Handling missing prefixed CSS properties

[JayPanoz]

This issue first appeared in ReadiumCSS when discussing vertical writing.

Indeed, there are a lot of EPUB stylesheets using -epub- prefixed properties and (optionally) the unprefixed standard one only. Problem is popular authoring software like InDesign can output CSS without all the necessary prefixes…

This has severe impacts in browsers that

1. don’t alias the -epub- properties and
2. don’t support the standard one

Basically, that can be Firefox, IE and Edge, depending on the CSS property involved e.g. IE + Edge need -ms-hyphens, IE needs the earlier spec values for writing-mode, etc.

I did a very quick and dirty proof of concept for PostCSS at the time we discussed this issue, to preprocess css files and correct them beforehand because you can’t rely on getComputedStyle in this case, but that’s an issue applying to web implementations only and we couldn’t discuss further details yet. So you’ll probably encounter it first and design something else entirely.

Needless to say I’ll be more than happy to contribute/help/follow-up if needed as it will help document this issue and provide a solution in Readium CSS docs.