Tags: background

Plus Equals #3, September 2021

Want to take a deep dive into tiling images? Like, a really deep dive. Rob has you covered.

Basic Pattern Repository

A nice little collection of very simple—and very lightweight—SVGs to use as background patterns.

Yesterday I wrote about how much I’d like to see silent push for the web:

I’d really like silent push for the web—the ability to update a cache with fresh content as soon as it’s published; that would be nifty! At the same time, I understand the concerns. It feels more powerful than other permission-based APIs like notifications.

Today, John Holt Ripley responded on Twitter:

hi there, just read your blog post about Silent Push for acthe web, and wondering if Periodic Background Sync would cover a few of those use cases?

Periodic background sync looks very interesting indeed!

It’s not the same as silent push. As the name suggests, this is about your service worker waking up periodically and potentially fetching (and caching) fresh content from the network. So the service worker is polling rather than receiving a push. But I’ll take it! It’s definitely close enough for the kind of use-cases I’ve been thinking about.

Interestingly, periodic background sync also ties into the other part of what I was writing about: permissions. I mentioned that adding a site the home screen could be interpreted as a signal to potentially allow more permissions (or at least allow prompts for more permissions).

Well, Chromium has a document outlining metrics for attempting to gauge site engagement. There’s some good thinking in there.

CSS-only chat

A truly monstrous async web chat using no JS whatsoever on the frontend.

This is …I mean …yes, but …it …I …

Here’s a tiny lesson that I picked up from Trys that I’d like to share with you…

I was working on some upcoming changes to the Clearleft site recently. One particular component needed some SVG background images. I decided I’d inline the SVGs in the CSS to avoid extra network requests. It’s pretty straightforward:

.myComponent {
    background-image: url('data:image/svg+xml;utf8,<svg> ... </svg>');
}

You can basically paste your SVG in there, although you need to a little bit of URL encoding: I found that converting # to %23 to was enough for my needs.

But here’s the thing. My component had some variations. One of the variations had multiple background images. There was a second background image in addition to the first. There’s no way in CSS to add an additional background image without writing a whole background-image declaration:

.myComponent--variant {
    background-image: url('data:image/svg+xml;utf8,<svg> ... </svg>'), url('data:image/svg+xml;utf8,<svg> ... </svg>');
}

So now I’ve got the same SVG source inlined in two places. That negates any performance benefits I was getting from inlining in the first place.

That’s where Trys comes in. He shared a nifty technique he uses in this exact situation: put the SVG source into a custom property!

:root {
    --firstSVG: url('data:image/svg+xml;utf8,<svg> ... </svg>');
    --secondSVG: url('data:image/svg+xml;utf8,<svg> ... </svg>');
}

Then you can reference those in your background-image declarations:

.myComponent {
    background-image: var(--firstSVG);
}
.myComponent--variant {
    background-image: var(--firstSVG), var(--secondSVG);
}

Brilliant! Not only does this remove any duplication of the SVG source, it also makes your CSS nice and readable: no more big blobs of SVG source code in the middle of your style sheet.

You might be wondering what will happen in older browsers that don’t support CSS custom properties (that would be Internet Explorer 11). Those browsers won’t get any background image. Which is fine. It’s a background image. Therefore it’s decoration. If it were an important image, it wouldn’t be in the background.

Progressive enhancement, innit?

Remove Background from Image – remove.bg

Well, this looks like it could come in handy—no more tedious time in Photoshop trying to select turn a person into a separate layer by hand; this does it for you.

Introducing Background Fetch  |  Web  |  Google Developers

I’m going to have to read through this article by Jake a few times before I begin to wrap my head around this background fetch thing, but it looks like it would be perfect for something like the dConstruct Audio Archive, where fairly large files can be saved for offline listening.

On the first day of Indie Web Camp Berlin, I led a session on going offline with service workers. This covered all the usual use-cases: pre-caching; custom offline pages; saving pages for offline reading.

But on the second day, Sebastiaan spent a fair bit of time investigating a more complex use of service workers with the Push API.

The Push API is what makes push notifications possible on the web. There are a lot of moving parts—browser, server, service worker—and, frankly, it’s way over my head. But I’m familiar with the general gist of how it works. Here’s a typical flow:

1. A website prompts the user for permission to send push notifications.
2. The user grants permission.
3. A whole lot of complicated stuff happens behinds the scenes.
4. Next time the website publishes something relevant, it fires a push message containing the details of the new URL.
5. The user’s service worker receives the push message (even if the site isn’t open).
6. The service worker creates a notification linking to the URL, interrupting the user, and generally adding to the weight of information overload.

Here’s what Sebastiaan wanted to investigate: what if that last step weren’t so intrusive? Here’s the alternate flow he wanted to test:

1. A website prompts the user for permission to send push notifications.
2. The user grants permission.
3. A whole lot of complicated stuff happens behinds the scenes.
4. Next time the website publishes something relevant, it fires a push message containing the details of the new URL.
5. The user’s service worker receives the push message (even if the site isn’t open).
6. The service worker fetches the contents of the URL provided in the push message and caches the page. Silently.

It worked.

I think this could be a real game-changer. I don’t know about you, but I’m very, very wary of granting websites the ability to send me push notifications. In fact, I don’t think I’ve ever given a website permission to interrupt me with push notifications.

You’ve seen the annoying permission dialogues, right?

In Firefox, it looks like this:

Will you allow name-of-website to send notifications?

[Not Now] [Allow Notifications]

In Chrome, it’s:

name-of-website wants to

Show notifications

[Block] [Allow]

But in actual fact, these dialogues are asking for permission to do two things:

1. Receive messages pushed from the server.
2. Display notifications based on those messages.

There’s no way to ask for permission just to do the first part. That’s a shame. While I’m very unwilling to grant permission to be interrupted by intrusive notifications, I’d be more than willing to grant permission to allow a website to silently cache timely content in the background. It would be a more calm technology.

Think of the use cases:

• I grant push permission to a magazine. When the magazine publishes a new article, it’s cached on my device.
• I grant push permission to a podcast. Whenever a new episode is published, it’s cached on my device.
• I grant push permission to a blog. When there’s a new blog post, it’s cached on my device.

Then when I’m on a plane, or in the subway, or in any other situation without a network connection, I could still visit these websites and get content that’s fresh to me. It’s kind of like background sync in reverse.

There’s plenty of opportunity for abuse—the cache could get filled with content. But websites can already do that, and they don’t need to be granted any permissions to do so; just by visiting a website, it can add multiple files to a cache.

So it seems that the reason for the permissions dialogue is all about displaying notifications …not so much about receiving push messages from the server.

I wish there were a way to implement this background-caching pattern without requiring the user to grant permission to a dialogue that contains the word “notification.”

I wonder if the act of adding a site to the home screen could implicitly grant permission to allow use of the Push API without notifications?

In the meantime, the proposal for periodic synchronisation (using background sync) could achieve similar results, but in a less elegant way; periodically polling for new content instead of receiving a push message when new content is published. Also, it requires permission. But at least in this case, the permission dialogue should be more specific, and wouldn’t include the word “notification” anywhere.

Finding Dead CSS – CSS Wizardry

Here’s a clever idea from Harry if you’re willing to play the long game in tracking down redundant CSS—add a transparent background image to the rule block and then sit back and watch your server logs for any sign of that sleeper agent ever getting activated.

If you do find entries for that particular image, you know that, somehow, the legacy feature is potentially still accessible—the number of entries should give you a clue as to how severe the problem might be.

Lisbon Azulejos

When I was in Porto a few weeks back, I took lots of pictures of the beautiful tiles. They reminded me of the ubiquitous repeating background images that were so popular on the early web. I was thinking about abstracting them into a collection of reusable patterns but now it looks like I’ve been beaten to it!

Send messages when you’re back online with Service Workers and Background Sync – Twilio Cloud Communications Blog

This example of using background sync looks like it’s specific to Twilio, but the breakdown of steps is broad enough to apply to many situations:

On the page we need to:

1. Register a Service Worker
2. Intercept the “submit” event for our message form
3. Place the message details into IndexedDB, an in browser database
4. Register the Service Worker to receive a “sync” event

Then, in the Service Worker we need to:

1. Listen for sync events
2. When a sync event is received, retrieve the messages from IndexedDB
3. For each message, send a request to our server to send the message
4. If the message is sent successfully, then remove the message from IndexedDB

And that’s it.

Enhancing a comment form: From basic to custom error message to BackgroundSync | justmarkup

This is a truly fantastic example of progressive enhancement applied to a form.

What I love about this is that it shows how progressive enhancement isn’t a binary on/off choice: there are layers and layers of enhancements here, from simple inline validation all the way to service workers and background sync, with many options in between.

Superb!

the new code – Even Stevens: Using Round and Space in Repeated Background Images

See, when I first heard about background-repeat: round; I thought it was something to do with making things circular. But no, it’s about tiling a background image so that nothing gets cut off. The amount of tiling required is rounded to the nearest whole number.

Now I get it.

Psiu Puxa Wallpapers

Yummy wallpapers for your desktop, tablet, and phone, from NASA and ESA.

ServiceWorker: A Basic Guide to BackgroundSync

A nice introduction to using Service Workers to enable syncing in the background: when the user is offline, tasks get queued up and then when the user is back online, those tasks execute.

The Pattern Library

Literally a library of patterns: y’know, for tiling background images. Old school!

Protip: All browsers that support SVG background images also supports multiple background images.

A very hand tip from Ben on using SVG background images with a PNG fallback for IE8 and below.

NoisePNG - Generate noisy PNG-images with alpha-transparency

If you’re adding some noise texture to your backgrounds, this little service might be handy. I usually base-64 encode these kinds of background images: it would be nice to see that added as an option here.

JoshEmerson.co.uk · Blog · Base64 and the tiling background

Josh explains the pros and cons of embedding background images in your CSS using base 64 encoding.

The Cicada Principle and Why It Matters to Web Designers » HTML & CSS, Layout » Design Festival

A lovely bit of experimentation with prime numbers and multiple background images.