Epub files created on Sigil close after cover on Kobo

[romanf]

Hi,
Thanks in advance for any help provided.
English is not my native language, but I'll try to be as clear as possible

Epub files I create on Sigil are recently crashing on Kobo devices. The ebook opens the cover page, shows the TOC, but after the cover it closes and is marked as finished. The same happens if I select any page from the TOC.

This only happens in Kobo e-ink devices, and only if I copy the file directly. If I convert it to Kepub beforehand or use the Calibre plugin, it shows correctly. Anyway, I would still like the epub to open directly, without any convertions needed.

I couldn't find any errors on 'epubcheck-4.2.6', Calibre Editor, or any other epub checking softwares. I checked the spine, nav and ncx files and couldn't find any problems either.

This only started happening a couple of months ago, as my ebooks prior to that work properly. I can't find any structural differences when comparing them.

I attached one of those problematic files. Any help would be very much appreciated!

[DiapDealer]

Upon opening your attached epub, I immediately get the warning that it has issues that Sigil wants to fix.

[romanf]

That must've been something related to the scrambled file, as the original gives no warnings. Anyway, this warning seems to be about the lack of DOCTYPE headers, but that's not the issue, as I tried with and without that header.

[DiapDealer]

Can you please verify that the attached scrambled epub also exhibits the same problem (exhibited on the Kobo device) that the original had? That may go a long way toward determining whether it's a structural issue, or something else.

[DiapDealer]

Originally Posted by romanf

That must've been something related to the scrambled file, as the original gives no warnings. Anyway, this warning seems to be about the lack of DOCTYPE headers, but that's not the issue, as I tried with and without that header.

Yes, but you said the EPUB was created with Sigil. And Sigil always includes the DOCTYPE.

[DiapDealer]

Also... I'm no expert on Kobo's epub3 support, but it used to be that getting one to use the epub3 renderer involved renaming the file (.kepub.epub) or actually converting to .kepub. Perhaps something has changed with the kobo firmware recently.

[KevinH]

Also did you test your problem issue with other epub3 compliant readers? Your scrambled one seems to not be showing any issues, even with my Kobo reading app on iOS.

[romanf]

Can you please verify that the attached scrambled epub also exhibits the same problem (exhibited on the Kobo device) that the original had?

I'll do that and see what happens, thank you.

Yes, but you said the EPUB was created with Sigil. And Sigil always includes the DOCTYPE.

The original file has the DOCTYPE header and does not present any errors or warnings when opening with Sigil. Only the scrambled version does, because for some reason scrambling removes the DOCTYPE header.

it used to be that getting one to use the epub3 renderer involved renaming the file (.kepub.epub) or actually converting to .kepub.

If that was the case, then why do different epub3 files, created in the same conditions, work?
Also, the Kobo guidelenes state the following:
"3. Drag your EPUB onto the device. To trigger the Kobo WebKit, change the file extension to “.kepub.epub”. To trigger the Kobo WebKit for a Fixed Layout title, change the extension to “.fxl.kepub.epub”. (If the extension is left unchanged it will render using the Adobe Digital Editions WebKit. This is the default display engine for sideloaded content to enable bookmarking, searching and highlighting.)"
I can send a couple of working epubs, also made by myself, to see if someone can find any relevant differences.

Also did you test your problem issue with other epub3 compliant readers?

I tested it on multiple apps (Android: Moon+Reader, Kobo App, Google Play Books; Windows: Calibre, ADE, Kobo App), and none of them present any issues. I don't have any e-reader device (I ask a friend to test it in the Kobo), but it seems to be working everywhere else.

Again, thank you for taking the time to give attention to this matter and answering me!

[KevinH]

Is by any chance your first real chapter bigger than 230kb in size? Some old epub readers had a file size limit.

[DiapDealer]

Also: what are the particulars of your cover image? Format and dimensions? It wouldn't be the first time a rendering engine took offense to oversized images

[romanf]

Is by any chance your first real chapter bigger than 230kb in size?

The biggest file is 112kb. The first file after the cover is 2kb.

what are the particulars of your cover image? Format and dimensions?

This particular file has a png cover with 1067x1600px and 2,31mb. But the same issue happens in over 20 different epubs with different sizes and file formats (png and jpeg).
On the other hand, I have hundreds of working files with bigger resolution and file size.

[jackie_w]

Originally Posted by romanf

The original file has the DOCTYPE header and does not present any errors or warnings when opening with Sigil. Only the scrambled version does, because for some reason scrambling removes the DOCTYPE header.

FYI, scrambling removes the DOCTYPE because scrambling runs under calibre's rules/conventions and calibre never creates epubs with DOCTYPE.

... but back to your epub3. The Kobo Adobe renderer does not seem to like the 3 style rules containing the 'vh' unit, e.g.

h1 {
  text-indent: 0;
  font-family: "Times", serif;
  margin: 30vh 0 2em;
  text-align: center;
  font-size: 1em;
  font-weight: normal;
  line-height: 2.5em;
}

'vh' is not something I ever use myself so I don't know what the best alternative is. However when I changed 'vh' to '%' (without the quotes) the epub3 behaved better on the Kobo.

[KevinH]

vh and vw units were not added until css3 so that means they are only valid in epub3. Is the Kobe ADE reader an epub2 or an epub3 reader?

[jackie_w]

Originally Posted by KevinH

vh and vw units were not added until css3 so that means they are only valid in epub3. Is the Kobe ADE reader an epub2 or an epub3 reader?

I'm not really sure. It is quite old I think (e.g. doesn't support font-variant:small-caps). It seems to read my epub3 books OK when I read them as epub (not kepub). Then again I only ever use simple CSS properties in my books that an older epub2 renderer would also be happy with.

[JSWolf]

Originally Posted by jackie_w

I'm not really sure. It is quite old I think (e.g. doesn't support font-variant:small-caps). It seems to read my epub3 books OK when I read them as epub (not kepub). Then again I only ever use simple CSS properties in my books that an older epub2 renderer would also be happy with.

The version of RMSDK is an old version and not all that ePub 3 compatible. The current version is but Kobo is not using it.