Page swipe does nothing in RTL manga

[linyaa-kiwi]

Page swipe, by either touchscreen or touchpad, does nothing in RTL manga.

Expected behavior

In RTL manga, the following works correctly:

• Changing pages with keyboard arrow keys.
• Changing pages with UI slider.
• Changing pages with the arrow buttons at each end of UI slider.

The following does not work. It does absolutely nothing.

• Changing pages with touchscreen swipe.
• Changing pages with touchpad swipe.

Version:

• Foliate version: 3.1.1
• OS/Distribution and version: Fedora 40
• Desktop environment: Gnome 46.0
• Installation method: Installed from source, and installed from Flatpak, both have bug.

Additional context

I love Foliate. Thanks for making a greap app!

I've never debugged a GTK app before, but I can help if you provide a little guidance. For example, how do I insert debug log messages into the javascript and view them?

I began examing the scroll code in epub.js, and how dx/dy and vx/vy are processed, but I became lost without the ability to insert debug messages.

[johnfactotum]

It's not really possible to do that with the current fixed-layout renderer, which doesn't support offsetting and snapping the page (the scrollBy() and snap() methods of the paginator). Apart from implementing those, one workaround would be to partially undo d3619e7acdb01e6f3841336b737ec90051905ca0, to get back non-1-to-1 gestures for fixed-layout books.

Technically this is a duplicate of #1225, as all fixed layout books, including PDF, use the same renderer and have the same problem.