Using Qt Undo Framework With QPainter - c++

Question

I am creating a drawing application with Qt and want to include undo and redo commands for whatever is drawn on a QImage. For this, I want to at least try and incorporate the Qt undo framework, since manually doing it will probably be above my skill level.
I have a MainWindow class where the main work is done and where I have the menu with undo and redo QActions.
The painting is done in a QWidget class called DrawingArea like this (PenShape is an enum of shapes):
void DrawingArea::drawLine(const QPoint &endPoint) {
QPainter painter(&image);
//some pen config code
switch (currentShape){
case PenShape::Polygon:
painter.drawPolygon(&endPoint, 5, Qt::OddEvenFill);
break;
case PenShape::Line:
painter.drawLine(lastPoint, endPoint);
break;
//other shapes and their draw methods..
}
update()
}
So as can be seen, the painter can draw in multiple shapes. I know I would have to somehow transfer this to a QUndoCommand class, but how? The drawline method is called only in DrawingArea's mouse event methods like this:
void DrawingArea::mousePressEvent(QMouseEvent *event){
if (event->button() == Qt::LeftButton) {
lastPoint = event->pos();
}
}
The QtUndoStack is located in MainWindow and the QActions are also there, but somehow I would have to connect the drawLine QtUndoCommand class and the mousePressEvent and mainWindow QAction with its connected slot method all together. This is what I don't know how to do.
Any help is appreciated!
Edit, here's the menu button actions:
m_undo = undoStack->createUndoAction(this, tr("&Undo"));
m_undo->setShortcuts(QKeySequence::Undo);
m_redo = undoStack->createRedoAction(this, tr("&Redo"));
m_redo->setShortcuts(QKeySequence::Redo);
I have no QUndoCommand classes because I'm unsure of how to create them yet.
In my MainWindow, I have a undoStack declared like this:
undoStack = new QUndoStack(this);