[SOLVED] Creating a QSector Class (using Qt and QPaint)

Creating a QSector Class (using Qt and QPaint)

I have created a class name QSector to draw a sector like the following : http://www.philadelphia-reflections.com/images/GDP_Composition_By_Sector_Graph.jpg

QValue is a class with 2 attributes Label (String) and Value (double) the QSector class is composed of 4 attributes and is inherited from QWidget

QPainter (to draw things)
QRect (size and position)
QVector (store all the data of the sector, values and labels)
Double total (compute the total of QValue's Values (to compute percentage later))

here is the code ::

// <c++>
class QValue
{
public:
    QValue(QString a = "", double b = 0): f_label(a), f_value(b) {}

    double value()  {   return f_value; }
    QString label() {   return f_label; }

    void setValue(double a)  {  f_value = a;    }
    void setLabel(QString a) {  f_label = a;    }

    void set(QString a, double b)   {   f_label = a;    f_value = b;    }

private:
    QString f_label;
    double  f_value;
};

class QSector : public QWidget
{
    Q_OBJECT

public:
    QSector(int width, int height, QWidget *parent = 0)
    : QWidget(parent), f_total(0)
    {
        f_rect = new QRect(1, 1, width - 3 , height - 3);
        this->resize(width, height);
        f_paint = new QPainter;
    }

    void paintEvent(QPaintEvent* event = 0)
    {
        QBrush brush;

        brush.setColor(QColor(25, 25, 255));
        brush.setStyle(Qt::SolidPattern);

        int startAngle  = 0;
        int spanAngle   = 0;

        f_paint->begin(this);

        for (int i = 0; i < f_data.size(); i++)
        {
            int c = ( i * 150) % 255;
            brush.setColor(QColor(c, 25, 255));
            f_paint->setBrush(brush);
    // 5760 = 360 * 16 = 100%;  total = 100% => Value * 5760 / total = span angle
            spanAngle = (5760 * f_data[i].value()) / f_total;

            f_paint->drawPie(*f_rect, startAngle, spanAngle);

            startAngle = spanAngle;
        }

        f_paint->end();
    }

    void add(QString Label, double Value)
    {
        f_data.push_back(QValue(Label, Value));
        f_total = f_total + Value;

        update();   //   => paintEvent();
    }

    void add(QValue a)
    {
        f_data.push_back(a);
        f_total = f_total + a.value();

        update();   //   => paintEvent();
    }

signals:

public slots:

private:
    QPainter *f_paint;
    QRect    *f_rect;

    QVector<QValue>  f_data;
    double  f_total;
};

Everything Compile.

the problem comes when I do ::

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    int w = 300;
    int h = 300;

    QSector test(w, h);

    for (int i = 0, n  = 10; i < n; i++)
        test.add("", 10);

    test.show();

    return app.exec();
}

the program only draws the first 2 parts and stops (the sector should have 10 equal parts it has only 2)

I don't understand why it stops drawing. if I cut the sector in two it works fine but starting with 3 it only draws 2 parts

summary of the problem : https://i.sstatic.net/5jyi6.png (image 1, sector divided in 1) (image 2, sector divided in 2) (image 3, sector divided in 3) (image 4, sector divided in 10)

Solution

I suspect that

startAngle = spanAngle;

should be

startAngle += spanAngle;

It looks like you're just repainting over the same pie slice over and over at the same angle.