Currently when dynamically changing the translation in use, any QUndoAction objects (a private class not part of the public API) created via QUndoStack::createUndoAction() cannot have their prefix changed and new actions must be created to replace the old actions.

The only current alternative to replacing the actions I can think of is to not use createUndoAction() and manually re-implement a QUndoAction equivalent that observes the QUndoStack's undoTextChanged() signal... seems like re-implementing too much of what is provided by QUndoStack to me.

I suggest that perhaps calling setText() on a QUndoAction (if it were to be made virtual) could change the prefix to the newly retranslated text (QUndoAction::setPrefixedText() would need to call QAction::setText() then). Since setText() on a QUndoAction is only effective until the next undoTextChanged() this seems like a reasonable semantic change to me.

Alternatively the QUndoAction class could be made part of the API and provide a method of changing/retranslating the prefix.

E.g.:

void MyMainWindow::setupMenus() {
    // ...
    undoAction = myUndoStack->createUndoAction(this, tr("&Undo"));
    editMenu->addAction(undoAction);
    // ...
}
void MyMainWindow::retranslateUi() {
    // ...
#ifdef NEW
    undoAction->setText(tr("&Undo"));
#else // currently:
    delete undoAction;
    undoAction = myUndoStack->createUndoAction(this, tr("&Undo"));
    editMenu->insertAction(someBeforeAction, undoAction);
#endif
    // ...
}

Thank you.