Compose key does not always work
Summary
I have mapped Compose key to CapsLock physical key. Then, I have noticed the behavior of the Compose key is ignored half of the time.
Steps to reproduce
Map CapsLock to Compose using KDE System Settings > Input Devices > Keyboard > Advanced > Position of Compose Key > Caps Lock.
Open a KDE application (tested with konsole and kontact). Keep Compose pressed, then type '=', then 'c', then release Compose. Repeat several times. Euro symbol (€) should be typed, but sometime you get "=c".
Useful observations
The behavior is correct if user release Compose before typing '=' and 'c'.
If you install ibus, ibus feedback show that maintaining Compose press quickly start/abort the compose sequence. So, the issue is somewhere in the repetition code of the Compose key.
I know this behavior happens in KDE applications, GIMP and LibreOffice. However, Chrome has a different behavior (it works very well with ibus).
libinput debug-events
and libinput record
does not bring interesting information.
I have to admit I am not sure this bug is related to libinput. My knowledge of this topic is rather limited and there are many actors in the room.
Required information
$ dpkg -l libinput* libxkbcommon*
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-========================-============-============-=======================================================================
ii libinput-bin 1.22.1-1 amd64 input device management and event handling library - udev quirks
ii libinput-tools 1.22.1-1 amd64 input device management and event handling library - command line tools
ii libinput10:amd64 1.22.1-1 amd64 input device management and event handling library - shared library
ii libxkbcommon-tools 1.5.0-1 amd64 library interface to the XKB compiler - tools
ii libxkbcommon-x11-0:amd64 1.5.0-1 amd64 library to create keymaps with the XKB X11 protocol
ii libxkbcommon0:amd64 1.5.0-1 amd64 library interface to the XKB compiler - shared library
ii libxkbcommon0:i386 1.5.0-1 i386 library interface to the XKB compiler - shared library