> I think another discouraging aspect is HTML CSS are so huge and bloated at this point that few people can implement a "reader" for EPUB/HTML. It's basically "go implement a new browser". It makes one think a easy-to-parse markdown (like Djot) with some extra rendering bells and whistles would be a more likely long term solution
This feels like the biggest hurdle to me. The author says "Portable HTML generation principle: when possible, systems that generate portable EPUBs should output portable HTML.". I don't think this is going far enough. If the goal is for this format to be everywhere and repeatable then it needs to be standardised and easy to implement a new rendering engine. Relying on webviews doesn't feel like the way forward. The beauty of PDF is that it is incredibly reliable - a PDF from a decade ago still renders the same today as it used to.
I suspect if an effort like this is to get off the ground, the scope of the document needs to be scaled right back. The subset of XHTML allowed should be very limited. The ability to render a document that looks the same everywhere should be prioritised - fixed layout at a fixed page size first, reflowable second. It needs a standard with a comprehensive test suite of documents + render outputs.
> The ability to render a document that looks the same everywhere should be prioritised
IMO actually this is the question the whole effort hinges on.
If the goal is to replace PDF for the uses that require pixel-perfect rendering on every client just as the designer intended, then this approach is dead-on-arrival.
But if that's not the goal, then that has to be extremely well-communicated by the project, so that people who need that know they need to stick with PDF. Indeed, the project needs to explicitly say that it's not a goal, and that clients should be free to make reasonable rendering decisions within certain specified bounds.
This feels like the biggest hurdle to me. The author says "Portable HTML generation principle: when possible, systems that generate portable EPUBs should output portable HTML.". I don't think this is going far enough. If the goal is for this format to be everywhere and repeatable then it needs to be standardised and easy to implement a new rendering engine. Relying on webviews doesn't feel like the way forward. The beauty of PDF is that it is incredibly reliable - a PDF from a decade ago still renders the same today as it used to.
I suspect if an effort like this is to get off the ground, the scope of the document needs to be scaled right back. The subset of XHTML allowed should be very limited. The ability to render a document that looks the same everywhere should be prioritised - fixed layout at a fixed page size first, reflowable second. It needs a standard with a comprehensive test suite of documents + render outputs.