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UndoableAction Class Referenceabstract

Used by the UndoManager class to store an action which can be done and undone. More...

Public Member Functions

virtual ~UndoableAction ()
 Destructor.
 
virtual bool perform ()=0
 Overridden by a subclass to perform the action.
 
virtual bool undo ()=0
 Overridden by a subclass to undo the action.
 
virtual int getSizeInUnits ()
 Returns a value to indicate how much memory this object takes up.
 
virtual UndoableActioncreateCoalescedAction (UndoableAction *nextAction)
 Allows multiple actions to be coalesced into a single action object, to reduce storage space.
 

Protected Member Functions

 UndoableAction () noexcept
 Creates an action.
 

Detailed Description

Used by the UndoManager class to store an action which can be done and undone.

See Also
UndoManager

Constructor & Destructor Documentation

UndoableAction::UndoableAction ( )
protectednoexcept

Creates an action.

virtual UndoableAction::~UndoableAction ( )
virtual

Destructor.

Member Function Documentation

virtual bool UndoableAction::perform ( )
pure virtual

Overridden by a subclass to perform the action.

This method is called by the UndoManager, and shouldn't be used directly by applications.

Be careful not to make any calls in a perform() method that could call recursively back into the UndoManager::perform() method

Returns
true if the action could be performed.
See Also
UndoManager::perform
virtual bool UndoableAction::undo ( )
pure virtual

Overridden by a subclass to undo the action.

This method is called by the UndoManager, and shouldn't be used directly by applications.

Be careful not to make any calls in an undo() method that could call recursively back into the UndoManager::perform() method

Returns
true if the action could be undone without any errors.
See Also
UndoManager::perform
virtual int UndoableAction::getSizeInUnits ( )
virtual

Returns a value to indicate how much memory this object takes up.

Because the UndoManager keeps a list of UndoableActions, this is used to work out how much space each one will take up, so that the UndoManager can work out how many to keep.

The default value returned here is 10 - units are arbitrary and don't have to be accurate.

See Also
UndoManager::getNumberOfUnitsTakenUpByStoredCommands, UndoManager::setMaxNumberOfStoredUnits
virtual UndoableAction* UndoableAction::createCoalescedAction ( UndoableAction nextAction)
virtual

Allows multiple actions to be coalesced into a single action object, to reduce storage space.

If possible, this method should create and return a single action that does the same job as this one followed by the supplied action.

If it's not possible to merge the two actions, the method should return zero.


The documentation for this class was generated from the following file: