GTK_LAYER_SHELL_KEYBOARD_MODE_NONE: This window should not receive keyboard events.
GTK_LAYER_SHELL_KEYBOARD_MODE_EXCLUSIVE: This window should have exclusive focus if it is on the top or overlay layer.
GTK_LAYER_SHELL_KEYBOARD_MODE_ON_DEMAND: The user should be able to focus and unfocues this window in an implementation
defined way. Not supported for protocol version < 4.
GTK_LAYER_SHELL_KEYBOARD_MODE_ENTRY_NUMBER: Should not be used except to get the number of entries. (NOTE: may change in
future releases as more entries are added)