class Kramdown::Converter::Base
Base class for converters¶ ↑
This class serves as base class for all converters. It provides methods that can/should be used by all converters (like generate_id
) as well as common functionality that is automatically applied to the result (for example, embedding the output into a template).
A converter object is used as a throw-away object, i.e. it is only used for storing the needed state information during conversion. Therefore one can’t instantiate a converter object directly but only use the Base::convert
method.
Implementing a converter¶ ↑
Implementing a new converter is rather easy: just derive a new class from this class and put it in the Kramdown::Converter
module (the latter is only needed if auto-detection should work properly). Then you need to implement the convert
method which has to contain the conversion code for converting an element and has to return the conversion result.
The actual transformation of the document tree can be done in any way. However, writing one method per element type is a straight forward way to do it - this is how the Html
and Latex
converters do the transformation.
Have a look at the Base::convert
method for additional information!
Attributes
Can be used by a converter for storing arbitrary information during the conversion process.
The hash with the conversion options.
The root element that is converted.
The warnings array.
Public Class Methods
Convert the element tree tree
and return the resulting conversion object (normally a string) and an array with warning messages. The parameter options
specifies the conversion options that should be used.
Initializes a new instance of the calling class and then calls the convert
method with tree
as parameter.
If the template
option is specified and non-empty, the template is evaluate with ERB before and/or after the tree conversion depending on the result of apply_template_before?
and apply_template_after?
. If the template is evaluated before, an empty string is used for the body; if evaluated after, the result is used as body. See ::apply_template.
The template resolution is done in the following way (for the converter ConverterName):
-
Look in the current working directory for the template.
-
Append
.converter_name
(e.g..html
) to the template name and look for the resulting file in the current working directory (the form.convertername
is deprecated). -
Append
.converter_name
to the template name and look for it in the kramdown data directory (the form.convertername
is deprecated). -
Check if the template name starts with ‘string://’ and if so, strip this prefix away and use the rest as template.
# File lib/kramdown/converter/base.rb, line 100 def self.convert(tree, options = {}) converter = new(tree, ::Kramdown::Options.merge(options.merge(tree.options[:options] || {}))) if !converter.options[:template].empty? && converter.apply_template_before? apply_template(converter, '') end result = converter.convert(tree) if result.respond_to?(:encode!) && result.encoding != Encoding::BINARY result.encode!(tree.options[:encoding] || (raise ::Kramdown::Error, "Missing encoding option on root element")) end if !converter.options[:template].empty? && converter.apply_template_after? result = apply_template(converter, result) end [result, converter.warnings] end
Public Instance Methods
Returns whether the template should be applied after the conversion of the tree.
Defaults to true.
# File lib/kramdown/converter/base.rb, line 72 def apply_template_after? true end
Returns whether the template should be applied before the conversion of the tree.
Defaults to false.
# File lib/kramdown/converter/base.rb, line 65 def apply_template_before? false end
The basic version of the ID generator, without any special provisions for empty or unique IDs.
# File lib/kramdown/converter/base.rb, line 236 def basic_generate_id(str) gen_id = str.gsub(/^[^a-zA-Z]+/, '') gen_id.tr!('^a-zA-Z0-9 -', '') gen_id.tr!(' ', '-') gen_id.downcase! gen_id end
Convert the element el
and return the resulting object.
This is the only method that has to be implemented by sub-classes!
# File lib/kramdown/converter/base.rb, line 121 def convert(_el) raise NotImplementedError end
Extract the code block/span language from the attributes.
# File lib/kramdown/converter/base.rb, line 173 def extract_code_language(attr) if attr['class'] && attr['class'] =~ /\blanguage-\S+/ attr['class'].scan(/\blanguage-(\S+)/).first.first end end
Warning: This version will modify the given attributes if a language is present.
# File lib/kramdown/converter/base.rb, line 182 def extract_code_language!(attr) lang = extract_code_language(attr) attr['class'] = attr['class'].sub(/\blanguage-\S+/, '').strip if lang attr.delete('class') if lang && attr['class'].empty? lang end
Format the given math element with the math engine configured through the option ‘math_engine’.
# File lib/kramdown/converter/base.rb, line 205 def format_math(el, opts = {}) return nil unless @options[:math_engine] engine = ::Kramdown::Converter.math_engine(@options[:math_engine]) if engine engine.call(self, el, opts) else warning("The configured math engine #{@options[:math_engine]} is not available.") nil end end
Generate an unique alpha-numeric ID from the the string str
for use as a header ID.
Uses the option auto_id_prefix
: the value of this option is prepended to every generated ID.
# File lib/kramdown/converter/base.rb, line 221 def generate_id(str) str = ::Kramdown::Utils::Unidecoder.decode(str) if @options[:transliterated_header_ids] gen_id = basic_generate_id(str) gen_id = 'section' if gen_id.empty? @used_ids ||= {} if @used_ids.key?(gen_id) gen_id += "-#{@used_ids[gen_id] += 1}" else @used_ids[gen_id] = 0 end @options[:auto_id_prefix] + gen_id end
Highlight the given text
in the language lang
with the syntax highlighter configured through the option ‘syntax_highlighter’.
# File lib/kramdown/converter/base.rb, line 191 def highlight_code(text, lang, type, opts = {}) return nil unless @options[:syntax_highlighter] highlighter = ::Kramdown::Converter.syntax_highlighter(@options[:syntax_highlighter]) if highlighter highlighter.call(self, text, lang, type, opts) else warning("The configured syntax highlighter #{@options[:syntax_highlighter]} is not available.") nil end end
Return true
if the header element el
should be used for the table of contents (as specified by the toc_levels
option).
# File lib/kramdown/converter/base.rb, line 161 def in_toc?(el) @options[:toc_levels].include?(el.options[:level]) && (el.attr['class'] || '') !~ /\bno_toc\b/ end
Return the output header level given a level.
Uses the header_offset
option for adjusting the header level.
# File lib/kramdown/converter/base.rb, line 168 def output_header_level(level) [[level + @options[:header_offset], 6].min, 1].max end
Return the entity that represents the given smart_quote element.
# File lib/kramdown/converter/base.rb, line 247 def smart_quote_entity(el) res = @options[:smart_quotes][SMART_QUOTE_INDICES[el.value]] ::Kramdown::Utils::Entities.entity(res) end
Add the given warning text
to the warning array.
# File lib/kramdown/converter/base.rb, line 155 def warning(text) @warnings << text end