ch20_04.htm

by Randal L. Schwartz and Tom Phoenix ISBN 0-596-00132-0 Third Edition, published July 2001. (See

</p></div>

<a name="INDEX-2604" /><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>tag</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>
$<em class="replaceable">h</em>-&gt;tag([<em class="replaceable">name</em>])
</pre><p><a name="INDEX-2604" />Sets or retrieves the tag
<em class="replaceable"><tt>name</tt></em> for the element. Tag names are always
converted to lowercase.
</p></div>

<a name="INDEX-2605" /><a name="INDEX-2606" /><a name="INDEX-2607" /><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>traverse</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>
$<em class="replaceable">h</em>-&gt;traverse(<em class="replaceable">sub</em>, [<em class="replaceable">ignoretext</em>])
</pre><p><a name="INDEX-2605" />Traverses the current element
and all of its children, invoking the callback routine
<em class="replaceable"><tt>sub</tt></em> for each element. The callback routine
is called with a reference to the current element (the node), a
startflag, and the depth as arguments. The start flag is
<tt class="literal">1</tt> when entering a node and <tt class="literal">0</tt>
when leaving (returning to a parent element). If the
<em class="replaceable"><tt>ignoretext</tt></em> parameter is true (the
default), then the callback routine will not be invoked for text
content. If the callback routine returns false, the method will not
traverse any child elements of that node.<a name="INDEX-2606" /><a name="INDEX-2607" />
</p></div>

</div>
<a name="perlnut2-CHP-20-SECT-4.4" /><div class="sect2">
<h3 class="sect2">20.4.4. HTML::TreeBuilder</h3>

<p><a name="INDEX-2608" /><a name="INDEX-2609" />The HTML::TreeBuilder class provides a
parser that creates an HTML syntax tree. Each node of the tree is an
HTML::Element object. This class inherits both HTML::Parser and
HTML::Elements, so methods from both of those classes can be used on
its objects.
</p>

<p>The methods provided by HTML::TreeBuilder control how the parsing is
performed. Values for these methods are set by providing a Boolean
value for their arguments.
</p>

<a name="INDEX-2610" /><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>ignore_text</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>
$<em class="replaceable">p</em>-&gt;ignore_text(<em class="replaceable">boolean</em>)
</pre><p><a name="INDEX-2610" />If set to true, text content of
elements will not be included in elements of the parse tree. The
default is false.
</p></div>

<a name="INDEX-2611" /><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>ignore_unknown</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>
$<em class="replaceable">p</em>-&gt;ignore_unknown(<em class="replaceable">boolean</em>)
</pre><p><a name="INDEX-2611" />If set
to true, unknown tags in the HTML will be represented as elements in
the parse tree.
</p></div>

<a name="INDEX-2612" /><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>implicit_tags</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>
$<em class="replaceable">p</em>-&gt;implicit_tags(<em class="replaceable">boolean</em>)
</pre><p><a name="INDEX-2612" />If set
to true, the parser will try to deduce implicit tags such as missing
elements or end tags that are required to conform to proper HTML
structure. If false, the parse tree will reflect the HTML as is.
</p></div>

<a name="INDEX-2613" /><a name="INDEX-2614" /><a name="INDEX-2615" /><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>warn</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>
$<em class="replaceable">p</em>-&gt;warn(<em class="replaceable">boolean</em>)
</pre><p><a name="INDEX-2613" />If set to true, the parser will make
calls to <tt class="literal">warn</tt> with messages describing syntax
errors when they occur. Error messages are off by default.<a name="INDEX-2614" /><a name="INDEX-2615" />
</p></div>

</div>
<a name="perlnut2-CHP-20-SECT-4.5" /><div class="sect2">
<h3 class="sect2">20.4.5. HTML::FormatPS</h3>

<p><a name="INDEX-2616" /><a name="INDEX-2617" /><a name="INDEX-2618" />The HTML::FormatPS module converts an
HTML parse tree into PostScript. The formatter object is created with
the <tt class="literal">new</tt> constructor, which can take parameters
that assign PostScript attributes. For example:
</p>

<blockquote><pre class="code">$formatter = HTML::FormatPS-&gt;new('papersize' =&gt; 'Letter');</pre></blockquote>

<p>You can now give parsed HTML to the formatter and produce PostScript
output for printing. HTML::FormatPS does not handle table or form
elements at this time.
</p>

<p><a name="INDEX-2619" />The method for this class is
<tt class="literal">format</tt>. <tt class="literal">format</tt> takes a
reference to an HTML TreeBuilder object, representing a parsed HTML
document. It returns a scalar containing the document formatted in
PostScript. The following example shows how to use this module to
print a file in PostScript:
</p>

<blockquote><pre class="code">use HTML::FormatPS;

$html = HTML::TreeBuilder-&gt;parse_file(somefile);
$formatter = HTML::FormatPS-&gt;new( );
print $formatter-&gt;format($html);</pre></blockquote>

<p>The following list describes the attributes that can be set in the
constructor:
</p>

<dl>
<dt><i><em class="replaceable"><tt>PaperSize</tt></em></i></dt>
<dd>
Possible values are <tt class="literal">3</tt>, <tt class="literal">A4</tt>,
<tt class="literal">A5</tt>, <tt class="literal">B4</tt>, <tt class="literal">B5</tt>,
<tt class="literal">Letter</tt>, <tt class="literal">Legal</tt>,
<tt class="literal">Executive</tt>, <tt class="literal">Tabloid</tt>,
<tt class="literal">Statement</tt>, <tt class="literal">Folio</tt>,
<tt class="literal">10x14</tt>, and <tt class="literal">Quarto</tt>. The default
is <tt class="literal">A4</tt>.
</p>
</dd>


<dt><i><em class="replaceable"><tt>PaperWidth</tt></em></i></dt>
<dd>
Width of the paper in points.</p>
</dd>


<dt><i><em class="replaceable"><tt>PaperHeight</tt></em></i></dt>
<dd>
Height of the paper in points.</p>
</dd>


<dt><i><em class="replaceable"><tt>LeftMargin</tt></em></i></dt>
<dd>
Left margin in points.</p>
</dd>


<dt><i><em class="replaceable"><tt>RightMargin</tt></em></i></dt>
<dd>
Right margin in points.</p>
</dd>


<dt><i><em class="replaceable"><tt>HorizontalMargin</tt></em></i></dt>
<dd>
Left and right margin. Default is 4 cm.</p>
</dd>


<dt><i><em class="replaceable"><tt>TopMargin</tt></em></i></dt>
<dd>
Top margin in points.</p>
</dd>


<dt><i><em class="replaceable"><tt>BottomMargin</tt></em></i></dt>
<dd>
Bottom margin in points.</p>
</dd>


<dt><i><em class="replaceable"><tt>VerticalMargin</tt></em></i></dt>
<dd>
Top and bottom margin. Default is 2 cm.</p>
</dd>


<dt><i><em class="replaceable"><tt>PageNo</tt></em></i></dt>
<dd>
Boolean value to display page numbers. Default is
<tt class="literal">0</tt> (off).
</p>
</dd>


<dt><i><em class="replaceable"><tt>FontFamily</tt></em></i></dt>
<dd>
Font family to use on the page. Possible values are
<tt class="literal">Courier</tt>, <tt class="literal">Helvetica</tt>, and
<tt class="literal">Times</tt>. Default is <tt class="literal">Times</tt>.
</p>
</dd>


<dt><i><em class="replaceable"><tt>FontScale</tt></em></i></dt>
<dd>
Scale factor for the font.</p>
</dd>


<dt><i><em class="replaceable"><tt>Leading</tt></em></i></dt>
<dd>
Space between lines, as a factor of the font size. Default is
<tt class="literal">0.1</tt>. <a name="INDEX-2620" /><a name="INDEX-2621" /><a name="INDEX-2622" /> 
</p>
</dd>

</dl>

</div>
<a name="perlnut2-CHP-20-SECT-4.6" /><div class="sect2">
<h3 class="sect2">20.4.6. HTML::FormatText</h3>

<p><a name="INDEX-2623" /><a name="INDEX-2624" />The HTML::FormatText module takes a
parsed HTML file and outputs a plain-text version of it. None of the
character attributes will be usable, i.e., bold or italic fonts, font
sizes, etc.
</p>

<p><a name="INDEX-2625" />This module is similar to FormatPS in
that the constructor takes attributes for formatting, and the
<tt class="literal">format</tt> method produces the output. A formatter
object can be constructed like this:
</p>

<blockquote><pre class="code">$formatter = HTML::FormatText-&gt;new(leftmargin =&gt; 10, rightmargin =&gt; 80);</pre></blockquote>

<p>The constructor can take two parameters:
<tt class="literal">leftmargin</tt> and <tt class="literal">rightmargin</tt>. The
value for the margins is given in column numbers. The aliases
<tt class="literal">lm</tt> and <tt class="literal">rm</tt> can also be used.
</p>

<p>The <tt class="literal">format</tt> method takes an HTML::TreeBuilder
object and returns a scalar containing the formatted text. You can
print it with:
</p>

<blockquote><pre class="code">print $formatter-&gt;format($html);</pre></blockquote>

</div>


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