worldtimeclock.cpp Example File

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  #include "worldtimeclock.h"

  #include <QMouseEvent>
  #include <QPainter>
  #include <QTimer>

  WorldTimeClock::WorldTimeClock(QWidget *parent)
      : QWidget(parent)
      , timeZoneOffset(0)

  {
      typedef void (QWidget::*WidgetUpdateSlot)();

      QTimer *timer = new QTimer(this);
      connect(timer, &QTimer::timeout, this, static_cast<WidgetUpdateSlot>(&QWidget::update));
      timer->start(1000);

      setWindowTitle(tr("World Time Clock"));
      resize(200, 200);
  }

  void WorldTimeClock::paintEvent(QPaintEvent *)
  {
      static const QPoint hourHand[3] = {
          QPoint(7, 8),
          QPoint(-7, 8),
          QPoint(0, -40)
      };
      static const QPoint minuteHand[3] = {
          QPoint(7, 8),
          QPoint(-7, 8),
          QPoint(0, -70)
      };

      QColor hourColor(127, 0, 127);
      QColor minuteColor(0, 127, 127, 191);

      int side = qMin(width(), height());
      QTime time = QTime::currentTime();
      time = time.addSecs(timeZoneOffset);

      QPainter painter(this);
      painter.setRenderHint(QPainter::Antialiasing);
      painter.translate(width() / 2, height() / 2);
      painter.scale(side / 200.0, side / 200.0);

      painter.setPen(Qt::NoPen);
      painter.setBrush(hourColor);

      painter.save();
      painter.rotate(30.0 * ((time.hour() + time.minute() / 60.0)));
      painter.drawConvexPolygon(hourHand, 3);
      painter.restore();

      painter.setPen(hourColor);

      for (int i = 0; i < 12; ++i) {
          painter.drawLine(88, 0, 96, 0);
          painter.rotate(30.0);
      }

      painter.setPen(Qt::NoPen);
      painter.setBrush(minuteColor);

      painter.save();
      painter.rotate(6.0 * (time.minute() + time.second() / 60.0));
      painter.drawConvexPolygon(minuteHand, 3);
      painter.restore();

      painter.setPen(minuteColor);

      for (int j = 0; j < 60; ++j) {
          if ((j % 5) != 0)
              painter.drawLine(92, 0, 96, 0);
          painter.rotate(6.0);
      }

      emit updated(time);
  }

  void WorldTimeClock::setTimeZone(int hourOffset)
  {
      timeZoneOffset = qMin(qMax(-12, hourOffset), 12) * 3600;
      update();
  }