Marks the start of a
block of operations.
VL : (vla-StartUndoMark
This method allows
AutoCAD to close the environment so operations from StartUndoMark to
EndUndoMark can be treated as a group of operations.
(defun c:al-undomark ()
;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 thisdrawing (vla-get-activedocument
(setq mspace (vla-get-modelspace thisdrawing))
(setq pt1 (getpoint "\nSpecify First Point: "))
(setq pt2 (getpoint "\nSpecify Second Point: " pt1))
(setq myline (vla-addline mspace
(vlax-3d-point pt1)(vlax-3d-point pt2)))