+* Connection #0 to host dds.cr.usgs.gov left intact
+* Closing connection #0
+** (viking:28778): DEBUG: dem_layer_add_file: /home/username/.viking-maps/srtm3-Eurasia/N48E008.hgt.zip
+</screen>
+Or for OSM Mapnik tile server:
+<screen>
+* About to connect() to tile.openstreetmap.org port 80 (#0)
+* Trying 193.63.75.28... * connected
+* Connected to tile.openstreetmap.org (193.63.75.28) port 80 (#0)
+ GET /13/4065/2748.png HTTP/1.1
+User-Agent: viking/0.9.96 libcurl/7.20.1 GnuTLS/2.8.6 zlib/1.2.3.4 libidn/1.18
+Host: tile.openstreetmap.org
+Accept: */*
+
+* HTTP 1.0, assume close after body
+ HTTP/1.0 200 OK
+ Date: Thu, 14 Oct 2010 22:18:42 GMT
+ Server: Apache/2.2.8 (Ubuntu)
+ ETag: "b66ff9d46474bab68262a3483428a232"
+** (viking:16704): DEBUG: curl_get_etag_func: ETAG found: "b66ff9d46474bab68262a3483428a232"
+ Content-Length: 17194
+ Cache-Control: max-age=94805
+ Expires: Sat, 16 Oct 2010 00:38:47 GMT
+ Content-Type: image/png
+ Age: 5153
+ X-Cache: HIT from konqi.openstreetmap.org
+ X-Cache-Lookup: HIT from konqi.openstreetmap.org:3128
+ Via: 1.1 konqi.openstreetmap.org:3128 (squid/2.7.STABLE7)
+ Connection: close
+
+* Closing connection #0
+* About to connect() to a.andy.sandbox.cloudmade.com port 80 (#0)
+* Trying 178.63.75.195... ** (viking:16704): DEBUG: curl_download_uri: uri=http://tile.openstreetmap.org/13/4065/2749.png
+* About to connect() to tile.openstreetmap.org port 80 (#0)
+* Trying 193.63.75.28... * connected
+* Connected to a.andy.sandbox.cloudmade.com (178.63.75.195) port 80 (#0)
+ GET /tiles/cycle/13/4065/2747.png HTTP/1.1
+User-Agent: viking/0.9.96 libcurl/7.20.1 GnuTLS/2.8.6 zlib/1.2.3.4 libidn/1.18
+Host: a.andy.sandbox.cloudmade.com
+Accept: */*
+
+* connected
+* Connected to tile.openstreetmap.org (193.63.75.28) port 80 (#0)
+ GET /13/4065/2749.png HTTP/1.1
+User-Agent: viking/0.9.96 libcurl/7.20.1 GnuTLS/2.8.6 zlib/1.2.3.4 libidn/1.18
+Host: tile.openstreetmap.org
+Accept: */*
+
+* HTTP 1.0, assume close after body
+ HTTP/1.0 200 OK
+ Date: Thu, 14 Oct 2010 23:44:35 GMT
+ Server: Apache/2.2.8 (Ubuntu)
+ ETag: "8e520ad47ce9c1b63430554886eb5fab"
+** (viking:16704): DEBUG: curl_get_etag_func: ETAG found: "8e520ad47ce9c1b63430554886eb5fab"
+ Content-Length: 18094
+ Cache-Control: max-age=87742
+ Expires: Sat, 16 Oct 2010 00:06:57 GMT
+ Content-Type: image/png
+ X-Cache: MISS from konqi.openstreetmap.org
+ X-Cache-Lookup: MISS from konqi.openstreetmap.org:3128
+ Via: 1.1 konqi.openstreetmap.org:3128 (squid/2.7.STABLE7)
+ Connection: close
+</screen>
+</para>
+</section>
+
+</section>
+<!-- End of Howtos -->
+
+<section id="extend_viking" xreflabel="Extending Viking">
+ <title>Extending Viking</title>
+
+ <para>Currently, &app; has some extention points based on configuration files. The file format is heavily inspired by the GtkBuilder file format: you specify the class of the GObject to build and set its properties. Technically, it is a XML file containing a "objects" root element. Inside this element, you set a collection of "object".</para>
+ <para>Here is an example:
+<programlisting><![CDATA[
+<objects>
+ <object class="ClassName">
+ <property name="property_name1">Property value</property>
+ <property name="property_name2">Property value</property>
+ </object>
+ ...
+<objects>
+]]>
+</programlisting>
+</para>
+ <para>You can find more examples in the documentation part of the distribution.</para>
+ <section>
+ <title>Map Source</title>
+ <para>It is possible to add new map's sources. The file is <filename>~/.viking/maps.xml</filename> for <trademark>UNIX</trademark> like systems, <filename>C:\Documents and Settings\<replaceable>username</replaceable>\.viking\maps.xml</filename> on <trademark>Windows XP</trademark> or <filename>C:\Users\<replaceable>username</replaceable>\.viking\maps.xml</filename> on <trademark>Windows 7</trademark> onwards.</para>
+ <para>An example of the file is in the distribution <filename>doc/examples/maps.xml</filename>. Further examples and values are online in the <ulink url="http://sourceforge.net/apps/mediawiki/viking/index.php?title=Maps">Maps Wiki</ulink></para>
+
+ <para>The <classname>VikSlippyMapSource</classname> allows to declare any map's source working like OpenStreetMap. It supports the following properties:
+ <variablelist>
+ <varlistentry>
+ <term>id</term>
+ <listitem><para>this is an integer and should be unique as it used to identify the map source</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>name</term>
+ <listitem><para>a string (should be unique) that is used for the OSM style cache directory name when the Map Cache directory is the default (<filename>~/.viking-maps</filename>)</para></listitem>
+ </varlistentry>
+ <varlistentry>