Books with large chapters cause extreme lag

[MrXyfir]

using v0.3.58

Testing on a book that has ~400 long paragraphs in most chapters and the browser slows dramatically, to where almost any action has a ~1 second delay. If I switch to a short chapter or another book with short chapters there's no problem. I've also tested on multiple books with large paragraphs and received the same results.

If I add display: none to the majority of the paragraph p elements then the lag instantly goes away. I was considering writing something to automatically hide and display only the appropriate elements but this screws up the pagination.

Any advice? At the current point certain books are basically unreadable. I can share a couple EPUB files I'm testing with but really any with large chapters should work.

[MrXyfir]

I've done some more testing and using visibility: hidden instead of display: none prevents the pagination from breaking and eases the lag a noticeable, although still unacceptable amount that is nowhere near as effective as display: none.

@fchasen Will there be any changes in v0.4 or beyond regarding how chapters (especially large ones) are rendered? Do you have any suggestions on how to deal with this now in v0.3? I have a few ideas but you know the code base the best, there might be an obvious solution I'm not seeing.

[MrXyfir]

Oddly, after many weeks, the lag has suddenly disappeared. I'll reopen if it returns.

[demeralde]

Hey @MrXyfir this still seems to be an issue, do you mind reopening it? See this issue for info.

[MrXyfir]

@dspacejs No problem!

[demeralde]

It'd be great if this can be fixed, it's been a huge pain.

@MrXyfir was it fixed when you switched to a different device or something with better specs?

[MrXyfir]

@dspacejs No, it just mysteriously disappeared. It's possible my browser updated? I haven't used this in a long time.

That being said, display: none worked for me at the time. If I had to solve this again I would probably try hiding the elements with display: none and inserting an empty div or something with the correct size to prevent pagination issues.

Edit: Actually if I had to fix this issue today I'd fork the repo and just work on it myself since the author rarely responds to anyone.

[demeralde]

@MrXyfir I'm using another app (Foliate) which uses this library. So I'd have to fork that, fork epub.js and update the package used to this, and then deploy it locally as an app. That's a huge pain lol. It also means I don't get other updates to Foliate.

[MrXyfir]

@dspacejs Ah, I see. Well best of luck finding a solution! Maybe you can convince the Foliate developer(s) to fork it.

[demeralde]

@MrXyfir good idea, I'll make a PR.