On Arch Linux with current version of packages in Dolphin, the thumbnail previews is broken for kra, xcf, png and probably others
jpg, mp4, mkv are showing just fine.
I've narrowed down the breakage to this package:
With the previous version of this package installed io-5.88.0-1-x86_64.pkg.tar.zst the KRA thumbnails appear as expected.
STEPS TO REPRODUCE
1. Create a test Kritta ~/test.kra
2. Open Dolphin ~/ and see the thumbnail not load despite Previews being enabled in View, and KRA enabled in the [ Configure ] dialog
No KRA, XCF or PNG previews -- meanwhile JPG, MP4 and MKV preview just fine
Expect KRA, XCF and other files to show thumbnails
Linux/KDE Plasma: Linux ArchBox 5.15.11-arch2-1 #1 SMP PREEMPT Wed, 22 Dec 2021 09:23:54 +0000 x86_64 GNU/Linux
KDE Plasma Version: plasma-desktop 5.23.4-1
KDE Frameworks Version: plasma-framework 5.89.0-1
Qt Version: qt5-base 5.15.2+kde+r274-1
Possibly related to 475a88870801ae304b6ed57bf54248271f2e72f4 or 60443fd2ef79442c46c30b08db3fb01dd463e0e7
FTR, there was some discussion on IRC and kioclient5 cat thumbnail://... worked as expected.
I can't reproduce the issue here with kio from git master or 9c98dd26f5 (close to 5.89).
I've observed this problem as well, there is a way to "fix" the problem and I've been able to replicate it on two Manjaro KDE 21.2.1 systems and also "fix" the problem.
In `~/.config/dolphinrc`, delete the `[PreviewSettings]` section. It will enable .kra files to show previews on Dolphin, effectively fixing the problem. Other file extensions seem to work just fine too. But, in the preview settings of Dolphin configuration GUI, the `Krita Docutments` checkbox is unticked. Ticking/Unticking this checkbox manually will recreate the `[PreviewSettings]` portion of the `dolphinrc` file and will cause the issue to come back.
From what I was told, interacting with the GUI or the listed set of thumbnailers might be causing a problem. Not entirely sure.
This will be contents of the `[PreviewSettings]` when I tick/untick the krita file option the preview settings for my particular systems.
A possibly relevant merge request was started @ https://invent.kde.org/frameworks/kimageformats/-/merge_requests/46
>In `~/.config/dolphinrc`, delete the `[PreviewSettings]` section. It will enable .kra files to show previews on Dolphin, effectively fixing the problem.
This is fixed by https://invent.kde.org/network/kio-extras/-/merge_requests/144. The config key dolphin was writing was not the same as the derived plugin id.
*** This bug has been marked as a duplicate of bug 447507 ***