Destructor overriding

**wysota** · 1st March 2013, 11:05

Ok, here is a small framework. Try completing it so that it works properly.

Qt Code:

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#include <QtGui>
#if QT_VERSION >= 0x050000
#include <QtWidgets>
#endif
 
class Arrow;
 
class RotatingItem : public QGraphicsRectItem {
public:
	RotatingItem(const QRectF &rect, QGraphicsItem *parent = 0) : QGraphicsRectItem(rect, parent){
		setFlag(ItemSendsGeometryChanges, true);
 
	}
protected:
	void wheelEvent(QGraphicsSceneWheelEvent *event) {
		if(event->modifiers() & Qt::ShiftModifier) {
			setScale(scale()* (event->delta() > 0 ? 1.1 : 0.9));
		} else {
			setRotation(rotation()+(event->delta()/15.0));
 
		}
	}
	QVariant itemChange(GraphicsItemChange change, const QVariant &value) {
		if(change ==  ItemPositionHasChanged && scene()) {
			foreach(Arrow *a, m_arrowStartsHere) updateStartArrowPosition(a);
			foreach(Arrow *a, m_arrowEndsHere) updateEndArrowPosition(a);
 
		}
		return QGraphicsRectItem::itemChange(change, value);
	}
	void updateStartArrowPosition(Arrow *);
 
	void updateEndArrowPosition(Arrow *);
 
private:
	QList<Arrow*> m_arrowStartsHere;
	QList<Arrow*> m_arrowEndsHere;
 
 
	friend class Arrow;
};
 
class Arrow : public QGraphicsLineItem {
public:
	Arrow(RotatingItem *st, RotatingItem *en) :QGraphicsLineItem(st) {
		startItem = st;
		endItem = en;
		QPointF end = mapFromItem(endItem, endItem->boundingRect().center());
		setLine(0,0, end.x(), end.y());
		startItem->m_arrowStartsHere << this;
		endItem->m_arrowEndsHere << this;
 
		m_text = new QGraphicsSimpleTextItem(this);
		QFont f;
		f.setPointSize(8);
		m_text->setFont(f);
		updateArrowContent();
	}
	RotatingItem *start() const { return startItem; }
	RotatingItem *end() const { return endItem; }
	void updateArrowContent() {
		m_text->setPos(line().pointAt(0.5));
		m_text->setText(QString::number(line().length()));
	}
 
protected:
	RotatingItem *startItem, *endItem;
	QGraphicsSimpleTextItem *m_text;
};
 
class GraphicsView : public QGraphicsView {
public:
	GraphicsView(QWidget *parent = 0) : QGraphicsView(parent){}
protected:
	void paintEvent(QPaintEvent *event) {
		QGraphicsView::paintEvent(event);
		QPainter p(viewport());
		p.drawText(viewport()->rect().adjusted(10,10,-10,-10), "Drag item to move\nWheel to rotate\nSHIFT+wheel to scale");
	}
};
 
int main(int argc, char **argv) {
	QApplication app(argc, argv);
	GraphicsView view;
	QGraphicsScene scene;
	view.setScene(&scene);
	RotatingItem *item1 = new RotatingItem(QRect(-50, -50, 100, 100));
	RotatingItem *item2 = new RotatingItem(QRect(-50, -50, 100, 100));
	scene.addItem(item1);
	scene.addItem(item2);
	item1->setPos(100,100);
	item2->setPos(200,200);
	item1->setFlag(QGraphicsItem::ItemIsMovable);
	item2->setFlag(QGraphicsItem::ItemIsMovable);
	item1->setBrush(Qt::red);
	item2->setBrush(Qt::yellow);
	Arrow *arr = new Arrow(item1, item2);
	QPen p;
	p.setWidth(4);
	p.setColor(Qt::blue);
	arr->setPen(p);
	item1->setZValue(10);
	item2->setZValue(0);
	arr->setZValue(10);
	view.setRenderHint(QPainter::Antialiasing);
	view.resize(400,400);
	view.show();
	return app.exec();
}
 
 
void RotatingItem::updateStartArrowPosition(Arrow *arrow)
{
	QLineF l = arrow->line();
	l.setP2(arrow->end()->mapToItem(arrow, arrow->end()->boundingRect().center()));
	arrow->setLine(l);
	arrow->updateArrowContent();
}
 
void RotatingItem::updateEndArrowPosition(Arrow *arrow)
{
	QLineF l = arrow->line();
	l.setP2(mapToItem(arrow, boundingRect().center()));
	arrow->setLine(l);
	arrow->updateArrowContent();
}

#include <QtGui>
#if QT_VERSION >= 0x050000
#include <QtWidgets>
#endif

class Arrow;

class RotatingItem : public QGraphicsRectItem {
public:
	RotatingItem(const QRectF &rect, QGraphicsItem *parent = 0) : QGraphicsRectItem(rect, parent){
		setFlag(ItemSendsGeometryChanges, true);

	}
protected:
	void wheelEvent(QGraphicsSceneWheelEvent *event) {
		if(event->modifiers() & Qt::ShiftModifier) {
			setScale(scale()* (event->delta() > 0 ? 1.1 : 0.9));
		} else {
			setRotation(rotation()+(event->delta()/15.0));

		}
	}
	QVariant itemChange(GraphicsItemChange change, const QVariant &value) {
		if(change ==  ItemPositionHasChanged && scene()) {
			foreach(Arrow *a, m_arrowStartsHere) updateStartArrowPosition(a);
			foreach(Arrow *a, m_arrowEndsHere) updateEndArrowPosition(a);

		}
		return QGraphicsRectItem::itemChange(change, value);
	}
	void updateStartArrowPosition(Arrow *);

	void updateEndArrowPosition(Arrow *);

private:
	QList<Arrow*> m_arrowStartsHere;
	QList<Arrow*> m_arrowEndsHere;


	friend class Arrow;
};

class Arrow : public QGraphicsLineItem {
public:
	Arrow(RotatingItem *st, RotatingItem *en) :QGraphicsLineItem(st) {
		startItem = st;
		endItem = en;
		QPointF end = mapFromItem(endItem, endItem->boundingRect().center());
		setLine(0,0, end.x(), end.y());
		startItem->m_arrowStartsHere << this;
		endItem->m_arrowEndsHere << this;

		m_text = new QGraphicsSimpleTextItem(this);
		QFont f;
		f.setPointSize(8);
		m_text->setFont(f);
		updateArrowContent();
	}
	RotatingItem *start() const { return startItem; }
	RotatingItem *end() const { return endItem; }
	void updateArrowContent() {
		m_text->setPos(line().pointAt(0.5));
		m_text->setText(QString::number(line().length()));
	}

protected:
	RotatingItem *startItem, *endItem;
	QGraphicsSimpleTextItem *m_text;
};

class GraphicsView : public QGraphicsView {
public:
	GraphicsView(QWidget *parent = 0) : QGraphicsView(parent){}
protected:
	void paintEvent(QPaintEvent *event) {
		QGraphicsView::paintEvent(event);
		QPainter p(viewport());
		p.drawText(viewport()->rect().adjusted(10,10,-10,-10), "Drag item to move\nWheel to rotate\nSHIFT+wheel to scale");
	}
};

int main(int argc, char **argv) {
	QApplication app(argc, argv);
	GraphicsView view;
	QGraphicsScene scene;
	view.setScene(&scene);
	RotatingItem *item1 = new RotatingItem(QRect(-50, -50, 100, 100));
	RotatingItem *item2 = new RotatingItem(QRect(-50, -50, 100, 100));
	scene.addItem(item1);
	scene.addItem(item2);
	item1->setPos(100,100);
	item2->setPos(200,200);
	item1->setFlag(QGraphicsItem::ItemIsMovable);
	item2->setFlag(QGraphicsItem::ItemIsMovable);
	item1->setBrush(Qt::red);
	item2->setBrush(Qt::yellow);
	Arrow *arr = new Arrow(item1, item2);
	QPen p;
	p.setWidth(4);
	p.setColor(Qt::blue);
	arr->setPen(p);
	item1->setZValue(10);
	item2->setZValue(0);
	arr->setZValue(10);
	view.setRenderHint(QPainter::Antialiasing);
	view.resize(400,400);
	view.show();
	return app.exec();
}


void RotatingItem::updateStartArrowPosition(Arrow *arrow)
{
	QLineF l = arrow->line();
	l.setP2(arrow->end()->mapToItem(arrow, arrow->end()->boundingRect().center()));
	arrow->setLine(l);
	arrow->updateArrowContent();
}

void RotatingItem::updateEndArrowPosition(Arrow *arrow)
{
	QLineF l = arrow->line();
	l.setP2(mapToItem(arrow, boundingRect().center()));
	arrow->setLine(l);
	arrow->updateArrowContent();
}

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Problems to solve:
1. make sure the line sticks to its items when rotation and scale of any of them changes
2. make sure the length reported by the line is consistent when the line's starting item is scaled
3. make sure the width of the line doesn't depend on the scale of the red item or that it depends on the scale of both the red and the yellow item (the choice is yours)
4. make it possible for the yellow item to be over the red item (in terms of Z-value) and the line to be on top of the yellow item (in other words make it possible so that the line is always on top of the other items regardless of the stacking order of the items themselves)