Perl 6 core CSS grammars
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README.md

perl6-CSS-Grammar

CSS::Grammar is under construction as an experimental set of Perl 6 grammars for the W3C family of CSS standards.

It aims to implement a reasonable portion of the base grammars with an emphasis on:

  • support for CSS1, CSS2.1 and CSS3
  • forward compatibility rules, scanning and error recovery

This module performs generic parsing of declarations in style-sheet rules.

Contents

Base Grammars

  • CSS::Grammar::CSS1 - CSS 1.0 compatible grammar
  • CSS::Grammar::CSS21 - CSS 2.1 compatible grammar
  • CSS::Grammar::CSS3 - CSS 3.0 (core) compatible grammar

The CSS 3.0 core grammar, CSS::Grammar::CSS3, is based on CSS2.1; it understands:

  • #hex and rgb(...) colors; but not rgba(..), hsl(...), hsla(...) or named colors
  • basic @media at-rules; but not advanced media queries, resolutions or embedded @page rules.
  • basic @page page description rules
  • basic css3 level selectors

Parser Actions

CSS::Grammar::Actions can be used with in conjunction with any of the CSS1 CSS21 or CSS3 base grammars. It produces an abstract syntax tree (AST), plus warnings for any unexpected input.

use v6;
use CSS::Grammar::CSS3;
use CSS::Grammar::Actions;

my $css = 'H1 { color: blue; gunk }';

my $actions =  CSS::Grammar::Actions.new;
my $p = CSS::Grammar::CSS3.parse($css, :actions($actions));
.note for $actions.warnings;
say "H1: " ~ $p.ast<stylesheet>[0]<ruleset><selectors>;
# output:
# dropping term: gunk
# H1: selector    simple-selector qname   element-name    h1

Actions Options

  • :lax Pass back, don't drop, quantities with unknown dimensions.

Installation (Rakudo Star)

You'll first need to download and build Rakudo Star 2015.07 or better (http://rakudo.org/downloads/star/ - don't forget the final make install):

Ensure that perl6 and panda are available on your path, e.g. :

% export PATH=~/src/rakudo-star-2015.07/install/bin:$PATH

You can then use panda to test and install CSS::Grammar:

% panda install CSS::Grammar

To try parsing some content:

% perl6 -MCSS::Grammar::CSS3 -e"say CSS::Grammar::CSS3.parse('H1 {color:blue}')"

See Also

  • CSS::Module::CSS3::Selectors extends CSS::Grammar::CSS3 to fully implement CSS Level 3 Selectors.
  • CSS::Module further extends CSS::Grammar levels 1, 2.1 and 3. It understands named colors and is able to perform property-specific parsing and validation.
  • CSS::Drafts further extends CSS::Module, adding support for further draft CSS Level 3 extension modules.
  • CSS::Writer - AST reserializer
  • CSSGrammar.pm from perl6-examples gives an introductory Perl 6 grammar for CSS 2.1.

References

This module been built from the W3C CSS Specifications. In particular: