NAME

CSS::DOM - Document Object Model for Cascading Style Sheets

VERSION

Version 0.05

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 module provides the CSS-specific interfaces described in the W3C DOM recommendation.

The CSS::DOM class itself implements the StyleSheet and CSSStyleSheet DOM interfaces.

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:

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|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 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.

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
     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
    [::Value::List            CSSValueList]
[::RGBColor                   RGBColor]
[::Rect                       Rect]
[::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

constant::lexical

Encode 2.10 or higher

BUGS

CSS 'shorthand' properties (such as 'font') are not supported yet. Right now they are treated as their own properties, unrelated to those they are short for.

'!important' is not supported yet.

To report bugs, please e-mail the author.

AUTHOR & COPYRIGHT

Copyright (C) 2007 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.

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

cpanm CSS::DOM

perl -MCPAN -e shell
install CSS::DOM