I was just going over the latest CSSWG minutes (you can subscribe to them at W3C.org) and came across a few interesting nuggets I wanted to jot down for another time. The group discussed the CSS Values, CSS Easing, and Selectors modules, but what really caught my eye was adding triggered delays to CSS for things like hover, long taps, and focus states.

The idea stems from an OpenUI proposal, the same group we can thank for raising things like the Popover API and customizable select element. The concept, if I understand it right, is that anytime someone hovers, taps, or focuses on, say, a <button> for a certain amount of time, we can invoke some sort of thing. A tooltip is the perfect illustration. Hovering over the trigger element, the reasoning goes, is an expression of interest and as web authors, we can do something with that interest, like displaying a tooltip.

Whoa, right?! There’s long been chatter about CSS encroaching on JavaScript territory (isn’t it ironic, don’t you think?). Firing events in response to interaction is quite literally the only thing I use JavaScript for. There’s no mistake about that in the CSSWG, as documented in the minutes:

So. Does this belong in CSS? Or should it be elsewhere? Does the approach make sense? Are there better ideas? Most interested in the last.

[…]

Other question; does this belong in CSS or HTML… maybe this is just a javascript feature? In JS you can determine MQ state and change things so it wouldn’t necessarily be in CSS.

And shortly later:

As you were talking; one thing that I kept thinking of; should developers be customizing the delay at all? Original use case for delay is that hover shouldn’t be instant. But if we don’t allow for customizing we can align to platform delay lengths.

But there’s an excellent point to be made about the way many of us are already doing this with CSS animations (animation-delay) and transitions (transition-delay). Sometimes even applying those globally with the Universal Selector or a prefers-* query.

Things get even hairier when considering how values are defined for this. Are they explicit delays (800ms), generic keywords (none/short/medium/long), a custom property, a pseudo-class… something else? I’m glad there’re incredibly smart folks noodling on this stuff.

I think here it would be good to go with time values. CSS is a good place to put it. We have all the ergonomics. The right declarative place to put it.

Whatever the eventual case may be:

I think this sounds reasonable and I’d like to explore it. Unsure if this is the exact shape, but this space seems useful to me.

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