PDF export: Add option to create one PDF page per fragment

[flying-sheep]

This can’t be done using just CSS.

We would need to enumerate the fragments for each slide and determine their order (indices) as normal.

but then, for the CSS export, we would need to do sth. like this:

const fragmentIndices =
    toArray(sortFragments(currentSlide.querySelectorAll('.fragment')))
    .map((f, i) => i)

let lastSlide = currentSlide
for (const i of fragmentIndices) {
    lastSlide = lastSlide.parentNode.insertBefore(
        lastSlide.cloneNode(true),
        lastSlide.nextSibling)

    const fragments = toArray(lastSlide.querySelectorAll('.fragment'))
    for (cost fragment of fragments.slice(0, i+1) {
        fragment.classList.add('.visible')
    }
}

[falexwolf]

Yes, this would be very helpful to have.

[ghost]

It would indeed be a very appreciated feature for times when you are forced to export your slides to PDF when you are not given the option to present using your own computer and there is no Internet connection, as is the case for me personally tomorrow. There is a hack posted on the issue tracker to get around this current limitation, but it is far from optimal as it exports every slide as an image.

[ThomasWeinert]

I implemented that function into a plugin. Not fully tested yet, so I would be thankful for feedback.

https://github.com/ThomasWeinert/reveal-print

[bnjmnt4n]

This seems like a pretty good idea, although having to duplicate nodes might cause additional side effects. I think this should belong in a plugin for now: any other opinions?

[hakimel]

This was added in #1955 which has been merged into the dev branch.

I like this as the default behavior since it better mimics how fragments work. That said, there's a config option for disabling it if you want the old behavior.