QPainter and Qt analog clock example

[Diph]

Hi.

I used this example as a template: http://doc.trolltech.com/4.5/widgets-analogclock.html

What is the correct way to repaint clock if I want to repaint hand when button is pressed? If I use paintEvent() function to initialize clock and other function to repaint hand it doesn't work because painter is not active when button is pressed.

Should I even reimplement paintEvent() function?

I tried something like this but how do I paint this to the widget?

void Clock::init()
{
    static const QPoint hand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -90)
    };
 
    QColor handColor(204, 0, 0);
    QColor lineColor(0, 0, 0);
 
    int side = qMin(width(), height());
 
    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(handColor);
    painter.save();
 
 
    painter.rotate(0.0);
    painter.drawConvexPolygon(hand, 3);
    painter.restore();
 
    painter.setPen(lineColor);
    for (int i=0; i < 12; ++i) {
        painter.drawLine(88, 0, 96, 0);
        painter.rotate(30.0);
    }
}
 
void Clock::btnPressed(qreal angle)
{
    static const QPoint hand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -40)
    };
 
    QColor handColor(204, 0 ,0);
 
    int side = qMin(width(), height());
 
    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(handColor);
    painter.save();
 
    painter.rotate(angle);
    painter.drawConvexPolygon(hand, 3);
    painter.restore();
}

void Clock::init()
{
    static const QPoint hand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -90)
    };

    QColor handColor(204, 0, 0);
    QColor lineColor(0, 0, 0);

    int side = qMin(width(), height());

    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(handColor);
    painter.save();


    painter.rotate(0.0);
    painter.drawConvexPolygon(hand, 3);
    painter.restore();

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

void Clock::btnPressed(qreal angle)
{
    static const QPoint hand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -40)
    };

    QColor handColor(204, 0 ,0);

    int side = qMin(width(), height());

    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(handColor);
    painter.save();

    painter.rotate(angle);
    painter.drawConvexPolygon(hand, 3);
    painter.restore();
}

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[dbzhang800]

from QPainter Class Reference

Warning: When the paintdevice is a widget, QPainter can only be used inside a paintEvent() function or in a function called by paintEvent(); that is unless the Qt::WA_PaintOutsidePaintEvent widget attribute is set. On Mac OS X and Windows, you can only paint in a paintEvent() function regardless of this attribute's setting.

[Diph]

So I just have to call paintEvent and update the variables like angle elsewhere?