* lisp/simple.el (undo-amalgamate-change-group): New function

[gnu-emacs] / lisp / simple.el

diff --git a/lisp/simple.el b/lisp/simple.el
index 4d35d7c27e67142258d89f44ec3338530909881e..51c9100d2c2969c9e11959bcaa3b078d61b0ca75 100644 (file)
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -2958,6 +2958,41 @@ behavior."
   (undo-auto--boundary-ensure-timer))
 ;; End auto-boundary section
 
   (undo-auto--boundary-ensure-timer))
 ;; 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))))))))
+
+

 (defcustom undo-ask-before-discard nil
   "If non-nil ask about discarding undo info for the current command.
 Normally, Emacs discards the undo info for the current command if
 (defcustom undo-ask-before-discard nil
   "If non-nil ask about discarding undo info for the current command.
 Normally, Emacs discards the undo info for the current command if


@@ -3239,7 +3274,7 @@ If OUTPUT-BUFFER is a buffer or buffer name, erase that buffer
 and insert the output there.
 If OUTPUT-BUFFER is not a buffer and not nil, insert the output
 in current buffer after point leaving mark after it.
 and insert the output there.
 If OUTPUT-BUFFER is not a buffer and not nil, insert the output
 in current buffer after point leaving mark after it.

-(This cannot be done asynchronously).
+This cannot be done asynchronously.

 
 If the command terminates without error, but generates output,
 and you did not specify \"insert it in the current buffer\",
 
 If the command terminates without error, but generates output,
 and you did not specify \"insert it in the current buffer\",


@@ -3328,6 +3363,8 @@ the use of a shell (with its need to quote arguments)."
                                     (current-buffer)))))
        ;; Output goes in a separate buffer.
        ;; Preserve the match data in case called from a program.
                                     (current-buffer)))))
        ;; Output goes in a separate buffer.
        ;; Preserve the match data in case called from a program.

+        ;; FIXME: It'd be ridiculous for an Elisp function to call
+        ;; shell-command and assume that it won't mess the match-data!

        (save-match-data
          (if (string-match "[ \t]*&[ \t]*\\'" command)
              ;; Command ending with ampersand means asynchronous.
        (save-match-data
          (if (string-match "[ \t]*&[ \t]*\\'" command)
              ;; Command ending with ampersand means asynchronous.