### # CSS::SAC::Condition - base class for SAC conditions # Robin Berjon # 24/02/2001 ### package CSS::SAC::Condition; use strict; use vars qw($VERSION); $VERSION = $CSS::SAC::VERSION || '0.03'; #---------------------------------------------------------------------# # build the fields for an array based object #---------------------------------------------------------------------# use Class::ArrayObjects define => { fields => [qw(_type_)], }; #---------------------------------------------------------------------# ### Constants ######################################################### # # # # sub UNKNOWN_CONDITION () { 1 } sub AND_CONDITION () { 2 } sub ATTRIBUTE_CONDITION () { 3 } sub BEGIN_HYPHEN_ATTRIBUTE_CONDITION () { 4 } sub CLASS_CONDITION () { 5 } sub CONTENT_CONDITION () { 6 } sub ID_CONDITION () { 7 } sub LANG_CONDITION () { 8 } sub NEGATIVE_CONDITION () { 9 } sub ONE_OF_ATTRIBUTE_CONDITION () { 10 } sub ONLY_CHILD_CONDITION () { 11 } sub ONLY_TYPE_CONDITION () { 12 } sub OR_CONDITION () { 13 } sub POSITIONAL_CONDITION () { 14 } sub PSEUDO_CLASS_CONDITION () { 15 } # new non-standard conditions for CSS3 selectors sub STARTS_WITH_ATTRIBUTE_CONDITION () { 16 } # [attr^='string'] sub ENDS_WITH_ATTRIBUTE_CONDITION () { 17 } # [attr$='string'] sub CONTAINS_ATTRIBUTE_CONDITION () { 18 } # [attr*='string'] sub IS_ROOT_CONDITION () { 19 } # :root sub IS_EMPTY_CONDITION () { 20 } # :empty #---------------------------------------------------------------------# # import() # all import can do is export the constants #---------------------------------------------------------------------# sub import { my $class = shift; my $tag = shift || ''; # check that we have the right tag return unless $tag eq ':constants'; # define some useful vars my $pkg = caller; my @constants = qw( UNKNOWN_CONDITION AND_CONDITION ATTRIBUTE_CONDITION BEGIN_HYPHEN_ATTRIBUTE_CONDITION CLASS_CONDITION CONTENT_CONDITION ID_CONDITION LANG_CONDITION NEGATIVE_CONDITION ONE_OF_ATTRIBUTE_CONDITION ONLY_CHILD_CONDITION ONLY_TYPE_CONDITION OR_CONDITION POSITIONAL_CONDITION PSEUDO_CLASS_CONDITION STARTS_WITH_ATTRIBUTE_CONDITION ENDS_WITH_ATTRIBUTE_CONDITION CONTAINS_ATTRIBUTE_CONDITION IS_ROOT_CONDITION IS_EMPTY_CONDITION ); # now lets create the constants in the caller's package no strict 'refs'; for my $c (@constants) { my $qname = "${pkg}::$c"; *$qname = \&{$c}; } } #---------------------------------------------------------------------# # # # # ### Constants ######################################################### ### Constructor ####################################################### # # # # #---------------------------------------------------------------------# # CSS::SAC::Condition->new($type) # creates a new sac condition object #---------------------------------------------------------------------# sub new { my $class = ref($_[0])?ref(shift):shift; my $type = shift; return bless [$type], $class; } #---------------------------------------------------------------------# # # # # ### Constructor ####################################################### ### Accessors ######################################################### # # # # #---------------------------------------------------------------------# # my $type = $cond->ConditionType() # $cond->ConditionType($type) # get/set the condition type #---------------------------------------------------------------------# sub ConditionType { (@_==2) ? $_[0]->[_type_] = $_[1] : $_[0]->[_type_]; } #---------------------------------------------------------------------# *CSS::SAC::Condition::getConditionType = \&ConditionType; #---------------------------------------------------------------------# # $cond->is_type($condition_constant) # returns true is this condition is of type $condition_constant #---------------------------------------------------------------------# sub is_type { return $_[0]->[_type_] == $_[1]; } #---------------------------------------------------------------------# # # # # ### Accessors ######################################################### 1; =pod =head1 NAME CSS::SAC::Condition - base class for SAC conditions =head1 SYNOPSIS use CSS::SAC::Condition qw(:constants); foo if $cond->is_type(CONDITION_TYPE_CONSTANT); =head1 DESCRIPTION SAC Conditions describe conditions that can be expressed in CSS such as AttributeConditions or PositionalConditions. This class provides everything that is needed to implement simple conditions (methods, constants) as well as what is needed by subclasses defining more complex conditions. The constants are those defined in the SAC spec, with the leading SAC_ removed. What the constants map to is to be considered an opaque token that can be tested for equality. If there is demand for it, I will add a way to add new constants (for people wishing to define new condition types). I have also added the UNKNOWN_CONDITION constant. It shouldn't occur in normal processing but it's always useful to have such fallback values. The Condition interface adds $cond->is_type($condition_type) to the interface defined in the SAC spec. This allows for more flexible type checking. For instance, if you create a subclass of ContentCondition that extends it with the ContentRegexCondition interface you will probably want software ignorant of your subclass's existence to still be able to do something useful with it. That software should also be able to treat ContentRegexConditions as if they were ContentConditions. If that software tests condition types the following way: $rcond->ConditionType == CONTENT_CONDITION then you've lost because the condition type of ContentRegexCondition is REGEX_CONTENT_CONDITION. If, however, it tests it that way: $rcond->is_type(CONTENT_CONDITION) then you can simply implement is_type() so that it returns true for it's own type and the type of it's superclass. I strongly recommend using the latter scheme except in cases when you want to know the exact type. =head1 CONSTANTS =over 4 =item * UNKNOWN_CONDITION =item * AND_CONDITION =item * ATTRIBUTE_CONDITION =item * BEGIN_HYPHEN_ATTRIBUTE_CONDITION =item * CLASS_CONDITION =item * CONTENT_CONDITION =item * ID_CONDITION =item * LANG_CONDITION =item * NEGATIVE_CONDITION =item * ONE_OF_ATTRIBUTE_CONDITION =item * ONLY_CHILD_CONDITION =item * ONLY_TYPE_CONDITION =item * OR_CONDITION =item * POSITIONAL_CONDITION =item * PSEUDO_CLASS_CONDITION =back =head1 METHODS =over 4 =item * CSS::SAC::Condition->new($type) or $cond->new($type) Creates a new condition. The $type must be one of the type constants. =item * $cond->ConditionType() Returns the constant corresponding to the type of this condition. =item * $cond->is_type($condition_type) Returns a boolean indicating whether this condition is of type $condition_type (a condition constant). =back =head1 AUTHOR Robin Berjon This module is licensed under the same terms as Perl itself. =cut