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397 lines
18 KiB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/tutorial.doc:2032 -->
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<title>TQt Tutorial - Chapter 13: Game Over</title>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>TQt Tutorial - Chapter 13: Game Over</h1>
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<p> <center><img src="t13.png" alt="Screenshot of tutorial thirteen"></center>
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<p> In this example we start to approach a real playable game with a
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score. We give MyWidget a new name (GameBoard) and add some slots.
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<p> We put the definition in gamebrd.h and the implementation in gamebrd.cpp.
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<p> The CannonField now has a game over state.
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<p> The layout problems in LCDRange are fixed.
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<p> <ul>
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<li> <a href="t13-lcdrange-h.html">t13/lcdrange.h</a> contains the LCDRange
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class definition.
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<li> <a href="t13-lcdrange-cpp.html">t13/lcdrange.cpp</a> contains the LCDRange
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implementation.
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<li> <a href="t13-cannon-h.html">t13/cannon.h</a> contains the CannonField class
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definition
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<li> <a href="t13-cannon-cpp.html">t13/cannon.cpp</a> contains the CannonField
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implementation.
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<li> <a href="t13-gamebrd-h.html">t13/gamebrd.h</a> contains the GameBoard
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class definition.
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<li> <a href="t13-gamebrd-cpp.html">t13/gamebrd.cpp</a> contains the GameBoard
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implementation.
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<li> <a href="t13-main-cpp.html">t13/main.cpp</a> contains MyWidget and main.
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</ul>
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<p> <h2> Line-by-line Walkthrough
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</h2>
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<a name="1"></a><p> <h3> <a href="t13-lcdrange-h.html">t13/lcdrange.h</a>
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</h3>
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<a name="1-1"></a><p>
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<p> <pre> #include <<a href="qwidget-h.html">ntqwidget.h</a>>
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class TQSlider;
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class TQLabel;
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class LCDRange : public <a href="ntqwidget.html">TQWidget</a>
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</pre>
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<p> We inherit <a href="ntqwidget.html">TQWidget</a> rather than <a href="ntqvbox.html">TQVBox</a>. TQVBox is very easy to use, but
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again it showed its limitations so we switch to the more powerful and
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slightly harder to use <a href="qvboxlayout.html">TQVBoxLayout</a>. (As you remember, TQVBoxLayout is
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not a widget, it manages one.)
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<p> <h3> <a href="t13-lcdrange-cpp.html">t13/lcdrange.cpp</a>
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</h3>
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<a name="1-2"></a><p>
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<p> <pre> #include <<a href="qlayout-h.html">ntqlayout.h</a>>
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</pre>
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<p> We need to include ntqlayout.h now to get the other layout management
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API.
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<p> <pre> LCDRange::LCDRange( <a href="ntqwidget.html">TQWidget</a> *parent, const char *name )
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: <a href="ntqwidget.html">TQWidget</a>( parent, name )
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</pre>
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<p> We inherit TQWidget in the usual way.
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<p> The other constructor has the same change. init() is unchanged,
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except that we've added some lines at the end:
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<p> <pre> <a href="qvboxlayout.html">TQVBoxLayout</a> * l = new <a href="qvboxlayout.html">TQVBoxLayout</a>( this );
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</pre>
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<p> We create a TQVBoxLayout with all the default values, managing this
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widget's children.
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<p> <pre> <a name="x2401"></a> l-><a href="qboxlayout.html#addWidget">addWidget</a>( lcd, 1 );
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</pre>
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<p> At the top we add the <a href="ntqlcdnumber.html">TQLCDNumber</a> with a non-zero stretch.
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<p> <pre> l-><a href="qboxlayout.html#addWidget">addWidget</a>( slider );
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l-><a href="qboxlayout.html#addWidget">addWidget</a>( label );
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</pre>
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<p> Then we add the other two, both with the default zero stretch.
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<p> This stretch control is something <a href="qvboxlayout.html">TQVBoxLayout</a> (and <a href="qhboxlayout.html">TQHBoxLayout</a>, and
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<a href="qgridlayout.html">TQGridLayout</a>) offers but classes like <a href="ntqvbox.html">TQVBox</a> do not. In this case
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we're saying that the TQLCDNumber should stretch and the others should
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not.
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<p> <h3> <a href="t13-cannon-h.html">t13/cannon.h</a>
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</h3>
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<a name="1-3"></a><p> The CannonField now has a game over state and a few new functions.
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<p>
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<p> <pre> bool gameOver() const { return gameEnded; }
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</pre>
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<p> This function returns TRUE if the game is over or FALSE if a game
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is going on.
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<p> <pre> void setGameOver();
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void restartGame();
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</pre>
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<p> Here are two new slots: setGameOver() and restartGame().
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<p> <pre> void canShoot( bool );
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</pre>
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<p> This new signal indicates that the CannonField is in a state where the
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shoot() slot makes sense. We'll use it below to enable/disable the
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Shoot button.
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<p> <pre> bool gameEnded;
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</pre>
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<p> This private variable contains the game state. TRUE means that the
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game is over, and FALSE means that a game is going on.
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<p> <h3> <a href="t13-cannon-cpp.html">t13/cannon.cpp</a>
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</h3>
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<a name="1-4"></a><p>
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<p> <pre> gameEnded = FALSE;
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</pre>
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<p> This line has been added to the constructor. Initially, the game is not
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over (luckily for the player :-).
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<p> <pre> void CannonField::shoot()
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{
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if ( isShooting() )
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return;
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timerCount = 0;
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shoot_ang = ang;
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shoot_f = f;
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<a name="x2407"></a> autoShootTimer-><a href="ntqtimer.html#start">start</a>( 50 );
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emit canShoot( FALSE );
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}
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</pre>
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<p> We added a new isShooting() function, so shoot() uses it instead of
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testing directly. Also, shoot tells the world that the CannonField
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cannot shoot now.
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<p> <pre> void CannonField::setGameOver()
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{
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if ( gameEnded )
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return;
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if ( isShooting() )
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autoShootTimer-><a href="ntqtimer.html#stop">stop</a>();
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gameEnded = TRUE;
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<a href="ntqwidget.html#repaint">repaint</a>();
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}
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</pre>
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<p> This slot ends the game. It must be called from outside CannonField,
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because this widget does not know when to end the game. This is an
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important design principle in component programming. We choose to
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make the component as flexible as possible to make it usable with
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different rules (for example, a multi-player version of this in which the
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first player to hit ten times wins could use the CannonField unchanged).
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<p> If the game has already been ended we return immediately. If a game is
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going on we stop the shot, set the game over flag, and repaint the entire
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widget.
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<p> <pre> void CannonField::restartGame()
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{
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if ( isShooting() )
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<a name="x2408"></a> autoShootTimer-><a href="ntqtimer.html#stop">stop</a>();
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gameEnded = FALSE;
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<a href="ntqwidget.html#repaint">repaint</a>();
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emit canShoot( TRUE );
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}
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</pre>
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<p> This slot starts a new game. If a shot is in the air, we stop shooting.
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We then reset the <tt>gameEnded</tt> variable and repaint the widget.
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<p> moveShot() too emits the new canShoot(TRUE) signal at the same time as
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either hit() or miss().
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<p> Modifications in CannonField::paintEvent():
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<p> <pre> void CannonField::<a href="ntqwidget.html#paintEvent">paintEvent</a>( <a href="qpaintevent.html">TQPaintEvent</a> *e )
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{
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<a name="x2405"></a> <a href="ntqrect.html">TQRect</a> updateR = e-><a href="qpaintevent.html#rect">rect</a>();
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<a href="ntqpainter.html">TQPainter</a> p( this );
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if ( gameEnded ) {
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p.<a href="ntqpainter.html#setPen">setPen</a>( black );
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<a name="x2403"></a> p.<a href="ntqpainter.html#setFont">setFont</a>( TQFont( "Courier", 48, TQFont::Bold ) );
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p.<a href="ntqpainter.html#drawText">drawText</a>( <a href="ntqwidget.html#rect">rect</a>(), AlignCenter, "Game Over" );
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}
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</pre>
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<p> The paint event has been enhanced to display the text "Game Over" if
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the game is over, i.e., <tt>gameEnded</tt> is TRUE. We don't bother to
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check the update rectangle here because speed is not critical when
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the game is over.
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<p> To draw the text we first set a black pen; the pen color is used
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when drawing text. Next we choose a 48 point bold font from the
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Courier family. Finally we draw the text centered in the widget's
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rectangle. Unfortunately, on some systems (especially X servers with
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Unicode fonts) it can take a while to load such a large font. Because
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TQt caches fonts, you will notice this only the first time the font is
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used.
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<p> <pre> <a name="x2406"></a> if ( updateR.<a href="ntqrect.html#intersects">intersects</a>( cannonRect() ) )
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paintCannon( &p );
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if ( isShooting() && updateR.<a href="ntqrect.html#intersects">intersects</a>( shotRect() ) )
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paintShot( &p );
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if ( !gameEnded && updateR.<a href="ntqrect.html#intersects">intersects</a>( targetRect() ) )
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paintTarget( &p );
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}
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</pre>
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<p> We draw the shot only when shooting and the target only when playing
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(that is, when the game is not ended).
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<p> <h3> <a href="t13-gamebrd-h.html">t13/gamebrd.h</a>
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</h3>
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<a name="1-5"></a><p> This file is new. It contains the definition of the GameBoard class,
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which was last seen as MyWidget.
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<p>
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<p> <pre> class TQPushButton;
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class LCDRange;
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class TQLCDNumber;
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class CannonField;
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#include "lcdrange.h"
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#include "cannon.h"
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class GameBoard : public <a href="ntqwidget.html">TQWidget</a>
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{
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<a href="metaobjects.html#TQ_OBJECT">TQ_OBJECT</a>
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public:
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GameBoard( <a href="ntqwidget.html">TQWidget</a> *parent=0, const char *name=0 );
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protected slots:
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void fire();
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void hit();
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void missed();
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void newGame();
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private:
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<a href="ntqlcdnumber.html">TQLCDNumber</a> *hits;
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<a href="ntqlcdnumber.html">TQLCDNumber</a> *shotsLeft;
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CannonField *cannonField;
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};
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</pre>
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<p> We have now added four slots. These are protected and are used internally.
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We have also added two TQLCDNumbers (<tt>hits</tt> and <tt>shotsLeft</tt>) which display
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the game status.
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<p> <h3> <a href="t13-gamebrd-cpp.html">t13/gamebrd.cpp</a>
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</h3>
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<a name="1-6"></a><p> This file is new. It contains the implementation of the GameBoard
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class, which was last seen as MyWidget.
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<p>
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<p> We have made some changes in the GameBoard constructor.
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<p> <pre> cannonField = new CannonField( this, "cannonField" );
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</pre>
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<p> <tt>cannonField</tt> is now a member variable, so we carefully change the
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constructor to use it. (The <em>good</em> programmers at Trolltech never
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forget this, but I do. Caveat programmor - if "programmor" is Latin,
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at least. Anyway, back to the code.)
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<p> <pre> <a href="ntqobject.html#connect">connect</a>( cannonField, TQ_SIGNAL(hit()),
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this, TQ_SLOT(hit()) );
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<a href="ntqobject.html#connect">connect</a>( cannonField, TQ_SIGNAL(missed()),
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this, TQ_SLOT(missed()) );
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</pre>
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<p> This time we want to do something when the shot has hit or missed the
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target. Thus we connect the hit() and missed() signals of the
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CannonField to two protected slots with the same names in this class.
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<p> <pre> <a href="ntqobject.html#connect">connect</a>( shoot, TQ_SIGNAL(<a href="ntqbutton.html#clicked">clicked</a>()), TQ_SLOT(fire()) );
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</pre>
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<p> Previously we connected the Shoot button's clicked() signal directly
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to the CannonField's shoot() slot. This time we want to keep track of
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the number of shots fired, so we connect it to a protected slot in
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this class instead.
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<p> Notice how easy it is to change the behavior of a program when you are
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working with self-contained components.
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<p> <pre> <a href="ntqobject.html#connect">connect</a>( cannonField, TQ_SIGNAL(canShoot(bool)),
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<a name="x2416"></a> shoot, TQ_SLOT(<a href="ntqwidget.html#setEnabled">setEnabled</a>(bool)) );
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</pre>
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<p> We also use the cannonField's canShoot() signal to enable or disable
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the Shoot button appropriately.
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<p> <pre> TQPushButton *restart
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= new <a href="ntqpushbutton.html">TQPushButton</a>( "&New Game", this, "newgame" );
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restart->setFont( TQFont( "Times", 18, TQFont::Bold ) );
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<a href="ntqobject.html#connect">connect</a>( restart, TQ_SIGNAL(clicked()), this, TQ_SLOT(newGame()) );
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</pre>
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<p> We create, set up, and connect the New Game button as we have done
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with the other buttons. Clicking this button will activate the
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newGame() slot in this widget.
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<p> <pre> hits = new <a href="ntqlcdnumber.html">TQLCDNumber</a>( 2, this, "hits" );
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shotsLeft = new <a href="ntqlcdnumber.html">TQLCDNumber</a>( 2, this, "shotsleft" );
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<a href="ntqlabel.html">TQLabel</a> *hitsL = new <a href="ntqlabel.html">TQLabel</a>( "HITS", this, "hitsLabel" );
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TQLabel *shotsLeftL
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= new <a href="ntqlabel.html">TQLabel</a>( "SHOTS LEFT", this, "shotsleftLabel" );
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</pre>
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<p> We create four new widgets. Note that we don't bother to keep the
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pointers to the <a href="ntqlabel.html">TQLabel</a> widgets in the GameBoard class because there's
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nothing much we want to do with them. TQt will delete them when the
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GameBoard widget is destroyed, and the layout classes will resize them
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appropriately.
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<p> <pre> <a href="qhboxlayout.html">TQHBoxLayout</a> *topBox = new <a href="qhboxlayout.html">TQHBoxLayout</a>;
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<a name="x2413"></a> grid-><a href="qgridlayout.html#addLayout">addLayout</a>( topBox, 0, 1 );
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topBox-><a href="qboxlayout.html#addWidget">addWidget</a>( shoot );
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topBox-><a href="qboxlayout.html#addWidget">addWidget</a>( hits );
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topBox-><a href="qboxlayout.html#addWidget">addWidget</a>( hitsL );
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topBox-><a href="qboxlayout.html#addWidget">addWidget</a>( shotsLeft );
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topBox-><a href="qboxlayout.html#addWidget">addWidget</a>( shotsLeftL );
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<a name="x2410"></a> topBox-><a href="qboxlayout.html#addStretch">addStretch</a>( 1 );
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<a name="x2411"></a> topBox-><a href="qboxlayout.html#addWidget">addWidget</a>( restart );
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</pre>
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<p> The number of widgets in the top-right cell is getting large. Once it
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was empty; now it's full enough that we group together the layout
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setting for better overview.
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<p> Notice that we let all the widgets have their preferred sizes, instead
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putting the stretch just to the left of the New Game button.
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<p> <pre> newGame();
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}
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</pre>
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<p> We're all done constructing the GameBoard, so we start it all using
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newGame(). (NewGame() is a slot, but as we said, slots can be used as
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ordinary functions, too.)
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<p> <pre> void GameBoard::fire()
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{
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if ( cannonField->gameOver() || cannonField->isShooting() )
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return;
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shotsLeft-><a href="ntqlcdnumber.html#display">display</a>( shotsLeft-><a href="ntqlcdnumber.html#intValue">intValue</a>() - 1 );
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cannonField->shoot();
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}
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</pre>
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<p> This function fires a shot. If the game is over or if there is a shot in the
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air, we return immediately. We decrement the number of shots left and tell
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the cannon to shoot.
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<p> <pre> void GameBoard::hit()
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{
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hits-><a href="ntqlcdnumber.html#display">display</a>( hits-><a href="ntqlcdnumber.html#intValue">intValue</a>() + 1 );
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if ( shotsLeft-><a href="ntqlcdnumber.html#intValue">intValue</a>() == 0 )
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cannonField->setGameOver();
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else
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cannonField->newTarget();
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}
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</pre>
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<p> This slot is activated when a shot has hit the target. We increment the
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number of hits. If there are no shots left, the game is over. Otherwise,
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we make the CannonField generate a new target.
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<p> <pre> void GameBoard::missed()
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{
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<a name="x2415"></a> if ( shotsLeft-><a href="ntqlcdnumber.html#intValue">intValue</a>() == 0 )
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cannonField->setGameOver();
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}
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</pre>
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<p> This slot is activated when a shot has missed the target. If there are no
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shots left, the game is over.
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<p> <pre> void GameBoard::newGame()
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{
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<a name="x2414"></a> shotsLeft-><a href="ntqlcdnumber.html#display">display</a>( 15 );
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hits-><a href="ntqlcdnumber.html#display">display</a>( 0 );
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cannonField->restartGame();
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cannonField->newTarget();
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}
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</pre>
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<p> This slot is activated when the user clicks the Restart button. It is
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also called from the constructor. First it sets the number of shots
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to 15. Note that this is the only place in the program where we set
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the number of shots. Change it to whatever you like to change the
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game rules. Next we reset the number of hits, restart the game, and
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generate a new target.
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<p> <h3> <a href="t13-main-cpp.html">t13/main.cpp</a>
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</h3>
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<a name="1-7"></a><p> This file has just been on a diet. MyWidget is gone, and the only
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thing left is the main() function, unchanged except for the name
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change.
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<p> <h2> Behavior
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</h2>
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<a name="2"></a><p> The cannon can shoot at a target; a new target is automatically created
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when one has been hit.
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<p> Hits and shots left are displayed and the program keeps track of them.
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The game can end, and there's a button to start a new game.
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<p> (See <a href="tutorial1-07.html#compiling">Compiling</a> for how to create a
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makefile and build the application.)
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<p> <h2> Exercises
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</h2>
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<a name="3"></a><p> Add a random wind factor and show it to the user.
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<p> Make some splatter effects when the shot hits the target.
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<p> Implement multiple targets.
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<p> You're now ready for <a href="tutorial1-14.html">Chapter 14.</a>
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<p> [<a href="tutorial1-12.html">Previous tutorial</a>]
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[<a href="tutorial1-14.html">Next tutorial</a>]
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[<a href="tutorial.html">Main tutorial page</a>]
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<p>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>TQt 3.3.8</div>
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</table></div></address></body>
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</html>
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