gatsby-background-image-es5

gatsby-background-image-es5

Speedy, optimized background-images without the work!

gatsby-background-image-es5 is a React component which for background-images provides,
what Gatsby's own gatsby-image does for the rest of your images.

Preamble

This version is completely transpiled to ES5 to target older browsers like IE11! Most polyfills are already built in, though this nearly triples the package size compared to gatsby-background-image!

Everything else just works the same as in gatsby-background-image, so this package has all the advantages of gatsby-image, including the "blur-up" technique or
a "traced placeholder" SVG to show a preview of the image while it loads,
plus being usable as a container (no more hacks with extra wrappers),
plus being able to work with multiple stacked background images.

All the glamour (and speed) of gatsby-image now for your Background Images!

And it's even styleable with styled-components and the like!

Table of Contents

• Example Repo
• Procedure
• Install
  • Important
• How to Use
• Configuration & props
• Styling & Passed Through Styles
  • Multiple Instances Of Same Component
  • Deprecated Styling
• Changed props
• props Not Available
• Handling of Remaining props
• Contributing
• TODO

Example Repo

gatsby-background-image has an example repository to see it's similarities & differences to gatsby-image side by side.
It's located at: gbitest To use it with gatsby-background-image-es5 change the dependency there.

Procedure

As gatsby-image is designed to work seamlessly with Gatsby's native image processing capabilities powered by GraphQL and Sharp, so is gatsby-background-image-es5. To produce optimized background-images, you need only to:

1. Import gatsby-background-image-es5 and use it in place of the built-in div or suchlike containers.
2. Write a GraphQL query using one of the GraphQL "fragments" provided by gatsby-transformer-sharp
   which specify the fields needed by gatsby-background-image-es5.

The GraphQL query creates multiple thumbnails with optimized JPEG and PNG compression (or even WebP files for browsers that support them). The gatsby-background-image-es5 component automatically sets up the "blur-up" effect as well as lazy loading of images further down the screen.

Install

To add gatsby-background-image-es5 as a dependency to your Gatsby-project use

npm install --save gatsby-background-image-es5

or

yarn add gatsby-background-image-es5

Depending on the gatsby starter you used, you may need to include gatsby-transformer-sharp and gatsby-plugin-sharp as well, and make sure they are installed and included in your gatsby-config.

npm install --save gatsby-transformer-sharp gatsby-plugin-sharp

or

yarn add gatsby-transformer-sharp gatsby-plugin-sharp

Then in your gatsby-config.js:

plugins: [`gatsby-transformer-sharp`, `gatsby-plugin-sharp`]

Also, make sure you have set up a source plugin, so your images are available in graphql queries. For example, if your images live in a project folder on the local filesystem, you would set up gatsby-source-filesystem in gatsby-config.js like so:

const path = require(`path`)

module.exports = {
  plugins: [
    {
      resolve: `gatsby-source-filesystem`,
      options: {
        name: `images`,
        path: path.join(__dirname, `src`, `images`),
      },
    },
    `gatsby-plugin-sharp`,
    `gatsby-transformer-sharp`,
  ],
}

Important:

If you support Safari and/or Internet Explorer, you have to install the IntersectionObserver polyfill.
As - at the time of writing - neither fully implements the feature (see caniuse.com).

A solution to this issue was mentioned in a comment over at gatsby-image/issues
and you are able to apply it the following way:

1. Install the intersection-observer polyfill package by running:

npm i --save intersection-observer

or

yarn add intersection-observer

2. Dynamically load the polyfill in your gatsby-browser.js:

// ES5 way
// exports.onClientEntry = () => {
// ES6 way
export const onClientEntry = () => {  
  // IntersectionObserver polyfill for gatsby-background-image-es5 (Safari, IE)
  if (typeof window.IntersectionObserver === `undefined`) {
    import(`intersection-observer`)
    console.log(`# IntersectionObserver is polyfilled!`)
  }
}

How to Use

This is what a component using gatsby-background-image-es5 might look like:

import React from 'react'
import { graphql, StaticQuery } from 'gatsby'
import styled from 'styled-components'

import BackgroundImage from 'gatsby-background-image-es5'

const BackgroundSection = ({ className }) => (
    <StaticQuery query={graphql`
      query {
        desktop: file(relativePath: { eq: "seamless-bg-desktop.jpg" }) {
          childImageSharp {
            fluid(quality: 90, maxWidth: 4160) {
              ...GatsbyImageSharpFluid_withWebp
            }
          }
        }
      }
    `}
     render={data => {
       // Set ImageData.
       const imageData = data.desktop.childImageSharp.fluid
       return (
          <BackgroundImage Tag="section"
                           className={className}
                           fluid={imageData}
                           backgroundColor={`#040e18`}
          >
            <h1>Hello gatsby-background-image-es5</h1>
          </BackgroundImage>
       )
     }
     }
    />
)

const StyledBackgroundSection = styled(BackgroundSection)`
  width: 100%;
  background-position: bottom center;
  background-repeat: repeat-y;
  background-size: cover;
`

export default StyledBackgroundSection

Configuration & props

gatsby-background-image-es5 nearly works the same as gatsby-image so have a look at their options & props to get started. But be sure to also throw a glance at Changed props, props Not Available and Handling of Remaining props as well ; )!

Styling & Passed Through Styles

You may style your gatsby-background-image-es5 BackgroundImage-component every way you like, be it global CSS, CSS-Modules or even with styled-components or your CSS-in-JS "framework" of choice. The style={{}} prop is supported as well.

Whichever way you choose, every background-* style declared in the main class (or the style={{}} prop) will directly get passed through to the pseudo-elements as well (so you would have no need for specifically styling them)!

The specificity hereby is in ascending order:

• class-styles
• extracted background-* styles
• style={{}} prop

The three background- styles seen above are necessary and will default to:

Name	Default Value
background-position	center
background-repeat	no-repeat
background-size	cover

To be able to overwrite them for each pseudo-element individually, you may reset their values in the style={{}} prop with an empty string like such:

style={{
  // Defaults are overwrite-able by setting one or each of the following:
  backgroundSize: '',
  backgroundPosition: '',
  backgroundRepeat: '',
}}

¡But be sure to target the :before and :after pseudo-elements in your CSS, lest your "blurred-up", traced placeholder SVG or lazy loaded background images might jump around!

Multiple Instances of Same Component

Should you decide to use a single instance of a styled <BackgroundImage /> for multiple different images, it will automatically add an additional className, a hashed 32bit integer of the current srcSet or className prefixed with gbi-, to prevent erroneous styling of individual instances.
You wouldn't have added the same class for different CSS background-image styles on your own, or would you have ; )?

Be warned: Styling the components :before & :after pseudo-elements within the main classes then only is going to work again for all instances if you use !important on its CSS-properties (cause of CSS-specifity).

Deprecated Styling

Though now considered deprecated and to be removed in 1.0.0 at the latest (feel free to open an issue, should you really need them : ), gatsby-background-image-es5 has an added classId (as we had to name pseudo-elements and introduce a className for the returned container in the beginning):

Name	Type	Description
classId	string	classID of the container element, defaults to a random lower case string of seven chars, followed by _depr

Only if present now, pseudo-elements are created on a class by the name of .gatsby-background-image-[YOUR_ID] and the class is added to BackgroundImage. Now you are able to access it through CSS / CSS-in-JS with:

.gatsby-background-image-[YOUR_ID]/*(:before, :after)*/ {
  background-repeat: repeat-y;
  background-position: bottom center;
  background-size: cover;
}

But as the paragraph-title states: This behavior is considered deprecated, so don't count on it in production ; ).

Changed props

As gatsby-image now has a changed behavior for already loaded images (no soft fade in, even if prop fadeIn is set to true per default), and this sometimes seemed a little hard for the eyes with background images, the fadeIn prop may now be set to soft to ignore cached images and always try to fade in if critical isn't set.

Name	Type	Description
fadeIn	boolean / string	Defaults to fading in the image on load, may be forced by soft

props Not Available

As gatsby-background-image-es5 doesn't use placeholder-images, the following props from gatsby-image are not available, of course.

Name	Type	Old Usage
placeholderStyle	object	Spread into the default styles of the placeholder img element
placeholderClassName	string	A class that is passed to the placeholder img element
imgStyle	object	Spread into the default styles of the actual img element

Handling of Remaining props

After every available prop is handled, the remaining ones get cleaned up and spread into the <BackgroundImage />'s container element. This way you can "safely" add every ARIA or data-* attribute you might need without having to use gatsby-image's itemProp ; ).

Contributing

Everyone is more than welcome to contribute to this little package!
Docs, Reviews, Testing, Code - whatever you want to add, just go for it : ). So have a look at our CONTRIBUTING file and give it a go. Thanks in advance!

TODO

• For the moment Internet Explorer 11 seems to have problems with _tracedSVG and parsing the background-* CSS props, gotta investigate further...

For anything else tell me by opening an issue or a PR : )!