Emacs key binding fallback

Question

I have a minor mode. If that mode is active and the user hits DEL, I want to do some action, but only if some condition holds. If the condition holds and the action is execu

Answer 1

This is what I use for my smart-tab package which does exactly that.

(defun smart-tab-default ()
  "Indents region if mark is active, or current line otherwise."
  (interactive)
  (if mark-active
      (indent-region (region-beginning)
                     (region-end))

    (call-interactively
     (or
      ;; Minor mode maps for tab (without smart-tab-mode)
      (cdar (assq-delete-all 'smart-tab-mode (minor-mode-key-binding "\t")))
      (cdar (assq-delete-all 'smart-tab-mode (minor-mode-key-binding [(tab)])))
      (local-key-binding "\t")
      (local-key-binding [(tab)])
      (global-key-binding "\t")
      (global-key-binding [(tab)])))))

And in the command smart-tab (which is the one bound to tab in the minor mode), it has the following:

(if (smart-tab-must-expand prefix)
    ;; use smart tab
  (smart-tab-default))

It first checks if there are any minor mode bindings for tab (not including smart-tab-mode), then local, and finally global keybindings.