Marks the beginning of a block of operations.
Supported platforms: Windows only
No return value.
This method allows AutoCAD to set up the necessary environment so operations done between this call and a call to EndUndoMark can be treated as a group of operations.
VBA:
Sub Example_StartUndoMark()
' This example creates a series of lines, each with an undo marker
' defined for it. After lines are created, you can switch to AutoCAD and type
' the Undo command, and only one line at a time will be undone. If StartUndoMark
' call is not made, an undo in AutoCAD will undo all the lines at once.
Dim line As AcadLine
Dim stPnt(0 To 2) As Double
Dim endPnt(0 To 2) As Double
stPnt(0) = 1: stPnt(1) = 2: stPnt(2) = 0
endPnt(0) = 2: stPnt(1) = 1: stPnt(2) = 0
' Create the lines
Dim j As Integer
For j = 0 To 3
ThisDrawing.StartUndoMark
Set line = ThisDrawing.ModelSpace.AddLine(stPnt, endPnt)
stPnt(0) = stPnt(0) + 3
endPnt(0) = endPnt(0) + 3
ThisDrawing.EndUndoMark
Next
ZoomAll
End Sub
Visual LISP:
(vl-load-com)
(defun c:Example_StartUndoMark()
;; This example creates a series of lines, each one with an undo marker
;; defined for it. After lines are created you can switch to AutoCAD and type
;; the Undo command, and only one line at a time will be undone. If StartUndoMark
;; call is not made, an undo in AutoCAD will undo all the lines at once.
(setq acadObj (vlax-get-acad-object))
(setq doc (vla-get-ActiveDocument acadObj))
(setq modelSpace (vla-get-ModelSpace doc))
(setq stPnt (vlax-3d-point 1 2 0)
endPnt (vlax-3d-point 2 1 0))
;; Create the lines
(setq j 0)
(while (>= 3 j)
(vla-StartUndoMark doc)
(setq line (vla-AddLine modelSpace stPnt endPnt))
(vlax-safearray-put-element (vlax-variant-value stPnt) 0 (+ (vlax-safearray-get-element (vlax-variant-value stPnt) 0) 3))
(vlax-safearray-put-element (vlax-variant-value endPnt) 0 (+ (vlax-safearray-get-element (vlax-variant-value endPnt) 0) 3))
(setq j (1+ j))
(vla-EndUndoMark doc)
)
(vla-ZoomAll acadObj)
)