| Classes - Annotated - Tree - Functions - Home - Structure

# A Rectangle Draw "Benchmark"

This example continuously draws rectangles in a window and has another widget that counts the number of rectangles that are drawn per second.

Header file:

    /****************************************************************************
    ** $Id: qt/examples/forever/forever.h   2.3.2   edited 2001-01-26 $
    **
    ** Definition of something or other
    **
    ** Created : 979899
    **
    ** Copyright (C) 1997 by 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 FOREVER_H
    #define FOREVER_H

    #include <qwidget.h>

    const int numColors = 120;

    class Forever : public QWidget
    {
        Q_OBJECT
    public:
        Forever( QWidget *parent=0, const char *name=0 );
    protected:
        void        timerEvent( QTimerEvent * );
    private slots:
        void        updateCaption();
    private:
        int         rectangles;
        QColor      colors[numColors];
    };

    #endif

Implementation:

    /****************************************************************************
    ** $Id: qt/examples/forever/forever.cpp   2.3.2   edited 2001-10-18 $
    **
    ** 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 <qtimer.h>
    #include <qpainter.h>
    #include <qapplication.h>
    #include <stdlib.h>                             // defines rand() function

    #include "forever.h"

    //
    // Forever - a widget that draws rectangles forever.
    //

    //
    // Constructs a Forever widget.
    //

    Forever::Forever( QWidget *parent, const char *name )
        : QWidget( parent, name )
    {
        for (int a=0; a<numColors; a++) {
            colors[a] = QColor( rand()&255,
                                rand()&255,
                                rand()&255 );
        }
        rectangles = 0;
        startTimer( 0 );                            // run continuous timer
        QTimer * counter = new QTimer( this );
        connect( counter, SIGNAL(timeout()),
                 this, SLOT(updateCaption()) );
        counter->start( 1000 );
    }

    void Forever::updateCaption()
    {
        QString s;
        s.sprintf( "Qt Example - Forever - %d rectangles/second", rectangles );
        rectangles = 0;
        setCaption( s );
    }

    //
    // Handles timer events for the Forever widget.
    //

    void Forever::timerEvent( QTimerEvent * )
    {
        QPainter paint( this );                     // painter object
        paint.setPen( NoPen );                      // do not draw outline
        int w = width();
        int h = height();
        if( w <= 0 || h <= 0 )
            return;
        for ( int i=0; i<100; i++ ) {
            paint.setBrush( colors[i % numColors]); // set random brush color
            QPoint p1( rand()%w, rand()%h );        // p1 = top left
            QPoint p2( rand()%w, rand()%h );        // p2 = bottom right
            QRect r( p1, p2 );
            paint.drawRect( r );                    // draw filled rectangle
            rectangles++;
        }
    }

    //
    // Create and display Forever widget.
    //

    int main( int argc, char **argv )
    {
        QApplication a( argc, argv );               // create application object
        Forever always;                             // create widget
        a.setMainWidget( &always );                 // set as main widget
        always.setCaption("Qt Example - Forever");
        always.show();                              // show widget
        return a.exec();                            // run event loop
    }