http://stackoverflow.com/questions/17118967/drawarc-are-not-drawen-correctly-qt-c

window.cpp

#include "window.h"
#include <QKeyEvent>
#include <QtCore/QRegExp>
#include <QtGui/QMessageBox>
#include <QGraphicsTextItem>
#include <QFont>
#include <QTransform>
#include <QTimeLine>
#include <QGraphicsItemAnimation>
#include <QDebug>
#include <QPainter>
#include <qmath.h>

QPointF my_find_ellipse_coords(const QRectF &r, qreal angle) {
  QPainterPath path;
  path.arcMoveTo(r, angle);
  return path.currentPosition();
}


class Circle: public QWidget {
public:
  int steps, value, maxValue;
  QPen pen;
  Circle(QWidget *parent): QWidget(parent)
  {
  }
  
  void setSteps(int i)
  {
    this->steps = i;
  }
  
  void setValue(int i)
  {
    this->value = i;
    repaint();
  }
  
  void setMaxValue(int i)
  {
    this->maxValue = i;
  }
  
  void paintEvent(QPaintEvent *)
  {
    QPainter painter(this);
    
    painter.setRenderHint(QPainter::Antialiasing, true);
    painter.setPen(this->pen);
    
    int stepSize = 360/this->steps;
    float devideValue = ((100.0/this->maxValue)*this->value)/100.0;
    int roundedSize = this->steps*devideValue;
    
    qDebug() << "steps: " << steps;
    qDebug() << "stepSize: " << stepSize;
    qDebug() << "devideValue: " << devideValue;
    qDebug() << "roundedSize: " << roundedSize;
    qDebug() << "stepSize*roundedSize: " << (stepSize*roundedSize);
    //qDebug() << "angel: " << angle;
    
    double angle = -1.0*(stepSize*roundedSize);
    QPainterPath path;
    QRectF outer_rect(0, 0, width(), height());
    QRectF inner_rect(pen.width(), pen.width(), width() - pen.width() * 2, height() - pen.width() * 2);
    path.arcMoveTo(outer_rect, 0);
    path.arcTo(outer_rect, 0, angle);
    path.lineTo(my_find_ellipse_coords(inner_rect, angle));
    path.arcTo(inner_rect, angle, -angle);
    path.lineTo(my_find_ellipse_coords(outer_rect, 0));
    path.closeSubpath();
    painter.fillPath(path, QBrush(pen.color()));
  }
  
  void setPen(QPen pen)
  {
    this->pen = pen;
  }
};


Window::Window(QWidget *parent, Qt::WFlags flags)
  : QMainWindow(parent, flags)
{
  ui.setupUi(this);
  
  //QRect mainWidgetGeo = geometry();
  int w = 450; //mainWidgetGeo.width();
  int h = 450; // mainWidgetGeo.height();
  
  QPen secondPen(Qt::yellow);
  secondPen.setWidth(50);
  secondPen.setCapStyle(Qt::FlatCap);
  
  Circle* circleSeconds = new Circle(this->centralWidget());
  circleSeconds->setMaxValue(60);
  circleSeconds->setValue(55);
  circleSeconds->setSteps(60);
  circleSeconds->setMouseTracking(true);
  circleSeconds->setPen(secondPen);
  circleSeconds->setGeometry(QRect(0, 0, w, h));
  
  QPen minutePen(Qt::red);
  minutePen.setWidth(100);
  minutePen.setCapStyle(Qt::FlatCap);
  
  Circle* circleMinutes = new Circle(this->centralWidget());
  circleMinutes->setMaxValue(60);
  circleMinutes->setValue(50);
  circleMinutes->setSteps(60);
  circleMinutes->setMouseTracking(true);
  circleMinutes->setPen(minutePen);
  circleMinutes->setGeometry(QRect(50, 50, w-100, h-100));
  
  QPen hourPen(Qt::green);
  hourPen.setWidth(50);
  hourPen.setCapStyle(Qt::FlatCap);
  
  Circle* circleHours = new Circle(this->centralWidget());
  circleHours->setMaxValue(12);
  circleHours->setValue(45);
  circleHours->setSteps(12);
  circleHours->setMouseTracking(true);
  circleHours->setPen(hourPen);
  circleHours->setGeometry(QRect(150, 150, w-300, h-300));
  resize(300, 300);
}

Window::~Window() {
  
}