Supposedly, new custom compose key combinations can be defined in the
~/.XCompose file. This seems to work well for GTK applications like gedit, firefox and gnome-terminal. But it isn't working for applications like atom, sublime and vscode even though the default compose key combinations are working. I tried adding new custom compose key combinations to the start of the system compose file at
/usr/share/X11/locale/en_US.UTF-8/Compose but that didn't work for any applications.
How can new compose key combinations be defined for all applications?
As UTF-8 is becoming increasingly prolific, the compose key feature of Linux keyboard input is more important than ever before. I'm interested in understanding what pieces of software is at play here.
I am using Ubuntu 18.04 with Gnome. Would it help if I were using KDE?
Edit: It seems that
.XCompose does work with QT applications like kate and kwrite but still not atom, sublime or vscode, using iBus or XIM.
Edit2: It seems that sublime works with the uim input method but not atom or vscode. It seems that the vscode team identified the problem in issue #34277 and points to issue #506838 in chromium. Comments on the chromium issue point out that the issue seems to be fixed now in the browser as of at least Feb 12 2018 but clearly what ever fixed it didn't make it to electron based applications yet.