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<chapter service="wax" number="1">
  <title>Web Application Extension Service</title>
  
  <p>
    The <em>Web Application Extension</em> service is an original
    implementation that provides the support for low level HTTP transaction
    as well as high level XHTML page generation. The service combines 
    various modules and provides access to the modern generation of
    web contents.
  </p>

  <!-- page service objects -->
  <section>
    <title>Page service objects</title>

    <p>
      The <code>XhtmlRoot</code> class is the primary interface to
      generate <em>xhtml page</em>. The class is derived from the
      <code>XmlRoot</code> class and the <code>Mime</code>object. for
      this reason, creating a xhtml page is equivalent to add xml nodes
      to the page. The xhtml version is assumed to be <em>1.1</em>.
    </p>

    <!-- page creation -->
    <subsect>
      <title>Page creation</title>

      <p>
	The <code>XhtmlRoot</code> constructor takes a string argument
	which is the title page. When the root page is created, a
	<em>head</em> and <em>body</em> nodes are automatically
	created. Once created, it is possible to retrieve the head and
	body nodes from the root node. The head and body nodes are part
	of the <em>html</em> node which is automatically instantiated as
	a <code>XhtmlHtml</code> object. The html node can always be
	retrieved from the root node with the <code>get-child</code>
	xml method.
      </p>

      <example>
	# create a new xhtml page
	const page (afnix:wax:XhtmlRoot "AFNIX wax service")
	# get the head node
	const head (page:get-head)
	# get the body node
	const body (page:get-body)
      </example>

      <p>
	The head and body nodes are part of the <em>html</em> node which
	is automatically instantiated as a <code>XhtmlHtml</code>
	object. The html node can always be retrieved from the root node
	with the <code>get-child</code> xml method. The root methods
	<code>get-head</code> and <code>get-body</code> are convenient
	methods that ease the page design by eliminating the references
	to the html node.
      </p>

      <example>
	# create a new xhtml page
	const page (afnix:wax:XhtmlRoot "AFNIX wax service")
	# get the html node
	const html (page:get-child "html")
	# get the head node
	const head (html:get-head)
	# get the body node
	const body (html:get-body)
      </example>
    </subsect>

    <!-- page header -->
    <subsect>
      <title>Page header</title>
      
      <p>
	The <code>XhtmlHead</code> class is the xml node that handles
	the xhtml head. The object is automatically created when calling
	the <code>XhtmlRoot</code> constructor. During the construction
	process, the head is automatically set with a title. Once
	created, the head can be filled with meta information and
	styles. The <code>add-meta</code> method is designed to add meta
	information, while the <code>add-style</code> add a link node
	with a style reference to the head.
      </p>

      <example>
	# add a meta tag
	head:add-meta "copyright" "© 2000"
	# add a style path
	head:add-style "/style.css"
      </example>

      <p>
	The <code>add-meta</code> method adds a <code>XhtmlMeta</code>
	object which is a xml tag node. The first argument is the meta
	descriptor while the second argument is the meta content. Note
	that the <code>add-meta</code> method can be simulated by
	calling the <code>XhtmlMeta</code> constructor and then adding
	the node to the head node.
      </p>

      <example>
	# create a meta node
	const node (afnix:wax:XhtmlMeta "copyright" "© 2013")
	# add the node to the head
	head:add node
      </example>

      <p>
	The <code>add-style</code> method adds a <code>XhtmlStyle</code>
	object which is a xml tag node. The string argument is the url
	style sheet path which gets automatically transformed to the
	form <em>@import(url)</em>. Note that the <code>add-style</code>
	method can be simulated by calling the <code>XhtmlStyle</code>
	constructor and then adding the node to the head node.
      </p>

      <example>
	# create a style node
	const node (afnix:wax:XhtmlStyle "/style.css")
	# add the node to the head
	head:add node
      </example>
    </subsect>

    <!-- page body -->
    <subsect>
      <title>Page body</title>
      
      <p>
	The <code>XhtmlBody</code> class is the xml node that handles
	the xhtml body. The object is automatically created when calling
	the <code>XhtmlRoot</code> constructor. Once created, the body
	node can be filled with any valid xhtml node. Since the node are
	initially xml tag node, it is always possible to create a tag by
	name and set the attributes and child nodes manually.
      </p>

      <example>
	# create a new xhtml page
	const page (afnix:wax:XhtmlRoot "AFNIX wax service")
	# get the body node
	const body (page:get-body)
	# add a node
	body:add-child node
      </example>
    </subsect>

    <!-- page emission -->
    <subsect>
      <title>Page emission</title>
      
      <p>
	Since the <code>XhtmlRoot</code> object is a xml root node, the
	node can be used to write the complete hierarchy. The xml node
	node provides the <code>write</code> method that write a xml
	tree into a buffer of an output stream.
      </p>

      <example>
	# create a new xhtml page
	const page (afnix:wax:XhtmlRoot "AFNIX wax service")
	# write to the output stream
	page:write
      </example>

      <p>
	Another mechanism for writing the page is to use the fact that
	the <code>XhtmlRoot</code> class implements also the
	<code>Mime</code> interface. With this in mind, the
	<code>XhtmlRoot</code> can be used within the
	<code>HttpReply</code>. This method is particularly useful when
	writing automated page generation, such like CGI scripts.
      </p>

      <example>
	# create a new xhtml page
	const page (afnix:wax:XhtmlRoot "AFNIX wax service")
	# create an http reply object
	const reply (afnix:wax:HttpReply)
	# write the page as a mime object
	reply:add-buffer page
	# write the result to the output
	reply:write
      </example>
    </subsect>
  </section>

  <!-- page design objects -->
  <section>
    <title>Page design objects</title>

    <p>
      The <em>wax service module</em> is designed to provide several
      object that ease the task of creating a xhtml page. Such objects
      range from comment to table. Most of the time, the construction is
      simple the resulting node only need to be added to the page
      tree. When it comes to add text, the problem is becoming more
      subtle and is discussed later in this section.
    </p>

    <!-- xhtml comment -->
    <subsect>
      <title>Comment node</title>
      
      <p>
	Adding a comment is done with the <code>XmlComment</code> class
	which take the comment string in the constructor. Once created,
	the comment node can be added to the tree.
      </p>

      <example>
	# add a comment to the body node
	body:add-child (
	  afnix:xml:XmlComment "this is a comment")
      </example>
    </subsect>

    <!-- node style class -->
    <subsect>
      <title>Node style class</title>
      
      <p>
	When the xhtml page is combined with the cascaded style sheet
	(CSS), the xhtml node tag often uses a <em>class</em> name to
	refer to a particular style. The <em>class style</em> is just a
	node attribute which can be set with the
	<code>add-attribute</code> method. However, most of the time,
	the library provides object which have the style as the first
	argument in the constructor. For example, the
	<code>XhtmlDiv</code> constructor take 0 or one argument. With
	one argument, the string argument is used as the style attribute.
      </p>

      <example>
	# create a xhtml div with a class attribute
	const div (afnix:wax:XhtmlDiv "nice")
	# create a xhtml div  and set the class manually
	const div (afnix:wax:XhtmlDiv)
	div:set-attribute "class" "nice"
      </example>
    </subsect>

    <!-- adding text paragraph -->
    <subsect>
      <title>Adding text paragraph</title>
      
      <p>
	Adding text to a page is not a trivial task when it comes to deal
	with text style. By default, a piece of text is stored in the
	<code>XmlText</code> node. Using this node is easy. However, in
	a programming context, its use can become heavy. For this reason,
	all xml nodes provide the <code>parse</code> method which can be 
	used to add a xml tree to the calling node. When it comes to add
	text that includes rendering tag, this method is quite handy.
      </p>

      <example>
	# add a text with some piece in italic
	node:parse "this is a &lt;i&gt;simple&lt;/i&gt; method"
      </example>

      <p>
	The <code>XhtmlPara</code> node is the preferred node for
	adding text to a xhtml page. The node takes optionally the style
	name in the constructor. A boolean flag can also be used to
	create an empty paragraph node.
      </p>

      <example>
	# create a paragraph node with a style
	const p (afnix:wax:XhtmlPara "title")
	# add some text
	p:parse "the paragraph text"
      </example>
    </subsect>

    <!-- adding reference -->
    <subsect>
      <title>Adding reference</title>
      
      <p>
	Adding reference or hyperlink to a page is achieved with the
	<code>XhtmlRef</code> class. Most of the time, the object is
	built with a uri and a text. when the node has been created, the
	node can be added to the page tree.
      </p>

      <example>
	# create a hyperlink
	const node (
	  afnix:wax:XhtmlRef "http://www.afnix.org" "afnix")
	# add the node in a paragraph
	p:add-child node
      </example>
    </subsect>

    <!-- formatting elements -->
    <subsect>
      <title>Formatting elements</title>
      
      <p>
	The <code>XhtmlDiv</code> and <code>XhtmlHr</code> classes
	are the basic formatting xhtml elements. The
	<code>XhtmlDiv</code> is a grouping element and the
	<code>XhtmlHr</code> is a simple horizontal ruler element. Both
	classes take 0 or one argument which is the style name.
      </p>

      <example>
	# create a div element
	const div (afnix:wax:XhtmlDiv "menu")
	# create a ruler element
	const hr  (afnix:wax:XhtmlHr)
      </example>
    </subsect>
  </section>

  <!-- managing table -->
  <section>
    <title>Managing table</title>

    <p>
      The <em>wax service module</em> provides an extensive support of
      he xhtml table element. There are basically two strategies for
      creating a table. One is to use the html elements or the other is
      to use a print table object and automatically feed the xhtml
      table. The first method provides a better control while the second
      one is easier to use.
    </p>

    <!-- xhtml table element -->
    <subsect>
      <title>The table element</title>

      <p>
	The <code>XhtmlTable</code> class is the class that manages
	xhtml table. As usual, a default style name can be specified in
	the constructor. Eventually, a default table row and table data
	default style can also be specified. Such default value are used
	when creating a new row with the <code>new-row</code> method.
      </p>

      <example>
	# create an element with a default tr and th/td style
	const tbl (afnix:wax:XhtmlTable "text" "text" "text")
	# get a new row with a default style
	const tr (tbl:new-row)
      </example>

      <p>
	In the previous example, a table is created with a default style
	for the table row. When a new row is created, the default style
	is used for that row. If there is no default style, the row is
	created without a style. Note that the <code>new-row</code>
	method  takes also a style argument that overwrites the default
	one.
      </p>
    </subsect>

    <!-- building the table -->
    <subsect>
      <title>Building the table</title>

      <p>
	A table is built by adding row and data element into the
	rows. A row is created with the <code>new-row</code> method or
	the object can be constructed directly and added to the node
	with the <code>add-child</code> method. The <code>XhtmlTr</code>
	class is the table row class.
      </p>

      <example>
	# get a new row with a default style
	trans tr (tbl:new-row)
	# create a row directly
	trans tr (afnix:wax:XhtmlTr "text")
      </example>

      <p>
	When a row has been created, the data can be added to the
	row. Normally, the <code>new-data</code> method is used to
	create a new table data element. If a default style is defined
	in the table row, the table data element is built with that
	style. The <code>new-head</code> method can also be used to
	create table header element. Again, if a default table header
	style exists in the table row, the element is built with that
	style. The <code>XhtmlTd</code> class is the table data class
	and the <code>XhtmlTh</code> class is the table header class.
      </p>

      <example>
	# get a new data element
	trans td (tr:new-data)
	# create new head element
	trans th (tr:new-head)
      </example>

      <p>
	When the table data node has been created, the
	<code>parse</code> method or the <code>add-child</code> method
	can be called to add other nodes. another method for building
	the table is to use the <code>add-table</code> method which uses
	a print table object. In such case, the table rows and data
	elements are automatically added in the table.
      </p>
    </subsect>

    <!-- the table structure -->
    <subsect>
      <title>The table structure</title>

      <p>
	The table can be designed directly with table rows with table
	headers and table data elements. Another method, which is more
	structured is to use the table head, table body and table footer
	elements. The <code>XhtmlThead</code> class is the table head
	element class. The <code>XhtmlTbody</code> class is the table body
	element class. The <code>XhtmlTfoot</code> class is the table footer
	element class. These classes behaves exactly like the
	<code>XhtmlTable</code> and are in fact all derived from the
	<code>XhtmlTelem</code> class.
      </p>

      <example>
	# create a xhtml table
	const table (afnix:wax:XhtmlTable "text")
	# create a table body
	const tbody (
	  afnix:wax:XhtmlTable "text" "text" "text")
	# add a print tbl in the body
	tbody:add-table ptbl
	# add the body to the table
	table:ad-child tbody
      </example>

      <p>
	A table caption node can also be set with the
	<code>set-caption</code> method. The method simply creates a
	<code>XhtmlCaption</code> node and adds it to the table. The
	caption text is part of the method call which is used by the
	caption node constructor. It is also possible to create the
	caption node by calling the <code>XhtmlCaption</code>
	constructor and adding it to the table with he
	<code>add-child</code> method.
      </p>

      <example>
	# create a xhtml table
	const table (afnix:wax:XhtmlTable "text")
	# set a table caption
	table:set-caption "the afnix table system"
      </example>

      <p>
	The table structure can also be defined with the
	<code>XhtmlCgr</code> class which corresponds to the xhtml column
	group element. The column group element is designed to support
	the <em>col</em> element that formats the table column.
      </p>

      <example>
	# create a table
	const table (afnix:wax:XhtmlTable "text")
	# set the table with to 100%
	table:add-attribute "width" "100%"
	# create a column group
	table:add-child (const xcgr (afnix:wax:XhtmlCgr))
	# add a column with 30% width
	cgr:add-child (afnix:wax:XhtmlCol "30%")
	# add a column with 70% width
	cgr:add-child (afnix:wax:XhtmlCol "70%")
      </example>
    </subsect>
  </section>
</chapter>
