Build Status Code Climate

Hologram is a Ruby gem that parses comments in your CSS and helps you turn them into a beautiful style guide.

There are two steps to building a great style guide:

  1. Documenting your css and javascript, and generating html examples.
  2. Styling the output of step 1.

The hologram gem itself is only concerned with step 1. This means you are free to make your style guide look however you would like. If you don't feel like going through this process yourself, you can take a look at the templates in our example repository, and use the assets defined there instead.


Add this line to your application's Gemfile:

gem 'hologram'

And then execute:

$ bundle

If you don't use bundler you can run gem install hologram.

Quick Start

hologram init

This will create a hologram_config.yml file (more on this below), and also create a starter _header.html and _footer.html file for you. You can then tweak the config values and start documenting your css.

Building the documentation is simply:


Command line flags

Hologram has a couple of command line flags:

  • -c or --config - specify the config file, by default hologram looks for hologram_config.yml
  • -r or --root - specify the directory to use when processing files (useful if you run hologram in a different directory than your assets. Defaults to current working directory)


There are two things you need to do to start using hologram:

  1. Create a YAML config file for your project.

  2. Go document some code!

Creating a YAML config file

Hologram needs a few configuration settings before it can begin to build your documentation for you. Once this is set up, you can execute hologram by simply running:

hologram path/to/your/config.yml or (using bundler) bundle exec hologram path/to/your/config.yml

Your config file needs to contain the following key/value pairs

  • source: relative path to your source files

  • destination: relative path where you want the documentation to be built

  • documentation_assets: The path that contains supporting assets for the documentation page. This typically includes html fragments (header/footer, etc), style guide specific CSS, javascript and any images. Hologram specifically looks for two files: _header.html and _footer.html. These are used to start and end every html page hologram generates.

Hologram treats _header.html and _footer.html as ERB files for each page that is generated. You can access the title, file_name, blocks, and categories.

blocks is a list of each documentation block on the page. Each item in the list has a title, name, category, and optionally a parent. This is useful for, say, building a menu that lists each component.

categories is a list of all the categories found in the documentation

Nota Bene: Filenames that begin with underscores will not be copied into the destination folder.

  • custom_markdown: (optional) this is the filename of a class that extends RedCarpet::Render::HTML class. Use this for when you need additional classes or html tags for different parts of the page. See example_markdown_renderer.rb.example for an example of what your class can look like.

  • index: (optional) this is a category (see Documenting your styles section below) that will be used as the index.html.

  • dependencies: a list of relative paths to folders containing any dependencies your style guide has. These folders will be copied over into the documentation output directory. ENSURE THE CSS/JS THAT IS ACTUALLY BEING DOCUMENTED IS LISTED HERE. You will also need to ensure that they are included on your pages. A simple way to do this is to add <link> and <script src=> tags to the _header.html file.

Example config file
# Hologram will run from same directory where this config file resides
# All paths should be relative to there

# The directory containing the source files to parse recursively
source: ./sass

# The directory that hologram will build to
destination: ./docs

# The assets needed to build the docs (includes header.html,
# footer.html, etc)
# You may put doc related assets here too: images, css, etc.
documentation_assets: ./doc_assets

# Any other asset folders that need to be copied to the destination
# folder. Typically this will include the css that you are trying to
# document. May also include additional folders as needed.
  - ./build

# Mark which category should be the index page
# Alternatively, you may have an index.md in the documentation assets
# folder instead of specifying this config.
index: basics

Documenting your styles and components

Hologram will scan for stylesheets (.css, .scss, .sass, .less, or .styl) and javascript source files (.js) within the source directory defined in your configuration. It will look for comments that match the following:

title: Buttons
name: button
category: Base CSS

Button styles can be applied to any element. Typically you'll want
to use either a `<button>` or an `<a>` element:

```html_example <button class="btn btnDefault">Click</button> <a
class="btn btnDefault" href="trulia.com">Trulia!</a> ```

If your button is actually a link to another page, please use the
`<a>` element, while if your button performs an action, such as
submitting a form or triggering some javascript event, then use a
`<button>` element.


The first section of the comment is a YAML block that defines certain aspects of this documentation block (more on that in the next section). The second part is simply markdown as defined by Redcarpet.

Notice the use of html_example. This tells the markdown renderer that it should treat the example as...well...html. If your project uses haml you can also use haml_example. In that case the output will be html for the example and the code block will show the haml used to generate the html.

For components that require javascript you can use js_example. In addition to outputting the javascript in a <code> block it will also wrap it in a <script> tag for execution.

Document YAML section

The YAML in the documentation block can have any key/value pairs you deem important, but it specifically looks for the following keys:

  • title: The title to display in the documents
  • category/categories: This is the broad categories for the component, all components in the same category will be written to the same page. It can be set to either a string or a YAML array. If you use an array, the component will be written to both pages. Note: There is no need to set a category if this component has a parent.
  • name: This is used for grouping components, by assigning a name, a component can be referenced in another component as a parent. Note that items in the same category are sorted alphabetically by name.
  • parent: (Optional.) This should be the name of another component. If this is set, the current component will be displayed as a section within the parent's documentation, but only if it specifies the same category, or allows the category to be inherited from its parent.

For example, you might have a component with the name buttons and another component named buttonSkins. You could set the parent for the buttonSkins component to be buttons. It would then nest the buttonSkins documentation inside the buttons documentation.

Each level of nesting (components are infinitely nestable) will have a heading tag that represents its depth. In the above example buttons would have an <h1> and buttonSkins would have an <h2>.

You can see this exact example in our demo repo, and the output of this nesting in our demo style guide.

Documentation Assets

The documentation assets folder contains the html, css, js and images you'll need for making your style guide look beautiful.

Hologram doesn't care too much about what is in here as it is intended to be custom for your style guide.

Styling Your Code Examples

Hologram uses pygments.rb gem to provide syntax highlighting for code examples. One of the assets that you probably want to include in your documentation assets folder is a css file that styles the "pygmentized" code examples. We use github.css which can be found along with the css we use to style code blocks here.

Supported Preprocessors/File Types

The following preprocessors/file types are supported by Hologram:

  • Sass (.scss, .sass)
  • Less (.less)
  • Stylus (.styl)
  • Vanilla CSS (.css)
  • Javascript (.js)
  • Markdown (.md, .markdown)

Extensions and Plugins

  • Guard Hologram is a sweet little gem that uses guard to monitor changes to your hologram project and rebuilds your style guide on the fly as you make changes.


  1. Fork it
  2. Create your feature/bug fix branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request


Hologram is written and maintained by August Flanagan and JD Cantrell.


These fine people have also contributed to making hologram a better gem:


Hologram is licensed under the MIT License