Question

This example displays an analog clock widget.

---

Header file:

/****************************************************************************
** $Id:  qt/aclock.h   3.0.5   edited Oct 12 2001 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#ifndef ACLOCK_H
#define ACLOCK_H

#include <qwidget.h>
#include <qdatetime.h>


class AnalogClock : public QWidget              // analog clock widget
{
    Q_OBJECT
public:
    AnalogClock( QWidget *parent=0, const char *name=0 );
    void setAutoMask(bool b);

public slots:
    void setTime( const QTime & t );

protected:
    void updateMask();
    void paintEvent( QPaintEvent *);
    void mousePressEvent( QMouseEvent *);
    void mouseMoveEvent( QMouseEvent *);

private slots:
    void drawClock( QPainter* );
    void        timeout();

private:
    QPoint clickPos;
    QTime       time;
};


#endif // ACLOCK_H

---

Implementation:

/****************************************************************************
** $Id:  qt/aclock.cpp   3.0.5   edited Oct 12 2001 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include "aclock.h"
#include <qtimer.h>
#include <qpainter.h>
#include <qbitmap.h>

//
// Constructs an analog clock widget that uses an internal QTimer.
//

AnalogClock::AnalogClock( QWidget *parent, const char *name )
    : QWidget( parent, name )
{
    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
}

void AnalogClock::mousePressEvent( QMouseEvent *e )
{
    if(isTopLevel())
        clickPos = e->pos() + QPoint(geometry().topLeft() - frameGeometry().topLeft());
}

void AnalogClock::mouseMoveEvent( QMouseEvent *e )
{
    if(isTopLevel())
        move( e->globalPos() - clickPos );
}

void AnalogClock::setTime( const QTime & t )
{
    time = t;
    timeout();
}

//
// The QTimer::timeout() signal is received by this slot.
//

void AnalogClock::timeout()
{
    QTime new_time = QTime::currentTime();      // get the current time
    time = time.addSecs( 5 );
    if ( new_time.minute() != time.minute() ) { // minute has changed
        if (autoMask())
            updateMask();
        else
            update();
    }
}


void AnalogClock::paintEvent( QPaintEvent * )
{
    if ( autoMask() )
        return;
    QPainter paint( this );
    paint.setBrush( colorGroup().foreground() );
    drawClock( &paint );
}

// If the clock is transparent, we use updateMask()
// instead of paintEvent()

void AnalogClock::updateMask()  // paint clock mask
{
    QBitmap bm( size() );
    bm.fill( color0 );                  //transparent

    QPainter paint;
    paint.begin( &bm, this );
    paint.setBrush( color1 );           // use non-transparent color
    paint.setPen( color1 );

    drawClock( &paint );

    paint.end();
    setMask( bm );
}

//
// The clock is painted using a 1000x1000 square coordinate system, in
// the a centered square, as big as possible.  The painter's pen and
// brush colors are used.
//
void AnalogClock::drawClock( QPainter *paint )
{
    paint->save();

    paint->setWindow( -500,-500, 1000,1000 );

    QRect v = paint->viewport();
    int d = QMIN( v.width(), v.height() );
    paint->setViewport( v.left() + (v.width()-d)/2,
                        v.top() + (v.height()-d)/2, d, d );

    // time = QTime::currentTime();
    QPointArray pts;

    paint->save();
    paint->rotate( 30*(time.hour()%12-3) + time.minute()/2 );
    pts.setPoints( 4, -20,0,  0,-20, 300,0, 0,20 );
    paint->drawConvexPolygon( pts );
    paint->restore();

    paint->save();
    paint->rotate( (time.minute()-15)*6 );
    pts.setPoints( 4, -10,0, 0,-10, 400,0, 0,10 );
    paint->drawConvexPolygon( pts );
    paint->restore();

    for ( int i=0; i<12; i++ ) {
        paint->drawLine( 440,0, 460,0 );
        paint->rotate( 30 );
    }

    paint->restore();
}


void AnalogClock::setAutoMask(bool b)
{
    if (b)
        setBackgroundMode( PaletteForeground );
    else
        setBackgroundMode( PaletteBackground );
    QWidget::setAutoMask(b);
}

---

Main:

/****************************************************************************
** $Id:  qt/main.cpp   3.0.5   edited Oct 12 2001 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include "aclock.h"
#include <qapplication.h>


int main( int argc, char **argv )
{
    QApplication a( argc, argv );
    AnalogClock *clock = new AnalogClock;
    if ( argc == 2 && strcmp( argv[1], "-transparent" ) == 0 )
        clock->setAutoMask( TRUE );
    clock->resize( 100, 100 );
    a.setMainWidget( clock );
    clock->setCaption("Qt Example - Analog Clock");
    clock->show();
    int result = a.exec();
    delete clock;
    return result;
}

See also Examples.