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# view.cpp Example File
graphicsview/portedasteroids/view.cpp

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     ** Copyright (C) 2006-2008 Trolltech ASA. All rights reserved.
     **
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     /*
      * KAsteroids - Copyright (c) Martin R. Jones 1997
      *
      * Part of the KDE project
      */

     #include <stdlib.h>
     #include <math.h>
     #include <qapplication.h>
     #include <qnamespace.h>
     #include <q3accel.h>
     #include <qmessagebox.h>
     #include <q3scrollview.h>
     #include <qdir.h>
     #include <QGraphicsItem>
     //Added by qt3to4:
     #include <QTimerEvent>
     #include <QPixmap>
     #include <QResizeEvent>
     #include <QShowEvent>

     #include "view.h"

     #define IMG_BACKGROUND ":/trolltech/examples/graphicsview/portedasteroids/bg.png"

     #define REFRESH_DELAY           33
     #define SHIP_SPEED              0.3
     #define MISSILE_SPEED           10.0
     #define SHIP_STEPS              64
     #define ROTATE_RATE             2
     #define SHIELD_ON_COST          1
     #define SHIELD_HIT_COST         30
     #define BRAKE_ON_COST           4

     #define MAX_ROCK_SPEED          2.5
     #define MAX_POWERUP_SPEED       1.5
     #define MAX_SHIP_SPEED          12
     #define MAX_BRAKES              5
     #define MAX_SHIELDS             5
     #define MAX_FIREPOWER           5

     #define TEXT_SPEED              4

     #define PI_X_2                  6.283185307
     #ifndef M_PI
     #define M_PI 3.141592654
     #endif

     static struct
     {
         int id;
         const char *path;
         int frames;
     }
     kas_animations [] =
     {
         { ID_ROCK_LARGE,       "rock1/rock1%1.png",       32 },
         { ID_ROCK_MEDIUM,      "rock2/rock2%1.png",       32 },
         { ID_ROCK_SMALL,       "rock3/rock3%1.png",       32 },
         { ID_SHIP,             "ship/ship%1.png",         32 },
         { ID_MISSILE,          "missile/missile.png",      1 },
         { ID_BIT,              "bits/bits%1.png",         16 },
         { ID_EXHAUST,          "exhaust/exhaust.png",      1 },
         { ID_ENERGY_POWERUP,   "powerups/energy.png",      1 },
     //    { ID_TELEPORT_POWERUP, "powerups/teleport%1.png", 12 },
         { ID_BRAKE_POWERUP,    "powerups/brake.png",       1 },
         { ID_SHIELD_POWERUP,   "powerups/shield.png",      1 },
         { ID_SHOOT_POWERUP,    "powerups/shoot.png",       1 },
         { ID_SHIELD,           "shield/shield%1.png",      6 },
         { 0,                   0,                          0 }
     };

     KAsteroidsView::KAsteroidsView( QWidget *parent, const char *name )
         : QWidget( parent, name ),
           field(0, 0, 640, 440),
           view(&field,this)
     {
         view.setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
         view.setHorizontalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
         view.setCacheMode(QGraphicsView::CacheBackground);
         view.setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);
         view.setOptimizationFlag(QGraphicsView::DontClipPainter);
         view.viewport()->setFocusProxy( this );
         rocks.setAutoDelete( TRUE );
         missiles.setAutoDelete( TRUE );
         bits.setAutoDelete( TRUE );
         powerups.setAutoDelete( TRUE );
         exhaust.setAutoDelete( TRUE );

         QPixmap pm( IMG_BACKGROUND );
         field.setBackgroundBrush( pm );

         textSprite = new QGraphicsTextItem( 0, &field );
         QFont font( "helvetica", 18 );
         textSprite->setFont( font );

         shield = 0;
         shieldOn = FALSE;
         refreshRate = REFRESH_DELAY;

         initialized = readSprites();

         shieldTimer = new QTimer( this );
         connect( shieldTimer, SIGNAL(timeout()), this, SLOT(hideShield()) );
         mTimerId = -1;

         shipPower = MAX_POWER_LEVEL;
         vitalsChanged = TRUE;
         can_destroy_powerups = FALSE;

         mPaused = TRUE;

         if ( !initialized ) {
             textSprite->setHtml( tr("<font color=red>Error: Cannot read sprite images</font>") );
             textSprite->setPos( (field.width()-textSprite->boundingRect().width()) / 2,
                                 (field.height()-textSprite->boundingRect().height()) / 2 );
         }
     }

     // - - -

     KAsteroidsView::~KAsteroidsView()
     {
     }

     // - - -

     void KAsteroidsView::reset()
     {
         if ( !initialized )
             return;
         rocks.clear();
         missiles.clear();
         bits.clear();
         powerups.clear();
         exhaust.clear();

         shotsFired = 0;
         shotsHit = 0;

         rockSpeed = 1.0;
         powerupSpeed = 1.0;
         mFrameNum = 0;
         mPaused = FALSE;

         ship->hide();
         shield->hide();
     /*
         if ( mTimerId >= 0 ) {
             killTimer( mTimerId );
             mTimerId = -1;
         }
     */
     }

     // - --

     void KAsteroidsView::newGame()
     {
         if ( !initialized )
             return;
         if ( shieldOn )
         {
           shield->hide();
           shieldOn = FALSE;
         }
         reset();
         if ( mTimerId < 0 )
             mTimerId = startTimer( REFRESH_DELAY );
         emit updateVitals();
     }

     // - - -

     void KAsteroidsView::endGame()
     {
     }

     void KAsteroidsView::pause( bool p )
     {
         if ( !initialized )
             return;
         if ( !mPaused && p ) {
             if ( mTimerId >= 0 ) {
                 killTimer( mTimerId );
                 mTimerId = -1;
             }
         } else if ( mPaused && !p )
             mTimerId = startTimer( REFRESH_DELAY );
         mPaused = p;
     }

     // - - -

     void KAsteroidsView::newShip()
     {
         if ( !initialized )
             return;
         ship->setPos( width()/2, height()/2 );
         ship->setFrame( 0 );
         shield->setPos( width()/2, height()/2 );
         shield->setFrame( 0 );
         ship->setVelocity( 0.0, 0.0 );
         shipDx = 0;
         shipDy = 0;
         shipAngle = 0;
         rotateL = FALSE;
         rotateR = FALSE;
         thrustShip = FALSE;
         shootShip = FALSE;
         brakeShip = FALSE;
         teleportShip = FALSE;
         shieldOn = TRUE;
         shootDelay = 0;
         shipPower = MAX_POWER_LEVEL;
         rotateRate = ROTATE_RATE;
         rotateSlow = 0;

         mBrakeCount = 0;
         mTeleportCount = 0;
         mShootCount = 0;

         ship->show();
         shield->show();
         mShieldCount = 1;   // just in case the ship appears on a rock.
         shieldTimer->start( 1000, TRUE );
     }

     void KAsteroidsView::setShield( bool s )
     {
         if ( !initialized )
             return;
         if ( shieldTimer->isActive() && !s ) {
             shieldTimer->stop();
             hideShield();
         } else {
             shieldOn = s && mShieldCount;
         }
     }

     void KAsteroidsView::brake( bool b )
     {
         if ( !initialized )
             return;
         if ( mBrakeCount )
         {
             if ( brakeShip && !b )
             {
                 rotateL = FALSE;
                 rotateR = FALSE;
                 thrustShip = FALSE;
                 rotateRate = ROTATE_RATE;
             }

             brakeShip = b;
         }
     }

     // - - -

     bool KAsteroidsView::readSprites()
     {
         QString sprites_prefix = ":/trolltech/examples/graphicsview/portedasteroids/sprites/";

         int i = 0;
         while ( kas_animations[i].id )
         {
             QList<QPixmap> anim;
             QString wildcard = sprites_prefix + kas_animations[i].path;
             wildcard.replace("%1", "*");
             QFileInfo fi(wildcard);
             foreach (QString entry, QDir(fi.path(), fi.fileName()).entryList())
                 anim << QPixmap(fi.path() + "/" + entry);
             animation.insert( kas_animations[i].id, anim );
             i++;
         }

         ship = new AnimatedPixmapItem( animation[ID_SHIP], &field );
         ship->hide();

         shield = new KShield( animation[ID_SHIELD], &field );
         shield->hide();

         return (!ship->image(0).isNull() && !shield->image(0).isNull());
     }

     // - - -

     void KAsteroidsView::addRocks( int num )
     {
         if ( !initialized )
             return;
         for ( int i = 0; i < num; i++ )
         {
             KRock *rock = new KRock( animation[ID_ROCK_LARGE], &field,
                                  ID_ROCK_LARGE, randInt(2), randInt(2) ? -1 : 1 );
             double dx = (2.0 - randDouble()*4.0) * rockSpeed;
             double dy = (2.0 - randDouble()*4.0) * rockSpeed;
             rock->setVelocity( dx, dy );
             rock->setFrame( randInt( rock->frameCount() ) );
             if ( dx > 0 )
             {
                 if ( dy > 0 )
                     rock->setPos( 5, 5 );
                 else
                     rock->setPos( 5, field.height() - 25 );
                 rock->setFrame( 0 );
             }
             else
             {
                 if ( dy > 0 )
                     rock->setPos( field.width() - 25, 5 );
                 else
                     rock->setPos( field.width() - 25, field.height() - 25 );
                 rock->setFrame( 0 );
             }
             rock->show();
             rocks.append( rock );
         }
     }

     // - - -

     void KAsteroidsView::showText( const QString &text, const QColor &color, bool scroll )
     {
         if ( !initialized )
             return;
         textSprite->setHtml( QString("<font color=#%1%2%3>%4</font>")
                              .arg(color.red(), 2, 16, QLatin1Char('0'))
                              .arg(color.green(), 2, 16, QLatin1Char('0'))
                              .arg(color.blue(), 2, 16, QLatin1Char('0'))
                              .arg(text) );
         Q_UNUSED(color);
         // ### Porting: no such thing textSprite->setColor( color );

         if ( scroll ) {
             textSprite->setPos( (field.width()-textSprite->boundingRect().width()) / 2,
                                 -textSprite->boundingRect().height() );
             textDy = TEXT_SPEED;
         } else {
             textSprite->setPos( (field.width()-textSprite->boundingRect().width()) / 2,
                                 (field.height()-textSprite->boundingRect().height()) / 2 );
             textDy = 0;
         }
         textSprite->show();
     }

     // - - -

     void KAsteroidsView::hideText()
     {
         textDy = -TEXT_SPEED;
     }

     // - - -

     void KAsteroidsView::resizeEvent(QResizeEvent* event)
     {
         QWidget::resizeEvent(event);
         field.setSceneRect(0, 0, width()-4, height()-4);
         view.resize(width(),height());
     }

     // - - -

     void KAsteroidsView::timerEvent( QTimerEvent * )
     {
         field.advance();

         AnimatedPixmapItem *rock;

         // move rocks forward
         for ( rock = rocks.first(); rock; rock = rocks.next() ) {
             ((KRock *)rock)->nextFrame();
             wrapSprite( rock );
         }

         wrapSprite( ship );

         // check for missile collision with rocks.
         processMissiles();

         // these are generated when a ship explodes
         for ( KBit *bit = bits.first(); bit; bit = bits.next() )
         {
             if ( bit->expired() )
             {
                 bits.removeRef( bit );
             }
             else
             {
                 bit->growOlder();
                 bit->setFrame( ( bit->frame()+1 ) % bit->frameCount() );
             }
         }

         for ( KExhaust *e = exhaust.first(); e; e = exhaust.next() )
             exhaust.removeRef( e );

         // move / rotate ship.
         // check for collision with a rock.
         processShip();

         // move powerups and check for collision with player and missiles
         processPowerups();

         if ( textSprite->isVisible() )
         {
             if ( textDy < 0 &&
                  textSprite->boundingRect().y() <= -textSprite->boundingRect().height() ) {
                 textSprite->hide();
             } else {
                 textSprite->moveBy( 0, textDy );
             }

             if ( textSprite->sceneBoundingRect().y() > (field.height()-textSprite->boundingRect().height())/2 )
                 textDy = 0;
         }

         if ( vitalsChanged && !(mFrameNum % 10) ) {
             emit updateVitals();
             vitalsChanged = FALSE;
         }

         mFrameNum++;
     }

     void KAsteroidsView::wrapSprite( QGraphicsItem *s )
     {
         int x = int(s->x() + s->boundingRect().width() / 2);
         int y = int(s->y() + s->boundingRect().height() / 2);

         if ( x > field.width() )
             s->setPos( s->x() - field.width(), s->y() );
         else if ( x < 0 )
             s->setPos( field.width() + s->x(), s->y() );

         if ( y > field.height() )
             s->setPos( s->x(), s->y() - field.height() );
         else if ( y < 0 )
             s->setPos( s->x(), field.height() + s->y() );
     }

     // - - -

     void KAsteroidsView::rockHit( AnimatedPixmapItem *hit )
     {
         KPowerup *nPup = 0;
         int rnd = int(randDouble()*30.0) % 30;
         switch( rnd )
         {
           case 4:
           case 5:
               nPup = new KPowerup( animation[ID_ENERGY_POWERUP], &field,
                                    ID_ENERGY_POWERUP );
             break;
           case 10:
     //        nPup = new KPowerup( animation[ID_TELEPORT_POWERUP], &field,
     //                             ID_TELEPORT_POWERUP );
             break;
           case 15:
               nPup = new KPowerup( animation[ID_BRAKE_POWERUP], &field,
                                    ID_BRAKE_POWERUP );
             break;
           case 20:
               nPup = new KPowerup( animation[ID_SHIELD_POWERUP], &field,
                                    ID_SHIELD_POWERUP );
             break;
           case 24:
           case 25:
               nPup = new KPowerup( animation[ID_SHOOT_POWERUP], &field,
                                    ID_SHOOT_POWERUP );
             break;
         }
         if ( nPup )
         {
             double r = 0.5 - randDouble();
             nPup->setPos( hit->x(), hit->y() );
             nPup->setFrame( 0 );
             nPup->setVelocity( hit->xVelocity() + r, hit->yVelocity() + r );
             powerups.append( nPup );
         }

         if ( hit->type() == ID_ROCK_LARGE || hit->type() == ID_ROCK_MEDIUM )
         {
             // break into smaller rocks
             double addx[4] = { 1.0, 1.0, -1.0, -1.0 };
             double addy[4] = { -1.0, 1.0, -1.0, 1.0 };

             double dx = hit->xVelocity();
             double dy = hit->yVelocity();

             double maxRockSpeed = MAX_ROCK_SPEED * rockSpeed;
             if ( dx > maxRockSpeed )
                 dx = maxRockSpeed;
             else if ( dx < -maxRockSpeed )
                 dx = -maxRockSpeed;
             if ( dy > maxRockSpeed )
                 dy = maxRockSpeed;
             else if ( dy < -maxRockSpeed )
                 dy = -maxRockSpeed;

             AnimatedPixmapItem *nrock;

             for ( int i = 0; i < 4; i++ )
             {
                 double r = rockSpeed/2 - randDouble()*rockSpeed;
                 if ( hit->type() == ID_ROCK_LARGE )
                 {
                     nrock = new KRock( animation[ID_ROCK_MEDIUM], &field,
                                        ID_ROCK_MEDIUM, randInt(2), randInt(2) ? -1 : 1 );
                     emit rockHit( 0 );
                 }
                 else
                 {
                     nrock = new KRock( animation[ID_ROCK_SMALL], &field,
                                        ID_ROCK_SMALL, randInt(2), randInt(2) ? -1 : 1 );
                     emit rockHit( 1 );
                 }

                 nrock->setPos( hit->x(), hit->y() );
                 nrock->setFrame( 0 );
                 nrock->setVelocity( dx+addx[i]*rockSpeed+r, dy+addy[i]*rockSpeed+r );
                 nrock->setFrame( randInt( nrock->frameCount() ) );
                 rocks.append( nrock );
             }
         }
         else if ( hit->type() == ID_ROCK_SMALL )
             emit rockHit( 2 );
         rocks.removeRef( hit );
         if ( rocks.count() == 0 )
             emit rocksRemoved();
     }

     void KAsteroidsView::reducePower( int val )
     {
         shipPower -= val;
         if ( shipPower <= 0 )
         {
             shipPower = 0;
             thrustShip = FALSE;
             if ( shieldOn )
             {
                 shieldOn = FALSE;
                 shield->hide();
             }
         }
         vitalsChanged = TRUE;
     }

     void KAsteroidsView::addExhaust( double x, double y, double dx,
                                      double dy, int count )
     {
         for ( int i = 0; i < count; i++ )
         {
             KExhaust *e = new KExhaust( animation[ID_EXHAUST], &field );
             e->setPos( x + 2 - randDouble()*4, y + 2 - randDouble()*4 );
             e->setVelocity( dx, dy );
             exhaust.append( e );
         }
     }

     void KAsteroidsView::processMissiles()
     {
         KMissile *missile;

         // if a missile has hit a rock, remove missile and break rock into smaller
         // rocks or remove completely.
         Q3PtrListIterator<KMissile> it(missiles);

         for ( ; it.current(); ++it )
         {
             missile = it.current();
             missile->growOlder();

             if ( missile->expired() )
             {
                 missiles.removeRef( missile );
                 continue;
             }

             wrapSprite( missile );

             QList<QGraphicsItem *> hits = missile->collidingItems();
             QList<QGraphicsItem *>::Iterator hit;
             for ( hit = hits.begin(); hit != hits.end(); ++hit )
             {
                 if ( (*hit)->type() >= ID_ROCK_LARGE &&
                      (*hit)->type() <= ID_ROCK_SMALL )
                 {
                     shotsHit++;
                     rockHit( static_cast<AnimatedPixmapItem *>(*hit) );
                     missiles.removeRef( missile );
                     break;
                 }
             }
         }
     }

     // - - -

     void KAsteroidsView::processShip()
     {
         if ( ship->isVisible() )
         {
             if ( shieldOn )
             {
                 shield->show();
                 reducePower( SHIELD_ON_COST );
                 static int sf = 0;
                 sf++;

                 if ( sf % 2 )
                     shield->setFrame( (shield->frame()+1) % shield->frameCount() );
                 shield->setPos( ship->x() - 9, ship->y() - 9 );

                 QList<QGraphicsItem *> hits = shield->collidingItems();
                 QList<QGraphicsItem *>::Iterator it;
                 for ( it = hits.begin(); it != hits.end(); ++it )
                 {
                     if ( (*it)->type() >= ID_ROCK_LARGE &&
                          (*it)->type() <= ID_ROCK_SMALL )
                     {
                         int factor;
                         switch ( (*it)->type() )
                         {
                             case ID_ROCK_LARGE:
                                 factor = 3;
                                 break;

                             case ID_ROCK_MEDIUM:
                                 factor = 2;
                                 break;

                             default:
                                 factor = 1;
                         }

                         if ( factor > mShieldCount )
                         {
                             // shield not strong enough
                             shieldOn = FALSE;
                             break;
                         }
                         rockHit( static_cast<AnimatedPixmapItem *>(*it) );
                         // the more shields we have the less costly
                         reducePower( factor * (SHIELD_HIT_COST - mShieldCount*2) );
                     }
                 }
             }

             if ( !shieldOn )
             {
                 shield->hide();
                 QList<QGraphicsItem *> hits = ship->collidingItems();
                 QList<QGraphicsItem *>::Iterator it;
                 for ( it = hits.begin(); it != hits.end(); ++it )
                 {
                     if ( (*it)->type() >= ID_ROCK_LARGE &&
                          (*it)->type() <= ID_ROCK_SMALL )
                     {
                         KBit *bit;
                         for ( int i = 0; i < 12; i++ )
                         {
                           bit = new KBit( animation[ID_BIT], &field );
                           bit->setPos( ship->x() + 5 - randDouble() * 10,
                                        ship->y() + 5 - randDouble() * 10 );
                           bit->setFrame( randInt(bit->frameCount()) );
                           bit->setVelocity( 1-randDouble()*2,
                                             1-randDouble()*2 );
                           bit->setDeath( 60 + randInt(60) );
                           bits.append( bit );
                         }
                         ship->hide();
                         shield->hide();
                         emit shipKilled();
                         break;
                     }
                 }
             }

             if ( rotateSlow )
                 rotateSlow--;

             if ( rotateL )
             {
                 shipAngle -= rotateSlow ? 1 : rotateRate;
                 if ( shipAngle < 0 )
                     shipAngle += SHIP_STEPS;
             }

             if ( rotateR )
             {
                 shipAngle += rotateSlow ? 1 : rotateRate;
                 if ( shipAngle >= SHIP_STEPS )
                     shipAngle -= SHIP_STEPS;
             }

             double angle = shipAngle * PI_X_2 / SHIP_STEPS;
             double cosangle = cos( angle );
             double sinangle = sin( angle );

             if ( brakeShip )
             {
                 thrustShip = FALSE;
                 rotateL = FALSE;
                 rotateR = FALSE;
                 rotateRate = ROTATE_RATE;
                 if ( fabs(shipDx) < 2.5 && fabs(shipDy) < 2.5 )
                 {
                     shipDx = 0.0;
                     shipDy = 0.0;
                     ship->setVelocity( shipDx, shipDy );
                     brakeShip = FALSE;
                 }
                 else
                 {
                     double motionAngle = atan2( -shipDy, -shipDx );
                     if ( angle > M_PI )
                         angle -= PI_X_2;
                     double angleDiff = angle - motionAngle;
                     if ( angleDiff > M_PI )
                         angleDiff = PI_X_2 - angleDiff;
                     else if ( angleDiff < -M_PI )
                         angleDiff = PI_X_2 + angleDiff;
                     double fdiff = fabs( angleDiff );
                     if ( fdiff > 0.08 )
                     {
                         if ( angleDiff > 0 )
                             rotateL = TRUE;
                         else if ( angleDiff < 0 )
                             rotateR = TRUE;
                         if ( fdiff > 0.6 )
                             rotateRate = mBrakeCount + 1;
                         else if ( fdiff > 0.4 )
                             rotateRate = 2;
                         else
                             rotateRate = 1;

                         if ( rotateRate > 5 )
                             rotateRate = 5;
                     }
                     else if ( fabs(shipDx) > 1 || fabs(shipDy) > 1 )
                     {
                         thrustShip = TRUE;
                         // we'll make braking a bit faster
                         shipDx += cosangle/6 * (mBrakeCount - 1);
                         shipDy += sinangle/6 * (mBrakeCount - 1);
                         reducePower( BRAKE_ON_COST );
                         addExhaust( ship->x() + 20 - cosangle*22,
                                     ship->y() + 20 - sinangle*22,
                                     shipDx-cosangle, shipDy-sinangle,
                                     mBrakeCount+1 );
                     }
                 }
             }

             if ( thrustShip )
             {
                 // The ship has a terminal velocity, but trying to go faster
                 // still uses fuel (can go faster diagonally - don't care).
                 double thrustx = cosangle/4;
                 double thrusty = sinangle/4;
                 if ( fabs(shipDx + thrustx) < MAX_SHIP_SPEED )
                     shipDx += thrustx;
                 if ( fabs(shipDy + thrusty) < MAX_SHIP_SPEED )
                     shipDy += thrusty;
                 ship->setVelocity( shipDx, shipDy );
                 reducePower( 1 );
                 addExhaust( ship->x() + 20 - cosangle*20,
                             ship->y() + 20 - sinangle*20,
                             shipDx-cosangle, shipDy-sinangle, 3 );
             }

             ship->setFrame( shipAngle >> 1 );

             if ( shootShip )
             {
                 if ( !shootDelay && (int)missiles.count() < mShootCount + 2 )
                 {
                   KMissile *missile = new KMissile( animation[ID_MISSILE], &field );
                   missile->setPos( 21+ship->x()+cosangle*21,
                                  21+ship->y()+sinangle*21 );
                   missile->setFrame( 0 );
                   missile->setVelocity( shipDx + cosangle*MISSILE_SPEED,
                                         shipDy + sinangle*MISSILE_SPEED );
                   missiles.append( missile );
                   shotsFired++;
                   reducePower( 1 );

                   shootDelay = 5;
                 }

                 if ( shootDelay )
                   shootDelay--;
             }

             if ( teleportShip )
             {
                 int ra = qrand() % 10;
                 if( ra == 0 )
                 ra += qrand() % 20;
                 int xra = ra * 60 + ( (qrand() % 20) * (qrand() % 20) );
                 int yra = ra * 50 - ( (qrand() % 20) * (qrand() % 20) );
                 ship->setPos( xra, yra );
             }

             vitalsChanged = TRUE;
         }
     }

     // - - -

     void KAsteroidsView::processPowerups()
     {
         if ( !powerups.isEmpty() )
         {
             // if player gets the powerup remove it from the screen, if option
             // "Can destroy powerups" is enabled and a missile hits the powerup
             // destroy it

             KPowerup *pup;
             Q3PtrListIterator<KPowerup> it( powerups );

             for( ; it.current(); ++it )
             {
                 pup = it.current();
                 pup->growOlder();

                 if( pup->expired() )
                 {
                     powerups.removeRef( pup );
                     continue;
                 }

                 wrapSprite( pup );

                 QList<QGraphicsItem *> hits = pup->collidingItems();
                 QList<QGraphicsItem *>::Iterator it;
                 for ( it = hits.begin(); it != hits.end(); ++it )
                 {
                     if ( (*it) == ship )
                     {
                         switch( pup->type() )
                         {
                           case ID_ENERGY_POWERUP:
                             shipPower += 150;
                             if ( shipPower > MAX_POWER_LEVEL )
                                 shipPower = MAX_POWER_LEVEL;
                             break;
                           case ID_TELEPORT_POWERUP:
                             mTeleportCount++;
                             break;
                           case ID_BRAKE_POWERUP:
                             if ( mBrakeCount < MAX_BRAKES )
                                 mBrakeCount++;
                             break;
                           case ID_SHIELD_POWERUP:
                             if ( mShieldCount < MAX_SHIELDS )
                                 mShieldCount++;
                             break;
                           case ID_SHOOT_POWERUP:
                             if ( mShootCount < MAX_FIREPOWER )
                                 mShootCount++;
                             break;
                         }

                         powerups.removeRef( pup );
                         vitalsChanged = TRUE;
                     }
                     else if ( (*it) == shield )
                     {
                         powerups.removeRef( pup );
                     }
                     else if ( (*it)->type() == ID_MISSILE )
                     {
                         if ( can_destroy_powerups )
                         {
                             powerups.removeRef( pup );
                         }
                     }
                 }
             }
         }         // -- if( powerups.isEmpty() )
     }

     // - - -

     void KAsteroidsView::hideShield()
     {
         shield->hide();
         mShieldCount = 0;
         shieldOn = FALSE;
     }

     double KAsteroidsView::randDouble()
     {
         int v = qrand();
         return (double)v / (double)RAND_MAX;
     }

     int KAsteroidsView::randInt( int range )
     {
         return qrand() % range;
     }

     void KAsteroidsView::showEvent( QShowEvent *e )
     {
     #if defined( QT_LICENSE_PROFESSIONAL )
         static bool wasThere = FALSE;

         if ( !wasThere ) {
             wasThere = TRUE;
             QMessageBox::information( this, tr("QCanvas demo"),
                                       tr("This game has been implemented using the QCanvas class.\n"
                                          "The QCanvas class is not part of the Professional Edition. Please \n"
                                          "contact Trolltech if you want to upgrade to the Enterprise Edition.") );
         }
     #endif

         QWidget::showEvent( e );
     }