QUndoStack problem

[swiety]

I have a QTreeWidget with rows:

A
B
C
D

and commands:
1:

QUndoStack *stack = new QUndoStack();
stack->push( new InsertCommand( new QTreeWidgetItem(), 0 ) );
stack->undo(); // insertTopLevelItem( 0, newitem );

QUndoStack *stack = new QUndoStack();
stack->push( new InsertCommand( new QTreeWidgetItem(), 0 ) );
stack->undo(); // insertTopLevelItem( 0, newitem );

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Result:

NewItem
A
B
C
D

2:

InsertCommand *cmd = new InsertCommand( new QTreeWidgetItem(), 0 );
cmd->undo(); //insertTopLevelItem( 0, newitem );

InsertCommand *cmd = new InsertCommand( new QTreeWidgetItem(), 0 );
cmd->undo(); //insertTopLevelItem( 0, newitem );

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Result:

NewItem
B
C
D

Why I have two different results. What's the difference between 1 and 2?

[jacek]

Does the InsertCommand's constructor do anything with the tree widget?

Qt invokes redo() to perform the command when you push it onto the stack, but it seems that in the first case the command was performed twice.