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4.7.5 AtomicUndo

Syntax: AtomicUndo [0|+|-]
Abbreviation: AU

increases, decreases, sets or clears the AtomicUndo level. The normal level is zero. All current document changes made while the AtomicUndo level is above zero are treated as a single change by the Undo and Redo commands. If no parameter is given, a level of 0 is set to 1; otherwise the current non-zero level is decremented. If 0 is given, the level is reset to zero. Parameters of ‘+’ and ‘-’ respectively increment and decrement the level, which in no case can be negative. If the level is above zero, the DoUndo flag in the status bar, which is normally a lower-case ‘u’, becomes upper case ‘U’.

Two other actions will reset the AtomicUndo level to zero: invoking the Undo command, and disabling the undo system with the DoUndo command. You cannot set a non-zero AtomicUndo level unless the undo system is enabled.

Note: macros that you wish to undo and redo atomically—i.e., as if they were single commands—should begin with AtomicUndo + and end with AtomicUndo - so that they can call and/or be called by other macros.