SUMMARY In Dolphin, when browsing a directory containing RAW image files (eg. Canon's .cr2), previews work for local files, but not remote files. I believe I've tracked down the reason: On the Dolphin side, when it runs the PreviewJob, it takes this code path for remote files: https://invent.kde.org/frameworks/kio/-/blob/v5.101.0/src/widgets/previewjob.cpp#L742. This creates a file called /tmp/dolphin.XXXXXX, which is passed to the thumbnailer. On the kioslave/thumbnail.so side, RAWCreator::create() is called as expected (https://invent.kde.org/graphics/kdegraphics-thumbnailers/-/blob/v22.12.0/raw/rawcreator.cpp#L47), which then calls https://invent.kde.org/graphics/libkdcraw/-/blob/v22.12.0/src/kdcraw.cpp#L87. KDcraw::loadEmbeddedPreview() returns false because of the `!rawFilesExt.toUpper().contains(ext)` condition. libkdcraw requires the filename to have a known file extension. Off the top of my head, it seems like there are a couple ways to solve this: 1. Change libkdcraw to not depend on the file extension (not sure how feasible this is). 2. Change kio so that the temporary file it creates has the original file extension. STEPS TO REPRODUCE 1. In Dolphin, change the settings for the max file limit for remote thumbnails. 2. Navigate to a remote folder containing RAW images. OBSERVED RESULT There are no thumbnails. EXPECTED RESULT Thumbnails should be shown. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Fedora 37 KDE Plasma Version: 5.26.4 KDE Frameworks Version: 5.101.0 Qt Version: 5.15.7 ADDITIONAL INFORMATION (Included above)
A possibly relevant merge request was started @ https://invent.kde.org/frameworks/kio/-/merge_requests/1103
In case approach #2 is acceptable, I've created an MR to implement that here: https://invent.kde.org/frameworks/kio/-/merge_requests/1103
Git commit 5e0b6cbf1b9ef5c1e181caa2726a5591ff0d5fde by Méven Car, on behalf of Andrew Gunnerson. Committed on 30/04/2024 at 10:14. Pushed by meven into branch 'master'. PreviewJob: Add file extension to thumbnail temp files Previously, when previewing remote files, kio would create a local copy of the file using QTemporaryFile's default template. This would result in filenames, like /tmp/dolphin.XXXXXX. However, some thumbnail plugins, like kdegraphics-thumbnailers' libkdcraw thumbnailer, require the file extension to be valid in order to produce a preview. This commit updates the temp file's naming template to include the original file extension (if any). Signed-off-by: Andrew Gunnerson <accounts+kde@chiller3.com> M +8 -0 src/gui/previewjob.cpp https://invent.kde.org/frameworks/kio/-/commit/5e0b6cbf1b9ef5c1e181caa2726a5591ff0d5fde