Bug 513974

Summary: Allow setting superclasses of file types
Product: [Applications] systemsettings Reporter: Philipp A. <flying-sheep>
Component: kcm_filetypesAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED INTENTIONAL    
Severity: wishlist CC: faure, nate
Priority: NOR    
Version First Reported In: 6.5.4   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Philipp A. 2025-12-30 13:03:41 UTC 
SUMMARY
Ark consults the superclasses of MIME types to see if it can handle a file type.

This means that to make a custom MIME type work with Ark, one has to
1. edit it in `~/.local/share/mime/packages/`
2. run `~/.local/share/mime/packages/`

Not too bad, but hard to figure out!

STEPS TO REPRODUCE
1. Create a custom MIME type for e.g. Python `*.whl` files (a subtype of `application/zip`)
2. Try to open it with Ark and see it fail

OBSERVED RESULT
No UI to add `<sub-class-of type="..."/>`

EXPECTED RESULT
UI that allows to make a custom MIME type work with Ark


SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.21.0
Qt Version: 6.10.1
Kernel Version: 6.18.2-arch2-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 3700X 8-Core Processor
Memory: 32 GiB of RAM (31.3 GiB usable)
Graphics Processor: AMD Radeon RX 6800 XT
Comment 1 Philipp A. 2025-12-30 13:04:55 UTC 
Sorry: one has to run `update-mime-database ~/.local/share/mime/` to make things work
Comment 2 Nate Graham 2026-01-08 19:30:29 UTC 
I don't think this is in the cards, sorry. Code that would only ever be used by a number of people you can count on the fingers of one hand tends to age poorly and bit-rot, and also clutter up the UI that everyone else uses.

Interesting idea, but no can do, sorry.
Comment 3 Philipp A. 2026-01-10 11:23:15 UTC 
You sure? This is part of how mime types work, and as said, Ark relies on this facet of how they work. I don’t think it’s good to have a mime type editor that allows to create mime types but doesn’t allow other parts of KDE to interact with them.