add points/path to QGraphicsView

[JohannesMunk]

Hi!

You should probably not set the boundingRect directly, but calculate it by how much space your diagram requires. But of course you can also do it the other way around and set the boundingRect from the outside and adapt the scale of your diagram accordingly. Depends on what you want to achieve.

addItem doesn't call paint. It just adds the item to an internal list of graphic items of the scene. Now whenever the view or the scene decides that something needs to be repainted then the paint method is being called. And it is the scene/view that initializes and passes the painter object to your code. No need to worry about that.

Joh

[szisziszilvi]

all right, thank you a lot, I'll come back soon with the errors...
but honestly thanks, I think now I get it. off to try.

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Added after 6 minutes:

Bearhug for JohannesMunk!

For some similarly beginner's interest the whole code together:
the derived class declaration:

class myQGraphichsItem : public QGraphicsItem
{
private:
    QRect bRect;
public:
    myQGraphichsItem();
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    QRectF boundingRect() const{ return bRect; }
    void setBoundingRect(int x1,int y1,int x2,int y2){bRect = QRect(x1,y1,x2,y2);}
};

class myQGraphichsItem : public QGraphicsItem
{
private:
    QRect bRect;
public:
    myQGraphichsItem();
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    QRectF boundingRect() const{ return bRect; }
    void setBoundingRect(int x1,int y1,int x2,int y2){bRect = QRect(x1,y1,x2,y2);}
};

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the paint method reimplemented:

void myQGraphichsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawRect(boundingRect());
}

void myQGraphichsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawRect(boundingRect());
}

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in useage:

QGraphicsScene *scene =  new QGraphicsScene;
myQGraphichsItem *mgi = new myQGraphichsItem;
mgi->setBoundingRect(30,60,90,100);
scene->addItem(mgi);
ui->graphicsView->setScene(scene);

QGraphicsScene *scene =  new QGraphicsScene;
myQGraphichsItem *mgi = new myQGraphichsItem;
mgi->setBoundingRect(30,60,90,100);
scene->addItem(mgi);
ui->graphicsView->setScene(scene);

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