fish-shell/share/functions/fish_vi_cursor.fish

function fish_vi_cursor -d 'Set cursor shape for different vi modes'
  set -l terminal $argv[1]
  set -q terminal[1]; or set terminal auto
  set -l uses_echo

  set fcn
  switch "$terminal"
    case auto
      if set -q KONSOLE_PROFILE_NAME
        set fcn __fish_cursor_konsole
        set uses_echo 1
      else if set -q XTERM_LOCALE
        set fcn __fish_cursor_xterm
        set uses_echo 1
      else
        return 1
      end
  end

  set -l tmux_prefix
  set -l tmux_postfix
  if begin; set -q TMUX; and set -q uses_echo[1]; end
    set tmux_prefix echo -ne "'\ePtmux;\e'"
    set tmux_postfix echo -ne "'\e\\\\'"
  end

  set -q fish_cursor_unknown
  or set -g fish_cursor_unknown block blink

  echo "
  function fish_vi_cursor_handle --on-variable fish_bind_mode
    set -l varname fish_cursor_\$fish_bind_mode
    if not set -q \$varname
      set varname fish_cursor_unknown
    end
    #echo \$varname \$\$varname
    $tmux_prefix
    $fcn \$\$varname
    $tmux_postfix
  end
  " | source
end