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Tagset.pm
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package HTML::Tagset; use strict; =head1 NAME HTML::Tagset - data tables useful in parsing HTML =head1 VERSION Version 3.24 =cut our $VERSION = '3.24'; =head1 SYNOPSIS use HTML::Tagset; # Then use any of the items in the HTML::Tagset package # as need arises =head1 DESCRIPTION This module contains several data tables useful in various kinds of HTML parsing operations. Note that all tag names used are lowercase. In the following documentation, a "hashset" is a hash being used as a set -- the hash conveys that its keys are there, and the actual values associated with the keys are not significant. (But what values are there, are always true.) =head1 VARIABLES Note that none of these variables are exported. =head2 hashset %HTML::Tagset::emptyElement This hashset has as values the tag-names (GIs) of elements that cannot have content. (For example, "base", "br", "hr".) So C<$HTML::Tagset::emptyElement{'hr'}> exists and is true. C<$HTML::Tagset::emptyElement{'dl'}> does not exist, and so is not true. =cut our %emptyElement = map { $_ => 1 } qw( base link meta isindex img br hr wbr input area param embed bgsound spacer basefont col frame ~comment ~literal ~declaration ~pi ); # The "~"-initial names are for pseudo-elements used by HTML::Entities # and TreeBuilder =head2 hashset %HTML::Tagset::optionalEndTag This hashset lists tag-names for elements that can have content, but whose end-tags are generally, "safely", omissible. Example: C<$HTML::Tagset::emptyElement{'li'}> exists and is true. =cut our %optionalEndTag = map { $_ => 1 } qw( p li dt dd ); # option th tr td); =head2 hash %HTML::Tagset::linkElements Values in this hash are tagnames for elements that might contain links, and the value for each is a reference to an array of the names of attributes whose values can be links. =cut our %linkElements = ( 'a' => ['href'], 'applet' => ['archive', 'codebase', 'code'], 'area' => ['href'], 'base' => ['href'], 'bgsound' => ['src'], 'blockquote' => ['cite'], 'body' => ['background'], 'del' => ['cite'], 'embed' => ['pluginspage', 'src'], 'form' => ['action'], 'frame' => ['src', 'longdesc'], 'iframe' => ['src', 'longdesc'], 'ilayer' => ['background'], 'img' => ['src', 'lowsrc', 'longdesc', 'usemap'], 'input' => ['src', 'usemap'], 'ins' => ['cite'], 'isindex' => ['action'], 'head' => ['profile'], 'layer' => ['background', 'src'], 'link' => ['href'], 'object' => ['classid', 'codebase', 'data', 'archive', 'usemap'], 'q' => ['cite'], 'script' => ['src', 'for'], 'table' => ['background'], 'td' => ['background'], 'th' => ['background'], 'tr' => ['background'], 'xmp' => ['href'], ); =head2 hash %HTML::Tagset::boolean_attr This hash (not hashset) lists what attributes of what elements can be printed without showing the value (for example, the "noshade" attribute of "hr" elements). For elements with only one such attribute, its value is simply that attribute name. For elements with many such attributes, the value is a reference to a hashset containing all such attributes. =cut our %boolean_attr = ( # TODO: make these all hashes 'area' => 'nohref', 'dir' => 'compact', 'dl' => 'compact', 'hr' => 'noshade', 'img' => 'ismap', 'input' => { 'checked' => 1, 'readonly' => 1, 'disabled' => 1 }, 'menu' => 'compact', 'ol' => 'compact', 'option' => 'selected', 'select' => 'multiple', 'td' => 'nowrap', 'th' => 'nowrap', 'ul' => 'compact', ); #========================================================================== # List of all elements from Extensible HTML version 1.0 Transitional DTD: # # a abbr acronym address applet area b base basefont bdo big # blockquote body br button caption center cite code col colgroup # dd del dfn dir div dl dt em fieldset font form h1 h2 h3 h4 h5 h6 # head hr html i iframe img input ins isindex kbd label legend li # link map menu meta noframes noscript object ol optgroup option p # param pre q s samp script select small span strike strong style # sub sup table tbody td textarea tfoot th thead title tr tt u ul # var # # Varia from Mozilla source internal table of tags: # Implemented: # xmp listing wbr nobr frame frameset noframes ilayer # layer nolayer spacer embed multicol # But these are unimplemented: # sound?? keygen?? server?? # Also seen here and there: # marquee?? app?? (both unimplemented) #========================================================================== =head2 hashset %HTML::Tagset::isPhraseMarkup This hashset contains all phrasal-level elements. =cut our %isPhraseMarkup = map { $_ => 1 } qw( span abbr acronym q sub sup cite code em kbd samp strong var dfn strike b i u s tt small big ins del a img br wbr nobr blink font basefont bdo spacer embed noembed ); # had: center, hr, table =head2 hashset %HTML::Tagset::is_Possible_Strict_P_Content This hashset contains all phrasal-level elements that be content of a P element, for a strict model of HTML. =cut our %isFormElement; # Forward declaration our %is_Possible_Strict_P_Content = ( %isPhraseMarkup, %isFormElement, map {; $_ => 1} qw( object script map ) # I've no idea why there's these latter exceptions. # I'm just following the HTML4.01 DTD. ); #from html4 strict: #<!ENTITY % fontstyle "TT | I | B | BIG | SMALL"> # #<!ENTITY % phrase "EM | STRONG | DFN | CODE | # SAMP | KBD | VAR | CITE | ABBR | ACRONYM" > # #<!ENTITY % special # "A | IMG | OBJECT | BR | SCRIPT | MAP | Q | SUB | SUP | SPAN | BDO"> # #<!ENTITY % formctrl "INPUT | SELECT | TEXTAREA | LABEL | BUTTON"> # #<!-- %inline; covers inline or "text-level" elements --> #<!ENTITY % inline "#PCDATA | %fontstyle; | %phrase; | %special; | %formctrl;"> =head2 hashset %HTML::Tagset::isHeadElement This hashset contains all elements that elements that should be present only in the 'head' element of an HTML document. =cut our %isHeadElement = map { $_ => 1 } qw(title base link meta isindex script style object bgsound); =head2 hashset %HTML::Tagset::isList This hashset contains all elements that can contain "li" elements. =cut our %isList = map { $_ => 1 } qw( ul ol dir menu ); =head2 hashset %HTML::Tagset::isTableElement This hashset contains all elements that are to be found only in/under a "table" element. =cut our %isTableElement = map { $_ => 1 } qw(tr td th thead tbody tfoot caption col colgroup); =head2 hashset %HTML::Tagset::isFormElement This hashset contains all elements that are to be found only in/under a "form" element. =cut # Declared earlier in the file %isFormElement = map { $_ => 1 } qw(input select option optgroup textarea button label); =head2 hashset %HTML::Tagset::isBodyElement This hashset contains all elements that are to be found only in/under the "body" element of an HTML document. =cut our %isBodyElement = map { $_ => 1 } qw( h1 h2 h3 h4 h5 h6 p div pre plaintext address blockquote xmp listing center multicol iframe ilayer nolayer bgsound hr ol ul dir menu li dl dt dd ins del fieldset legend map area applet param object isindex script noscript table center form ), keys %isFormElement, keys %isPhraseMarkup, # And everything phrasal keys %isTableElement, ; =head2 hashset %HTML::Tagset::isHeadOrBodyElement This hashset includes all elements that I notice can fall either in the head or in the body. =cut our %isHeadOrBodyElement = map { $_ => 1 } qw(script isindex style object map area param noscript bgsound); # i.e., if we find 'script' in the 'body' or the 'head', don't freak out. =head2 hashset %HTML::Tagset::isKnown This hashset lists all known HTML elements. =cut our %isKnown = (%isHeadElement, %isBodyElement, map{ $_ => 1 } qw( head body html frame frameset noframes ~comment ~pi ~directive ~literal )); # that should be all known tags ever ever =head2 hashset %HTML::Tagset::canTighten This hashset lists elements that might have ignorable whitespace as children or siblings. =cut our %canTighten = %isKnown; delete @canTighten{ keys(%isPhraseMarkup), 'input', 'select', 'xmp', 'listing', 'plaintext', 'pre', }; # xmp, listing, plaintext, and pre are untightenable, and # in a really special way. @canTighten{'hr','br'} = (1,1); # exceptional 'phrasal' things that ARE subject to tightening. # The one case where I can think of my tightening rules failing is: # <p>foo bar<center> <em>baz quux</em> ... # ^-- that would get deleted. # But that's pretty gruesome code anyhow. You gets what you pays for. #========================================================================== =head2 array @HTML::Tagset::p_closure_barriers This array has a meaning that I have only seen a need for in C<HTML::TreeBuilder>, but I include it here on the off chance that someone might find it of use: When we see a "E<lt>pE<gt>" token, we go lookup up the lineage for a p element we might have to minimize. At first sight, we might say that if there's a p anywhere in the lineage of this new p, it should be closed. But that's wrong. Consider this document: <html> <head> <title>foo</title> </head> <body> <p>foo <table> <tr> <td> foo <p>bar </td> </tr> </table> </p> </body> </html> The second p is quite legally inside a much higher p. My formalization of the reason why this is legal, but this: <p>foo<p>bar</p></p> isn't, is that something about the table constitutes a "barrier" to the application of the rule about what p must minimize. So C<@HTML::Tagset::p_closure_barriers> is the list of all such barrier-tags. =cut our @p_closure_barriers = qw( li blockquote ul ol menu dir dl dt dd td th tr table caption div ); # In an ideal world (i.e., XHTML) we wouldn't have to bother with any of this # monkey business of barriers to minimization! =head2 hashset %isCDATA_Parent This hashset includes all elements whose content is CDATA. =cut our %isCDATA_Parent = map { $_ => 1 } qw(script style xmp listing plaintext); # TODO: there's nothing else that takes CDATA children, right? # As the HTML3 DTD (Raggett 1995-04-24) noted: # The XMP, LISTING and PLAINTEXT tags are incompatible with SGML # and derive from very early versions of HTML. They require non- # standard parsers and will cause problems for processing # documents with standard SGML tools. =head1 CAVEATS You may find it useful to alter the behavior of modules (like C<HTML::Element> or C<HTML::TreeBuilder>) that use C<HTML::Tagset>'s data tables by altering the data tables themselves. You are welcome to try, but be careful; and be aware that different modules may or may react differently to the data tables being changed. Note that it may be inappropriate to use these tables for I<producing> HTML -- for example, C<%isHeadOrBodyElement> lists the tagnames for all elements that can appear either in the head or in the body, such as "script". That doesn't mean that I am saying your code that produces HTML should feel free to put script elements in either place! If you are producing programs that spit out HTML, you should be I<intimately> familiar with the DTDs for HTML or XHTML (available at C<http://www.w3.org/>), and you should slavishly obey them, not the data tables in this document. =head1 SEE ALSO L<HTML::Element>, L<HTML::TreeBuilder>, L<HTML::LinkExtor> =head1 COPYRIGHT & LICENSE Copyright 1995-2000 Gisle Aas. Copyright 2000-2005 Sean M. Burke. Copyright 2005-2024 Andy Lester. This library is free software; you can redistribute it and/or modify it under the terms of the Artistic License version 2.0. =head1 ACKNOWLEDGEMENTS Most of the code/data in this module was adapted from code written by Gisle Aas for C<HTML::Element>, C<HTML::TreeBuilder>, and C<HTML::LinkExtor>. Then it was maintained by Sean M. Burke. =head1 AUTHOR Current maintainer: Andy Lester, C<< <andy at petdance.com> >> =head1 BUGS Please report any bugs or feature requests to C<bug-html-tagset at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=HTML-Tagset>. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes. =cut 1;