On a new laptop with 22.04 installed I have a weird key binding on Ctrl-. (Control and dot/period character). If I use it in any text window, be it gedit, emacs, firefox or chromium text input box, even with the text input tool in a gimp image, I get a lowercase e underscored. If I then type more characters, these appear underscored. If I type Ctrl-. again, the typed sequence disappears, yet with Return the typed sequence of characters is kept with the underscores removed.
Emacs is extra weird in showing the characters typed after Ctrl-. in an extra flyout:
When asking emacs' describe-key function, it will never see the Ctrl-.. When asking xev it merely shows that Control and Dot where pressed. There is nothing in keyboard shortcuts or the keyboard setting for the window manager (Xfce4 in my case, but I get the same when running with Ubunut(Standard)).
One more pointer: Checking this little extra window on emacs with xwininfo, it has the name ibus-ui-gtk3.
Does anyone know what this is? Is there a way to figure out where the behaviour is generated, some tool to see what happens between what xev records and what emacs' describe-key sees.
