Quote:
Originally Posted by kovidgoyal
The point is that you can use EPUB 3 features in EPUB 2 books (the HTML/CSS/javascript features in particular) and they will work everywhere that EPUB 3 will work, except that epubcheck will complain about them.
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As you said, using epub3 features in epub2. You are going to run into epub2 renderers that will not behave properly when those features are used -- failing gracefully is not in their design.
Quote:
Originally Posted by kovidgoyal
Really, there are epub 3 renderers that do not render epub 2? If so, please point me to one. IIRC the reason Kobo does that has nothing to do with epub 3 they split their renderers long before epub 3, to support kepub.
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Kobo selected the ACCESS NetFront™ BookReader v1.0 EPUB Edition (in future, referred to as ACCESS) as an epub3 renderer. To quote part of a press release from 2012: "preparing to launch the Kobo eReading solution in Japan by implementing the NetFront BookReader v1.0 EPUB Edition, as a standard viewer engine for EPUB 3-compatible services, which can accurately reproduce complex Japanese characters and page layouts."
As for epub3 renderers that don't support epub2? The question for me is not if they support epub2 but if they support it to the point where I can't tell if I have an epub2 or an epub3 ebook open in calibre's ebook viewer, Datalogics DLReader, Edge, ADE4, Azardi, Readium, BlueFire and ghod alone knows how many others I've tried on my Windows desktop or in RMSDK and ACCESS on my Kobo ereaders. Some come very close but there are items that don't render the same and I find those annoying much as I find applications that do not follow the epub stylesheet(s) to be annoying. But then I also find Adobe's inability to support small caps as annoying.
Every now and then, I get enthused and try the epub3 test suite just to see how much has changed.
Last time through, I added "
Harry Potter: A Journey Through a History of Magic" from the British Library as a real word fixed layout epub3 (aka pdf for epub users). Looks great on my Kobo after being renamed to .fxl.kepub.epub (uses the ACCESS renderer in FLO mode), Edge opened it in a two page layout which looked good. Readium for Chrome insisted on unpacking the file but did a nice 1 page view. Most of the other applications I tested strove to look ugly at best.