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 100 def self.convert(tree, options = {}) 101 converter = new(tree, ::Kramdown::Options.merge(options.merge(tree.options[:options] || {}))) 102 103 if !converter.options[:template].empty? && converter.apply_template_before? 104 apply_template(converter, '') 105 end 106 result = converter.convert(tree) 107 if result.respond_to?(:encode!) && result.encoding != Encoding::BINARY 108 result.encode!(tree.options[:encoding] || 109 (raise ::Kramdown::Error, "Missing encoding option on root element")) 110 end 111 if !converter.options[:template].empty? && converter.apply_template_after? 112 result = apply_template(converter, result) 113 end 114 115 [result, converter.warnings] 116 end
Private Class Methods
Initialize the converter with the given root
element and options
hash.
# File lib/kramdown/converter/base.rb 54 def initialize(root, options) 55 @options = options 56 @root = root 57 @data = {} 58 @warnings = [] 59 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 72 def apply_template_after? 73 true 74 end
Returns whether the template should be applied before the conversion of the tree.
Defaults to false.
# File lib/kramdown/converter/base.rb 65 def apply_template_before? 66 false 67 end
The basic version of the ID generator, without any special provisions for empty or unique IDs.
# File lib/kramdown/converter/base.rb 236 def basic_generate_id(str) 237 gen_id = str.gsub(/^[^a-zA-Z]+/, '') 238 gen_id.tr!('^a-zA-Z0-9 -', '') 239 gen_id.tr!(' ', '-') 240 gen_id.downcase! 241 gen_id 242 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 121 def convert(_el) 122 raise NotImplementedError 123 end
Extract the code block/span language from the attributes.
# File lib/kramdown/converter/base.rb 173 def extract_code_language(attr) 174 if attr['class'] && attr['class'] =~ /\blanguage-\S+/ 175 attr['class'].scan(/\blanguage-(\S+)/).first.first 176 end 177 end
Warning: This version will modify the given attributes if a language is present.
# File lib/kramdown/converter/base.rb 182 def extract_code_language!(attr) 183 lang = extract_code_language(attr) 184 attr['class'] = attr['class'].sub(/\blanguage-\S+/, '').strip if lang 185 attr.delete('class') if lang && attr['class'].empty? 186 lang 187 end
Format the given math element with the math engine configured through the option ‘math_engine’.
# File lib/kramdown/converter/base.rb 205 def format_math(el, opts = {}) 206 return nil unless @options[:math_engine] 207 208 engine = ::Kramdown::Converter.math_engine(@options[:math_engine]) 209 if engine 210 engine.call(self, el, opts) 211 else 212 warning("The configured math engine #{@options[:math_engine]} is not available.") 213 nil 214 end 215 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 221 def generate_id(str) 222 str = ::Kramdown::Utils::Unidecoder.decode(str) if @options[:transliterated_header_ids] 223 gen_id = basic_generate_id(str) 224 gen_id = 'section' if gen_id.empty? 225 @used_ids ||= {} 226 if @used_ids.key?(gen_id) 227 gen_id += "-#{@used_ids[gen_id] += 1}" 228 else 229 @used_ids[gen_id] = 0 230 end 231 @options[:auto_id_prefix] + gen_id 232 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 191 def highlight_code(text, lang, type, opts = {}) 192 return nil unless @options[:syntax_highlighter] 193 194 highlighter = ::Kramdown::Converter.syntax_highlighter(@options[:syntax_highlighter]) 195 if highlighter 196 highlighter.call(self, text, lang, type, opts) 197 else 198 warning("The configured syntax highlighter #{@options[:syntax_highlighter]} is not available.") 199 nil 200 end 201 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 161 def in_toc?(el) 162 @options[:toc_levels].include?(el.options[:level]) && (el.attr['class'] || '') !~ /\bno_toc\b/ 163 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 168 def output_header_level(level) 169 [[level + @options[:header_offset], 6].min, 1].max 170 end
Return the entity that represents the given smart_quote element.
# File lib/kramdown/converter/base.rb 247 def smart_quote_entity(el) 248 res = @options[:smart_quotes][SMART_QUOTE_INDICES[el.value]] 249 ::Kramdown::Utils::Entities.entity(res) 250 end
Add the given warning text
to the warning array.
# File lib/kramdown/converter/base.rb 155 def warning(text) 156 @warnings << text 157 end