All of a sudden, my parallax perspective scroll effect did not work anymore in one of my recent web projects. I was not aware of any change, so what happened?

Why my parallax effect suddenly stopped working?

I saw no errors in the browser console, and everything else worked as expected. The website still worked on other devices but not on any desktop browser on my laptop. I had recently switched my operating system's color scheme from dark to light mode.

Diving deeper into the details, I found a CSS feature query that I had added last year to turn off the perspective effect in special cases. Shame on me, as the following code is anything but self-explanatory:

@supports (not (prefers-color-scheme: dark)) {
  body.archive .decoration__container,
  body.category .decoration__container,
  body.search .decoration__container,
  body.page.home .decoration__container {
    transform: translateZ(0);
  }
}

My commit message was even worse:

wip

But the previous commit pointed my to the right direction:

restrict progressive enhancement #59 (WIP)

Issue 59 contained detailed notes and screenshots of a device testing session in which I tried to make the site usable on every device, disabling the perspective effect when in doubt to prevent not being able to scroll on some older iPhones that don't get updated Safari or other web browsers anymore.

Quoting my own issue:

Unresolved aspects

scroll block on old iPhone restrict progressive enhancement, improve social media fallback #59 #61 #60

decoration z-index on old iPhone restrict progressive enhancement, improve social media fallback #59 #61 #60

I had merged my "wip" commit as part of a package of "partial fixes", tested and confirmed as "good enough" and "better than before" by several users.

What was that dirty code supposed to do, and where did it come from?

Apple seems to favor a Security through obscurity strategy for its older iPhones, which are outdated by its planned obsolescence policy. There are no modern browsers that people can use on an iPhone 8, and it is impossible to safely find out which buggy mobile Safari browser requests a website. So we either choose not to support outdated browsers or we must fiddle with unreliable "browser hacks" like the one above.

Progressive Enhancement vs. Planned Obsolescence

I was not even trying to make my perspective scroll effect work on the old device. I just wanted to ensure that users could browse and access the site's content using the "forgotten art" of Progressive Enhancement.

CSS Browser Hacks

In a perfect world, we do responsive web development and use media and feature queries only when needed. We don't rely on browsers' user agent strings and don't need any CSS hacks either. In a perfect world, z-index: 2 is enough to ensure an element is displayed on top of its siblings in any web browser since Internet Explorer 6. In a perfect world, people can install a modern mobile browser like Chrome, Chromium, or Firefox that doesn't use an outdated Safari engine due to Apple's software policies.

Many CSS hacks have been tested well and we can be quite sure to rule out undesired false positives when the code involves a vendor-prefixed property like -ms-high-contrast. Here is a classic example for Internet Explorer 10 and 11:

IE10 and IE11
==================
@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {

Detecting specific iPhone or MacOS Safari versions is less stable. I found the following in a DEV post from 2020 as a working but "NOT a recommended solution":

/* Only Safari 10.1+ */
@media not all and (min-resolution:.001dpcm)
{ @supports (-webkit-appearance:none) {

The one that broke my parallax scrolling effect was prone to fail from the start. It was supposed to target mobile iPhone browser engines up to Safari 12 (iPhone 8 or older), but not in Safari 13 and newer.

@supports (not (prefers-color-scheme: dark)) {

What does it even mean? A client that does not support dark color schemes? A client that supports color schemes that are not dark? Chromium does, but this feature query only fired after I did not use the supported dark mode option.

Alternatives to unstable CSS hacks?

Ironically, I could have removed the unstable hack. I had obsoleted it with a similar JavaScript detection that combines the JS equivalent of the same feature query with a user agent string match to restrict it to iPhones only.

var supportsColorSchemeQuery = window.matchMedia('(prefers-color-scheme: dark)');
config.supportsSuppportsColorSchemeQuery = (supportsColorSchemeQuery.matches);

// explicitly disable progressive enhancements to prevent bugs in outdated Apple browsers
// the following query / hack should target mobile Safari up to version 12
  if (/iPhone/.test(navigator.userAgent) && config.supportsSuppportsColorSchemeQuery) {
    window.kleiderordnung.config.prefersReducedMotion = true;
    if (document.body.classList && typeof(document.body.classList.add === 'function')) {
      document.body.classList.add('prefers-reduced-motion');
    }
  }

Now there are two discouraged techniques to rely on, and the code is not nice to read or maintain either. Maybe all modern browsers should implement a feature query isNoF******iPhoneSafariOrInternetExplorer.

Conclusion?

I don't know. These kind of problems used to be worse in the past. I remember Netscape Navigator, a historic browser notorious for its shortcomings compared to its "browser war" contender, Internet Explorer which seemed much better and more modern, implementing an early DOM interface (document.all) only to become the notorious legacy browser later.

Standards and best practices have improved much since then. We can do responsive web development with only some CSSmedia queries and feature queries most of the time. Most of my websites work (somehow) in Internet Explorer and probably even Netscape thanks to the web's Robustness principle. Now Apple has become notorious for legacy software. Who will be next?

An iPhone workaround broke my parallax scrolling effect 📵💔