Bookmark function unavailable on full screen images

[spinningvenus]

Problem

• Creating kepubs that have full-screen images won't allow me to bookmark said pages as detailed here. Epub pages can be bookmarked correctly so the issue only occurs after converting to kepub. Kepubs with text can be bookmarked normally. This primarily effect heavy image content like Manga.

Steps to reproduce:

1. Start with a directory or .cbz file containing the images of your comic/manga
2. Use Kindle Comic Convertor to convert the directory/.cbz into an epub3 document
3. Convert the newly generated epub to a kepub with Kepubify
4. Load the content into the device

Notes

• I'm using Kepubify 4.0.4 and KCC 5.6.1. My device is a Libra 2 with firmware 4.35
• I've included a sample file produced with the process above

[pgaskin]

Can you try a few comic books from the Kobo store (the preview should be enough) and see if they display full-screen, and if they let you bookmark pages?

[spinningvenus]

Okay, so I've done a little bit of testing to try and figure out the cause of the issue here are some more notes.

Previews directly from the Kobo store have several features disabled including booking marking 😔 Luckily free books aren't limited by this. I tested several manga as you suggested and they all have full screen images and bookmark functions.

To me the next step was to try and figure out what was different between the sideloaded manga and the stuff on the store. I used Claribre and with the plugin DeDRM to decrypt the content from the store and compare it to my samples with a diff checker. For sanity I tried sideloading the unencrypted copy back on the device with no changes and the bookmark function no longer worked!

This means any of the following could be true:

• This is a firmware issue or some restriction imposed directly by Kobo on sideloaded books
• The DeDRM strips whatever magic causes the device to allow fullscreen

Eitherway I think there's nothing to do about it unless you know something I don't. Thank you.

[pgaskin]

Thanks for looking into it thoroughly. I'm going to test your two theories when I get a chance, but you might be right about the bookmarking. Another thing you could compare are the rows in the content table for the book from the kobo store vs the same book sideloaded as a de-drm'd kepub, since that table is populated differently for sideloaded books.

[spinningvenus]

Table of contents are identical between the two books.

This reddit thread appears to have the same issue I'm encountering except they're using KCC to convert directly to kepubs instead of Kepubify. They reference being able to bookmark properly on an older device so I think my next step will be to try older firmwares.

I did some research on the DeDRM process and while it's possible it's removing important content, the more I learn the more I think it's another issue. Something I might return to if downgrading doesn't work.

Kobolabs says "Content should display identically whether sideloaded or downloaded to a device from the Kobo store". This documentation also says "Sideloaded EPUBs with the ".fxl.kepub.epub" or ".kepub.epub" will disable bookmarking and note keeping.", but I don't think that applies here because it's a properly converted kepub and not simply renaming the file.

I want to point out that there has been similar firmware issues in the past, which I want to reference here for documentation sake even though you clearly remember that.

I'll drop an update after playing with older firmware.

[spinningvenus]

All functions operate as expected under firmware 4.31.19086. The issue appears in any firmware versions following that. I'll submit a bug report officially to Kobo at a later date, but right now this workaround is fine for me. Thank you for your assistance.

[pgaskin]

You did most of the troubleshooting :).

Note that be "content table", I meant the table in the KoboReader.sqlite database, since that is more likely than not to at least be part of the difference.

[axu2]

@spinningvenus did you ever solve this?

[spinningvenus]

@spinningvenus did you ever solve this?

I downgraded my device and since I don't use network functions it's stayed that way ever since. Feel free to ping me with any other question though.