Jeremy Keith

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.

As you may already know, I’m a nerd for design principles. I collect them. I did a podcast episode on them. I even have a favourite design principle. It’s from the HTML design principles. The priority of constituencies:

In case of conflict, consider users over authors over implementors over specifiers over theoretical purity.

It’s all about priorities, see?

Prioritisation isn’t easy, and it gets harder the more factors come into play: user needs, business needs, technical constraints. But it’s worth investing the time to get agreement on the priority of your constituencies. And then formulate that agreement into design principles.

Jason is also a fan of the priority of constituencies. He recently wrote about applying it to design systems and came up with this:

User needs come before the needs of component consumers, which come before the needs of component developers, which come before the needs of the design system team, which come before theoretical purity.

That got me thinking about how this framing could be applied to other areas, like design.

Designers are used to juggling different needs (or constituencies); user needs, business needs, and so on. But what I’m interested in is how designers weigh up different inputs into the design process.

The obvious inputs are the insights you get from research. But even that can be divided into different categories. There’s qualitative research (talking to people) and qualitative research (sifting through numbers). Which gets higher priority?

There are other inputs too. Take best practices. If there’s a tried and tested solution to a problem, should that take priority over something new and untested? Maybe another way of phrasing it is to call it experience (whether that’s the designer’s own experience or the collective experience of the industry).

And though we might not like to acknowledge it because it doesn’t sound very scientific, gut instinct is another input into the design process. Although maybe that’s also related to experience.

Finally, how do you prioritise stakeholder wishes? What do you do if the client or the boss wants something that conflicts with user needs?

I could imagine a priority of design inputs that looks like this:

Qualitative research over quantitative research over stakeholder wishes over best practices over gut instinct.

But that could change over time. Maybe an experienced designer can put their gut instinct higher in the list, overruling best practices and stakeholder wishes …and maybe even some research insights? I don’t know.

I’ve talked before about how design principles should be reversible in a different context. The original priority of constituencies, for example, applies to HTML. But if you were to invert it, it would work for XML. Different projects have different priorities.

I could certainly imagine company cultures where stakeholder wishes take top billing. There are definitely companies that value qualitative research (data and analytics) above qualitative research (user interviews), and vice-versa.

Is a priority of design inputs something that should change from project to project? If so, maybe it would be good to hammer it out in the discovery phase so everyone’s on the same page.

Anyway, I’m just thinking out loud here. This is something I should chat more about with my colleagues to get their take.