Is there a way to reset (initialize - clear) the undo queue using autolisp?

[GeryKnee]

Hello everybody

Is there a way to reset (initialize - clear)  the undo queue using autolisp?

The goal is to ignore (_u :: "nothing to audo")  any changes to the drawing up to the present moment.

[Sea-Haven]

If you look into the help there are many settings for undo, one is using lisp is UNDOMARK.

(vla-startundomark (setq adoc (vla-get-activedocument (vlax-get-acad-object))))

(vla-endundomark adoc)

If you do undo it will go back to the mark point.

AutoCAD 2024 Help | UNDO (Command) | Autodesk

[GeryKnee]

;-----------------------------
(defun c:ClearUndoQueue nil
(vla-startundomark (setq adoc (vla-get-activedocument (vlax-get-acad-object))))
(vla-endundomark adoc)
(princ)
)

Command:
Command:
Command: _pline
Specify start point:
Current line-width is 0.000
Specify next point or [Arc/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Command:
Command:
Command: _circle Specify center point for circle or [3P/2P/Ttr (tan tan
radius)]:
Specify radius of circle or [Diameter]:
Command: ClearUndoQueue
Command:
Command: _u GROUP
Command: _u Circle GROUP
Command: _u Polyline GROUP
Command: _u PROPERTIES

instead of this , i want to see:

Command:
Command:
Command: _pline
Specify start point:
Current line-width is 0.000
Specify next point or [Arc/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Command:
Command:
Command: _circle Specify center point for circle or [3P/2P/Ttr (tan tan
radius)]:
Specify radius of circle or [Diameter]:
Command: ClearUndoQueue
Command:
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo
Command: _u Nothing to undo

[Sea-Haven]

The defun you made just starts and stops the undo, you need to take each line seperately put startmark at start of code and endmark at end of code.

Not sure if that is what you want.

[GeryKnee]

I see than cannot forget the undo history ( cannot protect a drawing created untill a moment the user wants to stop going back)

[Moshe-A · Accepted solution]

@GeryKnee  hi,

---

@GeryKnee wrote:

I see than cannot forget the undo history ( cannot protect a drawing created untill a moment the user wants to stop going back)

---

yes you can 😀

explore UNDO command options

undo control none

Moshe

[Kent1Cooper]

This is what I use:

;; DumpUndoHistory.lsp
(defun C:DUH ()
  (setvar 'cmdecho 0)
  (command "_.undo" "_control" "_none" "_.undo" "")
  (setvar 'cmdecho 1)
  (prompt "\nDumped Undo History.")
  (princ)
)

[GeryKnee]

Thank you Sir

[john.uhden]

@GeryKnee ,

I doubt that there is any way to do that programmatically, but you could SAVE or SAVEAS the drawing and then reopen it.

[GeryKnee]

Dear John, hello.

Thank you for your time and interest.

But as you see , I have informed the forun , the solution has been provided by kent1Kooper.

The function works.

Sincearly,
Gery