|
In general downgrading an epub3 to an epub2 may not be easy given the epub3 version may use features not available under epub2, such as epub3 extended metadata, scripts, html5 specific tags, epub3 specific attributes, and etc. So simply allowing you to change from 3 to 2 inside Sigil means the ebook would be in some sort of intermediate state preventing Sigil epub version specific tools or menus from working. So that is not going to happen.
That said, we can write an epub_3to2_plugin that will use the nav to create the ncx and guide, strip out the nav, strip out epub:type attributes, replaces section tags with divs, downconvert epub3 metadata to 2, etc. The user would have to search for other html5 specific tags and replace them with some epub2 code equivalents, place comments around or any scripts, or delete them, etc, etc.
Since calibre's editor isn't epub version specific, you may be better off handling the downgrade to epub2 using calibre until we get such a plugin written.
KevinH
|