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:

Qt Code: 
  1. class SimpleItem : public QGraphicsItem
  2. {
  3. public:
  4.  
  5.     qreal dx, dy;
  6.     qreal subtract_x, subtract_y;
  7.     qreal scale_factor;
  8.     bool test;
  9.     bool highlight_flag;
  10.     qint32 vector_color_type;
  11.     qreal snr;
  12.     qreal scale_max;
  13.     QPen textPen;
  14.     QColor color;
  15.     qreal dmag;
  16.  
  17.     SimpleItem(qreal x_i, qreal y_i, qreal dx_i, qreal dy_i,
  18.                qreal subtract_x_i, qreal subtract_y_i,
  19.                qreal snr_i, bool test_i,
  20.                qreal scale_factor_i, qint32 vector_color_type_i,
  21.                qreal scale_max_i,
  22.                bool highlight_flag_i) {
  23.  
  24.         this->setPos(x_i,y_i);
  25.         this->setAcceptHoverEvents(true);
  26.         this->setBoundingRegionGranularity(1);
  27.  
  28.         dx = dx_i;
  29.         dy = dy_i;
  30.  
  31.         subtract_x = subtract_x_i;
  32.         subtract_y = subtract_y_i;
  33.  
  34.         snr = snr_i;
  35.         test = test_i;
  36.  
  37.         highlight_flag = highlight_flag_i;
  38.  
  39.         scale_factor = scale_factor_i;
  40.         vector_color_type = vector_color_type_i;
  41.  
  42.         scale_max = scale_max_i;
  43.  
  44.         dmag = sqrt(pow(dx-subtract_x,2) + pow(dy-subtract_y,2));
  45.         findColor();
  46.  
  47.     }
  48.  
  49.     QRectF boundingRect() const
  50.     {
  51.         return QRectF(-10,-10,20,20);
  52.     }
  53.  
  54.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
  55.                QWidget *widget)
  56.     {
  57.  
  58.         textPen = QPen(color);
  59.  
  60.         qreal tangent = atan2 ((dy-subtract_y),(dx-subtract_x));
  61.         qreal x2 = (dx-subtract_x)*scale_factor;
  62.         qreal y2 = (dy-subtract_y)*scale_factor;
  63.         qreal pa_x = x2 - (scale_factor*dmag/6) * cos (tangent + M_PI / 7);
  64.         qreal pa_y = y2 - (scale_factor*dmag/6) * sin (tangent + M_PI / 7);
  65.         qreal pb_x = x2 - (scale_factor*dmag/6) * cos (tangent - M_PI / 7);
  66.         qreal pb_y = y2 - (scale_factor*dmag/6) * sin (tangent - M_PI / 7);
  67.  
  68.         QVector<QLineF> points(3);
  69.         points[0] = QLineF(0,0,x2,y2);
  70.         points[1] = QLineF(pa_x,pa_y,x2,y2);
  71.         points[2] = QLineF(pb_x,pb_y,x2,y2);
  72.  
  73.         textPen.setWidth(2);
  74.         textPen.setCapStyle(Qt::RoundCap);
  75.         painter->setPen(textPen);
  76.         painter->drawLines(points);
  77.  
  78.     }
  79.  
  80.  
  81. };
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