Bug 427877

Created attachment 132487 [details]
xrdb -query output. Are colour definitions missing?

STEPS TO REPRODUCE
1. Use plasma-desktop 5.20 on Linux
2. Try to start a Tk based gui application, like gitk

OBSERVED RESULT
Fails to start with the following in the console:
```
$ gitk
application-specific initialization failed: unknown color name "BACKGROUND"
Error in startup script: unknown color name "BACKGROUND"
    (database entry for "-background" in widget ".")
    invoked from within
"load /usr/lib64/libtk8.6.so Tk"
    ("package ifneeded Tk 8.6.8" script)
    invoked from within
"package require Tk"
    (file "/usr/bin/gitk" line 10)
```

EXPECTED RESULT
Tk apps start normally. This was the case with Plasma 5.19.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Gentoo Linux (X11)
KDE Plasma Version: 5.20.0
KDE Frameworks Version: 5.74.0
Qt Version: 5.15.1

ADDITIONAL INFORMATION

This has the same symptoms as one old issue reported to Red Hat Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1043686
This has been patched by Red Hat somehow, but I was unable to find the exact patch.

The problem seems to stem from krdb trying to update xrdb so that colours of non-KDE apps match ones set in KDE settings as mentioned in https://github.com/KDE/plasma-workspace/blob/master/kcms/krdb/ad/README

I'm adding output of `xrdb -query`.

One work-around mentioned on the Red Had bugzilla was to disable `Apply colors to non-KDE4 applications` in System Settings -> Application Appearance -> Colors -> Options - but I was unable to find this setting in Plasma 5.20.

Another harsher work-around is to reset xrdb with `xrdb -load /dev/null` - but that has unwanted side-effects.

This seems to be happening to multiple people with Plasma 5.20, e.g. https://www.reddit.com/r/kdeneon/comments/jckwxk/help_cant_run_gitk_on_kde_520/

Reading https://stackoverflow.com/questions/25357156/gitk-package-require-tk (which is not directly related to the bug), it seems that krdb should put entries like:
`#define BACKGROUND        #b58900`
into xrdb, but it may not be doing so properly (just guessing)