Provided by: libcss-dom-perl_0.17-1_all 
NAME
CSS::DOM - Document Object Model for Cascading Style Sheets
VERSION
Version 0.17
This is an alpha version. The API is still subject to change. Many features have not been implemented yet
(but patches would be welcome :-).
The interface for feeding CSS code to CSS::DOM changed incompatibly in version 0.03.
SYNOPSIS
use CSS::DOM;
my $sheet = CSS::DOM::parse( $css_source );
use CSS::DOM::Style;
my $style = CSS::DOM::Style::parse(
'background: red; font-size: large'
);
my $other_sheet = new CSS::DOM; # empty
$other_sheet->insertRule(
'a{ text-decoration: none }',
$other_sheet->cssRules->length,
);
# etc.
# access DOM properties
$other_sheet->cssRules->[0]->selectorText('p'); # change it
$style->fontSize; # returns 'large'
$style->fontSize('small'); # change it
DESCRIPTION
This set of modules provides the CSS-specific interfaces described in the W3C DOM recommendation.
The CSS::DOM class itself implements the StyleSheet and CSSStyleSheet DOM interfaces.
This set of modules has two modes:
1. It can validate property values, ignoring those that are invalid (just like a real web browser), and
support shorthand properties. This means you can set font to '13px/15px My Font' and have the font-
size, line-height, and font-family properties (among others) set automatically. Also, "color: green;
color: kakariki" will assign 'green' to the color property, 'kakariki' not being a recognised color
value.
2. It can blithely accept all property assignments as being valid. In the case of "color: green; color:
kakariki", 'kakariki' will be assigned, since it overrides the previous assignment.
These two modes are controlled by the "property_parser" option to the constructors.
CONSTRUCTORS
CSS::DOM::parse( $string )
This method parses the $string and returns a style sheet object. If you just have a CSS style
declaration, e.g., from an HTML "style" attribute, see "parse" in CSS::DOM::Style.
new CSS::DOM
Creates a new, empty style sheet object. Use this only if you plan to build the style sheet piece by
piece, instead of parsing a block of CSS code.
You can pass named arguments to both of those. "parse" accepts all of them; "new" understands only the
first two, "property_parser" and "url_fetcher".
property_parser
Set this to a PropertyParser object to specify which properties are supported and how they are
parsed.
If this option is not specified or is set to "undef", all property values are treated as valid.
See CSS::DOM::PropertyParser for more details.
url_fetcher
This has to be a code ref that returns the contents of the style sheet at the URL passed as the sole
argument. E.g.,
# Disclaimer: This does not work with relative URLs.
use LWP::Simple;
use CSS::DOM;
$css = '@import "file.css"; /* other stuff ... ';
$ss = CSS::DOM::parse $css, url_fetcher => sub { get shift };
$ss->cssRules->[0]->styleSheet; # returns a style sheet object
# corresponding to file.css
The subroutine can choose to return "undef" or an empty list, in which case the @import rule's
"styleSheet" method will return null (empty list or "undef"), as it would if no "url_fetcher" were
specified.
It can also return named items after the CSS code, like this:
return $css_code, decode => 1, encoding_hint => 'iso-8859-1';
These correspond to the next two items:
decode
If this is specified and set to a true value, then CSS::DOM will treat the CSS code as a string of
bytes, and try to decode it based on @charset rules and byte order marks.
By default it assumes that it is already in Unicode (i.e., decoded).
encoding_hint
Use this to provide a hint as to what the encoding might be.
If this is specified, and "decode" is not, then "decode => 1" is assumed.
STYLE SHEET ENCODING
See the options above. This section explains how and when you should use those options.
According to the CSS spec, any encoding specified in the 'charset' field on an HTTP Content-Type header,
or the equivalent in other protocols, takes precedence. In such a case, since CSS::DOM doesn't deal with
HTTP, you have to decode it yourself.
Otherwise, you should use "decode => 1" to instruct CSS::DOM to use byte order marks or @charset rules.
If neither of those is present, then encoding data in the referencing document (e.g., <link
charset="..."> or an HTML document's own encoding), if available/applicable, should be used. In this
case, you should use the "encoding_hint" option, so that CSS::DOM has something to fall back to.
If you use "decode => 1" with no encoding hint, and no BOM or @charset is to be found, UTF-8 is assumed.
SYNTAX ERRORS
The two constructors above, and also "CSS::DOM::Style::parse", set $@ to the empty string upon success.
If they encounter a syntax error, they set $@ to the error and return an object that represents whatever
was parsed up to that point.
Other methods that parse CSS code might die on encountering syntax errors, and should usually be wrapped
in an "eval".
The parser follows the 'future-compatible' syntax described in the CSS 2.1 specification, and also the
spec's rules for handling parsing errors. Anything not handled by those two is a syntax error.
In other words, a syntax error is one of the following:
• An unexpected closing bracket, as in these examples
a { text-decoration: none )
*[name=~'foo'} {}
#thing { clip: rect( ]
• An HTML comment delimiter within a rule; e.g.,
a { text-decoration : none <!-- /* Oops! */ }
<!-- /*ok*/ @media --> /* bad! */ print { }
• An extra "@" keyword or semicolon where it doesn't belong; e.g.,
@media @print { .... }
@import "file.css" @print;
td, @page { ... }
#tabbar td; #tab1 { }
OBJECT METHODS
Attributes
type
Returns the string 'text/css'.
disabled
Allows one to specify whether the style sheet is used. (This attribute is not actually used yet by
CSS::DOM.) You can set it by passing an argument.
ownerNode
Returns the node that 'owns' this style sheet.
parentStyleSheet
If the style sheet belongs to an '@import' rule, this returns the style sheet containing that rule.
Otherwise it returns an empty list.
href
Returns the style sheet's URI, if applicable.
title
Returns the value of the owner node's title attribute.
media
Returns the MediaList associated with the style sheet (or a plain list in list context). This
defaults to an empty list. You can pass a comma-delimited string to the MediaList's "mediaText"
method to initialise it.
(The medium information is not actually used [yet] by CSS::DOM, but you can put it there.)
ownerRule
If this style sheet was created by an @import rule, this returns the rule; otherwise it returns an
empty list (or undef in scalar context).
cssRules
In scalar context, this returns a CSS::DOM::RuleList object (simply a blessed array reference) of
CSS::DOM::Rule objects. In list context it returns a list.
Methods
insertRule ( $css_code, $index )
Parses the rule contained in the $css_code, inserting it in the style sheet's list of rules at the
given $index.
deleteRule ( $index )
Deletes the rule at the given $index.
hasFeature ( $feature, $version )
You can call this either as an object or class method.
This is actually supposed to be a method of the 'DOMImplementation' object. (See, for instance,
HTML::DOM::Interface's method of the same name, which delegates to this one.) This returns a boolean
indicating whether a particular DOM module is implemented. Right now it returns true only for the
'CSS2' and 'StyleSheets' features (version '2.0').
Non-DOM Methods
set_ownerNode
This allows you to set the value of "ownerNode". Passing an argument to "ownerNode" does nothing,
because it is supposed to be read-only. But you have to be able to set it somehow, so that's why this
method is here.
The style sheet will hold a weak reference to the object passed to this method.
set_href
Like "set_ownerNode", but for "href".
property_parser
url_fetcher
These two both return what was passed to the constructor. The second one, "url_fetcher" also allows
an assignment, but this is not propagated to sub-rules and is intended mainly for internal use.
FUNCTIONS
CSS::DOM::parse
See "CONSTRUCTORS", above.
CSS::DOM::compute_style( %options )
Warning: This is still highly experimental and crawling with bugs.
This computes the style for a given HTML element. It does not yet calculate actual measurements
(e.g., converting percentages to pixels), but simply applies the cascading rules and selectors.
Pseudo-classes are not yet supported (but pseudo-elements are).
The precedence rules for normal vs important declarations in the CSS 2 specification are used. (CSS
2.1 is unclear.) The precedence is as follows, from lowest to highest:
user agent normal declarations
user normal declarations
author normal "
user agent !important declarations
author !important "
user " "
The %options are as follows. They are all optional except for "element".
ua_sheet
The user agent style sheet
user_sheet
The user style sheet
author_sheets
Array ref of style sheets that the HTML document defines or links to.
element
The element, as an HTML::DOM::Element object.
pseudo
The pseudo-element (e.g., 'first-line'). This can be specified with no colons (the way Opera
requires it) or with one or two colons (the way Firefox requires it).
medium
height
width
ppi (To be implemented)
The
CLASSES AND DOM INTERFACES
Here are the inheritance hierarchy of CSS::DOM's various classes and the DOM interfaces those classes
implement. For brevity's sake, a simple '::' at the beginning of a class name in the left column is used
for 'CSS::DOM::'. Items in brackets do not exist yet. (See also CSS::DOM::Interface for a machine-
readable list of standard methods.)
Class Inheritance Hierarchy Interfaces
--------------------------- ----------
CSS::DOM StyleSheet, CSSStyleSheet
::Array
::MediaList MediaList
::StyleSheetList StyleSheetList
::RuleList CSSRuleList
::Rule CSSRule, CSSUnknownRule
::Rule::Style CSSStyleRule
::Rule::Media CSSMediaRule
::Rule::FontFace CSSFontFaceRule
::Rule::Page CSSPageRule
::Rule::Import CSSImportRule
::Rule::Charset CSSCharsetRule
::Style CSSStyleDeclaration, CSS2Properties
::Value CSSValue
::Value::Primitive CSSPrimitiveValue, RGBColor, Rect
::Value::List CSSValueList
[::Counter Counter]
CSS::DOM does not implement the following interfaces (see HTML::DOM for these):
LinkStyle
DocumentStyle
ViewCSS
DocumentCSS
DOMImplementationCSS
ElementCSSInlineStyle
IMPLEMENTATION NOTES
• Attributes of objects are accessed via methods of the same name. When the method is invoked, the
current value is returned. If an argument is supplied, the attribute is set (unless it is read-only)
and its old value returned.
• Where the DOM spec. says to use null, undef or an empty list is used.
• Instead of UTF-16 strings, CSS::DOM uses Perl's Unicode strings.
• Each method that the specification says returns an array-like object (e.g., a RuleList) will return
such an object in scalar context, or a simple list in list context. You can use the object as an
array ref in addition to calling its "item" and "length" methods.
PREREQUISITES
perl 5.8.2 or higher
Exporter 5.57 or later
Encode 2.10 or higher
Clone 0.09 or higher
BUGS
The parser has not been updated to conform to the April 2009 revision of the CSS 2.1 candidate
recommendation. Specifically, unexpected closing brackets are not ignored, but cause syntax errors; and
@media rules containing unrecognised statements are themselves currently treated as unrecognised (the
unrecognised inner statements should be ignored, rendering the outer @media rule itself valid).
If you create a custom property parser that defines 'list-style-type' to include multiple tokens, then
counters will become "CSS_CUSTOM" CSSValue objects instead of "CSS_COUNTER" CSSPrimitiveValue objects.
If you change a property parser's property definitions such that a primitive value becomes a list, or
vice versa, and then try to modify the "cssText" property of an existing value object belonging to that
property, things will go awry.
Whitespace and comments are sometimes preserved in serialised CSS and sometimes not. Expect
inconsistency.
To report bugs, please e-mail the author.
ACKNOWLEDGEMENTS
Thanks to Ville Skyttä, Nicholas Bamber and Gregor Herrmann for their contributions.
AUTHOR & COPYRIGHT
Copyright (C) 2007-18 Father Chrysostomos <sprout [at] cpan [dot] org>
This program is free software; you may redistribute it and/or modify it under the same terms as perl. The
full text of the license can be found in the LICENSE file included with this module.
SEE ALSO
All the classes listed above under "CLASSES AND DOM INTERFACES".
CSS::SAC, CSS.pm and HTML::DOM
The DOM Level 2 Style specification at <http://www.w3.org/TR/DOM-Level-2-Style>
The CSS 2.1 specification at <http://www.w3.org/TR/CSS21/>