[Bug] page number not updating on horizontal scroll in epub with vertical text

[Bouby308]

Describe the bug

When I try to open a epub with vertial text and scroll horizontally, the page number does not update until I scroll to another chapter. This does not happen on epub with horizontal text.

How to reproduce?

book.epub.zip

Readium version

3.1

OS version

18.0.1

Testing device

iPad Pro M4

Environment

macOS: 15.3.1
platform: arm64

Additional context

No response

[russgrav]

Just chiming in to add some additional context from the issue that I initially raised: On the Test App, when I'm reading a Japanese book in vertical text mode, paging or scrolling through the current resource does not save the current progress or update the page number. This happens regardless of whether I'm viewing the book in paginated mode (where pages within a resource are flipped to via a vertical scroll gesture) or continuous/scroll mode (where you can scroll from left to right to advance the text). Progress is only saved and page numbers are only updated when I switch to the next resource/chapter. This also affects the bookmarking functionality, as bookmarks will just navigate me to the first page of the resource where that bookmark was added, rather than the page where I was last reading.

Note that this is not the case when reading books in Japanese in horizontal text mode, whether in scrolling or paginated mode.

Here's a video of the issue:

vertical-text-issue1.mp4