[anenefan]

The TLDR version is Abode supports backward compatibility ... and epub - * International Digital Publishing Forum* - is playing with a sprawling mess opting for the race to the top newest standards ... that always works so well and ensures the user base is always upgrading.

I'm very grateful for this information and it explains why I've avoided epub opting for pdf over epub as my reader software is old.

I'm am very much on the side of supporting backwards compatibility. It reminds me of the times the M$ used to upgrade their doc standards ... where if one hadn't upgraded, well bad luck.

[gsnedders]

To be clear, ADE’s behaviour is not conforming to any version of the standards it claims to implement. If it had been, it would reject that specific max-width property declaration as having an invalid value and ignore it, not reject the entire document: every single version of CSS has required that forwards-compatible behaviour.

PDF is not somehow immune to this either — a non-conforming implementation could similarly break what are meant to be forward-compatible extension points by raising an error on an unknown stream or object instead of (as required by the standard) ignoring it.

[anenefan]

So if I understand correctly a struggling epub viewer or ADE should skip css that it considers malformed - which means the reason my viewers have considered a epub to be not able to be viewed / corrupt / whatever it is for some other reason than more recent / current css implementation.

PDFs certainly can suck, more often those that will only work with abode's software and other viewers I've tried can not.

[gsnedders]

While plausible, I would suspect it’s more likely you’ve just run into bugs than forwards-compatible error behaviour — most ePubs don’t get anywhere near actually interesting CSS!

[MrLeap]

An epub is just a plain html webpage compressed into a zip and its extension changed from .zip to ".epub". Assuming you have a web browser, you have something that will almost certainly render your epubs contents.

PDF is not nearly as pleasant under the hood. It's down right lovecraftian.

[ablob]

The lovecraftian horror of pdf mostly comes into play through the sheer amount of software that supply almost correct pdf. It's not enough to be able to read pdf anymore, you also have to be able to deal with software that emits subtly wrong documents.

[PunchyHamster]

Adobe really have perfected act of making the most shoddy software that is still possible to sell

[m463]

I'm reminded of "PSD is not my favourite file format."

https://b3n.org/psd-is-not-my-favourite-file-format/

or in the code:

https://github.com/gco/xee/blob/master/XeePhotoshopLoader.m

[rcxdude]

That's part of it, but the design of PDF really doesn't help

[goodmythical]

I was floored to discover this recently when I clicked "edit" in calibre for the first time a few weeks ago.

Straight HTML, edit anything everywhere. Super slick.

[anenefan]

I'm aware thanks. Mostly it's just my preferred viewer is older than css4 but it's been nice to find out why that was the case.

PDFs can be painful as well, more often it's then using abode's pdf viewer, but it's far less common for me. There was a time many years ago when I understood PDF structures better, back when I chose to manually edit and fix a couple of malformed PDFs.

[simcop2387]

I think its one reason ive been happy with software based epub readers where upgrading is usually reasonable to do. Either on my phone or android based eink reader. That said if they change too much then yea nobody will produce the new standard and only support the old one if it isnt carefully designed for graceful degredation.