When a paperclip attachment gains a new style and you have many attachments, reprocessing can take ages. This is because all styles are being recomputed.

To create only missing images, patch Paperclip like this in your script that does the reprocessing:

Paperclip <2.3.2

class Paperclip::Attachment
  private

  def post_process_styles_with_extreme_lazyness
    @old_styles = @styles

    @styles = @styles.reject do |name, _|
      exists?(name)
    end

    post_process_styles_without_extreme_...

has_attached_file(
  :avatar,
  :styles => { :large => "300x300", :small => "100x100" },
  :convert_options => { all => "-colorspace RGB" }
)

To parse XML-documents, I recommend the gem nokogiri.

A few hints:

• xml = Nokogiri::XML("<list><item>foo</item><item>bar</item></list>") parses an xml string. You can also call Nokogiri::HTML to be more liberal about accepting invalid XML.
• xml / 'list item' returns all matching nodes; list item is used like a CSS selector
• xml / './/list/item' also returns all matching nodes, but .//list/item is now an XPath selector
  • XPath seems to be triggered by a leading .…

How it works

See the lemonade descriptions.

Unfortunately, the gem has a few problems:

• it does not work with Sass2
• it always generates all sprites when the sass file changes, which is too slow for big projects
• it expects a folder structure quite different to our usual

All these problems are solved for us, in our own lemonade fork. This fork has since been merged to the original gem, maybe we can use t…

.notice,
.error,
.information,
.warning {
    font-weight: bold;
}

.notice {
    color: #11bb00;
}

.error {
    color: #F53A31;
}

.information {
    color: #557;
}

.warning {
    color: #d07d2d;
}

log/*
tmp/*
storage/*
db/*.sqlite3
db/schema.rb
db/structure.sql
public/system
.project
.idea/
public/javascripts/all*
public/stylesheets/all*
public/stylesheets/*.css
config/database.yml
*~
*#*
.#*
.DS_Store
webrat-*.html
capybara-*.html
rerun.txt
coverage.data
coverage/*
dump_for_download.dump
.~lock.*
.*.swp
C:\\nppdf32Log\\debuglog.txt

This is more tricky than it should be because url_for, asset_path, etc. all rely on different mechanisms.

Anyway, you can use the attached trait like this:

class ExampleController < ApplicationController
  does 'host_enforcement', :for => 'some_action'
end

Short explanation:

• asset_host is used for links to stylesheets and javascripts
• asset_host belongs to ActionController::Base – changes are persistent and will not be reset after a request
• rewrite_options is used by the ..._path methods in the views
  ^…