[Not sure if this bug belongs to gnome-shell, caribou, or some other
package.]

Current gnome-shell pops up an on-screen keyboard under various
circumstances, when it thinks one is needed for input.  Notably, using
the touchscreen on a window expecting text input will often bring up the
on-screen keyboard.

However, the circumstances under which gnome-shell hides that keyboard
again are not obvious.  gnome-shell seems to hide the keyboard if I
use the touchpad.  However, typing on a physical keyboard doesn't affect
the on-screen keyboard.  I would expect that typing on a physical
keyboard would imply no need for an on-screen keyboard, so gnome-shell
should hide the on-screen keyboard when it gets keyboard events from a
physical keyboard.

- Josh Triplett

I'm still observing this bug in current gnome-shell.

In addition to not going away when typing at the keyboard, I've also
noticed that the keyboard sometimes gets into a state where it returns
every time I alt-tab to a terminal window.

Also, occasionally, it pops up in a very tiny (phone-sized) form in the
corner of the screen, rather than at its normal size.

- Josh Triplett