[tannhaeuser]

Unfortunately, epub and epubcheck isn't the great uncontroversial resource the author makes it out to be. When W3C, Inc. took over maintenance of the EPub spec around when 3.1 was current, they just referenced WHATWG HTML and other ever-expanding browser specs ([1]). Being "living standards", these have no versioning or QA. As a consequence of being based on a version of HTML that redefined headers and sectioning, Epub 3.2 just made existing epubs non-conforming. Which is why Calibre and other tool still recommend 3.1 or better yet 2.

The case mentioned where the CSS min() function is rejected is another place where bulk import of the extremely complex CSS spec is just not helpful. Ebook readers aren't evergreen browsers after all.

[1]: https://news.ycombinator.com/item?id=41326179

[ramblurr]

Yes, it is widely known in the epub space that targeting 3.1 or 2 is the more sane option.

With EPUB compatibility issues CSS should always be suspect number 1. Using "modern" CSS features and complaining about missing flex boxz grid, etc is a web developer's mindset.

Just because EPUB shares some of the stack with the web doesn't mean they perfectly overlap (or even should).

Hardly any e-ink embedded e-reader devices use a browser for rendering, they all use purpose built HTML/CSS parsing and rendering toolchains, are baked into firmware and updated once in a blue moon. (If you're interested look at koreader's crengine or Crosspoint reader which runs on an ESP32!)

The blog post reeks of overly confident AI prose. But don't be fooled.

[lavela]

Shouldn't a CSS engine just ignore directives it doesn't know? At least it shouldn't fail without an error.

[jiehong]

Came here to say exactly that: CSS was designed to be friendly and just ignore any line it doesn’t understand. It’s the whole point of browsers and progressive improvements.

[gsnedders]

Yes, every single CSS standard ever has required that.

[port11]

Are we blaming the spec and the author of the post for trying to conform to the checks, instead of blaming Adobe or Kobo for using 16-year old technology that ISN’T spec-compliant? -.-

[qubidt]

Yes. sometimes specs are badly designed. Targeting a constantly moving goalpost for a spec mainly implemented by embedded devices seems to me like, best case, questionable judgement

[cygx]

True, but that doesn't get Adobe off the hook: CSS mandates that unrecognized declarations should just be ignored, so the worst that's supposed to happen in the average case is some layout funkiness - not catastrophic failure.