— Function: make-sparse-keymap &optional prompt

This function creates and returns a new sparse keymap with no entries. (A sparse keymap is the kind of keymap you usually want.) The new keymap does not contain a char-table, unlike make-keymap, and does not bind any events.

          (make-sparse-keymap)
              ⇒ (keymap)

If you specify prompt, that becomes the overall prompt string for the keymap. You should specify this only for menu keymaps (see Defining Menus). A keymap with an overall prompt string will always present a mouse menu or a keyboard menu if it is active for looking up the next input event. Don't specify an overall prompt string for the main map of a major or minor mode, because that would cause the command loop to present a keyboard menu every time.

— Function: make-keymap &optional prompt

This function creates and returns a new full keymap. That keymap contains a char-table (see Char-Tables) with slots for all characters without modifiers. The new keymap initially binds all these characters to nil, and does not bind any other kind of event. The argument prompt specifies a prompt string, as in make-sparse-keymap.

          (make-keymap)
              ⇒ (keymap #^[nil nil keymap nil nil nil ...])

A full keymap is more efficient than a sparse keymap when it holds lots of bindings; for just a few, the sparse keymap is better.

— Function: copy-keymap keymap

This function returns a copy of keymap. This is almost never needed. If you want a keymap that's like another yet with a few changes, you should use map inheritance rather than copying. I.e., something like:

          (let ((map (make-sparse-keymap)))
            (set-keymap-parent map <theirmap>)
            (define-key map ...)
            ...)

When performing copy-keymap, any keymaps that appear directly as bindings in keymap are also copied recursively, and so on to any number of levels. However, recursive copying does not take place when the definition of a character is a symbol whose function definition is a keymap; the same symbol appears in the new copy.

          (setq map (copy-keymap (current-local-map)))
          ⇒ (keymap
               ;; (This implements meta characters.)
               (27 keymap
                   (83 . center-paragraph)
                   (115 . center-line))
               (9 . tab-to-tab-stop))
          
          (eq map (current-local-map))
              ⇒ nil
          (equal map (current-local-map))
              ⇒ t