Function: undo-amalgamate-change-group

undo-amalgamate-change-group is a byte-compiled function defined in simple.el.gz.

Signature

(undo-amalgamate-change-group HANDLE)

Documentation

Amalgamate changes in change-group since HANDLE.

Remove all undo boundaries between the state of HANDLE and now. HANDLE is as returned by prepare-change-group.

View in manual

Probably introduced at or before Emacs version 26.1.

Source Code

;; Defined in /usr/src/emacs/lisp/simple.el.gz
;; End auto-boundary section

(defun undo-amalgamate-change-group (handle)
  "Amalgamate changes in change-group since HANDLE.
Remove all undo boundaries between the state of HANDLE and now.
HANDLE is as returned by `prepare-change-group'."
  (dolist (elt handle)
    (with-current-buffer (car elt)
      (setq elt (cdr elt))
      (when (consp buffer-undo-list)
        (let ((old-car (car-safe elt))
              (old-cdr (cdr-safe elt)))
          (unwind-protect
              (progn
                ;; Temporarily truncate the undo log at ELT.
                (when (consp elt)
                  (setcar elt t) (setcdr elt nil))
                (when
                    (or (null elt)        ;The undo-log was empty.
                        ;; `elt' is still in the log: normal case.
                        (eq elt (last buffer-undo-list))
                        ;; `elt' is not in the log any more, but that's because
                        ;; the log is "all new", so we should remove all
                        ;; boundaries from it.
                        (not (eq (last buffer-undo-list) (last old-cdr))))
                  (cl-callf (lambda (x) (delq nil x))
                      (if (car buffer-undo-list)
                          buffer-undo-list
                        ;; Preserve the undo-boundaries at either ends of the
                        ;; change-groups.
                        (cdr buffer-undo-list)))))
            ;; Reset the modified cons cell ELT to its original content.
            (when (consp elt)
              (setcar elt old-car)
              (setcdr elt old-cdr))))))))