Using boundingRegion instead of boundingRect

[lynchkp]

Hello,

I'm trying to implement some hovering commands on a quiver plot I've made using a QGraphicsItem. I would like the arrows to be highlighted when the mouse is over them, but I'm running into issues because a rectangular boundingRect() causes overlap sometimes. Because of this I'd like to use boundingRegion() with a high granularity, however I am unsure how to implement this in my class. I've looked all around for examples of its use but I havent found too many. How is boundingRegion() used instead of boundingRect? Thanks for all the help!!

Here is a snippet of the code I have for the items:

class SimpleItem : public QGraphicsItem
{
public:
 
    qreal dx, dy;
    qreal subtract_x, subtract_y;
    qreal scale_factor;
    bool test;
    bool highlight_flag;
    qint32 vector_color_type;
    qreal snr;
    qreal scale_max;
    QPen textPen;
    QColor color;
    qreal dmag;
 
    SimpleItem(qreal x_i, qreal y_i, qreal dx_i, qreal dy_i,
               qreal subtract_x_i, qreal subtract_y_i,
               qreal snr_i, bool test_i,
               qreal scale_factor_i, qint32 vector_color_type_i,
               qreal scale_max_i,
               bool highlight_flag_i) {
 
        this->setPos(x_i,y_i);
        this->setAcceptHoverEvents(true);
        this->setBoundingRegionGranularity(1);
 
        dx = dx_i;
        dy = dy_i;
 
        subtract_x = subtract_x_i;
        subtract_y = subtract_y_i;
 
        snr = snr_i;
        test = test_i;
 
        highlight_flag = highlight_flag_i;
 
        scale_factor = scale_factor_i;
        vector_color_type = vector_color_type_i;
 
        scale_max = scale_max_i;
 
        dmag = sqrt(pow(dx-subtract_x,2) + pow(dy-subtract_y,2));
        findColor();
 
    }
 
    QRectF boundingRect() const
    {
        return QRectF(-10,-10,20,20);
    }
 
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
               QWidget *widget)
    {
 
        textPen = QPen(color);
 
        qreal tangent = atan2 ((dy-subtract_y),(dx-subtract_x));
        qreal x2 = (dx-subtract_x)*scale_factor;
        qreal y2 = (dy-subtract_y)*scale_factor;
        qreal pa_x = x2 - (scale_factor*dmag/6) * cos (tangent + M_PI / 7);
        qreal pa_y = y2 - (scale_factor*dmag/6) * sin (tangent + M_PI / 7);
        qreal pb_x = x2 - (scale_factor*dmag/6) * cos (tangent - M_PI / 7);
        qreal pb_y = y2 - (scale_factor*dmag/6) * sin (tangent - M_PI / 7);
 
        QVector<QLineF> points(3);
        points[0] = QLineF(0,0,x2,y2);
        points[1] = QLineF(pa_x,pa_y,x2,y2);
        points[2] = QLineF(pb_x,pb_y,x2,y2);
 
        textPen.setWidth(2);
        textPen.setCapStyle(Qt::RoundCap);
        painter->setPen(textPen);
        painter->drawLines(points);
 
    }
 
 
};

class SimpleItem : public QGraphicsItem
{
public:

    qreal dx, dy;
    qreal subtract_x, subtract_y;
    qreal scale_factor;
    bool test;
    bool highlight_flag;
    qint32 vector_color_type;
    qreal snr;
    qreal scale_max;
    QPen textPen;
    QColor color;
    qreal dmag;

    SimpleItem(qreal x_i, qreal y_i, qreal dx_i, qreal dy_i,
               qreal subtract_x_i, qreal subtract_y_i,
               qreal snr_i, bool test_i,
               qreal scale_factor_i, qint32 vector_color_type_i,
               qreal scale_max_i,
               bool highlight_flag_i) {

        this->setPos(x_i,y_i);
        this->setAcceptHoverEvents(true);
        this->setBoundingRegionGranularity(1);

        dx = dx_i;
        dy = dy_i;

        subtract_x = subtract_x_i;
        subtract_y = subtract_y_i;

        snr = snr_i;
        test = test_i;

        highlight_flag = highlight_flag_i;

        scale_factor = scale_factor_i;
        vector_color_type = vector_color_type_i;

        scale_max = scale_max_i;

        dmag = sqrt(pow(dx-subtract_x,2) + pow(dy-subtract_y,2));
        findColor();

    }

    QRectF boundingRect() const
    {
        return QRectF(-10,-10,20,20);
    }

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

        textPen = QPen(color);

        qreal tangent = atan2 ((dy-subtract_y),(dx-subtract_x));
        qreal x2 = (dx-subtract_x)*scale_factor;
        qreal y2 = (dy-subtract_y)*scale_factor;
        qreal pa_x = x2 - (scale_factor*dmag/6) * cos (tangent + M_PI / 7);
        qreal pa_y = y2 - (scale_factor*dmag/6) * sin (tangent + M_PI / 7);
        qreal pb_x = x2 - (scale_factor*dmag/6) * cos (tangent - M_PI / 7);
        qreal pb_y = y2 - (scale_factor*dmag/6) * sin (tangent - M_PI / 7);

        QVector<QLineF> points(3);
        points[0] = QLineF(0,0,x2,y2);
        points[1] = QLineF(pa_x,pa_y,x2,y2);
        points[2] = QLineF(pb_x,pb_y,x2,y2);

        textPen.setWidth(2);
        textPen.setCapStyle(Qt::RoundCap);
        painter->setPen(textPen);
        painter->drawLines(points);

    }


};

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[wysota]

Collisions are checked against shape() and not boundingRect(). Whatever you do with the granularity, it will not change anything until you reimplement shape() for your item.