While the keyboard is running, it may want to automatically show or hide
itself depending on whether a text input is active. Add functions to
show and hide the surface by destroying and re-creating it.
Phosh's compositor, phoc, does not emit configure events in reaction to
a surface being committed with no buffer attached. The complicated
surface creation/destruction process is for compatibility with phoc.
Keeping the keys pressed can confuse some compositors, and the key codes
may change. Release any keys that are pressed while the keymap is
changing, and press them again afterwards.
