Default ibus-daemon causes high cpu usage and startup delay for a tcl / tk application
Affected version
I tested Ubuntu 18.04 / 20.04 & Centos 7 / 8 (also current beta versions) but I think every gnome3 Version will be affected.
Bug summary
If we start our big TCL/TK application using gnome3 the startup time increases from 1 sec (KDE, Mate, ...) up to 60 sec. In the meantime ibus-daemon & ibus-X11 are using both a full CPU. After the application is started, it can be used without any problems. If I stop the ibus-damon (ibus exit) and restart the application everything is working fine.
After playing around a bit I could nail it down to the "--xim" option. If I remove this option, the application starts fast.
As a workaround I restart ibus-daemon without the --xim option at session login.
I tested many other environments like KDE, Xfce, Mate also using the ibus-daemon but there the problem does not occur (also with the --xim option). So I think it could be a problem between the gnome3 ibus implementation & tcl/tk (8.5.X)?
Has anybody seen this before? Please tell me, what you need to analyze the problem and I will do (strace, ...).
Since our application is a commercial software I cannot easily provide a testdriver to reproduce this behavior (but I will do, if really necessary).
Thanks in advance for your help!
Best regards, Roland