When developing customizable components, one often wants to expose various parameters of the styling as custom properties, and form a sort of CSS API. This is still underutlized, but there are libraries, e.g. Shoelace, that already listcustomproperties alongside other parts of each component’s API (even CSS parts!).
Note: I’m using “component” here broadly, as any reusable chunk of HTML/CSS/JS, not necessarily a web component or framework component. What we are going to discuss applies to reusable chunks of HTML just as much as it does to “proper” web components.
Let’s suppose we are designing a certain button styling, that looks like this:
Five years ago, I had written this extensive Smashing Magazine article detailing multiple different methods for creating simple pie charts, either with clever use of transforms and pseudo-elements, or with SVG stroke-dasharray. In the end, I mentioned creating pie charts with conic gradients, as a future technique. It was actually a writeup of my “The Missing Slice” talk, and an excerpt of my CSS Secrets book, which had just been published.
I was reminded of this article today by someone on Twitter:
Indeed, unless you really need to display conic gradients, even I would not recommend using the polyfill on a production facing site. It requires -prefix-free, which re-fetches (albeit from cache) your entire CSS and sticks it in a <style> element, with no sourcemaps since those were not a thing back when -prefix-free was written. If you’re already using -prefix-free, the polyfill is great, but if not, it’s way too heavy a dependency.
Pie charts with fallback (modern browsers)
Instead, what I would recommend is graceful degradation, i.e. to use the same color stops, but in a linear gradient.
What if I told you you could use a single property value to turn multiple different values on and off across multiple different properties and even across multiple CSS rules?
What if I told you you could turn this flat button into a glossy skeuomorphic button by just tweaking one custom property --is-raised, and that would set its border, background image, box and text shadows in one fell swoop?
I’ve posted before about my work for the Web Almanac this year. To make it easier to calculate the stats about CSS selectors, we looked to use an existing selector parser, but most were too big and/or had dependencies or didn’t account for all selectors we wanted to parse, and we’d need to write our own walk and specificity methods anyway. So I did what I usually do in these cases: I wrote my own!
For some of the statistics we are going to study for this year’s Web Almanac we may end up needing a list of CSS shorthands and their longhands. Now this is typically done by maintaining a data structure by hand or guessing based on property name structure. But I knew that if we were going to do it by hand, it’s very easy to miss a few of the less popular ones, and the naming rule where shorthands are a prefix of their longhands has failed to get standardized and now has even more exceptions than it used to. And even if we do an incredibly thorough job, next year the data structure will be inaccurate, because CSS and its implementations evolve fast. The browser knows what the shorthands are, surely we should be able to get the information from it …right? Then we could use it directly if this is a client-side library, or in the case of the Almanac, where code needs to be fast because it will run on millions of websites, paste the precomputed result into whatever script we run.
So what is the Cicada Principle and how does it relate to web design in a nutshell? It boils down to: when using repeating elements (tiled backgrounds, different effects on multiple elements etc), using prime numbers for the size of the repeating unit maximizes the appearance of organic randomness. Note that this only works when the parameters you set are independent.
When I recently redesigned my blog, I ended up using a variation of the Cicada principle to pseudo-randomize the angles of code snippets. I didn’t think much of it until I saw this tweet:
One of my side projects these days is a color space agnostic color conversion & manipulation library, which I’m developing together with my husband, Chris Lilley (you can see a sneak peek of its docs above). He brings his color science expertise to the table, and I bring my JS & API design experience, so it’s a great match and I’m really excited about it! (if you’re serious about color and you’re building a tool or demo that would benefit from it contact me, we need as much early feedback on the API as we can get! )
For the documentation, I wanted to have the page navigation on the side (when there is enough space), right under the header when scrolled all the way to the top, but I wanted it to scroll with the page (as if it was absolutely positioned) until the header is out of view, and then stay at the top for the rest of the scrolling (as if it used fixed positioning).
Recently, when I was making the minisite for markapp.io, I realized a neat trick one can do with CSS variables, precisely due to their dynamic nature. Let’s say you want to use a property that has multiple versions: an unprefixed one and one or more prefixed ones. In this example we are going to use clip-path, which currently needs both an unprefixed version and a -webkit- prefixed one, however the technique works for any property and any number of prefixes or different property names, as long as the value is the same across all variations of the property name.
The first part is to define a --clip-path property on every element with a value of initial. This prevents the property from being inherited every time it’s used, and since the * has zero specificity, any declaration that uses --clip-path can override it. Then you define all variations of the property name with var(--clip-path) as their value:
Even !important should work, because it affects the cascading of CSS variables. Furthermore, if for some reason you want to explicitly set -webkit-clip-path, you can do that too, again because * has zero specificity. The main downside to this is that it limits browser support to the intersection of the support for the feature you are using and support for CSS Variables. However, all browsers except Edge support CSS variables, and Edge is working on it. I can’t see any other downsides to it (except having to use a different property name obvs), but if you do, let me know in the comments!
I think there’s still a lot to be discovered about cool uses of CSS variables. I wonder if there exists a variation of this technique to produce custom longhands, e.g. breaking box-shadow into --box-shadow-x, --box-shadow-y etc, but I can’t think of anything yet. Can you? 😉
Today, I was giving the opening keynote at Codemania in Auckland, New Zealand. It was a talk about color from a math/dev perspective. It went quite well, despite my complete lack of sleep. I mean that quite literally: I hadn’t slept all night. No, it wasn’t the jetlag or the nervousness that kept me up. It was my late minute decision to replace the static, low-res image of an RGB cube I was using until then with a 3D cube generated with CSS and animated with CSS animations. Next thing I knew, it was light outside and I had to start getting ready. However, I don’t regret literally losing sleep to make a slide that is only shown for 20 seconds at most. Not only it was super fun to develop, but also yielded a few things that I thought were interesting enough to blog about.
The most challenging part wasn’t actually the 3D cube. This has been done tons of times before, it was probably the most common demo for CSS 3D transforms a couple of years ago. The only part of this that could be of interest is that mine only used 2 elements for the cube. This is a dabblet of the cube, without any RGB gradients on it:
The challenging part was creating the gradients for the 6 sides. These are not plain gradients, as you can see below:
These are basically two linear gradients from left to right, with the topmost one being masked with a gradient from top to bottom. You can use CSS Masking to achieve this (for Chrome/Safari) and SVG Masks for Firefox, but this masks the whole element, which would hide the pseudo-elements needed for the sides. What I needed was masks applied to backgrounds only, not the whole element.
However, I didn’t want to have 6 separate SVG files, especially with this kind of repetition (cross-linking to reuse gradients and masks across different files is still fairly buggy in certain browsers). I wanted to be able to edit this straight from my CSS. And then it hit me: I was using SASS already. I could code SASS functions that generate SVG data URIs!
Here’s the set of SVG generating SASS functions I ended up writing: