IOleUndoUnit::Do method (ocidl.h)

Article
02/22/2024

Instructs the undo unit to carry out its action. Note that if it contains child undo units, it must call their Do methods as well.

Syntax

HRESULT Do(
  [in] IOleUndoManager *pUndoManager
);

Parameters

[in] pUndoManager

A pointer to the undo manager. See IOleUndoManager.

Return value

This method returns S_OK on success.

Remarks

The undo unit is responsible for carrying out its action. Performing its own undo action results in another action that can potentially be reversed. However, if pUndoManager is NULL, the undo unit should perform its undo action but should not attempt to put anything on the redo or undo stack.

If pUndoManager is not NULL, then the unit is required to put a corresponding unit on the redo or undo stack. As a result, this method either moves itself to the redo or undo stack, or it creates a new undo unit and adds it to the appropriate stack. After creating a new undo unit, this undo unit calls IOleUndoManager::Open or IOleUndoManager::Add. The undo manager will put the new undo unit on the undo or redo stack depending on its current state.

A parent unit must pass to its children the same undo manager, possibly NULL, that was given to the parent. It is permissible, but not necessary, when pUndoManager is NULL to open a parent unit on the redo or undo stack as long as it is not committed. A blocked parent unit ensures that nothing is added to the stack by child units.

If this undo unit is a parent unit, it should put itself on the redo or undo stack before calling the Do method on its children.

After calling this method, the undo manager must release the undo unit.

Notes to Implementers

See the IOleUndoManager interface for error handling strategies for undo units. The error handling strategy affects the implementation of this method, particularly for parent units.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	ocidl.h