key_state(+Displayable, +Keymap, -Key, -State)
     key_state(+Keymap, -Key, -State)

Allows the user to find out the state of a key in a keymap.

Displayable is a ProXL Displayable. If omitted, the default Display is used.

Keymap is a keymap, typically obtained by get_keyboard_attributes/N.

Key is the name of a key.

State is either up or down.