stop(struct content *c)
{
	unsigned int i;
	struct content *object;

	assert(c->status == CONTENT_STATUS_READY);

	for (i = 0; i != c->data.html.object_count; i++) {
		object = c->data.html.object[i].content;
		if (!object)
			continue;

		if (object->status == CONTENT_STATUS_DONE)
			; /* already loaded: do nothing */
		else if (object->status == CONTENT_STATUS_READY)
			content_stop(object, html_object_callback,
					(intptr_t) c, i);
		else {
			content_remove_user(c->data.html.object[i].content,
					 html_object_callback, (intptr_t) c, i);
			c->data.html.object[i].content = 0;
		}
	}
	c->status = CONTENT_STATUS_DONE;
}


/**
 * Reformat a CONTENT_HTML to a new width.
 */

void html_reformat(struct content *c, int width, int height)
{
	struct box *layout;

	layout_document(c, width, height);
	layout = c->data.html.layout;

	/* width and height are at least margin box of document */
	c->width = layout->x + layout->padding[LEFT] + layout->width +
			layout->padding[RIGHT] + layout->border[RIGHT].width +
			layout->margin[RIGHT];
	c->height = layout->y + layout->padding[TOP] + layout->height +
			layout->padding[BOTTOM] + layout->border[BOTTOM].width +
			layout->margin[BOTTOM];

	/* if boxes overflow right or bottom edge, expand to contain it */
	if (c->width < layout->x + layout->descendant_x1)
		c->width = layout->x + layout->descendant_x1;
	if (c->height < layout->y + layout->descendant_y1)
		c->height = layout->y + layout->descendant_y1;
}


/**
 * Destroy a CONTENT_HTML and free all resources it owns.
 */

void html_destroy(struct content *c)
{
	unsigned int i;
	struct form *f, *g;

	LOG(("content %p", c));

	/* Destroy forms */
	for (f = c->data.html.forms; f != NULL; f = g) {
		g = f->prev;

		form_free(f);
	}

	imagemap_destroy(c);

	if (c->bitmap) {
	  	bitmap_destroy(c->bitmap);
	  	c->bitmap = NULL;
	}

	if (c->data.html.parser_binding)
		binding_destroy_tree(c->data.html.parser_binding);

	if (c->data.html.document)
		xmlFreeDoc(c->data.html.document);

	/* Free base target */
	if (c->data.html.base_target) {
	 	talloc_free(c->data.html.base_target);
	 	c->data.html.base_target = NULL;
	}

	/* Free frameset */
	if (c->data.html.frameset) {
		html_destroy_frameset(c->data.html.frameset);
		talloc_free(c->data.html.frameset);
		c->data.html.frameset = NULL;
	}

	/* Free iframes */
	if (c->data.html.iframe) {
		html_destroy_iframe(c->data.html.iframe);
		c->data.html.iframe = NULL;
	}

	/* Destroy selection context */
	if (c->data.html.select_ctx) {
		css_select_ctx_destroy(c->data.html.select_ctx);
		c->data.html.select_ctx = NULL;
	}

	/* Free stylesheets */
	if (c->data.html.stylesheet_count) {
		for (i = 0; i != c->data.html.stylesheet_count; i++) {
			if (c->data.html.stylesheets[i].c)
				content_remove_user(c->data.html.
						stylesheets[i].c,
						html_convert_css_callback,
						(intptr_t) c, i);
		}
	}

	/* Free objects */
	for (i = 0; i != c->data.html.object_count; i++) {
		LOG(("object %i %p", i, c->data.html.object[i].content));
		if (c->data.html.object[i].content) {
			content_remove_user(c->data.html.object[i].content,
					 html_object_callback, (intptr_t) c, i);
			if (c->data.html.object[i].content->type == CONTENT_HTML)
				schedule_remove(html_object_refresh,
					c->data.html.object[i].content);
		}
	}

	lwc_context_unref(c->data.html.dict);
}

void html_destroy_frameset(struct content_html_frames *frameset) {
	int i;

	if (frameset->name) {
		talloc_free(frameset->name);
		frameset->name = NULL;
	}
	if (frameset->url) {
		talloc_free(frameset->url);
		frameset->url = NULL;
	}
	if (frameset->children) {
		for (i = 0; i < (frameset->rows * frameset->cols); i++) {
			if (frameset->children[i].name) {
				talloc_free(frameset->children[i].name);
				frameset->children[i].name = NULL;
			}
			if (frameset->children[i].url) {
				talloc_free(frameset->children[i].url);
				frameset->children[i].url = NULL;
			}
		  	if (frameset->children[i].children)
		  		html_destroy_frameset(&frameset->children[i]);
		}
		talloc_free(frameset->children);
		frameset->children = NULL;
	}
}

void html_destroy_iframe(struct content_html_iframe *iframe) {
	struct content_html_iframe *next;
	next = iframe;
	while ((iframe = next) != NULL) {
		next = iframe->next;
		if (iframe->name)
			talloc_free(iframe->name);
		if (iframe->url)
			talloc_free(iframe->url);
		talloc_free(iframe);
	}
}


/**
 * Set the content status.
 */

void html_set_status(struct content *c, const char *extra)
{
	unsigned int stylesheets = 0, objects = 0;
	if (c->data.html.object_count == 0)
		stylesheets = c->data.html.stylesheet_count - c->active;
	else {
		stylesheets = c->data.html.stylesheet_count;
		objects = c->data.html.object_count - c->active;
	}
	content_set_status(c, "%u/%u %s %u/%u %s  %s",
			stylesheets, c->data.html.stylesheet_count,
			messages_get((c->data.html.stylesheet_count == 1) ?
					"styl" : "styls"),
			objects, c->data.html.object_count,
			messages_get((c->data.html.object_count == 1) ?
					"obj" : "objs"),
			extra);
}


/**
 * Handle a window containing a CONTENT_HTML being opened.
 */

void html_open(struct content *c, struct browser_window *bw,
		struct content *page, unsigned int index, struct box *box,
		struct object_params *params)
{
	unsigned int i;
	c->data.html.bw = bw;
	c->data.html.page = page;
	c->data.html.index = index;
	c->data.html.box = box;
	for (i = 0; i != c->data.html.object_count; i++) {
		if (c->data.html.object[i].content == 0)
			continue;
		if (c->data.html.object[i].content->type == CONTENT_UNKNOWN)
			continue;
               	content_open(c->data.html.object[i].content,
				bw, c, i,
				c->data.html.object[i].box,
				c->data.html.object[i].box->object_params);
	}
}


/**
 * Handle a window containing a CONTENT_HTML being closed.
 */

void html_close(struct content *c)
{
	unsigned int i;
	c->data.html.bw = 0;
	schedule_remove(html_object_refresh, c);
	for (i = 0; i != c->data.html.object_count; i++) {
		if (c->data.html.object[i].content == 0)
			continue;
		if (c->data.html.object[i].content->type == CONTENT_UNKNOWN)
			continue;
               	content_close(c->data.html.object[i].content);
	}
}

#if ALWAYS_DUMP_FRAMESET
/**
 * Print a frameset tree to stderr.
 */

void html_dump_frameset(struct content_html_frames *frame,
		unsigned int depth)
{
	unsigned int i;
	int row, col, index;
	const char *unit[] = {"px", "%", "*"};
	const char *scrolling[] = {"auto", "yes", "no"};

	assert(frame);

	fprintf(stderr, "%p ", frame);

	fprintf(stderr, "(%i %i) ", frame->rows, frame->cols);

	fprintf(stderr, "w%g%s ", frame->width.value, unit[frame->width.unit]);
	fprintf(stderr, "h%g%s ", frame->height.value,unit[frame->height.unit]);
	fprintf(stderr, "(margin w%i h%i) ",
			frame->margin_width, frame->margin_height);

	if (frame->name)
		fprintf(stderr, "'%s' ", frame->name);
	if (frame->url)
		fprintf(stderr, "<%s> ", frame->url);

	if (frame->no_resize)
		fprintf(stderr, "noresize ");
	fprintf(stderr, "(scrolling %s) ", scrolling[frame->scrolling]);
	if (frame->border)
		fprintf(stderr, "border %x ",
				(unsigned int) frame->border_colour);

	fprintf(stderr, "\n");

	if (frame->children) {
		for (row = 0; row != frame->rows; row++) {
			for (col = 0; col != frame->cols; col++) {
				for (i = 0; i != depth; i++)
					fprintf(stderr, "  ");
				fprintf(stderr, "(%i %i): ", row, col);
				index = (row * frame->cols) + col;
				html_dump_frameset(&frame->children[index],
						depth + 1);
			}
		}
	}
}

#endif