Class: Premailer

Inherits:
Object
  • Object
show all
Includes:
CssParser, Warnings
Defined in:
lib/premailer/premailer.rb

Overview

Premailer by Alex Dunae (dunae.ca, e-mail ‘code’ at the same domain), 2008-09

Premailer processes HTML and CSS to improve e-mail deliverability.

Premailer’s main function is to render all CSS as inline style attributes. It also converts relative links to absolute links and checks the ‘safety’ of CSS properties against a CSS support chart.

Example

premailer = Premailer.new('http://example.com/myfile.html', :warn_level => Premailer::Warnings::SAFE)

# Write the HTML output
fout = File.open("output.html", "w")
fout.puts premailer.to_inline_css
fout.close

# Write the plain-text output
fout = File.open("ouput.txt", "w")
fout.puts premailer.to_plain_text
fout.close

# List any CSS warnings
puts premailer.warnings.length.to_s + ' warnings found'
premailer.warnings.each do |w|
  puts "#{w[:message]} (#{w[:level]}) may not render properly in #{w[:clients]}"
end

premailer = Premailer.new(html_file, :warn_level => Premailer::Warnings::SAFE)
puts premailer.to_inline_css

Defined Under Namespace

Modules: Warnings

Constant Summary collapse

VERSION = 
'1.5.4'
CLIENT_SUPPORT_FILE = 
File.dirname(__FILE__) + '/../../misc/client_support.yaml'
RE_UNMERGABLE_SELECTORS = 
/(\:(visited|active|hover|focus|after|before|selection|target|first\-(line|letter))|^\@)/i
WARN_LABEL = 
%w(NONE SAFE POOR RISKY)

Constants included from Warnings

Warnings::NONE, Warnings::POOR, Warnings::RISKY, Warnings::SAFE

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(path, options = {}) ⇒ Premailer

Create a new Premailer object.

path is the path to the HTML file to process. Can be either the URL of a remote file or a local path.

Options

line_length

Line length used by to_plain_text. Boolean, default is 65.

warn_level

What level of CSS compatibility warnings to show (see Warnings).

link_query_string

A string to append to every <a href=“”> link. Do not include the initial ?.

base_url

Used to calculate absolute URLs for local files.



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# File 'lib/premailer/premailer.rb', line 73

def initialize(path, options = {})
  @options = {:warn_level => Warnings::SAFE, 
              :line_length => 65, 
              :link_query_string => nil, 
              :base_url => nil,
              :local_file => true,
              :remove_classes => false}.merge(options)
  @html_file = path
  
  if options[:local_file] == false
    @is_local_file = false
  elsif path =~ /^(http|https|ftp)\:\/\//i
    @is_local_file = false
  else
    @is_local_file = true
  end

  @css_warnings = []

  @css_parser = CssParser::Parser.new({:absolute_paths => true,
                                       :import => true,
                                       :io_exceptions => false
                                      })
  
  @doc, @html_charset = load_html(@html_file)
  @processed_doc = @doc
  
  if @is_local_file and @options[:base_url]
    @processed_doc = convert_inline_links(@processed_doc, @options[:base_url])
  elsif not @is_local_file
    @processed_doc = convert_inline_links(@processed_doc, @html_file)
  end
  load_css_from_html!
end

Instance Attribute Details

#doc ⇒ Object (readonly)

source HTML document (Hpricot)



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# File 'lib/premailer/premailer.rb', line 51

def doc
  @doc
end

#html_file ⇒ Object (readonly)

URI of the HTML file used



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# File 'lib/premailer/premailer.rb', line 45

def html_file
  @html_file
end

#processed_doc ⇒ Object (readonly)

processed HTML document (Hpricot)



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# File 'lib/premailer/premailer.rb', line 48

def processed_doc
  @processed_doc
end

Instance Method Details

#to_inline_css ⇒ Object

Merge CSS into the HTML document.

Returns a string.



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# File 'lib/premailer/premailer.rb', line 136

def to_inline_css
  doc = @processed_doc
  unmergable_rules = CssParser::Parser.new
  
  # Give all styles already in style attributes a specificity of 1000 
  # per http://www.w3.org/TR/CSS21/cascade.html#specificity
  doc.search("*[@style]").each do |el| 
    el['style'] = '[SPEC=1000[' + el.attributes['style'] + ']]'
  end

  # Iterate through the rules and merge them into the HTML
  @css_parser.each_selector(:all) do |selector, declaration, specificity|
    # Save un-mergable rules separately
    selector.gsub!(/:link([\s]|$)+/i, '')

    # Convert element names to lower case
    selector.gsub!(/([\s]|^)([\w]+)/) {|m| $1.to_s + $2.to_s.downcase }

    if selector =~ RE_UNMERGABLE_SELECTORS
      unmergable_rules.add_rule_set!(RuleSet.new(selector, declaration))
    else
      
      doc.search(selector) do |el|
        if el.elem?
          # Add a style attribute or append to the existing one  
          block = "[SPEC=#{specificity}[#{declaration}]]"
          el['style'] = (el.attributes['style'] ||= '') + ' ' + block
        end
      end
    end
  end

  # Read <style> attributes and perform folding
  doc.search("*[@style]").each do |el|
    style = el.attributes['style'].to_s
    
    declarations = []

    style.scan(/\[SPEC\=([\d]+)\[(.[^\]\]]*)\]\]/).each do |declaration|
      rs = RuleSet.new(nil, declaration[1].to_s, declaration[0].to_i)
      declarations << rs
    end

    # Perform style folding and save
    merged = CssParser.merge(declarations)

    el['style'] = Premailer.escape_string(merged.declarations_to_s)
  end

  doc = write_unmergable_css_rules(doc, unmergable_rules)

  doc.search('*').remove_class if @options[:remove_classes]  

  @processed_doc = doc

  doc.to_html
end

#to_plain_text ⇒ Object

Converts the HTML document to a format suitable for plain-text e-mail.

Returns a string.



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# File 'lib/premailer/premailer.rb', line 123

def to_plain_text
  html_src = ''
  begin
    html_src = @doc.search("body").innerHTML
  rescue
    html_src = @doc.to_html
  end
  convert_to_text(html_src, @options[:line_length], @html_charset)
end

#to_s ⇒ Object

Returns the original HTML as a string.



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# File 'lib/premailer/premailer.rb', line 116

def to_s
  @doc.to_html
end

#warnings ⇒ Object

Array containing a hash of CSS warnings.



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# File 'lib/premailer/premailer.rb', line 109

def warnings
  return [] if @options[:warn_level] == Warnings::NONE
  @css_warnings = check_client_support if @css_warnings.empty?
  @css_warnings
end