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

There doesn't seem to be a way to do what you want reliably. If your new command is bound to DEL, then whatever was bound to DEL before in the current keymap isn't there anymore. The other approach you proposed won't work because pre-command-hooks don't prevent the following action from taking place. You might also think to interrupt further execution with ^G (Keyboard-Quit), but that's an uncontrolled interrupt that might stop more things than you want.

Even if you make the process of setting up the new binding a little more sophisticated than just re-bind, and remember what was bound there before, so you can call it afterwards, you don't really have what your looking for. If someone wants to rebind the "default" action, they have to do it by modifying to your function rather than replacing the key binding.

What you want to do doesn't fit Emacs' model of how key binding works.