Combine QGraphicsPathItem

[mvbhavsar]

Hello,


I have 2 QGraphicsPathItem having there own QPainterPath set within it.
Now I want 2nd QGraphicsPathItem to get connected to 1st QGraphicsPathItem using connectPath or any other function so that resultant QGraphicsPathItem is 1st QGraphicsPathItem.

I don't want to do this within single QGraphicsPathItem since I will not be able to modify individual elements at run time.

How to implement this?


Thanks

Manish

[wysota]

Subclass the item, teach it to accept pointers to other instances of that class and use itemChange() method to move those items when your item moves.

[mvbhavsar]

I have following code but still it is not working.



#include "cubeitem.h"

CubeItem::CubeItem(QGraphicsItem *parent):QGraphicsPathItem(parent),
m_Point1(10,10),
m_Point2(100,100),
m_Point3(50,150)
{
startPoint = m_Point1;
setFlags(ItemIsSelectable|ItemIsMovable);
setShapePath();
}

CubeItem::~CubeItem()
{

}

void CubeItem::setLastItem(QGraphicsPathItem *pi)
{
startPoint = pi->shape().currentPosition();
QPainterPath path1 = pi->shape();
QPainterPath path2;
path2.moveTo(path1.currentPosition());
path2.addPath(shape());
path1.connectPath(path2);
pi->setPath(path1);
setPath(path2);
update();
}

void CubeItem::setPoint1(QPointF arg)
{
m_Point1 = arg;
setShapePath();
update();
}
void CubeItem::setPoint2(QPointF arg)
{
m_Point2 = arg;
setShapePath();
update();
}

void CubeItem::setPoint3(QPointF arg)
{
m_Point3 = arg;
setShapePath();
update();
}

void CubeItem::setShapePath()
{
QPainterPath path;
// path.moveTo(startPoint);
path.cubicTo(m_Point1, m_Point2, m_Point3);
setPath(path);
setBrush(QBrush(Qt::yellow));
QPen pen(Qt::gray);
pen.setWidth(0);
setPen(pen);
}



Also, in mainwindow class, I have following code written on button clicked.



void MainWindow::on_tbCube_clicked()
{
cbi = new CubeItem;
scene->addItem(cbi);
if (scene->selectedItems().size()>0){
QGraphicsPathItem *pi = qgraphicsitem_cast<QGraphicsPathItem*>(scene->selectedItems().last());
if (pi){
cbi->setLastItem(pi);
}
}
}

[wysota]

In what way is this code supposed to "be working"?

[mvbhavsar]

Made the changes as below. Now what is happening is that if I move the second item after selecting, it does not retain first item's last point. And hence both looks detached.




#include "cubeitem.h"

CubeItem::CubeItem(QGraphicsPathItem *pi, QGraphicsItem *parent):QGraphicsPathItem(parent),QObject(),
m_Point1(10,10),
m_Point2(100,100),
m_Point3(50,150),
m_pi(pi)
{
if (pi){
startPoint = pi->shape().currentPosition();
startPoint = mapFromItem(pi,startPoint);
}
else{
startPoint = m_Point1;
}
setFlags(ItemIsSelectable|ItemIsMovable|ItemSendsG eometryChanges);
setData(0,"CubeItem");
setShapePath();
qDebug() << startPoint;
}

CubeItem::~CubeItem()
{

}

void CubeItem::setPoint1(QPointF arg)
{
m_Point1 = arg;
setShapePath();
update();
}
void CubeItem::setPoint2(QPointF arg)
{
m_Point2 = arg;
setShapePath();
update();
}

void CubeItem::setPoint3(QPointF arg)
{
m_Point3 = arg;
setShapePath();
update();
}

void CubeItem::setShapePath()
{
QPainterPath path;
path.moveTo(startPoint);
qDebug() << m_Point1 << "=="<< m_Point2 << "=="<< m_Point3;
path.cubicTo(m_Point1, m_Point2, m_Point3);
setPath(path);
QPen pen(Qt::gray);
pen.setWidth(0);
setPen(pen);
}



QVariant CubeItem::itemChange(GraphicsItemChange change, const QVariant &value)
{
if (change==ItemPositionChange){
if (m_pi){
setPoint1(startPoint);
}
}
return value;
}