Explicitly calling redo() under the Qt Undo Framework

Question

I am using the Qt Undo Framework (http://qt-project.org/doc/qt-4.8/qundo.html), and I want to explicitly call the undo() and redo() on the QUndoStack. I looked up the Qt docs and searched to see if this was supported, but couldn't find anything. So, I went ahead and did it.

Results - Explicit call to undo() works fine. canRedo() returns true thereafter. A subsequent call to redo() does not enter any of the redo() functions I have defined.

Please provide some insights into this. Please let me know if I need to share more information. Thanks!

score 1 · Accepted Answer · answered Apr 15 '14 at 08:28

Seems to work as expected and documented. Note that pushing a command to the stack will always call redo() on the command object.

class DummyCmd : public QUndoCommand
{
public:
    DummyCmd()
        : QUndoCommand(){ qDebug() << "DummyCmd c-tor"; }
    virtual void undo()
        { qDebug() << "undo"; }
    virtual void redo()
        { qDebug() << "redo"; }
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    DummyCmd c1;
    QUndoStack s;
    qDebug() << "pushing to stack";
    s.push(&c1);
    qDebug() << "calling undo";
    s.undo();
    qDebug() << "canRedo after undo: " << s.canRedo();
    s.redo();
    qDebug() << "canRedo after redo: " << s.canRedo();

    return a.exec();
}

Output:

DummyCmd c-tor
pushing to stack
redo
calling undo
undo
canRedo after undo:  true
redo
canRedo after redo:  false

Explicitly calling redo() under the Qt Undo Framework

1 Answers1