How to undo call-last-kbd-macro in emacs

Question

In emacs, I sometimes invoke call-last-kbd-macro by mistake. When undoing I would have expected undo to undo the entire effect of the keyboard macro atomically, but that does not happen. Instead I find myself having to undo each step of the macro one at a time. How can I get emacs to return to the buffer state before the execution of the macro?

Answer 1

I'm afraid you can't do that with just the built-in 'undo mechanism. The macro system in Emacs actually plays things back as though the user were actually typing in the keystrokes (or mouse events), and so the undo history (buffer-undo-list) gets updated as normal.

Here's a suggestion of how to extend the current undo mechanism to do what you want.

1. extend 'undo to understand a new entry in the undo list, a macro-begin marker and a macro-end element

2. advise/change the macro playback to insert the markers at the beginning/end of the macro playback

3. have the undo code treat all undo events between the two markers as a unit and undo them all (and add the appropriate markers on the end of the undo history so when you redo things, they're still treated as a single block)

Caveats:

• This would only work for macros that operate in a single buffer, if your macro switched buffers (or had side effects in other buffers), those changes would not be treated as a block.
• If your macro ended in a different buffer than it started, then you'd have to handle that cleanly - you don't want "unbalanced" macro-begin and macro-end markers in the undo list.

Needless to say, this is a complicated endeavor. I wish you luck.

Answer 2

This can be done pretty easily by overriding undo-boundary with e.g. the noflet package.

Given a macro definition (as generated by insert-kbd-macro) as follows:

(fset 'my-macro
   [... keys ...])

or:

(fset 'my-macro
   (lambda (&optional arg) "Keyboard macro." (interactive "p") (kmacro-exec-ring-item (quote ([...keys...] 0 "%d")) arg)))

Edit it as such:

(require 'noflet)

(fset 'my-macro
      (lambda (&optional arg) "Keyboard macro." (interactive "p")
        (undo-boundary)
        (noflet ((undo-boundary ()))
          (kmacro-exec-ring-item (quote ([...keys...] 0 "%d")) arg))
        (undo-boundary)))

If you don't want to edit all your macro definitions, you could alternatively add a wrapper which invokes a macro given as an argument, while creating / suppressing undo boundaries as above.