Tags: properties

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Wednesday, May 4th, 2022

Fluid Type Scale - Generate responsive font-size variables

This is kind of a Utopia lite: pop in your minimum and maximum font sizes along with a modular scale and it spits out some custom properties for clamp() declarations.

Contextual Spacing For Intrinsic Web Design | Modern CSS Solutions

To complement her talk at Beyond Tellerrand, Stephanie goes through some of the powerful CSS features that enable intrinsic web design. These are all great tools for the declarative design approach I was talking about:

Sunday, November 28th, 2021

Modern CSS in a Nutshell - Cloud Four

I like this high-level view of the state of CSS today. There are two main takeaways:

  1. Custom properties, flexbox, and grid are game-changers.
  2. Pre- and post-processers are becoming less and less necessary.

This is exactly the direction we should be going in! More and more power from the native web technologies (while still remaining learnable), with less and less reliance on tooling. For CSS, the tools have been like polyfills that we can now start to remove.

Alas, while the same should be true of JavaScript (there’s so much you can do in native JavaScript now), people seem to have tied their entire identities to the tooling they use.

They could learn a thing or two from the trajectory of CSS: treat your frameworks as cattle, not pets.

Wednesday, November 24th, 2021

Faulty logic

I’m a fan of logical properties in CSS. As I wrote in the responsive design course on web.dev, they’re crucial for internationalisation.

Alaa Abd El-Rahim has written articles on CSS tricks about building multi-directional layouts and controlling layout in a multi-directional website. Not having to write separate stylesheets—or even separate rules—for different writing modes is great!

More than that though, I think understanding logical properties is the best way to truly understand CSS layout tools like grid and flexbox.

It’s like when you’re learning a new language. At some point your brain goes from translating from your mother tongue into the other language, and instead starts thinking in that other language. Likewise with CSS, as some point you want to stop translating “left” and “right” into “inline-start” and “inline-end” and instead start thinking in terms of inline and block dimensions.

As is so often the case with CSS, I think new features like these are easier to pick up if you’re new to the language. I had to unlearn using floats for layout and instead learn flexbox and grid. Someone learning layout from scatch can go straight to flexbox and grid without having to ditch the cognitive baggage of floats. Similarly, it’s going to take time for me to shed the baggage of directional properties and truly grok logical properties, but someone new to CSS can go straight to logical properties without passing through the directional stage.

Except we’re not quite there yet.

In order for logical properties to replace directional properties, they need to be implemented everywhere. Right now you can’t use logical properties inside a media query, for example:

@media (min-inline-size: 40em)

That wont’ work. You have to use the old-fashioned syntax:

@media (min-width: 40em)

Now you could rightly argue that in this instance we’re talking about the physical dimensions of the viewport. So maybe width and height make more sense than inline and block.

But then take a look at how the syntax for container queries is going to work. First you declare the axis that you want to be contained using the syntax from logical properties:

main {
  container-type: inline-size;
}

But then when you go to declare the actual container query, you have to use the corresponding directional property:

@container (min-width: 40em)

This won’t work:

@container (min-inline-size: 40em)

I kind of get why it won’t work: the syntax for container queries should match the syntax for media queries. But now the theory behind disallowing logical properties in media queries doesn’t hold up. When it comes to container queries, the physical layout of the viewport isn’t what matters.

I hope that both media queries and container queries will allow logical properties sooner rather than later. Until they fall in line, it’s impossible to make the jump fully to logical properties.

There are some other spots where logical properties haven’t been fully implemented yet, but I’m assuming that’s a matter of time. For example, in Firefox I can make a wide data table responsive by making its container side-swipeable on narrow screens:

.table-container {
  max-inline-size: 100%;
  overflow-inline: auto;
}

But overflow-inline and overflow-block aren’t supported in any other browsers. So I have to do this:

.table-container {
  max-inline-size: 100%;
  overflow-x: auto;
}

Frankly, mixing and matching logical properties with directional properties feels worse than not using logical properties at all. The inconsistency is icky. This feels old-fashioned but consistent:

.table-container {
  max-width: 100%;
  overflow-x: auto;
}

I don’t think there are any particular technical reasons why browsers haven’t implemented logical properties consistently. I suspect it’s more a matter of priorities. Fully implementing logical properties in a browser may seem like a nice-to-have bit of syntactic sugar while there are other more important web standard fish to fry.

But from the perspective of someone trying to use logical properties, the patchy rollout is frustrating.

Monday, April 19th, 2021

Home · castastrophe/wc-theming-standards Wiki

I really like the idea of a shared convention for styling web components with custom properties—feels like BEM meets microformats.

Monday, March 29th, 2021

CSS { In Real Life } | Quick Tip: Style Pseudo-elements with Javascript Using Custom Properties

Oh, this is smart! You can’t target pseudo-elements in JavaScript, but you can use custom properties as a proxy instead.

Wednesday, March 17th, 2021

Fluid Space Calculator | Utopia

Type and space are linked, so if you’re going to have a fluid type calculator, it makes sense to have a fluid space calculator too. More great work from Trys and James!

Building Dark Mode | Product Blog • Sentry

Robin makes a good point here about using dark mode thinking as a way to uncover any assumptions you might have unwittingly baked into your design:

Given its recent popularity, you might believe dark mode is a fad. But from a design perspective, dark mode is exceptionally useful. That’s because a big part of design is about building relationships between colors. And so implementing dark mode essentially forced everyone on the team to think long, hard, and consistently about our front-end design components. In short, dark mode helped our design system not only look good, but make sense.

So even if you don’t actually implement dark mode, acting as though it’s there will give you a solid base to build in.

I did something similar with the back end of Huffduffer and The Session—from day one, I built them as though the interface would be available in multiple languages. I never implemented multi-language support, but just the awareness of it saved me from baking in any shortcuts or assumptions, and enforced a good model/view/controller separation.

For most front-end codebases, the design of your color system shows you where your radioactive styles are. It shows you how things are tied together, and what depends on what.

Saturday, December 12th, 2020

What Can You Put in a CSS Variable? / Coder’s Block

A reminder that the contens of custom properties don’t have to be valid property values:

From a syntax perspective, CSS variables are “extremely permissive”.

Thursday, September 24th, 2020

The failed promise of Web Components – Lea Verou

A spot-on summary of where we’ve ended up with web components.

Web Components had so much potential to empower HTML to do more, and make web development more accessible to non-programmers and easier for programmers.

But then…

Somewhere along the way, the space got flooded by JS frameworks aficionados, who revel in complex APIs, overengineered build processes and dependency graphs that look like the roots of a banyan tree.

Alas, that’s true. Lea wonders how this can be fixed:

I’m not sure if this is a design issue, or a documentation issue.

I worry that is a cultural issue.

Using a custom element from the directory often needs to be preceded by a ritual of npm flugelhorn, import clownshoes, build quux, all completely unapologetically because “here is my truckload of dependencies, yeah, what”.

Friday, July 24th, 2020

Custom Property Coverup | Amber’s Website

This is a great bit of detective work by Amber! It’s the puzzling case of The Browser Dev Tools and the Missing Computed Values from Custom Properties.

Who do I know working on dev tools for Chrome, Firefox, or Safari that can help Amber find an answer to this mystery?

Tuesday, July 7th, 2020

Custom properties

I made the website for the Clearleft podcast last week. The design is mostly lifted straight from the rest of the Clearleft website. The main difference is the masthead. If the browser window is wide enough, there’s a background image on the right hand side.

I mostly added that because I felt like the design was a bit imbalanced without something there. On the home page, it’s a picture of me. Kind of cheesy. But the image can be swapped out. On other pages, there are different photos. All it takes is a different class name on that masthead.

I thought about having the image be completely random (and I still might end up doing this). I’d need to use a bit of JavaScript to choose a class name at random from a list of possible values. Something like this:

var names = ['jeremy','katie','rich','helen','trys','chris'];
var name = names[Math.floor(Math.random() * names.length)];
document.querySelector('.masthead').classList.add(name);

(You could paste that into the dev tools console to see it in action on the podcast site.)

Then I read something completely unrelated. Cassie wrote a fantastic article on her site called Making lil’ me - part 1. In it, she describes how she made the mouse-triggered animation of her avatar in the footer of her home page.

It’s such a well-written technical article. She explains the logic of what she’s doing, and translates that logic into code. Then, after walking you through the native code, she shows how you could use the Greeksock library to achieve the same effect. That’s the way to do it! Instead of saying, “Here’s a library that will save you time—don’t worry about how it works!”, she’s saying “Here’s it works without a library; here’s how it works with a library; now you can make an informed choice about what to use.” It’s a very empowering approach.

Anyway, in the article, Cassie demonstrates how you can use custom properties as a bridge between JavaScript and CSS. JavaScript reads the mouse position and updates some custom properties accordingly. Those same custom properties are used in CSS for positioning. Voila! Now you’ve got the position of an element responding to mouse movements.

That’s what made me think of the code snippet I wrote above to update a class name from JavaScript. I automatically thought of updating a class name because, frankly, that’s how I’ve always done it. I’d say about 90% of the DOM scripting I’ve ever done involves toggling the presence of class values: accordions, fly-out menus, tool-tips, and other progressive disclosure patterns.

That’s fine. But really, I should try to avoid touching the DOM at all. It can have performance implications, possibly triggering unnecessary repaints and reflows.

Now with custom properties, there’s a direct line of communication between JavaScript and CSS. No need to use the HTML as a courier.

This made me realise that I need to be aware of automatically reaching for a solution just because that’s the way I’ve done something in the past. I should step back and think about the more efficient solutions that are possible now.

It also made me realise that “CSS variables” is a very limiting way of thinking about custom properties. The fact that they can be updated in real time—in CSS or JavaScript—makes them much more powerful than, say, Sass variables (which are more like constants).

But I too have been guilty of underselling them. I almost always refer to them as “CSS custom properties” …but a lot of their potential comes from the fact that they’re not confined to CSS. From now on, I’m going to try calling them custom properties, without any qualification.

Friday, July 3rd, 2020

Uncommon CSS Properties

I count at least three clever CSS techniques I didn’t know about.

Saturday, June 13th, 2020

CSS Custom Properties Fail Without Fallback · Matthias Ott – User Experience Designer

Matthias has a good solution for dealing with the behaviour of CSS custom properties I wrote about: first set your custom properties with the fallback and then use feature queries (@supports) to override those values.

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.)

Saturday, June 6th, 2020

Hybrid positioning with CSS variables and max() – Lea Verou

Yet another clever technique from Lea. But I’m also bookmarking this one because of something she points out about 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.

That explains an issue I was seeing recently! I couldn’t understand why an older browser wasn’t getting the fallback I had declared earlier in the CSS. Turns out that custom properties mess with that expectation.

Monday, June 1st, 2020

Global and Component Style Settings with CSS Variables — Sara Soueidan

Sara shares how she programmes with custom properties in CSS. It sounds like her sensible approach aligns quite nicely with Andy’s CUBE CSS methodology.

Oh, and she’s using Fractal to organise her components:

I’ve been using Fractal for a couple of years now. I chose it over other pattern library tools because it fit my needs perfectly — I wanted a tool that was unopinionated and flexible enough to allow me to set up and structure my project the way I wanted to. Fractal fit the description perfectly because it is agnostic as to the way I develop or the tools I use.

Sass Color Functions in CSS | Jim Nielsen’s Weblog

I’m not the only one swapping out Sass with CSS for colour functions:

Because of the declarative nature of CSS, you’re never going to get something as terse as what you could get in Sass. So sure, you’re typing more characters. But you know what you’re not doing? Wrangling build plugins and updating dependencies to get Sass to build. What you write gets shipped directly to the browser and works as-is, now and for eternity. It’s hard to say that about your Sass code.

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.

Global CSS options with custom properties | @mdo

This is clever—using custom properties to enable if/else logic in CSS.