nsITransactionManager
The nsITransactionManager interface.
This interface is implemented by an object that wants to
manage/track transactions.
## Methods ##
### doTransaction(aTransaction) ###
Calls a transaction's doTransaction() method, then pushes it on the
undo stack.
This method calls the transaction's AddRef() method.
The transaction's Release() method will be called when the undo or redo
stack is pruned or when the transaction manager is destroyed.
#### Parameters ####
| aTransaction |
the transaction to do.
|
### undoTransaction() ###
Pops the topmost transaction on the undo stack, calls its
undoTransaction() method, then pushes it on the redo stack.
### redoTransaction() ###
Pops the topmost transaction on the redo stack, calls its
redoTransaction() method, then pushes it on the undo stack.
### clear() ###
Clears the undo and redo stacks.
### clearUndoStack() ###
Clears the undo stack only.
### clearRedoStack() ###
Clears the redo stack only.
### beginBatch(aData) ###
Turns on the transaction manager's batch mode, forcing all transactions
executed by the transaction manager's doTransaction() method to be
aggregated together until EndBatch() is called. This mode allows an
application to execute and group together several independent transactions
so they can be undone with a single call to undoTransaction().
#### Parameters ####
| aData |
An arbitrary nsISupports object that is associated with the
batch. Can be retrieved from nsITransactionList.
|
### endBatch(aAllowEmpty) ###
Turns off the transaction manager's batch mode.
#### Parameters ####
| aAllowEmpty |
If true, a batch containing no children will be
pushed onto the undo stack. Otherwise, ending a batch with no
children will result in no transactions being pushed on the undo stack.
|
### batchTopUndo() ###
Combines the transaction at the top of the undo stack (if any) with the
preceding undo transaction (if any) into a batch transaction. Thus,
a call to undoTransaction() will undo both transactions.
### removeTopUndo() ###
Removes the transaction at the top of the undo stack (if any) without
transacting.
### peekUndoStack() ###
Returns an AddRef'd pointer to the transaction at the top of the
undo stack. Callers should be aware that this method could return
return a null in some implementations if there is a batch at the top
of the undo stack.
### peekRedoStack() ###
Returns an AddRef'd pointer to the transaction at the top of the
redo stack. Callers should be aware that this method could return
return a null in some implementations if there is a batch at the top
of the redo stack.
### getUndoList() ###
Returns the list of transactions on the undo stack. Note that the
transaction at the top of the undo stack will actually be at the
index 'n-1' in the list, where 'n' is the number of items in the list.
### getRedoList() ###
Returns the list of transactions on the redo stack. Note that the
transaction at the top of the redo stack will actually be at the
index 'n-1' in the list, where 'n' is the number of items in the list.
### AddListener(aListener) ###
Adds a listener to the transaction manager's notification list. Listeners
are notified whenever a transaction is done, undone, or redone.
The listener's AddRef() method is called.
#### Parameters ####
| aListener |
the lister to add.
|
### RemoveListener(aListener) ###
Removes a listener from the transaction manager's notification list.
The listener's Release() method is called.
#### Parameters ####
| aListener |
the lister to remove.
|
## Attributes ##
### numberOfUndoItems ###
The number of items on the undo stack.
### numberOfRedoItems ###
The number of items on the redo stack.
### maxTransactionCount ###
Sets the maximum number of transaction items the transaction manager will
maintain at any time. This is commonly referred to as the number of levels
of undo.
@param aMaxCount A value of -1 means no limit. A value of zero means the
transaction manager will execute each transaction, then immediately release
all references it has to the transaction without pushing it on the undo
stack. A value greater than zero indicates the max number of transactions
that can exist at any time on both the undo and redo stacks. This method
will prune the necessary number of transactions on the undo and redo
stacks if the value specified is less than the number of items that exist
on both the undo and redo stacks.