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Sunday, July 12th, 2020

Checked in at Fox On the Downs. Sunday roast and a pint in the sun — with Jessica map

Checked in at Fox On the Downs. Sunday roast and a pint in the sun — with Jessica

Saturday, July 11th, 2020

Playing The Ships In Full Sail (jig) on mandolin:

https://thesession.org/tunes/261

https://www.youtube.com/watch?v=VQiftGz_GeE

Sunday, July 5th, 2020

Thursday, July 2nd, 2020

Replying to

Strong same! 😢

Monday, June 22nd, 2020

Friday, June 19th, 2020

Playing The Woman Of The House (reel) on mandolin:

https://thesession.org/tunes/321

https://www.youtube.com/watch?v=jlVoytkfNy0

Thursday, June 18th, 2020

Playing The Lark On The Strand (jig) on mandolin:

https://thesession.org/tunes/1634

https://www.youtube.com/watch?v=2fP-4GRWTgc

Tuesday, June 16th, 2020

Happy Valentina’s Day, world!

Replying to

Painting all disagreement as people being “enraged” isn’t helpful.

And there’s a big difference between “some humans can’t read some URLs” and “humans can’t read URLs”.

Monday, June 15th, 2020

Replying to

I really like this approach!

https://adactio.com/links/17006

Thursday, June 11th, 2020

CSS custom properties and the cascade

When I wrote about programming CSS to perform Sass colour functions I said this about the brilliant Lea Verou:

As so often happens when I’m reading something written by Lea—or seeing her give a talk—light bulbs started popping over my head (my usual response to Lea’s knowledge bombs is either “I didn’t know you could do that!” or “I never thought of doing that!”).

Well, it happened again. This time I was reading her post about hybrid positioning with CSS variables and max() . But the main topic of the post wasn’t the part that made go “Huh! I never knew that!”. Towards the end of her article she explained something about the way that browsers evaluate CSS custom properties:

The browser doesn’t know if your property value is valid until the variable is resolved, and by then it has already processed the cascade and has thrown away any potential fallbacks.

I’m used to being able to rely on the cascade. Let’s say I’m going to set a background colour on paragraphs:

p {
  background-color: red;
  background-color: color(display-p3 1 0 0);
}

First I’ve set a background colour using a good ol’ fashioned keyword, supported in browsers since day one. Then I declare the background colour using the new-fangled color() function which is supported in very few browsers. That’s okay though. I can confidently rely on the cascade to fall back to the earlier declaration. Paragraphs will still have a red background colour.

But if I store the background colour in a custom property, I can no longer rely on the cascade.

:root {
  --myvariable: color(display-p3 1 0 0);
}
p {
  background-color: red;
  background-color: var(--myvariable);
}

All I’ve done is swapped out the hard-coded color() value for a custom property but now the browser behaves differently. Instead of getting a red background colour, I get the browser default value. As Lea explains:

…it will make the property invalid at computed value time.

The spec says:

When this happens, the computed value of the property is either the property’s inherited value or its initial value depending on whether the property is inherited or not, respectively, as if the property’s value had been specified as the unset keyword.

So if a browser doesn’t understand the color() function, it’s as if I’ve said:

background-color: unset;

This took me by surprise. I’m so used to being able to rely on the cascade in CSS—it’s one of the most powerful and most useful features in this programming language. Could it be, I wondered, that the powers-that-be have violated the principle of least surprise in specifying this behaviour?

But a note in the spec explains further:

Note: The invalid at computed-value time concept exists because variables can’t “fail early” like other syntax errors can, so by the time the user agent realizes a property value is invalid, it’s already thrown away the other cascaded values.

Ah, right! So first of all browsers figure out the cascade and then they evaluate custom properties. If a custom property evaluates to gobbledygook, it’s too late to figure out what the cascade would’ve fallen back to.

Thinking about it, this makes total sense. Remember that CSS custom properties aren’t like Sass variables. They aren’t evaluated once and then set in stone. They’re more like let than const. They can be updated in real time. You can update them from JavaScript too. It’s entirely possible to update CSS custom properties rapidly in response to events like, say, the user scrolling or moving their mouse. If the browser had to recalculate the cascade every time a custom property didn’t evaluate correctly, I imagine it would be an enormous performance bottleneck.

So even though this behaviour surprised me at first, it makes sense on reflection.

I’ve probably done a terrible job explaining the behaviour here, so I’ve made a Codepen. Although that may also do an equally terrible job.

(Thanks to Amber for talking through this with me and encouraging me to blog about it. And thanks to Lea for expanding my mind. Again.)

Friday, June 5th, 2020

Playing The Belles Of Tipperary (reel) on mandolin:

https://thesession.org/tunes/769

https://www.youtube.com/watch?v=7EFrgn2fGmY

Monday, June 1st, 2020

A virtual edition of the Brighton Acoustic Club is now live (and myself and @WordRidden might make an appearance):

https://www.facebook.com/brighton.acoustic.club/videos/353913525586816/

Saturday, May 30th, 2020

Programming CSS to perform Sass colour functions

I wrote recently about moving away from Sass to using native CSS features. I had this to say on the topic of mixins in Sass:

These can be very useful, but now there’s a lot that you can do just in CSS with calc(). The built-in darken() and lighten() mixins are handy though when it comes to colours.

I know we will be getting these in the future but we’re not there yet with CSS.

Anyway, I had all this in the back of my mind when I was reading Lea’s excellent feature in this month’s Increment: A user’s guide to CSS variables. She’s written about a really clever technique of combining custom properites with hsl() colour values for creating colour palettes. (See also: Una’s post on dynamic colour theming with pure CSS.)

As so often happens when I’m reading something written by Lea—or seeing her give a talk—light bulbs started popping over my head (my usual response to Lea’s knowledge bombs is either “I didn’t know you could do that!” or “I never thought of doing that!”).

I immediately set about implementing this technique over on The Session. The trick here is to use separate custom properties for the hue, saturation, and lightness parts of hsl() colour values. Then, when you want to lighten or darken the colour—say, on hover—you can update the lightness part.

I’ve made a Codepen to show what I’m doing.

Let’s say I’m styling a button element. I make custom propertes for hsl() values:

button {
  --button-colour-hue: 19;
  --button-colour-saturation: 82%;
  --button-colour-lightness: 38%;
  background-color: hsl(
    var(--button-colour-hue),
    var(--button-colour-saturation),
    var(--button-colour-lightness)
  );
}

For my buttons, I want the borders to be slightly darker than the background colour. When I was using Sass, I used the darken() function to this. Now I use calc(). Here’s how I make the borders 10% darker:

border-color: hsl(
  var(--button-colour-hue),
  var(--button-colour-saturation),
  calc(var(--button-colour-lightness) - 10%)
);

That calc() function is substracting a percentage from a percentage: 38% minus 10% in this case. The borders will have a lightness of 28%.

I make the bottom border even darker and the top border lighter to give a feeling of depth.

On The Session there’s a “cancel” button style that’s deep red.

Here’s how I set its colour:

.cancel {
  --button-colour-hue: 0;
  --button-colour-saturation: 100%;
  --button-colour-lightness: 40%;
}

That’s it. The existing button declarations take care of assigning the right shades for the border colours.

Here’s another example. Site admins see buttons for some actions only available to them. I want those buttons to have their own colour:

.admin {
  --button-colour-hue: 45;
  --button-colour-saturation: 100%;
  --button-colour-lightness: 40%;
}

You get the idea. It doesn’t matter how many differently-coloured buttons I create, the effect of darkening or lightening their borders is all taken care of.

So it turns out that the lighten() and darken() functions from Sass are available to us in CSS by using a combination of custom properties, hsl(), and calc().

I’m also using this combination to lighten or darken background and border colours on :hover. You can poke around the Codepen if you want to see that in action.

I love seeing the combinatorial power of these different bits of CSS coming together. It really is a remarkably powerful programming language.

Wednesday, May 27th, 2020

This was the second most exciting livestream of the day (we can’t really compete with crewed rocket launches):

https://twitter.com/clearleft/status/1265592025409368064

Thursday, May 21st, 2020

Replying to

No, the CSS from by blog entry is applied to the :root element (and then everything cascades from there). In your example, the max-width: 70ch ensures that only the minimum size (100%) will ever be used.

Monday, May 18th, 2020

Hard to break

I keep thinking about some feedback that Cassie received recently.

She had delivered the front-end code for a project at Clearleft, and—this being Cassie we’re talking about—the code was rock solid. The client’s Quality Assurance team came back with the verdict that it was “hard to break.”

Hard to break. I love that. That might be the best summation I’ve heard for describing resilience on the web.

If there’s a corollary to resilient web design, it would be brittle web design. In a piece completely unrelated to web development, Jamais Cascio describes brittle systems:

When something is brittle, it’s susceptible to sudden and catastrophic failure.

That sounds like an inarguably bad thing. So why would anyone end up building something in a brittle way? Jamais Cascio continues:

Things that are brittle look strong, may even be strong, until they hit a breaking point, then everything falls apart.

Ah, there’s the rub! It’s not that brittle sites don’t work. They work just fine …until they don’t.

Brittle systems are solid until they’re not. Brittleness is illusory strength. Things that are brittle are non-resilient, sometimes even anti-resilient — they can make resilience more difficult.

Kilian Valkhof makes the same point when it comes to front-end development. For many, accessibility is an unknown unknown:

When you start out it’s you, notepad and a browser against the world. You open up that notepad, and you type

<div onclick="alert('hello world');">Click me!</div>

You fire up your browser, you click your div and …it works! It just works! Awesome. You open up the devtools. No errors. Well done! Clearly you did a good job. On to the next thing.

At the surface level, there’s no discernable difference between a resilient solution and a brittle one:

For all sorts of reasons, both legitimate and, as always, weird browser legacy reasons, a clickable div will mostly work. Well enough to fool someone starting out anyway.

If everything works, how would they know it kinda doesn’t?

Killian goes on to suggest ways to try to make this kind of hidden brittleness more visible.

Furthermore we could envision a browser that is much stricter when developing.

This something I touched on when I was talking about web performance with Gerry on his podcast:

There’s a disconnect in the process we go through when we’re making something, and then how that thing is experienced when it’s actually on the web, which is dependent on network speeds and processing speeds and stuff.

I spend a lot of time wondering why so many websites are badly built. Sure, there’s a lot can be explained by misaligned priorities. And it could just be an expression of Sturgeon’s Law—90% of websites are crap because 90% of everything is crap. But I’ve also come to realise that even though resilience is the antithesis to brittleness, they both share something in common: they’re invisible.

We have a natural bias towards what’s visible. Being committed to making sure something is beautiful to behold is, in some ways, the easy path to travel. But being committed to making sure something is also hard to break? That takes real dedication.

Sunday, May 17th, 2020

Replying to

Thanks!

(It’s not a patch on The Housekeepers though—great album!)

Friday, May 15th, 2020