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| author | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-07-10 15:24:15 -0500 |
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| committer | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-07-10 15:24:15 -0500 |
| commit | bd0f3345a938b35ce6a12f6150373b0955b8dd12 (patch) | |
| tree | 7a520322212d48ebcb9fbe1087e7fca28b76185c /doc/html/tutorial1-14.html | |
| download | qt3-bd0f3345a938b35ce6a12f6150373b0955b8dd12.tar.gz qt3-bd0f3345a938b35ce6a12f6150373b0955b8dd12.zip | |
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diff --git a/doc/html/tutorial1-14.html b/doc/html/tutorial1-14.html new file mode 100644 index 0000000..dcc50ff --- /dev/null +++ b/doc/html/tutorial1-14.html @@ -0,0 +1,271 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/tutorial.doc:2381 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>Qt Tutorial - Chapter 14: Facing the Wall</title> +<style type="text/css"><!-- +fn { margin-left: 1cm; text-indent: -1cm; } +a:link { color: #004faf; text-decoration: none } +a:visited { color: #672967; text-decoration: none } +body { background: #ffffff; color: black; } +--></style> +</head> +<body> + +<table border="0" cellpadding="0" cellspacing="0" width="100%"> +<tr bgcolor="#E5E5E5"> +<td valign=center> + <a href="index.html"> +<font color="#004faf">Home</font></a> + | <a href="classes.html"> +<font color="#004faf">All Classes</font></a> + | <a href="mainclasses.html"> +<font color="#004faf">Main Classes</font></a> + | <a href="annotated.html"> +<font color="#004faf">Annotated</font></a> + | <a href="groups.html"> +<font color="#004faf">Grouped Classes</font></a> + | <a href="functions.html"> +<font color="#004faf">Functions</font></a> +</td> +<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Qt Tutorial - Chapter 14: Facing the Wall</h1> + + +<p> <center><img src="t14.png" alt="Screenshot of tutorial fourteen"></center> +<p> This is the final example: a complete game. +<p> We add keyboard accelerators and introduce mouse events to CannonField. We +put a frame around the CannonField and add a barrier (wall) to make the +game more challenging. +<p> <ul> +<li> <a href="t14-lcdrange-h.html">t14/lcdrange.h</a> contains the LCDRange +class definition. +<li> <a href="t14-lcdrange-cpp.html">t14/lcdrange.cpp</a> contains the LCDRange +implementation. +<li> <a href="t14-cannon-h.html">t14/cannon.h</a> contains the CannonField class +definition. +<li> <a href="t14-cannon-cpp.html">t14/cannon.cpp</a> contains the CannonField +implementation. +<li> <a href="t14-gamebrd-h.html">t14/gamebrd.h</a> contains the GameBoard +class definition. +<li> <a href="t14-gamebrd-cpp.html">t14/gamebrd.cpp</a> contains the GameBoard +implementation. +<li> <a href="t14-main-cpp.html">t14/main.cpp</a> contains MyWidget and main. +</ul> +<p> <h2> Line-by-line Walkthrough +</h2> +<a name="1"></a><p> <h3> <a href="t14-cannon-h.html">t14/cannon.h</a> +</h3> +<a name="1-1"></a><p> The CannonField can now receive mouse events to make the user aim the +barrel by clicking on it and dragging. CannonField also has a barrier +wall. +<p> + +<p> <pre> protected: + void paintEvent( <a href="qpaintevent.html">QPaintEvent</a> * ); + void mousePressEvent( <a href="qmouseevent.html">QMouseEvent</a> * ); + void mouseMoveEvent( <a href="qmouseevent.html">QMouseEvent</a> * ); + void mouseReleaseEvent( <a href="qmouseevent.html">QMouseEvent</a> * ); +</pre> +<p> In addition to the familiar event handlers, CannonField implements +three mouse event handlers. The names say it all. +<p> <pre> void paintBarrier( <a href="qpainter.html">QPainter</a> * ); +</pre> +<p> This private function paints the barrier wall. +<p> <pre> <a href="qrect.html">QRect</a> barrierRect() const; +</pre> +<p> This private function returns the enclosing rectangle of the barrier. +<p> <pre> bool barrelHit( const <a href="qpoint.html">QPoint</a> & ) const; +</pre> +<p> This private function checks if a point is inside the barrel of the cannon. +<p> <pre> bool barrelPressed; +</pre> +<p> This private variable is TRUE if the user has pressed the mouse on the +barrel and not released it. +<p> <h3> <a href="t14-cannon-cpp.html">t14/cannon.cpp</a> +</h3> +<a name="1-2"></a><p> + +<p> <pre> barrelPressed = FALSE; +</pre> +<p> This line has been added to the constructor. Initially, the mouse is +not pressed on the barrel. +<p> <pre> <a name="x2429"></a> } else if ( shotR.<a href="qrect.html#x">x</a>() > width() || shotR.<a href="qrect.html#y">y</a>() > height() || + shotR.<a href="qrect.html#intersects">intersects</a>(barrierRect()) ) { +</pre> +<p> Now that we have a barrier, there are three ways to miss. We test for +the third, too. +<p> <pre> void CannonField::<a href="qwidget.html#mousePressEvent">mousePressEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> *e ) + { + if ( e-><a href="qmouseevent.html#button">button</a>() != LeftButton ) + return; + <a name="x2418"></a> if ( barrelHit( e-><a href="qmouseevent.html#pos">pos</a>() ) ) + barrelPressed = TRUE; + } +</pre> +<p> This is a Qt event handler. It is called when the user presses a +mouse button when the mouse cursor is over the widget. +<p> If the event was not generated by the left mouse button, we return +immediately. Otherwise, we check if the position of the mouse cursor +is within the cannon's barrel. If it is, we set <tt>barrelPressed</tt> to +TRUE. +<p> Notice that the pos() function returns a point in the widget's +coordinate system. +<p> <pre> void CannonField::<a href="qwidget.html#mouseMoveEvent">mouseMoveEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> *e ) + { + if ( !barrelPressed ) + return; + <a href="qpoint.html">QPoint</a> pnt = e-><a href="qmouseevent.html#pos">pos</a>(); + <a name="x2424"></a> if ( pnt.<a href="qpoint.html#x">x</a>() <= 0 ) + <a name="x2422"></a> pnt.<a href="qpoint.html#setX">setX</a>( 1 ); + <a name="x2425"></a> if ( pnt.<a href="qpoint.html#y">y</a>() >= <a href="qwidget.html#height">height</a>() ) + <a name="x2423"></a> pnt.<a href="qpoint.html#setY">setY</a>( <a href="qwidget.html#height">height</a>() - 1 ); + double rad = atan(((double)<a href="qwidget.html#rect">rect</a>().bottom()-pnt.<a href="qpoint.html#y">y</a>())/pnt.<a href="qpoint.html#x">x</a>()); + setAngle( qRound ( rad*180/3.14159265 ) ); + } +</pre> +<p> This is another Qt event handler. It is called when the user already +has pressed the mouse button inside this widget and then moves/drags +the mouse. (You can make Qt send mouse move events even when no +buttons are pressed. See <a href="qwidget.html#setMouseTracking">QWidget::setMouseTracking</a>().) +<p> This handler repositions the cannon's barrel according to the position of +the mouse cursor. +<p> First, if the barrel is not pressed, we return. Next, we fetch the +mouse cursor's position. If the mouse cursor is to the left or below +the widget, we adjust the point to be inside the widget. +<p> Then we calculate the angle between the bottom edge of the widget and +the imaginary line between the bottom-left corner of the widget and +the cursor position. Finally we set the cannon's angle to the new +value converted to degrees. +<p> Remember that setAngle() redraws the cannon. +<p> <pre> <a name="x2432"></a>void CannonField::<a href="qwidget.html#mouseReleaseEvent">mouseReleaseEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> *e ) + { + <a name="x2417"></a> if ( e-><a href="qmouseevent.html#button">button</a>() == LeftButton ) + barrelPressed = FALSE; + } +</pre> +<p> This Qt event handler is called whenever the user releases a mouse +button and it was pressed inside this widget. +<p> If the left button is released, we can be sure that the barrel is no +longer pressed. +<p> The paint event has two extra lines: +<p> <pre> <a name="x2427"></a> if ( updateR.<a href="qrect.html#intersects">intersects</a>( barrierRect() ) ) + paintBarrier( &p ); +</pre> +<p> paintBarrier() does the same sort of thing as paintShot(), +paintTarget(), and paintCannon(). +<p> <pre> void CannonField::paintBarrier( <a href="qpainter.html">QPainter</a> *p ) + { + p-><a href="qpainter.html#setBrush">setBrush</a>( yellow ); + p-><a href="qpainter.html#setPen">setPen</a>( black ); + p-><a href="qpainter.html#drawRect">drawRect</a>( barrierRect() ); + } +</pre> +<p> This private function paints the barrier as a rectangle filled with +yellow and with a black outline. +<p> <pre> QRect CannonField::barrierRect() const + { + return QRect( 145, height() - 100, 15, 100 ); + } +</pre> +<p> This private function returns the rectangle of the barrier. We fix +the bottom edge of the barrier to the bottom edge of the widget. +<p> <pre> bool CannonField::barrelHit( const <a href="qpoint.html">QPoint</a> &p ) const + { + <a href="qwmatrix.html">QWMatrix</a> mtx; + <a name="x2436"></a> mtx.<a href="qwmatrix.html#translate">translate</a>( 0, height() - 1 ); + <a name="x2435"></a> mtx.<a href="qwmatrix.html#rotate">rotate</a>( -ang ); + <a name="x2433"></a> mtx = mtx.<a href="qwmatrix.html#invert">invert</a>(); + <a name="x2434"></a><a name="x2426"></a> return barrelRect.<a href="qrect.html#contains">contains</a>( mtx.<a href="qwmatrix.html#map">map</a>(p) ); + } +</pre> +<p> This function returns TRUE if the point is in the barrel; otherwise it returns +FALSE. +<p> Here we use the class <a href="qwmatrix.html">QWMatrix</a>. It is defined in the header file +qwmatrix.h, which is included by qpainter.h. +<p> <a href="qwmatrix.html">QWMatrix</a> defines a coordinate system mapping. It can perform the same +transformations as the <a href="qpainter.html">QPainter</a>. +<p> Here we perform the same transformation steps as we do when drawing +the barrel in the paintCannon() function. First we translate the +coordinate system and then we rotate it. +<p> Now we need to check whether the point <tt>p</tt> (in widget coordinates) lies +inside the barrel. To do this, we invert the <a href="qwmatrix.html#TransformationMode">transformation matrix</a>. +The inverted matrix performs the inverse transformation that we used +when drawing the barrel. We map the point <tt>p</tt> using the inverted +matrix and return TRUE if it is inside the original barrel rectangle. +<p> <h3> <a href="t14-gamebrd-cpp.html">t14/gamebrd.cpp</a> +</h3> +<a name="1-3"></a><p> + +<p> <pre> #include <<a href="qaccel-h.html">qaccel.h</a>> +</pre> +<p> We include the class definition of <a href="qaccel.html">QAccel</a>. +<p> <pre> <a href="qvbox.html">QVBox</a> *box = new <a href="qvbox.html">QVBox</a>( this, "cannonFrame" ); + box-><a href="qframe.html#setFrameStyle">setFrameStyle</a>( QFrame::WinPanel | QFrame::Sunken ); + cannonField = new CannonField( box, "cannonField" ); +</pre> +<p> We create and set up a <a href="qvbox.html">QVBox</a>, set its frame style, and then create +<tt>CannonField</tt> as a child of that box. Because nothing else is in the +box, the effect is that the <a href="qvbox.html">QVBox</a> will put a frame around the +CannonField. +<p> <pre> <a href="qaccel.html">QAccel</a> *accel = new <a href="qaccel.html">QAccel</a>( this ); + <a name="x2438"></a><a name="x2437"></a> accel-><a href="qaccel.html#connectItem">connectItem</a>( accel-><a href="qaccel.html#insertItem">insertItem</a>( Key_Enter ), + this, SLOT(fire()) ); + accel-><a href="qaccel.html#connectItem">connectItem</a>( accel-><a href="qaccel.html#insertItem">insertItem</a>( Key_Return ), + this, SLOT(fire()) ); +</pre> +<p> Here we create and set up an accelerator. An accelerator is an object +that intercepts keyboard events to an application and calls slots if +certain keys are pressed. This mechanism is also called shortcut +keys. Note that an accelerator is a child of a widget and will be +destroyed when that widget is destroyed. <a href="qaccel.html">QAccel</a> is <em>not</em> a widget +and has no visible effect on its parent. +<p> We define two shortcut keys. We want the slot fire() to be called +when the user presses Enter, and we want the application to quit when +key Ctrl+Q is pressed. Because Enter is sometimes Return and there +are even keyboards with <em>both</em> keys, we make both Enter and Return +invoke fire(). +<p> <pre> accel-><a href="qaccel.html#connectItem">connectItem</a>( accel-><a href="qaccel.html#insertItem">insertItem</a>( CTRL+Key_Q ), + qApp, SLOT(<a href="qapplication.html#quit">quit</a>()) ); +</pre> +<p> And then we set up Ctrl+Q to do the same thing as Alt+Q. Some +people are more used to Ctrl+Q (and anyway it shows how do do it). +<p> CTRL, Key_Enter, Key_Return and Key_Q are all constants provided by +Qt. They're actually Qt::Key_Enter, etc., but practically all classes +inherit the <a href="qt.html">Qt</a> namespace class. +<p> <pre> <a href="qgridlayout.html">QGridLayout</a> *grid = new <a href="qgridlayout.html">QGridLayout</a>( this, 2, 2, 10 ); + <a name="x2441"></a> grid-><a href="qgridlayout.html#addWidget">addWidget</a>( quit, 0, 0 ); + grid-><a href="qgridlayout.html#addWidget">addWidget</a>( box, 1, 1 ); + <a name="x2442"></a> grid-><a href="qgridlayout.html#setColStretch">setColStretch</a>( 1, 10 ); +</pre> +<p> We put <tt>box</tt> (the <a href="qvbox.html">QVBox</a>), not the CannonField, in the lower-right +cell. +<p> <h2> Behavior +</h2> +<a name="2"></a><p> The cannon now shoots when you press Enter. You can also position the +cannon's angle using the mouse. The barrier makes it a little more +challenging to play the game. We also have a nice looking frame +around the CannonField. +<p> (See <a href="tutorial1-07.html#compiling">Compiling</a> for how to create a +makefile and build the application.) +<p> <h2> Exercises +</h2> +<a name="3"></a><p> Write a space invaders game. +<p> (This exercise was first done by +<a href="mailto:igorr@ifi.uio.no">Igor Rafienko</a>. You can +<a href="http://www.stud.ifi.uio.no/~igorr/download.html">download his game</a>.) +<p> The new exercise is: Write a Breakout game. +<p> Final exhortation: Go forth now and create <em>masterpieces of the programming art!</em> +<p> +<p> [<a href="tutorial1-13.html">Previous tutorial</a>] +[<a href="tutorial1-01.html">First tutorial</a>] +[<a href="tutorial.html">Main tutorial page</a>] +<p> +<!-- eof --> +<p><address><hr><div align=center> +<table width=100% cellspacing=0 border=0><tr> +<td>Copyright © 2007 +<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a> +<td align=right><div align=right>Qt 3.3.8</div> +</table></div></address></body> +</html> |