Adding processed styles from stylesheet to HTML template

Phoenix Forum Questions / Help
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Hi there! :grinning:

For SEO purposes, I’m trying to improve loading performance by not having render blocking stylesheets and loading critical styles inside <style> tags directly in the HTML.

Does anybody have any idea or recommendation on how to put my webpack-processed stylesheet inside <style> tags in the HTML layout.

Any help would be really appreciated!

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You can read and output compiled app.css file (or other target if you have one). This should work in development and in prod, also with Erlang releases. In your layout or template do:

  <style type="text/css">
    <%= {:safe, File.read!(Path.join(:code.priv_dir(:ui), "static/css/app.css"))} %>
  </style>

And it will output the compiled CSS in place, provided your compiled file ends up in priv/css/app.css and that your application name is :ui. Replace these with your own if needed :slight_smile:

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Is it read once during compilation or every time the template is invoked / rendered?

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I’m exploring loading it as Module attributes so it isn’t read every time the template is invoked.

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If you load the contents into a module attribute, it’s read from the filesystem only once during the compilation.

Oh, I misunderstood you. Ignore me.

I’d put it in a function instead of a module attribute though. This way you would be able to invoke it from other modules as well, not just within the module where you defined the module attribute.

defmodule Web.CSSView do
  app_css = File.read!(Path.join(:code.priv_dir(:your_app_name), "static/css/app.css"))
  def inline_css(:app) do
    {:safe, unquote(app_css)}
  end
end

and then in any template

<style type="text/css"><%= Web.CSSView.inline_css(:app) %></style>
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Every time it is rendered. OS should keep it in cache if that file is being read over and over again, I would probably not bother too much with making it module attribute.

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Thanks for the replies.

I ended up getting the file from priv/static and I used https://github.com/melpon/memoize to memoize the contents of the file and avoid opening the file with each rendering of the template.

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