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Inline SVG

Unit tests Integration Tests

Styling a SVG document with CSS for use on the web is most reliably achieved by adding classes to the document and embedding it inline in the HTML.

This gem adds Rails helper methods (inline_svg_tag and inline_svg_pack_tag) that read an SVG document (via Sprockets or Webpacker, so works with the Rails Asset Pipeline), applies a CSS class attribute to the root of the document and then embeds it into a view.

Inline SVG supports:

Inline SVG no longer officially supports Rails 3 or Rails 4 (although they may still work). In order to reduce the maintenance cost of this project we now follow the Rails Maintenance Policy.

Changelog

This project adheres to Semantic Versioning. All notable changes are documented in the CHANGELOG.

Installation

Add this line to your application's Gemfile:

gem 'inline_svg'

And then execute:

$ bundle

Or install it yourself as:

$ gem install inline_svg

Usage

# Sprockets
inline_svg_tag(file_name, options={})

# Webpacker
inline_svg_pack_tag(file_name, options={})

Note: The remainder of this README uses inline_svg_tag for examples, but the exact same principles work for inline_svg_pack_tag.

The file_name can be a full path to a file, the file's basename or an IO object. The actual path of the file on disk is resolved using a configurable finder class (Propshaft, Sprockets, Webpack) or a custom class, and will fall back to a naive static file finder (/public/assets/...) -- or in the case of IO objects the SVG data will be read from the object. This means you can pre-process and fingerprint your SVG files like other Rails assets, or choose to find SVG data yourself.

Here's an example of embedding an SVG document and applying a 'class' attribute:

<html>
  <head>
    <title>Embedded SVG Documents<title>
  </head>
  <body>
    <h1>Embedded SVG Documents</h1>
    <div>
      <%= inline_svg_tag "some-document.svg", class: 'some-class' %>
    </div>
  </body>
</html>

Here's some CSS to target the SVG, resize it and turn it an attractive shade of blue:

.some-class {
  display: block;
  margin: 0 auto;
  fill: #3498db;
  width: 5em;
  height: 5em;
}

Options

key description
id set a ID attribute on the SVG
class set a CSS class attribute on the SVG
style set a CSS style attribute on the SVG
data add data attributes to the SVG (supply as a hash)
size set width and height attributes on the SVG
Can also be set using height and/or width attributes, which take precedence over size
Supplied as "{Width} * {Height}" or "{Number}", so "30px*45px" becomes width="30px" and height="45px", and "50%" becomes width="50%" and height="50%"
title add a <title> node inside the top level of the SVG document
desc add a <desc> node inside the top level of the SVG document
nocomment remove comment tags from the SVG document
preserve_aspect_ratio adds a preserveAspectRatio attribute to the SVG
aria adds common accessibility attributes to the SVG (see PR #34 for details)
aria_hidden adds the aria-hidden=true attribute to the SVG
fallback set fallback SVG document

Example:

inline_svg_tag(
  "some-document.svg",
  id: 'some-id',
  class: 'some-class',
  data: {some: "value"},
  size: '30% * 20%',
  title: 'Some Title',
  desc: 'Some description',
  nocomment: true,
  preserve_aspect_ratio: 'xMaxYMax meet',
  aria: true,
  aria_hidden: true,
  fallback: 'fallback-document.svg'
)

Accessibility

Use the aria: true option to make inline_svg_tag add the following accessibility (a11y) attributes to your embedded SVG:

  • Adds a role="img" attribute to the root SVG element
  • Adds a aria-labelled-by="title-id desc-id" attribute to the root SVG element, if the document contains <title> or <desc> elements

Here's an example:

<%=
  inline_svg_tag('iconmonstr-glasses-12-icon.svg',
    aria: true, title: 'An SVG',
    desc: 'This is my SVG. There are many like it. You get the picture')
%>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" \
  role="img" aria-labelledby="bx6wix4t9pxpwxnohrhrmms3wexsw2o m439lk7mopdzmouktv2o689pl59wmd2">
  <title id="bx6wix4t9pxpwxnohrhrmms3wexsw2o">An SVG</title>
  <desc id="m439lk7mopdzmouktv2o689pl59wmd2">This is my SVG. There are many like it. You get the picture</desc>
</svg>

Note: The title and desc id attributes generated for, and referenced by, aria-labelled-by are one-way digests based on the value of the title and desc elements and an optional "salt" value using the SHA1 algorithm. This reduces the chance of inline_svg_tag embedding elements inside the SVG with id attributes that clash with other elements elsewhere on the page.

Custom Transformations

The transformation behavior of inline_svg_tag can be customized by creating custom transformation classes.

For example, inherit from InlineSvg::CustomTransformation and implement the #transform method:

# Sets the `custom` attribute on the root SVG element to supplied value
# Remember to return a document, as this will be passed along the transformation chain

class MyCustomTransform < InlineSvg::CustomTransformation
  def transform(doc)
    with_svg(doc) do |svg|
      svg["custom"] = value
    end
  end
end

Add the custom configuration in an initializer (E.g. ./config/initializers/inline_svg.rb):

# Note that the named `attribute` will be used to pass a value to your custom transform
InlineSvg.configure do |config|
  config.add_custom_transformation(attribute: :my_custom_attribute, transform: MyCustomTransform)
end

The custom transformation can then be called like so:

%div
  = inline_svg_tag "some-document.svg", my_custom_attribute: 'some value'

In this example, the following transformation would be applied to a SVG document:

<svg custom="some value">...</svg>

You can also provide a default_value to the custom transformation, so even if you don't pass a value it will be triggered

# Note that the named `attribute` will be used to pass a value to your custom transform
InlineSvg.configure do |config|
  config.add_custom_transformation(attribute: :my_custom_attribute, transform: MyCustomTransform, default_value: 'default value')
end

The custom transformation will be triggered even if you don't pass any attribute value

%div
  = inline_svg_tag "some-document.svg"
  = inline_svg_tag "some-document.svg", my_custom_attribute: 'some value'

In this example, the following transformation would be applied to a SVG document:

<svg custom="default value">...</svg>

And

<svg custom="some value">...</svg>

Passing a priority option with your custom transformation allows you to control the order that transformations are applied to the SVG document:

InlineSvg.configure do |config|
  config.add_custom_transformation(attribute: :custom_one, transform: MyCustomTransform, priority: 1)
  config.add_custom_transformation(attribute: :custom_two, transform: MyOtherCustomTransform, priority: 2)
end

Transforms are applied in ascending order (lowest number first).

Note: Custom transformations are always applied after all built-in transformations, regardless of priority.

Custom asset file loader

An asset file loader returns a String representing a SVG document given a filename. Custom asset loaders should be a Ruby object that responds to a method called named, that takes one argument (a string representing the filename of the SVG document).

A simple example might look like this:

class MyAssetFileLoader
  def self.named(filename)
    # ... load SVG document however you like
    return "<svg>some document</svg>"
  end
end

Configure your custom asset file loader in an initializer like so:

InlineSvg.configure do |config|
  config.asset_file = MyAssetFileLoader
end

Custom asset finder

Similarly, an asset finder class should have a find_asset class method, and respond to a pathname instance method which returns the path to the file. If no class is configured, a default static file class will be used.

A configuration example to use the Propshaft finder would look like:

InlineSvg.configure do |config|
  config.asset_finder = InlineSvg::PropshaftAssetFinder
end

Caching all assets at boot time

When your deployment strategy prevents dynamic asset file loading from disk it can be helpful to cache all possible SVG assets in memory at application boot time. In this case, you can configure the InlineSvg::CachedAssetFile to scan any number of paths on disks and load all the assets it finds into memory.

For example, in this configuration we load every *.svg file found beneath the configured paths into memory:

InlineSvg.configure do |config|
  config.asset_file = InlineSvg::CachedAssetFile.new(
    paths: [
      "#{Rails.root}/public/path/to/assets",
      "#{Rails.root}/public/other/path/to/assets"
    ],
    filters: /\.svg/
  )
end

Note: Paths are read recursively, so think about keeping your SVG assets restricted to as few paths as possible, and using the filter option to further restrict assets to only those likely to be used by inline_svg_tag.

Missing SVG Files

If the specified SVG file cannot be found a helpful, empty SVG document is embedded into the page instead. The embedded document contains a single comment displaying the filename of the SVG image the helper tried to render:

<svg><!-- SVG file not found: 'some-missing-file.svg' --></svg>

You may apply a class to this empty SVG document by specifying the following configuration:

InlineSvg.configure do |config|
  config.svg_not_found_css_class = 'svg-not-found'
end

Which would instead render:

<svg class='svg-not-found'><!-- SVG file not found: 'some-missing-file.svg' --></svg>

Alternatively, inline_svg_tag can be configured to raise an exception when a file is not found:

InlineSvg.configure do |config|
  config.raise_on_file_not_found = true
end

Contributing

  1. Fork it ( http://github.com/jamesmartin/inline_svg/fork )
  2. Create your feature 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

Please write tests for anything you change, add or fix. There is a basic Rails app that demonstrates the gem's functionality in use.