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is, we generate files in our cache, and generate <img /> HTML tags that
references these files. This is fast, and saves us multiple renderings of the
same image. You should look into these techniques if your tags are graphically
intensive or otherwise ressource consuming. Also, <img:gtext /> uses a lot of
parameters, and often these are similar across multiple calls of <img:gtext />
on the same page. We supply <img:gtextdefault /> as a mechanism to provide
sensible defaults to subsequent calls. Look into our code to learn how we did
this.

The PHP namespace implements <php:define />, which gobbles up its contents
unparsed. In order to do this it uses getLock() and releaseLock() in
transformer. If you need code that is read as-is and evaluated later, look into
this. Also, the PHP namespace uses PHP's eval function extensively to generate
namespace classes at run-time. This is not a recommended practice, but probably
interesting code.


2.4.1 XML_Transformer_Namespace_Anchor

The Anchor namespace implements a number of tags that create indirect named
links (URNs): The link is specified by name, and the actual link location and
title are supplied from a database internal to the class. Additionally, a tag
that selects a random link is supplied.

The default namespace prefix for this Namespace is "a".


2.4.1.1 Link database

The link database is maintained internally as an array, _anchorDatabase and is
accessible through the setDatabase($db) and $db = getDatabase() accessor
methods.

  $a = new XML_Transformer_Namespace_Anchor();
  $t = new XML_Transformer();
  $t->overloadNamespace('a', $a);

  $a->setDatabase(
        array(
          'php'  => array(
                      'href'  => 'http://www.php.net',
                      'title' => 'PHP Homepage'
                    ),
          'pear' => array(
                      'href'  => 'http://pear.php.net',
                      'title' => 'PEAR Homepage'
                    )
        )
      );

Additionally, items may be added to or dropped from the database using the
addItem() and dropItem() methods. Also, individual items can be queried with
getItem().

  $a->addItem(
    'dclpfaq',
    array(
      'href'  => 'http://www.dclp-faq.de',
      'title' => 'de.comp.lang.php FAQ Homepage'
    )
  );

  $dclpfaq = $a->getItem('dclpfaq');
  echo $dclpfaq['href'];

  $a->dropItem('dclpfaq');

Note that neither database nor the tags place any restrictions on the number or
kind of attributes ("href", "title", ...) stored in the database. All attributes
will be reproduced "as is" on the generated links.


2.4.1.2 The <a:iref> tag

The <a:iref iref="name" /> container will look the given name up in the database
and produce a HTML <a /> container. The attributes find in the link database
will be produced literally as attributes to the <a /> container and the contents
of the <a:iref /> will become the contents of the <a /> container.

Example:

<a:iref iref="php">The PHP Homepage</a:iref>

Result:

<a href="http://www.php.net" title="PHP Homepage">The PHP
Homepage</a>


2.4.1.3 The <a:random> tag

The <a:random /> container will select a random name from the database and link
to it. The contents of the <a:random /> become the contents of the generated
<a /> container.

Example:

<a:random>A random link</a:random>

Result:

<a href="http://www.php.net" title="PHP Homepage">A random link</a>


2.4.1.4 The <a:link> tag

The link tag will add a link to the database, and vanishes (generates no
output). The name attribute to link will define the link name, the other
attributes are copied into the database literally.

Example:

<a:link name="php"
        href="http://www.php.net"
        title="PHP Homepage" />

Result:

The link is added to the database. No output is being generated.


2.4.2 XML_Transformer_Namespace_DocBook


* TODO (sb)


2.4.3 XML_Transformer_Namespace_Image

The Image namespace implements a number of tags that are loosely related to
images. At the moment there is a tag that autogenerates height/width attributes
and another tag that turns its content text into a PNG with that text.

The default namespace prefix for this namespace is "img".


2.4.3.1 The <img> tag.

This tag will generate a <img /> tag with the original attributes, and will add
width and height attributes if possible.

Example:

<img:img src="somepng.png" alt="blah" />

Result:

<img alt="blah" height="168" src="somepng.png" width="320" />


2.4.3.2 The <gtext> tag

Gtext is short for graphical text. The tag will take its content and turn it
into a single PNG or a series of PNGs using ImageTTFText() internally.

Gtext takes a very large number of attributes. All of them can be specified as
defaults with <img:gtextdefault /> (see below) and individually overridden.

Limitations:

Gtext requires a directory called "/cache/gtext" below DocumentRoot that is
writeable by the webserver. Also, Fonts are looked for in
/usr/X11R6/lib/X11/fonts/truetype. Currently there is no API to override this.

Attributes:

- split

  Split is either "none", "word" or "char". If it is "none", the complete
  content of a gtext is set as a single image. If it is "word", each word of the
  content is set as a separate image. This does not look as good as a single
  image, but can be word wrapped. If it is "char", each character is rendered as
  a single image. This loads very fast (multiple occurences of the same
  character are mapped onto the same file), but does not look right.

- font

  Name of the TTF font to use.

  If an absolute pathname is supplied, that font is being used. Otherwise
  /usr/X11R6/lib/X11/fonts/truetype/ is prepended to the font name and that file
  is tried.

- fontsize

  What size to render the font in (TTF points).


- alt

  By default, each generated image is created with the text on the image as alt
  Tag. This can be overridden by specifying an alt tag (not recommended).

  Note that XML attributes may not contain tags. Thus, all markup is being
  stripped from the automatically generated alt tag in order to ensure well-
  formed HTML.

- bgcolor, fgcolor

  The generated image is initially filled with bgcolor. This color is then set
  to transparent (unless prohibited, see below). After that, text is rendered in
  fgcolor into this image.

- antialias

  The rendered text is by default generated with antialiasing. If you do not
  want the text to be antialiased, set the antialias attribute to "no".

- transparency

  The background color is by default set to transparent. If you do not want the
  bgcolor to be set transparent, set the transparency attribute to "no".

- cacheable

  By default, the generated image is stored in the gtext cache. After that,
  subsequent renderings of that image are not done. Instead the cached image is
  referenced.

  If you set the cacheable attribute to "no", the image is recreated on each
  <img:gtext /> call. This is recommended during development.

- spacing

  <img:gtext /> tries to create the generated PNG as small as possible. If you
  specify a spacing attribute, a transparent border of x pixels is added around
  all four borders of the generated image.

- border

  Additionally, if you specify a border, an x pixel border is added around the
  text and the spacing. Unlike spacing the border is painted in bordercolor.

- bordercolor

  The color to paint the border in is specified using the
  bordercolor attribute.

Example:

  <img:gtextdefault bgcolor="888888" fgcolor="#000000"
                    font="arial.ttf" fontsize="33"
                    border="2" spacing="2"
                    split="" cacheable="no"/>

  <img:gtext>Antialias</img:gtext><br/>
  <img:gtext antialias="no">No Antialias</img:gtext><br/>
  <img:gtext>OoAaMmXxGgQqpP