Restrict QGraphicsLineItem movement

Artemus

Hallo,

I want to restrict the movement of some QGraphicsLineItem and want to create a "snap to grid" behavior.

I created a new class called "QGraphicsLineItemMember" wich inherits QGraphicsLineItem to modify the itemChange() function.
The Problem is that with the new class i cant use @scene->addLine()@

to create the line at the specified scene.

Is it posible to cast QGraphicsLineItemMember* to QGraphicsLineItem* ?

cincirin

If QGraphicsLineItemMember is derived from QGraphicsLineItem, then you do not need to cast. QGraphicsLineItemMember is already an QGraphicsLineItem object. For example in any QGraphicsLineItemMember function member you can use
@
scene()->addLine(this);
@

Artemus

but i get this error when i replace my lineitems with the new class:
@error: invalid conversion from 'QGraphicsLineItem*' to 'QGraphicsLineItemMember*'@

at this line:
@pq_line1 = pq_scn->addLine(0,0,0,0,pen);@

my sourcecode:
@
class QGraphicsLineItemMember : public QGraphicsLineItem
{
public:
int test;
};

class CL_STATE
{
public:
CL_STATE( QGraphicsScene* pq_scene );
void setPoint1(qreal x, qreal y);
void setPoint2(qreal x, qreal y);
void setNorth(qreal n);
void setSouth(qreal s);
void setEast(qreal e);
void setWest(qreal w);
void redraw(void);

signals:

public slots:

private:
qreal x1,y1,x2,y2;
QGraphicsScene* pq_scn;
QGraphicsLineItem* pq_line1; //works
QGraphicsLineItem* pq_line2;
QGraphicsLineItemMember* pq_line3; //does not work
QGraphicsLineItemMember* pq_line4;
};
@

@
CL_STATE::CL_STATE( QGraphicsScene* pq_scene ):
pq_scn(pq_scene)
{
QPen pen;
pen.setWidth(2);

//add lines
pq_line1 = pq_scn->addLine(0,0,0,0,pen);
pq_line2 = pq_scn->addLine(0,0,0,0,pen);
pq_line3 = pq_scn->addLine(0,0,0,0,pen);
pq_line4 = pq_scn->addLine(0,0,0,0,pen);

//make movable
pq_line1->setFlag(QGraphicsItem::ItemIsMovable);
pq_line2->setFlag(QGraphicsItem::ItemIsMovable);
pq_line3->setFlag(QGraphicsItem::ItemIsMovable);
pq_line4->setFlag(QGraphicsItem::ItemIsMovable);
pq_line1->setFlag(QGraphicsItem::ItemSendsGeometryChanges);
pq_line2->setFlag(QGraphicsItem::ItemSendsGeometryChanges);
pq_line3->setFlag(QGraphicsItem::ItemSendsGeometryChanges);
pq_line4->setFlag(QGraphicsItem::ItemSendsGeometryChanges);

//set move cursor
pq_line1->setCursor(Qt::SizeAllCursor);
pq_line2->setCursor(Qt::SizeAllCursor);
pq_line3->setCursor(Qt::SizeAllCursor);
pq_line4->setCursor(Qt::SizeAllCursor);

}
@

cincirin

If you want to add QGraphicsLineItemMember object to scene you need to use "QGraphicsScene::addItem":http://developer.qt.nokia.com/doc/qt-4.8/qgraphicsscene.html#addItem
@
QGraphicsLineItemMember* lineItemMember = new QGraphicsLineItemMember();
pq_scn->addItem(lineItemMember);

@

Artemus

[quote author="cincirin" date="1327748569"]If you want to add QGraphicsLineItemMember object to scene you need to use "QGraphicsScene::addItem":http://developer.qt.nokia.com/doc/qt-4.8/qgraphicsscene.html#addItem
@
QGraphicsLineItemMember* lineItemMember = new QGraphicsLineItemMember();
pq_scn->addItem(lineItemMember);

@[/quote]
works perfect, thank you!