The Staggering Frontiers of CSS

I recommend the game Flexbox Froggy, which is how I learnt it

and one that we probably Moore'd past pretty rapidly anyway.

Well… not the viewport you’d expect. They reflect the viewport including document scrollbars, which means that, if scrollbars are, say, 17px wide, then on a vertically-scrolling document with no margins, 100vw is equal to 100% of the body width plus 17px.

The result of this is that viewport units have always been fundamentally broken and incorrect in the main place people wanted to use them: 100vw will cause overflow if scrollbars take any space.

Then along comes this new generation of viewport units, fixing an artificial problem (as you say), and continuing to ignore the actual bug, because the browser makers don’t care much about non-overlay scrollbars any more, even though that’s still the considerable majority of non-mobile users, and supported even on those non-mobile platforms that default to overlay scrollbars. (Aside: I’m glad that even when Windows is heading in the direction of overlay scrollbars, they’re at least not hiding the thumb whenever possible like macOS and all mobile platforms do. Also I miss Ubuntu’s Ayatana overlay scrollbars from about a decade ago—a bit gimmicky, but they showed care in balancing considerations and generally worked very well.)

And perhaps the worst part of it all? The spec actually included a practical workaround (give the document `overflow-y: scroll` so there’s always a vertical scrollbar, and vw will exclude any space allocated to that scrollbar—and the same for overflow-x/vh), but only Firefox implemented it, and no one else wanted to, and so it was eventually removed from the spec and from Firefox.

Flash had its share of footguns in terms of code organization, but animating interaction was never a weak point.

The feature was a gimmick, and it shows in the design. Not one of the transitions is one you’d actually want to use on, y’know, a web page. No fade (only pixel fade, 12), no slide (only wipe, 4–7). And Page-Enter/Page-Exit was obviously the wrong primitive if you wanted to indicate any sort of relationship between pages, because it would only be “correct” if you navigated in one direction. Basically, it was obviously only even vaguely suitable for slide shows, and not very good even there.

So: the feature was useless. But being proprietary was a part of that: if they’d proposed to Anyone Else “let’s add this thing”, Anyone Else would have said “that’s a stupid design, no one is going to use that well, let’s either do nothing or completely redesign the concept to be useful”.

In fact, the feature is so bad that I suspect it was an idea from someone who didn’t know what they were doing but had power, and the developers put it in half-heartedly rather than resisting. If the developers had been serious about it, it’d surely have ended up with named rather than numbered transitions, and at least a couple of useful transitions rather than the useless ones it got, and some better arrangement for varying transition per link or by navigation direction.