Welcome to django-critical’s documentation!¶

Documentation¶

The full documentation is at https://django-critical.readthedocs.org.

Quickstart¶

• Install django-critical:

  pip install django-critical
  

• Add critical to your INSTALLED_APPS setting:

  INSTALLED_APPS = (
      # other apps
      "critical",
  )
  

• Add critical.middleware.CriticalCssMiddleware to your MIDDLEWARE_CLASSES setting:

  MIDDLEWARE_CLASSES = (
      # other middlewares
      "critical.middleware.CriticalCssMiddleware",
  )
  

• Point your CRITICAL_PENTHOUSE_PATH setting to the correct path, e.g.:

  CRITICAL_PENTHOUSE_PATH = os.path.join(
      BASE_DIR, 'node_modules/penthouse/penthouse.js')
  

• If phantomjs is not in your PATH, you have to set CRITICAL_PHANTOMJS_PATH and point it to your phantomjs binary:

  CRITICAL_PHANTOMJS_PATH = os.path.join(
      BASE_DIR, 'node_modules/phantomjs/bin/phantomjs')
  

How it works¶

django-critical is activated by adding {% load critical %} to your template.

django-critical then parses the HTML between {% critical %} and {% endcritical %} and searches for CSS.

{% critical %}
<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<style>
  .jumbotron h1 {
    color: red;
  }
</style>
{% endcritical %}

It downloads and concatenates all that CSS and uses penthouse to extract the critical path CSS rules from it, which end up inlined and minified in place of the original CSS.

<style>html{font-family:sans-serif;-webkit-text-size-adjust:100%…</style>

Later in the HTML, before the closing </body> tag, the {% critical_async %} template tag takes care of loading the rest of the CSS using FilamentGroup’s loadCSS.

Caching¶

django-critical calculates the critical path CSS for the first request, caches the result and reuses this CSS verbatim for further requests. Most web applications have different critical path CSS for different groups of pages, though. This can be solved using the {% critical_key "<key>" %} template tag, so that different templates can have different caching keys.

Is this stable and ready for production use?¶

No. django-critical is in a very early stage of development, so you should use it at your own risk. Bug reports and contributions are welcome, though!

Types of Contributions¶

Get Started!¶

Ready to contribute? Here’s how to set up django-critical for local development.

1. Fork the django-critical repo on GitHub.

2. Clone your fork locally:

   $ git clone git@github.com:your_name_here/django-critical.git
   

3. Install your local copy into a virtualenv. Assuming you have virtualenvwrapper installed, this is how you set up your fork for local development:

   $ mkvirtualenv django-critical
   $ cd django-critical/
   $ python setup.py develop
   

4. Create a branch for local development:

   $ git checkout -b name-of-your-bugfix-or-feature
   

Now you can make your changes locally.

5. When you’re done making changes, check that your changes pass flake8 and the tests, including testing other Python versions with tox:

$ flake8 critical tests
$ python setup.py test
$ tox

To get flake8 and tox, just pip install them into your virtualenv.

6. Commit your changes and push your branch to GitHub:

   $ git add .
   $ git commit -m "Your detailed description of your changes."
   $ git push origin name-of-your-bugfix-or-feature
   

7. Submit a pull request through the GitHub website.

Pull Request Guidelines¶

Before you submit a pull request, check that it meets these guidelines:

1. The pull request should include tests.
2. If the pull request adds functionality, the docs should be updated. Put your new functionality into a function with a docstring, and add the feature to the list in README.rst.
3. The pull request should work for Python 2.6, 2.7, and 3.3, and for PyPy. Check https://travis-ci.org/martinblech/django-critical/pull_requests and make sure that the tests pass for all supported Python versions.

Tips¶

To run a subset of tests:

$ python -m unittest tests.test_critical

Development Lead¶

• Martín Blech <martinblech@gmail.com>

Contributors¶

None yet. Why not be the first?

0.1.0 (2014-08-02)¶

• First release on PyPI.