t13.html

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used. <pre>
        if ( updateR.<a href="qrect.html#5b3d2b">intersects</a>( cannonRect() ) )
            paintCannon( &amp;p );
        if ( isShooting() &amp;&amp; updateR.<a href="qrect.html#5b3d2b">intersects</a>( shotRect() ) )
            paintShot( &amp;p );
        if ( !gameEnded &amp;&amp; updateR.<a href="qrect.html#5b3d2b">intersects</a>( targetRect() ) )
            paintTarget( &amp;p );
    }
</pre>
<p>
We only draw the shot when shooting and the target only when playing
(that is, when the game is not ended).
<p>
<h3><a href="t13-gamebrd-h.html">gamebrd.h</a></h3>
<p>
This file is new.  It contains the definition of the GameBoard class,
which was last seen as MyWidget.    <pre>
    class QPushButton;
    class LCDRange;
    class QLCDNumber;
    class CannonField;
    
    #include "lcdrange.h"
    #include "cannon.h"
    
    class GameBoard : public QWidget
    {
        Q_OBJECT
    public:
        GameBoard( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
    
    protected slots:
        void  fire();
        void  hit();
        void  missed();
        void  newGame();
    
    private:
        <a href="qlcdnumber.html">QLCDNumber</a>  *hits;
        <a href="qlcdnumber.html">QLCDNumber</a>  *shotsLeft;
        CannonField *cannonField;
    };
</pre>
<p>
We have now added four slots.  These are protected and are used internally.
We have also added two QLCDNumbers: <code>hits</code> and <code>shotsLeft,</code> which display
the game status.
<p>
<h3><a href="t13-gamebrd-cpp.html">gamebrd.cpp</a></h3>
<p>
This file is new.  It contains the implementation of the GameBoard
class, which was last seen as MyWidget. 
<p>
We have made some changes in the GameBoard constructor.   <pre>
        cannonField = new CannonField( this, "cannonField" );
</pre>
<p>
<code>cannonField</code> is now a member variable, so we carefully change the
constructor to use it.  (The <em>good</em> programmers at Trolltech never
forget this, but I do.  Caveat programmor.  If "programmor" is latin,
at least.  Anyway, back to the code.)  <pre>
        <a href="qobject.html#fbde73">connect</a>( cannonField, SIGNAL(hit()),
                 this, SLOT(hit()) );
        <a href="qobject.html#fbde73">connect</a>( cannonField, SIGNAL(missed()),
                 this, SLOT(missed()) );
</pre>
<p>
This time we want to do something when the shot has hit or missed the
target.  Thus we connect the hit() and missed() signals of the
CannonField to two protected slots with the same names in this class.   <pre>
        <a href="qobject.html#fbde73">connect</a>( shoot, SIGNAL(clicked()), SLOT(fire()) );
</pre>
<p>
Previously, we connected the shoot button's clicked() signal directly
to the CannonField's shoot() slot.  This time we want to keep track of
the number of shots fired, so we connect it to a protected slot in
this class instead.
<p>
Notice how easy it is to change the behavior of a program when you are
working with self-contained components. <pre>
        <a href="qobject.html#fbde73">connect</a>( cannonField, SIGNAL(canShoot(bool)),
                 shoot, SLOT(<a href="qwidget.html#4b103c">setEnabled</a>(bool)) );
</pre>
<p>
We also use the cannonField's canShoot() signal to enable or disable
the Shoot button appropriately.  <pre>
        <a href="qpushbutton.html">QPushButton</a> *restart 
            = new <a href="qpushbutton.html">QPushButton</a>( "&amp;New Game", this, "newgame" );
        restart-&gt;<a href="qwidget.html#090d60">setFont</a>( <a href="qfont.html">QFont</a>( "Times", 18, QFont::Bold ) );
    
        <a href="qobject.html#fbde73">connect</a>( restart, SIGNAL(clicked()), this, SLOT(newGame()) );
</pre>
<p>
We create, set up and connect the New Game button like we have done
with the other buttons.  Clicking this button will activate the
newGame() slot in this widget. <pre>
        hits = new <a href="qlcdnumber.html">QLCDNumber</a>( 2, this, "hits" );
        shotsLeft = new <a href="qlcdnumber.html">QLCDNumber</a>( 2, this, "shotsleft" );
        <a href="qlabel.html">QLabel</a> *hitsL = new <a href="qlabel.html">QLabel</a>( "HITS", this, "hitsLabel" );
        <a href="qlabel.html">QLabel</a> *shotsLeftL 
            = new <a href="qlabel.html">QLabel</a>( "SHOTS LEFT", this, "shotsleftLabel" );
</pre>
<p>
We create four new widgets.  Note that we don't bother to keep the
pointers to the QLabel widgets in the GameBoard class since there's
nothing much we want to do with them.  Qt will delete them when the
GameBoard widget is destroyed, and the layout classes will resize them
appropriately.  <pre>
        <a href="qhboxlayout.html">QHBoxLayout</a> *topBox = new <a href="qhboxlayout.html">QHBoxLayout</a>;
        grid-&gt;<a href="qgridlayout.html#a409bc">addLayout</a>( topBox, 0, 1 );
        topBox-&gt;<a href="qboxlayout.html#ebba99">addWidget</a>( shoot );
        topBox-&gt;<a href="qboxlayout.html#ebba99">addWidget</a>( hits );
        topBox-&gt;<a href="qboxlayout.html#ebba99">addWidget</a>( hitsL );
        topBox-&gt;<a href="qboxlayout.html#ebba99">addWidget</a>( shotsLeft );
        topBox-&gt;<a href="qboxlayout.html#ebba99">addWidget</a>( shotsLeftL );
        topBox-&gt;<a href="qboxlayout.html#0226eb">addStretch</a>( 1 );
        topBox-&gt;<a href="qboxlayout.html#ebba99">addWidget</a>( restart );
</pre>
<p>
The number of widgets in the top-right cell is getting large.  Once it
was empty, now it's full enough that we group together the layout
setting for better overview.
<p>
Notice how we let all the widgets have their preferred sizes, instead
putting the stretch just to the left of the New Game button.  <pre>
        newGame();
    }
</pre>
<p>
We're all done constructing the GameBoard, so we start it all using
newGame().  (newGame() is a slot, but as we said, slots can be used as
ordinary functions too.)  <pre>
    void GameBoard::fire()
    {
        if ( cannonField-&gt;gameOver() || cannonField-&gt;isShooting() )
            return;
        shotsLeft-&gt;display( shotsLeft-&gt;intValue() - 1 );
        cannonField-&gt;shoot();
    }
</pre>
<p>
This function fires a shot.  If the game is over or there is a shot in the
air, we return immediately.  We decrement number of shots left and tell
the cannon to shoot.  <pre>
    void GameBoard::hit()
    {
        hits-&gt;display( hits-&gt;intValue() + 1 );
        if ( shotsLeft-&gt;intValue() == 0 )
            cannonField-&gt;setGameOver();
        else
            cannonField-&gt;newTarget();
    }
</pre>
<p>
This slot is activated when a shot has hit the target.  We increment the
number of hits.  If there are no shots left, the game is over.  Otherwise,
we make the CannonField generate a new target.  <pre>
    void GameBoard::missed()
    {
        if ( shotsLeft-&gt;intValue() == 0 )
            cannonField-&gt;setGameOver();
    }
</pre>
<p>
This slot is activated when a shot has missed the target.  If there are no
shots left, the game is over.  <pre>
    void GameBoard::newGame()
    {
        shotsLeft-&gt;display( 15 );
        hits-&gt;display( 0 );
        cannonField-&gt;restartGame();
        cannonField-&gt;newTarget();
    }
</pre>
<p>
This slot is activated when the user clicks the restart button.  It is
also called from the constructor.  First, it sets the number of shots
to 15.  Note that this is the only place in the program that we set
the number of shots.  Change it to whatever you like to change the
game rules.  Next, we reset the number of hits, restart the game and
generate a new target.
<p>
<h3><a href="t13-main-cpp.html">main.cpp</a></h3>
<p>
This file has just been on a diet.  MyWidget is gone and the only
thing left is the main() function, unchanged except for the name
change.
<p>
<h2>Behavior</h2>
<p>
Hits and shots left are displayed and the program keeps track of them.
The game can end and there's a button to start a new game.
<p>
<h2>Exercises</h2>
<p>
Add a random wind factor and show it to the user.
<p>
Make some splatter effects when the shot hits the target.
<p>
Implement multiple targets.
<p>
You may now go on to <a href="t14.html">chapter fourteen.</a>
<p>
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