Modify QPainterPath object

[Annabela_Cortez]

Hi,
I have a class "Node" which is inherited from QGraphicsItem class, and there is a method called shape where I wanna use ellipse to draw node.

QPainterPath Cvor::shape() const
{
    QPainterPath temp;
    temp.addEllipse(-10, -10, 30, 30);
    return temp;
}

I want to make this ellipse bigger, but I can't make it. Size is very small and I think it's default. Is there any way to resize it?
Thanks in advance

[mrjj]

Hi
Make sure your
https://doc.qt.io/qt-5/qgraphicsitem.html#boundingRect
returns a rect big enough for the ellipse you want.
Also note the info about calling prepareGeometryChange()
as else you get odd redrawing.

[Annabela_Cortez]

@mrjj It's not working. I tried

[SGaist]

Hi,

What about drawing an ellipse that takes into account the size of your item ?

[KillerSmath]

@Annabela_Cortez

1. How are you overriding these functions: Boundingrect, Shape, Paint ?

Boundingrect - notifies the view about item area (necessary for redraw) and make your item supports click events.
Shape - is used for more accurate collision detection or Clip Area (when QGraphicsItem::ItemClipsToShape flag is activated)

2. Are you trying to redefine the node size at run time? If yes, have you tried to store a QRect item or a Size Variable? Because you could redefine the size and call prepareGeometryChanges ().

YourItem::YourItem()
{
   _size = 10; // radius
}

QRectF YourItem::boundingRect() const
{
    return QRectF(-_size/2, -_size/2, _size, _size);
}

void YourItem::setSize(qreal size)
{
    _size = size;
    prepareGeometryChange();
}

[Annabela_Cortez]

@KillerSmath I tried, but still the same

[KillerSmath]

@Annabela_Cortez
Did you read my first question ?

How are you overriding these functions: Boundingrect, Shape, Paint ?

We cannot help you without a knowledge of how you are implementing your solution.

[Annabela_Cortez]

QRectF Cvor::boundingRect() const
{
    qreal adjust = 2;
    return QRectF(-10 - adjust, -10 - adjust,23 + adjust, 23 + adjust);
}

QPainterPath Cvor::shape() const
{
    QPainterPath temp;
    temp.addEllipse(-10, -10, 30, 30);
    return temp;
}


void Cvor::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
{

    painter->setPen(Qt::NoPen);
    painter->setBrush(Qt::darkGray);
    painter->drawEllipse(-7, -7, 20, 20);

    QRadialGradient gradient(-3, -3, 10);
    if (option->state & QStyle::State_Sunken) {

        gradient.setCenter(3, 3);
        gradient.setFocalPoint(3, 3);
        gradient.setColorAt(1, QColor(Qt::black).light(120));
        gradient.setColorAt(0, QColor(Qt::darkRed).light(120));
    }
    else {
        gradient.setColorAt(0, Qt::black);
        gradient.setColorAt(1, Qt::darkRed);
    }
    painter->setBrush(gradient);
    painter->setPen(QPen(Qt::black, 0));
    painter->drawEllipse(-10, -10, 20, 20);
}

[KillerSmath]

@Annabela_Cortez
Shape has not directly effect on way which your item is painted. The only exception is when QGraphicsItem::ItemClipsToShape flag is activated like i mentioned in the above response.

If your goal is change the size of this node then say to the code Paint a bigger node instead of change the Shape value. (Replace YOUR_SIZE to your prefered size).

void Cvor::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
{

    painter->setPen(Qt::NoPen);
    painter->setBrush(Qt::darkGray);
    painter->drawEllipse(-YOUR_SIZE/2 - 3, -YOUR_SIZE/2 - 3, YOUR_SIZE, YOUR_SIZE);

    QRadialGradient gradient(-3, -3, 10);
    if (option->state & QStyle::State_Sunken) {

        gradient.setCenter(3, 3);
        gradient.setFocalPoint(3, 3);
        gradient.setColorAt(1, QColor(Qt::black).light(120));
        gradient.setColorAt(0, QColor(Qt::darkRed).light(120));
    }
    else {
        gradient.setColorAt(0, Qt::black);
        gradient.setColorAt(1, Qt::darkRed);
    }
    painter->setBrush(gradient);
    painter->setPen(QPen(Qt::black, 0));
    painter->drawEllipse(-YOUR_SIZE/2, -YOUR_SIZE/2, YOUR_SIZE, YOUR_SIZE);
}