[dolphin] [Bug 496072] New: Dolphin overwrites correct and already existing thumbnails with invalid and wrong ones.

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=496072

            Bug ID: 496072
           Summary: Dolphin overwrites correct and already existing
                    thumbnails with invalid and wrong ones.
    Classification: Applications
           Product: dolphin
           Version: 24.08.2
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: view-engine: general
          Assignee: dolphin-bugs-null at kde.org
          Reporter: navid.zamani+kde at gmail.com
                CC: kfm-devel at kde.org
  Target Milestone: ---

[I don’t know if this is part of Dolphin or some other “framework” thing, so I
had to choose Dolphin, as that is where it appeared. Please feel free to move
it to the correct product/component, if that is wrong.]

SUMMARY
It seems, KDE offers no way to drop/hook one’s own thumbnailing scripts
anywhere, so I had to write my own scanner/generator, based on the official
spec:
https://specifications.freedesktop.org/thumbnail-spec/latest/thumbsave.html

But instead of using them, Dolphin just overwrites them with its own, using the
wrong sizes too. (According to above spec, normal is 128x128. But dolphin uses
160px and 320px width for large and x-large.)

Even when I make my own thumbnails read-only, Dolphin simply ignores them.

If Dolphin was a human, I would describe that as literally hostile.


STEPS TO REPRODUCE
0. Open Dolphin in video directory $x, make sure you are in icon view with
previews, choose the largest size with the slider. If necessary, press F5 to
refresh.
1. Clear the thumbnails with `rm -rf .cache/thumbnails/*/*`, or move them
somewhere else.
2. Generate your own thumbnails for e.g. your video directory $x, in the
correct format, and store them correctly, in accordance to above spec. (Correct
subdir; correct file name from correct hash from correct URI from file name;
correct image size, correct file format. All of which I have verified multiple
times for my code. The resulting files are just of higher quality and a
different size (due to different content) than the ones Dolphin generates.)
3. Use `ls -lahvF ~/.cache/thumbnails/*/` and `file ~/.cache/thumbnails/*/*` to
list the thumbnails.
4. In Dolphin, press F5 to refresh.
5. Use `ls -lahvF ~/.cache/thumbnails/*/` and `file ~/.cache/thumbnails/*/*` to
list the thumbnails again.

OBSERVED RESULT
In step 4, the Video preview pictures flash, and stay as the ones Dolphin
generated.
In step 5, the file metadata (file size, image size, creation time, …) visibly
changed.
Your self-generated thumbnails are gone.

EXPECTED RESULT
There should of course be a simple directory to put one’s thumbnailers in (e.g.
like in Cinnamon/Gnome). Or at least a way to add a hook for one’s own scripts.
In lack of that, Dolphin should of course not overwrite already existing good
thumbnails. Let alone with weird non-standard sizes.

SOFTWARE/OS VERSIONS
Operating System: Gentoo Linux (profile:
default/linux/amd64/23.0/desktop/plasma; last (full) update on: 2024-11-07) 
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.7.0
Qt Version: 6.7.3

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