Actions `views/lighttable/move/vertical;previous` and `views/lighttable/move/vertical;next` behave strangely in the filemanager layout

Is there an existing issue for this?

• I checked and did not find my issue in the already reported ones

Describe the bug

I have defined the following shortcuts:

Left=views/lighttable/move/horizontal;previous
Right=views/lighttable/move/horizontal;next
Up=views/lighttable/move/vertical;previous
Down=views/lighttable/move/vertical;next

horizontal;previous (and horizontal;next) behave as expected. They move horizontally in a row of thumbnails and continue to the end (beginning) of the previos (next) row when reaching the beginning (end) of the current row.

However, verical;previous and vertical;next do not.

There are two issues:

• Direction: In my mental model, when looking at a grid of items vertical;previous (vertical;next) should move one line up (down). Instead, the direction is inverted. This may be by design, but it's very counterintuitive based on the effect name and the context.

• Erratic movement: while the horizontal movement is predictable, vertical movement is not. If you move up (down) one row, sometimes you will move to the thumbnail just above (below), sometimes it will move also one step to the left (right). Sometimes, e.g., when moving down from the last row that fits in the view, the view will scroll but the focused thumbnail won't change. Sometimes, when scrolling up (down) there will be no vertical movement at all and the next (previous) thumbnail on the same row is focused.

I suspect that there is some error with the logic that computes the indices of elements in different rows.

Steps to reproduce

1. Go to the lighttable and select the file manager layout
2. Filter thumbnails so that you have enough to overflow the view
3. Focus a thumbnail in the top or bottom row
4. Start moving up and down using your keyboard using whatever shortcuts you have for that
5. Occasionally, especially when view needs to scroll up/down, the focus will stay on the same thumbnail, or move side-to-side

Expected behavior

The focus should only move up and down

Logfile | Screenshot | Screencast

E.g.: a sequence of three vertical;next. Notice how triggering the action the second time moves to the left instead of moving up.

https://github.com/user-attachments/assets/def94ddb-3ccd-448c-92be-cceb41d915a9

Commit

No response

Where did you obtain darktable from?

darktable.org / GitHub release

darktable version

5.3.0+653~ga8a01fbcf5

What OS are you using?

Mac

What is the version of your OS?

Tahoe 26.0.1

Describe your system

No response

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

Apple M4 Pro

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

No response

Reproduce the issue in darktable's lighttable using the file manager layout, overflowing thumbnails, and the views/lighttable/move/vertical;previous and ...;next actions. Trace the vertical movement and scrolling behavior from those action entry points, then verify that repeated moves change focus only one row vertically, including at viewport boundaries, without unintended horizontal movement or focus staying put.