Keyboard layout switching popup steals focus and blocks input.
New install of Fedora 28 w/Gnome 3.28, I have noticed a really annoying issue where switching keyboards using the "zenkaku hankaku" key on the Japanese keyboard results in the keyboard switch popup staying in the middle of the screen for ~1-2 seconds.
This wouldn't be an issue except for the fact that this popup steals focus and makes it impossible to type anything immediately after switching layouts. To make things worse, pressing any key during that period resets the timer for the popup.
When using the default key for switching super+space there is no popup with an abnormally long hang time. That being said... why not just use the default hotkey.. well.. in Japan this key is commonly used to switch keyboard layouts in Japan. Myself as well as many Japanese people I know are used to using this key to switch layouts. There should be no reason why this key cannot be used.
I myself switch layouts often and cannot wait 1-2 seconds or more to begin typing again.