Selecting an image on film strip has a noticable (500ms or more?) delay

Is there an existing issue for this?

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

Describe the bug

When selecting (= single-clicking) an image in the film strip in darkroom mode, there's a long noticable delay (>500ms) before the image gets its brighter background indicating that its selected. This is not the case for lighttable mode.

It's probably not a performance issue per-se, because darktable is otherwise very fast and snappy and it is indeed faster to double-click an image and have it load than waiting for the selection to update.

Steps to reproduce

1. Open a film roll with more than one image.
2. Open an image in darkroom mode.
3. Click on another image in the film strip and move the mouse away so you can see the selection update.

Expected behavior

The selection should update immediately, as it does in lighttable mode.

Logfile | Screenshot | Screencast

-d common log: foo.log

Commit

No response

Where did you obtain darktable from?

distro packaging

darktable version

5.2.1

What OS are you using?

Linux

What is the version of your OS?

Debian testing

Describe your system

CPU: Intel(R) Core(TM) Ultra 9 185H

               total        used        free      shared  buff/cache   available
Mem:            62Gi        13Gi       7.9Gi       3.5Gi        43Gi        49Gi
Swap:           63Gi       642Mi        63Gi

Are you using OpenCL GPU in darktable?

No

If yes, what is the GPU card and driver?

No response

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

Can you reproduce with another darktable version(s)?

Yes, with 5.3.0+888~g0224217809-dirty (recent-ish master, changes are to lua-scripts and rawspeed submodules only).

Is the issue still present using an empty/new config-dir (e.g. start darktable with --configdir "/tmp")?

Yes.

Start by reproducing the delay in darkroom mode with a multi-image film roll, then compare single-click selection behavior with lighttable mode. Use the provided -d common log as context and verify the selection highlight updates immediately without waiting for image loading.