If the name of a brush tag group has a space or underscore in it, e.g. "comic ink" or "comic_ink", and that tag group is selected in the brush presets docker when Krita is closed, upon restart no icons or details show in the docker. The docker will be blank. Switching to another tag group and back again is required to get the brush icons to show. This behavior started when the new brush engine was introduced. The old engine didn't have this issue. Steps to reproduce: 1. Assign a brush to a new tag group with a space or underscore in its name. 2. Select that brush group in the brush presets docker. 3. Quit Krita. 4. Restart Krita.
Created attachment 113939 [details] (Video example) Thanks for the clear steps. For some reason I'm not able to reproduce the issue on Ubuntu 14.04 - Unity using Krita krita-4.2.0-pre-alpha-a12d9dd-x86_64.appimage.
It's still happening to me on 4.1.1.
I can reproduce the issue. I'm not sure whether it's really spaces or underscores that cause the problem, but I'm rewriting the tagging code in any case.
This has been fixed in master. Tested with 60caab4673.