Qt resize child rectangles - c++

Question

Working on a school project, but I'm completely stuck. I have to write a paint application, in which you can draw Rectangles & Ellipses, select them, group them, move and resize them. After that I have to start implementing several design patterns.
I have to following problem. I have an abstract class Figure which inherits QRect, then there are the classes Rectangle, Ellipse and Group which all inherit the Figure class.
I am able to resize a single figure (ellipse or shape), by clicking on the corner of a selected shape, but the problem is resizing a group which contains several other figures (group, rectangle or ellipse), they have to resize relatively to their parent figure:
Mouse move event
void MainWindow::OnPaintBoxMouseMove(PaintBox *sender, QMouseEvent *event) {
//Mouse move event based on which tool is selected
switch(tool){
//When rectangle tool is selected, update rectangle size to mouse position
//in command
case rectangle: {
tempCmd->update(event->pos());
break;
}
//When ellipse tool is selected, update ellipse size to mouse position
//in command
case ellipse: {
tempCmd->update(event->pos());
break;
}
//When select tool is selected
case select: {
//If moving is selected, update shape in command
if (moving){
sRect->move(startPoint,event->pos());
tempCmd->update(event->pos());
startPoint = event->pos();
}
//If resizing is selected, update shape in command
else if (resizing){
sRect->resize(startPoint,event->pos());
tempCmd->update(event->pos());
startPoint = event->pos();
}
//Otherwise update size of selection rectangle
else if (sRect != nullptr) {
sRect->updateDimensions(event->pos());
}
break;
}
}
paintBox->update();
}
Resize method in resize command
called 'update' here
void ResizeCmd::update(QPoint mousePosition) {
switch (direction){
case 1: {
_figure->setTopLeft(_figure->topLeft()+mousePosition-startMousePosition);
break;
}
case 2: {
_figure->setTopRight(_figure->topRight()+mousePosition-startMousePosition);
break;
}
case 3: {
_figure->setBottomLeft(_figure->bottomLeft()+mousePosition-startMousePosition);
break;
}
case 4: {
_figure->setBottomRight(_figure->bottomRight()+mousePosition-startMousePosition);
break;
}
}
startMousePosition = mousePosition;
}
So the question is, how am I going to implement the resize method in the group class, which may contain other child groups as well?

Answer 1

I think you are looking for something like this Repo :
https://github.com/cl0ne/resizer-item
For doing your project you should use graphics libs of Qt like QGraphicsItem ,QGraphicsScene, and QGraphicsView
you shouldn't separate all your Items and write a resizer.
this repo is general for all QGraphicsItems which means that If you want Rectangle you should define one QGraphicsRectItem and add this resizer to it like this :
QGraphicsScene *scene = new QGraphicsScene(this);
QGraphicsRectItem *item = new QGraphicsRectItem(QRectF(0, 0, 100, 100));
item->setPos(10, 10);
item->setFlag(QGraphicsItem::ItemIsMovable);
item->setPen(QColor(102, 102, 102));
item->setBrush(QColor(158, 204, 255));
scene->addItem(item);
GraphicsItemResizer *resizer = new GraphicsItemResizer(item);
resizer->setBrush(QColor(64, 64, 64));
resizer->setMinSize(QSizeF(30, 30));
resizer->setTargetSize(item->boundingRect().size());
resizer->setHandlersIgnoreTransformations(true);
QObject::connect(
resizer,
&GraphicsItemResizer::targetRectChanged,
[item](const QRectF & rect)
{
QPointF pos = item->pos();
item->setPos(pos + rect.topLeft());
QRectF old = item->rect();
item->setRect(QRectF(old.topLeft(), rect.size()));
}
);
ui->graphicsView->setScene(scene);