It is possible to define own file name extensions to show such files in the album view. However, when the user clicks on the "preview", a message appears saying "error loading file" and a blank area is displayed. It would be great if - for unsupported file types - digiKam calls an external program defined as the first item in the list of associated applications in "Open with ..." right-click menu. (In my case, I care about PDFs, but I believe the behaviour should be general for any unsupported file type.) Reproducible: Always
In Image menu, you can see an option : Open With Default Application (META+F4) This is exactly what's you need... Just put pdf as new type mime to support as image type in setup dialog page. I just tested and it's work well with 4.14.0. Gilles Caulier
Thanks for your support Gilles, it is really faster to open the unsupported file types at least via a keyboard shortcut... However, it is not exactly the bug I reported - it would be user friendlier if digiKam runs such an external app automatically as a fall back when the preview fails (and remains in the Thumbnail view layout). Anyway, if you feel it is not how it should work, keep the report as "RESOLVED" and "WON'T FIX". Milan