Moved from camel/camel-formatter, and changed slightly. (More to come.)

2000-04-14  Dan Winship  <danw@helixcode.com>

	* mail-format.[ch]: Moved from camel/camel-formatter, and changed
	slightly. (More to come.)

	* html-stream.[ch]: No longer necessary. mail-format uses
	GtkHTMLStreamHandles directly.

	* mail-display.[ch]: update for new message formatting code.

svn path=/trunk/; revision=2438

1 files changed, 793 insertions, 0 deletions

diff --git a/mail/mail-format.c b/mail/mail-format.c
new file mode 100644
index 0000000000..08c6e81073
--- /dev/null
+++ b/mail/mail-format.c
@@ -0,0 +1,793 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
+
+/*
+ * Author :
+ *  Matt Loper <matt@helixcode.com>
+ *
+ *  Copyright 2000, Helix Code, Inc. (http://www.helixcode.com)
+ *
+ *  This program 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; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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, write to the Free Software
+ *  Foundation, Inc., 59 Temple Street #330, Boston, MA 02111-1307, USA.
+ *
+ */
+
+#include <config.h>
+#include "mail-format.h"
+#include "camel/hash-table-utils.h"
+
+#include <libgnome/libgnome.h>
+#include <ctype.h>    /* for isprint */
+#include <string.h>   /* for strstr  */
+
+/* We shouldn't be doing this, but I don't feel like fixing it right
+ * now. (It's for gtk_html_stream_write.) When gtkhtml has nicer
+ * interfaces, we can fix it.
+ */
+#include <gtkhtml/gtkhtml-private.h>
+
+static void handle_text_plain           (CamelDataWrapper *wrapper,
+			                 GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_text_html            (CamelDataWrapper *wrapper,
+			                 GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_image                (CamelDataWrapper *wrapper,
+				         GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_vcard                (CamelDataWrapper *wrapper,
+				         GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_mime_part            (CamelDataWrapper *wrapper,
+			                 GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_multipart_mixed      (CamelDataWrapper *wrapper,
+				         GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_multipart_related    (CamelDataWrapper *wrapper,
+				         GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_multipart_alternative(CamelDataWrapper *wrapper,
+				         GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+static void handle_unknown_type         (CamelDataWrapper *wrapper,
+				         GtkHTMLStreamHandle *stream,
+					 CamelDataWrapper *root);
+
+/* encodes some characters into their 'escaped' version;
+ * so '<' turns into '&lt;', and '"' turns into '&quot;' */
+static gchar *text_to_html (const guchar *input,
+			    guint len,
+			    guint *encoded_len_return,
+			    gboolean convert_newlines_to_br);
+
+/* writes the header info for a mime message into an html stream */
+static void write_header_info_to_stream (CamelMimeMessage* mime_message,
+					 GtkHTMLStreamHandle *stream);
+
+/* dispatch html printing via mimetype */
+static void call_handler_function (CamelDataWrapper *wrapper,
+				   gchar *mimetype_whole, 
+				   gchar *mimetype_main,
+				   GtkHTMLStreamHandle *stream,
+				   CamelDataWrapper *root);
+
+#if 0
+/**
+ * camel_formatter_wrapper_to_html: 
+ * @formatter: the camel formatter object
+ * @data_wrapper: the data wrapper
+ * @stream: byte stream where data will be written 
+ *
+ * Writes a CamelDataWrapper out, as html, into a stream passed in as
+ * a parameter.
+ **/
+void camel_formatter_wrapper_to_html (CamelFormatter* formatter,
+				      CamelDataWrapper* data_wrapper,
+				      CamelStream* stream_out)
+{
+	CamelFormatterPrivate* fmt = formatter->priv;
+	gchar *mimetype_whole =
+		g_strdup_printf ("%s/%s",
+				 data_wrapper->mime_type->type,
+				 data_wrapper->mime_type->subtype);
+
+	debug ("camel_formatter_wrapper_to_html: entered\n");
+	g_assert (formatter && data_wrapper && stream_out);
+
+	/* give the root CamelDataWrapper and the stream to the formatter */
+	initialize_camel_formatter (formatter, data_wrapper, stream_out);
+	
+	if (stream_out) {
+		
+		/* write everything to the stream */
+		camel_stream_write_string (
+			fmt->stream, "<html><body bgcolor=\"white\">\n");
+		call_handler_function (
+			formatter,
+			data_wrapper,
+			mimetype_whole,
+			data_wrapper->mime_type->type);
+		
+		camel_stream_write_string (fmt->stream, "\n</body></html>\n");
+	}
+	
+
+	g_free (mimetype_whole);
+}
+#endif
+
+/**
+ * mail_format_mime_message: 
+ * @mime_message: the input mime message
+ * @header_stream: HTML stream to write headers to
+ * @body_stream: HTML stream to write data to
+ *
+ * Writes a CamelMimeMessage out, as html, into streams passed in as
+ * a parameter. Either stream may be #NULL.
+ **/
+void
+mail_format_mime_message (CamelMimeMessage *mime_message,
+			  GtkHTMLStreamHandle *header_stream,
+			  GtkHTMLStreamHandle *body_stream)
+{
+	g_return_if_fail (CAMEL_IS_MIME_MESSAGE (mime_message));
+
+	/* Write the headers fields out as HTML to the header stream. */
+	if (header_stream)
+		write_header_info_to_stream (mime_message, header_stream);
+
+	/* Write the contents of the MIME message to the body stream. */
+	if (body_stream) {
+		mail_write_html (body_stream, "<html><body>\n");
+		call_handler_function (CAMEL_DATA_WRAPPER (mime_message),
+				       "message/rfc822",
+				       "message",
+				       body_stream,
+				       CAMEL_DATA_WRAPPER (mime_message));
+		mail_write_html (body_stream, "\n</body></html>\n");
+	}
+}
+
+/* We're maintaining a hashtable of mimetypes -> functions;
+ * Those functions have the following signature...
+ */
+typedef void (*mime_handler_fn) (CamelDataWrapper *wrapper,
+				 GtkHTMLStreamHandle *stream,
+				 CamelDataWrapper *root);
+
+static gchar*
+lookup_unique_id (CamelDataWrapper *root, CamelDataWrapper *child)
+{
+	/* ** FIXME : replace this with a string representing
+	   the location of the objetc in the tree */
+	/* TODO: assert our return value != NULL */
+
+	gchar *temp_hack_uid;
+
+	temp_hack_uid = g_strdup_printf ("%p", camel_data_wrapper_get_output_stream (child));
+
+	return temp_hack_uid;
+}
+
+static GHashTable *mime_function_table;
+
+/* This tries to create a tag, given a mimetype and the child of a
+ * mime message. It can return NULL if it can't match the mimetype to
+ * a bonobo object.
+ */
+static gchar *
+get_bonobo_tag_for_object (CamelDataWrapper *wrapper,
+			   gchar *mimetype, CamelDataWrapper *root)
+{
+	char *uid = lookup_unique_id (root, wrapper);
+	const char *goad_id = gnome_mime_get_value (mimetype,
+						    "bonobo-goad-id");
+
+	if (goad_id) {
+		return g_strdup_printf ("<object classid=\"%s\"> "
+					"<param name=\"uid\" "
+					"value=\"camel://%s\"> </object>",
+					goad_id, uid);
+	} else
+		return NULL;
+}
+
+
+/*
+ * This takes a mimetype, and tries to map that mimetype to a function
+ * or a bonobo object.
+ *
+ * - If it's mapped to a bonobo object, this function prints a tag
+ *   into the stream, designating the bonobo object and a place that
+ *   the bonobo object can find data to hydrate from
+ *
+ * - otherwise, the mimetype is mapped to another function, which can
+ *   print into the stream
+ */
+static void
+call_handler_function (CamelDataWrapper *wrapper,
+		       gchar *mimetype_whole_in, /* ex. "image/jpeg" */
+		       gchar *mimetype_main_in, /* ex. "image" */
+		       GtkHTMLStreamHandle *stream,
+		       CamelDataWrapper *root)
+{
+	mime_handler_fn handler_function = NULL;
+	gchar *mimetype_whole = NULL;
+	gchar *mimetype_main = NULL;
+
+	g_return_if_fail (mimetype_whole_in || mimetype_main_in);
+	g_return_if_fail (CAMEL_IS_DATA_WRAPPER (wrapper));
+	g_return_if_fail (CAMEL_IS_DATA_WRAPPER (root));
+
+	if (mime_function_table == NULL) {
+		mime_function_table = g_hash_table_new (g_strcase_hash,
+							g_strcase_equal);
+
+		/* hook up mime types to functions that handle them */
+		g_hash_table_insert (mime_function_table, "text/plain",
+				     handle_text_plain);
+		g_hash_table_insert (mime_function_table, "text/richtext",
+				     handle_text_plain);
+		g_hash_table_insert (mime_function_table, "text/html",
+				     handle_text_html);
+		g_hash_table_insert (mime_function_table, "multipart/alternative",
+				     handle_multipart_alternative);
+		g_hash_table_insert (mime_function_table, "multipart/related",
+				     handle_multipart_related);
+		g_hash_table_insert (mime_function_table, "multipart/mixed",
+				     handle_multipart_mixed);
+		g_hash_table_insert (mime_function_table, "message/rfc822",
+				     handle_mime_part);
+		g_hash_table_insert (mime_function_table, "image",
+				     handle_image);
+		g_hash_table_insert (mime_function_table, "vcard",
+				     handle_vcard);
+
+		/* RFC 2046 says unrecognized multipart subtypes should
+		 * be treated like multipart/mixed.
+		 */
+		g_hash_table_insert (mime_function_table, "multipart",
+				     handle_multipart_mixed);
+
+		/* Body parts don't have mime parts per se, so Camel
+		 * sticks on the following one.
+		 */
+		g_hash_table_insert (mime_function_table, "mime/body-part",
+				     handle_mime_part);
+	}
+
+	/* Try to find a handler function in our own lookup table */
+	if (mimetype_whole_in) {
+		mimetype_whole = g_strdup (mimetype_whole_in);
+		g_strdown (mimetype_whole);
+
+		handler_function = g_hash_table_lookup (mime_function_table,
+							mimetype_whole);
+	}
+
+	if (mimetype_main_in && !handler_function) {
+		mimetype_main = g_strdup (mimetype_main_in);
+		g_strdown (mimetype_main);
+
+		handler_function = g_hash_table_lookup (mime_function_table,
+							mimetype_main);
+	}
+
+	/* Upon failure, try to find a bonobo object to show the object */
+	if (!handler_function) {
+		gchar *bonobo_tag = NULL;
+
+		if (mimetype_whole)
+			bonobo_tag = get_bonobo_tag_for_object (
+				wrapper, mimetype_whole, root);
+
+		if (mimetype_main && !bonobo_tag)
+			bonobo_tag = get_bonobo_tag_for_object (
+				wrapper, mimetype_main, root);
+
+		if (bonobo_tag) {
+			/* We can print a tag, and return! */
+
+			mail_write_html (stream, bonobo_tag);
+			g_free (bonobo_tag);
+			if (mimetype_whole)
+				g_free (mimetype_whole);
+			if (mimetype_main)
+				g_free (mimetype_main);
+
+			return; 
+		}
+	}
+
+	/* Use either a handler function we've found, or a default handler. */
+	if (handler_function)
+		(*handler_function) (wrapper, stream, root);
+	else
+		handle_unknown_type (wrapper, stream, root);
+	if (mimetype_whole)
+		g_free (mimetype_whole);
+	if (mimetype_main)
+		g_free (mimetype_main);
+}
+
+
+/* Convert plain text in equivalent-looking valid HTML. */
+static gchar *
+text_to_html (const guchar *input, guint len,
+	      guint *encoded_len_return,
+	      gboolean convert_newlines_to_br)
+{
+	const guchar *cur = input;
+	guchar *buffer = NULL;
+	guchar *out = NULL;
+	gint buffer_size = 0;
+	guint count;
+
+	/* Allocate a translation buffer.  */
+	buffer_size = len * 2;
+	buffer = g_malloc (buffer_size);
+
+	out = buffer;
+	count = 0;
+
+	while (len--) {
+		if (out - buffer > buffer_size - 100) {
+			gint index = out - buffer;
+
+			buffer_size *= 2;
+			buffer = g_realloc (buffer, buffer_size);
+			out = buffer + index;
+		}
+
+		switch (*cur) {
+		case '<':
+			strcpy (out, "&lt;");
+			out += 4;
+			break;
+
+		case '>':
+			strcpy (out, "&gt;");
+			out += 4;
+			break;
+
+		case '&':
+			strcpy (out, "&amp;");
+			out += 5;
+			break;
+
+		case '"':
+			strcpy (out, "&quot;");
+			out += 6;
+			break;
+
+		case '\n':
+			*out++ = *cur;
+			if (convert_newlines_to_br) {
+				strcpy (out, "<br>");
+				out += 4;
+			}
+			break;
+
+		default:
+			if ((*cur >= 0x20 && *cur < 0x80) ||
+			    (*cur == '\r' || *cur == '\t')) {
+				/* Default case, just copy. */
+				*out++ = *cur;
+			} else
+				out += g_snprintf(out, 9, "&#%d;", *cur);
+			break;
+		}
+
+		cur++;
+	}
+
+	*out = '\0';
+	if (encoded_len_return)
+		*encoded_len_return = out - buffer;
+
+	return buffer;
+}
+
+
+static void
+write_field_to_stream (const gchar *description, const gchar *value,
+		       GtkHTMLStreamHandle *stream)
+{
+	gchar *s;
+	gchar *encoded_value;
+
+	if (value) {
+		unsigned char *p;
+
+		encoded_value = text_to_html (value, strlen(value),
+					      NULL, TRUE);
+		for (p = (unsigned char *)encoded_value; *p; p++) {
+			if (!isprint (*p))
+				*p = '?';
+		}
+	} else
+		encoded_value = g_strdup ("");
+
+	s = g_strdup_printf ("<tr valign=top><th align=right>%s</th>"
+			     "<td>%s</td></tr>", description, encoded_value);
+	mail_write_html (stream, s);
+	g_free (encoded_value);
+	g_free (s);
+}
+
+static void
+write_recipients_to_stream (const gchar *recipient_type,
+			    const GList *recipients,
+			    GtkHTMLStreamHandle *stream)
+{
+	gchar *recipients_string = NULL;
+
+ 	while (recipients) {
+		gchar *old_string = recipients_string;
+		recipients_string =
+			g_strdup_printf ("%s%s%s",
+					 old_string ? old_string : "",
+					 old_string ? "; " : "",
+					 (gchar *)recipients->data);
+		g_free (old_string);
+
+		recipients = recipients->next;
+	}
+
+	write_field_to_stream (recipient_type, recipients_string, stream);
+	g_free (recipients_string);
+}
+
+
+
+static void
+write_header_info_to_stream (CamelMimeMessage *mime_message,
+			     GtkHTMLStreamHandle *stream)
+{
+	GList *recipients;
+
+	mail_write_html (stream, "<table>");
+
+	/* A few fields will probably be available from the mime_message;
+	 * for each one that's available, write it to the output stream
+	 * with a helper function, 'write_field_to_stream'.
+	 */
+
+	write_field_to_stream ("From:",
+			       camel_mime_message_get_from (mime_message),
+			       stream);
+
+	write_recipients_to_stream ("To:",
+				    camel_mime_message_get_recipients (mime_message, CAMEL_RECIPIENT_TYPE_TO),
+				    stream);
+
+	recipients = camel_mime_message_get_recipients (mime_message, CAMEL_RECIPIENT_TYPE_CC);
+	if (recipients)
+		write_recipients_to_stream ("Cc:", recipients, stream);
+	write_field_to_stream ("Subject:",
+			       camel_mime_message_get_subject (mime_message),
+			       stream);
+
+	mail_write_html (stream, "</table>");	
+}
+
+/* case-insensitive string comparison */
+static gint
+strcase_equal (gconstpointer v, gconstpointer v2)
+{
+	return g_strcasecmp ((const gchar*) v, (const gchar*)v2) == 0;
+}
+
+#define MIME_TYPE_WHOLE(a)  (gmime_content_field_get_mime_type ( \
+                                      camel_mime_part_get_content_type (CAMEL_MIME_PART (a))))
+#define MIME_TYPE_MAIN(a)  ((camel_mime_part_get_content_type (CAMEL_MIME_PART (a)))->type)
+#define MIME_TYPE_SUB(a)   ((camel_mime_part_get_content_type (CAMEL_MIME_PART (a)))->subtype)
+
+
+/*----------------------------------------------------------------------*
+ *                     Mime handling functions
+ *----------------------------------------------------------------------*/
+
+static void
+handle_text_plain (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
+		   CamelDataWrapper *root)
+{
+	gchar *text;
+	CamelStream *wrapper_output_stream;
+	gchar tmp_buffer[4096];
+	gint nb_bytes_read;
+	gboolean empty_text = TRUE;
+
+	
+	mail_write_html (stream, "\n<!-- text/plain below -->\n");
+	mail_write_html (stream, "<pre>\n");
+
+	/* FIXME: text/richtext is not difficult to translate into HTML */
+	if (strcmp (wrapper->mime_type->subtype, "richtext") == 0) {
+		mail_write_html (stream, "<center><b>"
+				 "<table bgcolor=\"b0b0ff\" cellpadding=3>"
+				 "<tr><td>Warning: the following "
+				 "richtext may not be formatted correctly. "
+				 "</b></td></tr></table></center><br>");
+	}
+
+	/* Get the output stream of the data wrapper. */
+	wrapper_output_stream = camel_data_wrapper_get_output_stream (wrapper);
+	camel_stream_reset (wrapper_output_stream);
+
+	do {
+		/* Read next chunk of text. */
+		nb_bytes_read = camel_stream_read (wrapper_output_stream,
+						   tmp_buffer, 4096);
+
+		/* If there's any text, write it to the stream. */
+		if (nb_bytes_read > 0) {
+			int returned_strlen;
+
+			empty_text = FALSE;
+
+			/* replace '<' with '&lt;', etc. */
+			text = text_to_html (tmp_buffer,
+					     nb_bytes_read,
+					     &returned_strlen,
+					     FALSE);
+			mail_write_html (stream, text);
+			g_free (text);
+		}
+	} while (!camel_stream_eos (wrapper_output_stream));
+
+	if (empty_text)
+		mail_write_html (stream, "<b>(empty)</b>");
+
+	mail_write_html (stream, "</pre>\n");	
+}
+
+static void
+handle_text_html (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
+		  CamelDataWrapper *root)
+{
+	CamelStream *wrapper_output_stream;
+	gchar tmp_buffer[4096];
+	gint nb_bytes_read;
+	gboolean empty_text = TRUE;
+
+	/* Get the output stream of the data wrapper. */
+	wrapper_output_stream = camel_data_wrapper_get_output_stream (wrapper);
+	camel_stream_reset (wrapper_output_stream);
+
+	/* Write the header. */
+	mail_write_html (stream, "\n<!-- text/html below -->\n");
+
+	do {
+		/* Read next chunk of text. */
+		nb_bytes_read = camel_stream_read (wrapper_output_stream,
+						   tmp_buffer, 4096);
+
+		/* If there's any text, write it to the stream */
+		if (nb_bytes_read > 0) {
+			empty_text = FALSE;
+			
+			/* Write the buffer to the html stream */
+			gtk_html_stream_write (stream, tmp_buffer,
+					       nb_bytes_read);
+		}
+	} while (!camel_stream_eos (wrapper_output_stream));
+
+	if (empty_text)
+		mail_write_html (stream, "<b>(empty)</b>");
+}
+
+static void
+handle_image (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
+	      CamelDataWrapper *root)
+{
+	gchar *uuid;
+	gchar *tag;
+
+	uuid = lookup_unique_id (root, wrapper);
+
+	mail_write_html (stream, "\n<!-- image below -->\n");
+	tag = g_strdup_printf ("<img src=\"camel://%s\">\n", uuid);
+	mail_write_html (stream, tag);
+	g_free (uuid);
+	g_free (tag);		
+}
+
+static void
+handle_vcard (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
+	      CamelDataWrapper *root)
+{
+	mail_write_html (stream, "\n<!-- vcard below -->\n");
+
+	/* FIXME: do something here. */
+}
+
+static void
+handle_mime_part (CamelDataWrapper *wrapper, GtkHTMLStreamHandle *stream,
+		  CamelDataWrapper *root)
+{
+	CamelMimePart *mime_part; 
+	CamelDataWrapper *message_contents; 
+	gchar *whole_mime_type;
+
+	g_return_if_fail (CAMEL_IS_MIME_PART (wrapper));
+
+	mime_part = CAMEL_MIME_PART (wrapper);
+	message_contents =
+		camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));
+
+	g_assert (message_contents);
+
+	mail_write_html (stream, "\n<!-- mime message below -->\n");
+
+//	mail_write_html (stream,
+//				   "<table width=95% border=1><tr><td>\n\n");		
+
+	/* dispatch the correct handler function for the mime type */
+	whole_mime_type = MIME_TYPE_WHOLE (mime_part);
+	call_handler_function (message_contents,
+			       whole_mime_type,
+			       MIME_TYPE_MAIN (mime_part),
+			       stream, root);
+	g_free (whole_mime_type);
+
+	/* close up the table we opened */
+//	mail_write_html (stream,
+//				   "\n\n</td></tr></table>\n\n");
+}
+
+
+/* called for each body part in a multipart/mixed */
+static void
+display_camel_body_part (CamelMimeBodyPart *body_part,
+			 GtkHTMLStreamHandle *stream,
+			 CamelDataWrapper *root)
+{
+	gchar *whole_mime_type;
+
+	CamelDataWrapper* contents =
+		camel_medium_get_content_object (CAMEL_MEDIUM (body_part));
+
+	whole_mime_type = MIME_TYPE_WHOLE (body_part);
+	call_handler_function (contents, whole_mime_type,
+			       MIME_TYPE_MAIN (body_part),
+			       stream, root);
+	g_free (whole_mime_type);
+
+	mail_write_html (stream, "\n<hr>\n");
+}
+
+
+/* Our policy here is this:
+   (1) print text/(plain|html) parts found
+   (2) print vcards and images inline
+   (3) treat all other parts as attachments */
+static void
+handle_multipart_mixed (CamelDataWrapper *wrapper,
+			GtkHTMLStreamHandle *stream, CamelDataWrapper *root)
+{
+	CamelMultipart *mp;
+	int i, nparts;
+
+	g_return_if_fail (CAMEL_IS_MULTIPART (wrapper));
+
+	mp = CAMEL_MULTIPART (wrapper);
+
+	nparts = camel_multipart_get_number (mp);	
+	for (i = 0; i < nparts; i++) {
+		CamelMimeBodyPart *body_part =
+			camel_multipart_get_part (mp, i);
+
+		display_camel_body_part (body_part, stream, root);
+	}
+}
+
+static void
+handle_multipart_related (CamelDataWrapper *wrapper,
+			  GtkHTMLStreamHandle *stream,
+			  CamelDataWrapper *root)
+{
+//	CamelMultipart* mp = CAMEL_MULTIPART (wrapper);
+
+	/* FIXME: read RFC, in terms of how a one message
+	   may refer to another object */	
+}
+
+/* multipart/alternative helper function --
+ * Returns NULL if no displayable msg is found
+ */
+static CamelMimePart *
+find_preferred_alternative (CamelMultipart* multipart)
+{
+	int i, nparts;
+	CamelMimePart* html_part = NULL;
+	CamelMimePart* plain_part = NULL;	
+
+	/* Find out out many parts are in it. */
+	nparts = camel_multipart_get_number (multipart);
+
+	/* FIXME: DO LEAF-LOOKUP HERE FOR OTHER MIME-TYPES!!! */
+
+	for (i = 0; i < nparts; i++) {
+		CamelMimeBodyPart *body_part =
+			camel_multipart_get_part (multipart, i);
+
+		if (strcasecmp (MIME_TYPE_MAIN (body_part), "text") != 0)
+			continue;
+
+		if (strcasecmp (MIME_TYPE_SUB (body_part), "plain") == 0)
+			plain_part = CAMEL_MIME_PART (body_part);
+		else if (strcasecmp (MIME_TYPE_SUB (body_part), "html") == 0)
+			html_part = CAMEL_MIME_PART (body_part);
+	}
+
+	if (html_part)
+		return html_part;
+	if (plain_part)
+		return plain_part;
+	return NULL;
+}
+
+/* The current policy for multipart/alternative is this: 
+ *
+ * if (we find a text/html body part)
+ *     we print it
+ * else if (we find a text/plain body part)
+ *     we print it
+ * else
+ *     we print nothing
+ */
+static void
+handle_multipart_alternative (CamelDataWrapper *wrapper,
+			      GtkHTMLStreamHandle *stream,
+			      CamelDataWrapper *root)
+{
+	CamelMultipart *multipart = CAMEL_MULTIPART (wrapper);
+	CamelMimePart *mime_part;
+	gchar *whole_mime_type;
+
+	mime_part = find_preferred_alternative (multipart);	
+	if (mime_part) {
+		CamelDataWrapper *contents =
+			camel_medium_get_content_object (
+				CAMEL_MEDIUM (mime_part));
+
+		whole_mime_type = MIME_TYPE_WHOLE (mime_part);
+		call_handler_function (contents, whole_mime_type,
+				       MIME_TYPE_MAIN (mime_part),
+				       stream, root);
+		g_free (whole_mime_type);
+	}
+}
+
+static void
+handle_unknown_type (CamelDataWrapper *wrapper,
+		     GtkHTMLStreamHandle *stream,
+		     CamelDataWrapper *root)
+{
+	gchar *tag;
+	char *uid = lookup_unique_id (root, wrapper);	
+
+	tag = g_strdup_printf ("<a href=\"camel://%s\">click-me-to-save</a>\n",
+			       uid);
+
+	mail_write_html (stream, tag);
+}
+
+
+void
+mail_write_html (GtkHTMLStreamHandle *stream, const char *data)
+{
+	gtk_html_stream_write (stream, data, strlen (data));
+}