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Analog Clock
This example displays an analog clock widget.
//
// Qt Example Widget: AnalogClock (aclock.h)
//
// Definition of AnalogClock widget.
//
// The AnalogClock widget is a stand-alone widget that you may
// freely use in your Qt application (at your own risk!)
// See the widgets/widgets.cpp demo application for how to add
// an AnalogClock to your application.
//
#ifndef ACLOCK_H
#define ACLOCK_H
#include <qwidget.h>
#include <qdatetm.h>
class AnalogClock : public QWidget // analog clock widget
{
Q_OBJECT
public:
AnalogClock( QWidget *parent=0, const char *name=0 );
protected:
void paintEvent( QPaintEvent * );
private slots:
void timeout();
private:
QTime time;
};
#endif // ACLOCK_H
//
// Qt Example Widget: AnalogClock (aclock.cpp)
//
// Implementation of AnalogClock widget.
//
// The AnalogClock widgets uses the sophisticated QTimer object
// to redraw the clock every 5 seconds. The advantage of QTimers
// over standard timer events is that QTimer emits a signal
// when the timer is activated.
// The DigitalClock (dclock) example uses standard timer events.
//
#include "aclock.h"
#include <qtimer.h>
#include <qpainter.h>
//
// Constructs an analog clock widget that uses an internal QTimer.
//
AnalogClock::AnalogClock( QWidget *parent, const char *name )
: QWidget( parent, name )
{
initMetaObject(); // initialize meta object
time = QTime::currentTime(); // get current time
QTimer *internalTimer = new QTimer( this ); // create internal timer
connect( internalTimer, SIGNAL(timeout()), SLOT(timeout()) );
internalTimer->start( 5000 ); // emit signal every 5 seconds
}
//
// The QTimer::timeout() signal is received by this slot.
//
void AnalogClock::timeout()
{
QTime new_time = QTime::currentTime(); // get the current time
if ( new_time.minute() != time.minute() ) // minute has changed
update();
}
//
// The clock is painted using a 1000x1000 square coordinate system.
//
void AnalogClock::paintEvent( QPaintEvent * ) // paint clock
{
if ( !isVisible() ) // is is invisible
return;
time = QTime::currentTime(); // save current time
QPointArray pts;
QPainter paint;
paint.begin( this );
paint.setBrush( foregroundColor() ); // fill with foreground color
QPoint cp = rect().center(); // widget center point
int d = QMIN(width(),height()); // we want a circular clock
QWMatrix matrix; // setup transformation matrix
matrix.translate( cp.x(), cp.y() ); // origin at widget center
matrix.scale( d/1000.0F, d/1000.0F ); // scale coordinate system
float h_angle = 30*(time.hour()%12-3) + time.minute()/2;
matrix.rotate( h_angle ); // rotate to draw hour hand
paint.setWorldMatrix( matrix );
pts.setPoints( 4, -20,0, 0,-20, 300,0, 0,20 );
paint.drawPolygon( pts ); // draw hour hand
matrix.rotate( -h_angle ); // rotate back to zero
float m_angle = (time.minute()-15)*6;
matrix.rotate( m_angle ); // rotate to draw minute hand
paint.setWorldMatrix( matrix );
pts.setPoints( 4, -10,0, 0,-10, 400,0, 0,10 );
paint.drawPolygon( pts ); // draw minute hand
matrix.rotate( -m_angle ); // rotate back to zero
for ( int i=0; i<12; i++ ) { // draw hour lines
paint.setWorldMatrix( matrix );
paint.drawLine( 450,0, 500,0 );
matrix.rotate( 30 );
}
paint.end();
}
Generated at 23:50, 1998/03/16 for Qt version 1.33 by the webmaster at Troll Tech