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# QUndoGroup Class Reference
[QtGui module]

The QUndoGroup class is a group of QUndoStack objects. More...

Inherits QObject.

### Methods

- __init__ (self, QObject parent = None)
- QUndoStack activeStack (self)
- addStack (self, QUndoStack)
- bool canRedo (self)
- bool canUndo (self)
- QAction createRedoAction (self, QObject, QString prefix = QString())
- QAction createUndoAction (self, QObject, QString prefix = QString())
- bool isClean (self)
- redo (self)
- QString redoText (self)
- removeStack (self, QUndoStack)
- setActiveStack (self, QUndoStack)
- list-of-QUndoStack stacks (self)
- undo (self)
- QString undoText (self)

### Qt Signals

- void activeStackChanged (QUndoStack *)
- void canRedoChanged (bool)
- void canUndoChanged (bool)
- void cleanChanged (bool)
- void indexChanged (int)
- void redoTextChanged (const QString&)
- void undoTextChanged (const QString&)

## Detailed Description

The QUndoGroup class is a group of QUndoStack objects.

For an overview of the Qt's undo framework, see the overview.

An application often has multiple undo stacks, one for each opened document. At the same time, an application usually has one undo action and one redo action, which triggers undo or redo in the active document.

QUndoGroup is a group of QUndoStack objects, one of which may be active. It has an undo() and redo() slot, which calls QUndoStack.undo() and QUndoStack.redo() for the active stack. It also has the functions createUndoAction() and createRedoAction(). The actions returned by these functions behave in the same way as those returned by QUndoStack.createUndoAction() and QUndoStack.createRedoAction() of the active stack.

Stacks are added to a group with addStack() and removed with removeStack(). A stack is implicitly added to a group when it is created with the group as its parent QObject.

It is the programmer's responsibility to specify which stack is active by calling QUndoStack.setActive(), usually when the associated document window receives focus. The active stack may also be set with setActiveStack(), and is returned by activeStack().

When a stack is added to a group using addStack(), the group does not take ownership of the stack. This means the stack has to be deleted separately from the group. When a stack is deleted, it is automatically removed from a group. A stack may belong to only one group. Adding it to another group will cause it to be removed from the previous group.

A QUndoGroup is also useful in conjunction with QUndoView. If a QUndoView is set to watch a group using QUndoView.setGroup(), it will update itself to display the active stack.

## Method Documentation

### QUndoGroup.__init__ (self, QObject parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Creates an empty QUndoGroup object with parent parent.

See also addStack().

### QUndoStack QUndoGroup.activeStack (self)

Returns the active stack of this group.

If none of the stacks are active, or if the group is empty, this function returns 0.

See also setActiveStack() and QUndoStack.setActive().

### QUndoGroup.addStack (self, QUndoStack)

Adds stack to this group. The group does not take ownership of the stack. Another way of adding a stack to a group is by specifying the group as the stack's parent QObject in QUndoStack.QUndoStack(). In this case, the stack is deleted when the group is deleted, in the usual manner of QObjects.

See also removeStack(), stacks(), and QUndoStack.QUndoStack().

### bool QUndoGroup.canRedo (self)

Returns the value of the active stack's QUndoStack.canRedo().

If none of the stacks are active, or if the group is empty, this function returns false.

See also canUndo() and setActiveStack().

### bool QUndoGroup.canUndo (self)

Returns the value of the active stack's QUndoStack.canUndo().

If none of the stacks are active, or if the group is empty, this function returns false.

See also canRedo() and setActiveStack().

### QAction QUndoGroup.createRedoAction (self, QObject, QString prefix = QString())

The QObject argument, if not None, causes self to be owned by Qt instead of PyQt.

Creates an redo QAction object with parent parent.

Triggering this action will cause a call to QUndoStack.redo() on the active stack. The text of this action will always be the text of the command which will be redone in the next call to redo(), prefixed by prefix. If there is no command available for redo, if the group is empty or if none of the stacks are active, this action will be disabled.

If prefix is empty, the default prefix "Undo" is used.

See also createUndoAction(), canRedo(), and QUndoCommand.text().

### QAction QUndoGroup.createUndoAction (self, QObject, QString prefix = QString())

The QObject argument, if not None, causes self to be owned by Qt instead of PyQt.

Creates an undo QAction object with parent parent.

Triggering this action will cause a call to QUndoStack.undo() on the active stack. The text of this action will always be the text of the command which will be undone in the next call to undo(), prefixed by prefix. If there is no command available for undo, if the group is empty or if none of the stacks are active, this action will be disabled.

If prefix is empty, the default prefix "Undo" is used.

See also createRedoAction(), canUndo(), and QUndoCommand.text().

### bool QUndoGroup.isClean (self)

Returns the value of the active stack's QUndoStack.isClean().

If none of the stacks are active, or if the group is empty, this function returns true.

See also setActiveStack().

### QUndoGroup.redo (self)

This method is also a Qt slot with the C++ signature `void redo()`.

Calls QUndoStack.redo() on the active stack.

If none of the stacks are active, or if the group is empty, this function does nothing.

See also undo(), canRedo(), and setActiveStack().

### QString QUndoGroup.redoText (self)

Returns the value of the active stack's QUndoStack.redoText().

If none of the stacks are active, or if the group is empty, this function returns an empty string.

See also undoText() and setActiveStack().

### QUndoGroup.removeStack (self, QUndoStack)

Removes stack from this group. If the stack was the active stack in the group, the active stack becomes 0.

See also addStack(), stacks(), and QUndoStack.~QUndoStack().

### QUndoGroup.setActiveStack (self, QUndoStack)

This method is also a Qt slot with the C++ signature `void setActiveStack(QUndoStack *)`.

Sets the active stack of this group to stack.

If the stack is not a member of this group, this function does nothing.

Synonymous with calling QUndoStack.setActive() on stack.

The actions returned by createUndoAction() and createRedoAction() will now behave in the same way as those returned by stack's QUndoStack.createUndoAction() and QUndoStack.createRedoAction().

See also QUndoStack.setActive() and activeStack().

### list-of-QUndoStack QUndoGroup.stacks (self)

Returns a list of stacks in this group.

See also addStack() and removeStack().

### QUndoGroup.undo (self)

This method is also a Qt slot with the C++ signature `void undo()`.

Calls QUndoStack.undo() on the active stack.

If none of the stacks are active, or if the group is empty, this function does nothing.

See also redo(), canUndo(), and setActiveStack().

### QString QUndoGroup.undoText (self)

Returns the value of the active stack's QUndoStack.undoText().

If none of the stacks are active, or if the group is empty, this function returns an empty string.

See also redoText() and setActiveStack().

## Qt Signal Documentation

### void activeStackChanged (QUndoStack *)

This is the default overload of this signal.

This signal is emitted whenever the active stack of the group changes. This can happen when setActiveStack() or QUndoStack.setActive() is called, or when the active stack is removed form the group. stack is the new active stack. If no stack is active, stack is 0.

See also setActiveStack() and QUndoStack.setActive().

### void canRedoChanged (bool)

This is the default overload of this signal.

This signal is emitted whenever the active stack emits QUndoStack.canRedoChanged() or the active stack changes.

canRedo is the new state, or false if the active stack is 0.

See also QUndoStack.canRedoChanged() and setActiveStack().

### void canUndoChanged (bool)

This is the default overload of this signal.

This signal is emitted whenever the active stack emits QUndoStack.canUndoChanged() or the active stack changes.

canUndo is the new state, or false if the active stack is 0.

See also QUndoStack.canUndoChanged() and setActiveStack().

### void cleanChanged (bool)

This is the default overload of this signal.

This signal is emitted whenever the active stack emits QUndoStack.cleanChanged() or the active stack changes.

clean is the new state, or true if the active stack is 0.

See also QUndoStack.cleanChanged() and setActiveStack().

### void indexChanged (int)

This is the default overload of this signal.

This signal is emitted whenever the active stack emits QUndoStack.indexChanged() or the active stack changes.

idx is the new current index, or 0 if the active stack is 0.

See also QUndoStack.indexChanged() and setActiveStack().

### void redoTextChanged (const QString&)

This is the default overload of this signal.

This signal is emitted whenever the active stack emits QUndoStack.redoTextChanged() or the active stack changes.

redoText is the new state, or an empty string if the active stack is 0.

See also QUndoStack.redoTextChanged() and setActiveStack().

### void undoTextChanged (const QString&)

This is the default overload of this signal.

This signal is emitted whenever the active stack emits QUndoStack.undoTextChanged() or the active stack changes.

undoText is the new state, or an empty string if the active stack is 0.

See also QUndoStack.undoTextChanged() and setActiveStack().