Qt Toolkit - forever/forever.cpp example file

# 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.

    /****************************************************************************
    ** $Id: forever.cpp,v 2.4 1998/06/16 11:39:32 warwick Exp $
    **
    ** Copyright (C) 1992-1998 Troll Tech 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 <qlabel.h>
    #include <qwidget.h>
    #include <qpainter.h>
    #include <qapplication.h>
    #include <stdlib.h>                             // defines rand() function

    #define COLORS 120                              // number of colors to use

    //
    // Counter - a widget that displays an unsigned int continuously.
    //

    class Counter : public QLabel
    {
    public:
        Counter( int *number, QWidget *parent=0, const char *name=0 );
    protected:
        void  timerEvent( QTimerEvent * );
    private:
        int  *number;                               // number to display
    };

    //
    // Constructs a Counter
    //

    Counter::Counter( int *c, QWidget *parent, const char *name )
        : QLabel( parent, name )
    {
        number = c;
        setText( "  0  rectangles/second" );
        setAutoResize( TRUE );                      // resize to fit the contents
        startTimer( 1000 );                         // one second timeout
    }

    //
    // Timer event is called every second and prints out number
    //

    void Counter::timerEvent( QTimerEvent * )
    {
        if ( number ) {
            QString s;
            s.sprintf( "%d rectangles/second", *number );
            setText( s );
            *number = 0;
        }
        repaint( TRUE );
    }

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

    class Forever : public QWidget
    {
    public:
        Forever( QWidget *parent=0, const char *name=0 );
    protected:
        void        paintEvent( QPaintEvent * );
        void        timerEvent( QTimerEvent * );
    private:
        Counter    *counter;
        int         rectangles;
        QColor      colors[COLORS];
    };

    //
    // Constructs a Forever widget.
    //

    Forever::Forever( QWidget *parent, const char *name )
        : QWidget( parent, name )
    {
        for (int a=0; a<COLORS; a++) {
            colors[a] = QColor( rand()&255,
                                rand()&255,
                                rand()&255 );
        }
        rectangles = 0;
        counter = new Counter( &rectangles );       // counter in its own window
        counter->show();                            // show the counter
        startTimer( 0 );                            // run continuous timer
    }

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

    void Forever::paintEvent( QPaintEvent * )
    {
        QPainter paint( this );                     // painter object
        paint.setWindow( 0, 0, 1024, 1024 );        // define coordinate system
        paint.setPen( NoPen );                      // do not draw outline
        paint.setBrush( colors[rand() % COLORS]);   // set random brush color
        QPoint p1( rand()&1023, rand()&1023 );      // p1 = top left
        QPoint p2( rand()&1023, rand()&1023 );      // p2 = bottom right
        QRect r( p1, p2 );
        paint.drawRect( r );                        // draw filled rectangle
    }

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

    void Forever::timerEvent( QTimerEvent * )
    {
        repaint( FALSE );                           // repaint, don't erase
        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.show();                              // show widget
        return a.exec();                            // run event loop
    }