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Package wx :: Package lib :: Module docview :: Class Command |
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object
--+ |Object
--+ | Command
Method Summary | |
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Constructor. | |
Returns true if the command can be undone, false otherwise. | |
Override this member function to execute the appropriate action when called. | |
Returns the command name. | |
Override this member function to un-execute a previous Do. |
Method Details |
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__init__(self,
canUndo=False,
name=None)
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CanUndo(self)Returns true if the command can be undone, false otherwise. |
Do(self)Override this member function to execute the appropriate action when called. Return true to indicate that the action has taken place, false otherwise. Returning false will indicate to the command processor that the action is not undoable and should not be added to the command history. |
GetName(self)Returns the command name. |
Undo(self)Override this member function to un-execute a previous Do. Return true to indicate that the action has taken place, false otherwise. Returning false will indicate to the command processor that the action is not redoable and no change should be made to the command history. How you implement this command is totally application dependent, but typical strategies include: Perform an inverse operation on the last modified piece of data in the document. When redone, a copy of data stored in command is pasted back or some operation reapplied. This relies on the fact that you know the ordering of Undos; the user can never Undo at an arbitrary position in he command history. Restore the entire document state (perhaps using document transactioning). Potentially very inefficient, but possibly easier to code if the user interface and data are complex, and an 'inverse execute' operation is hard to write. |
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