<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>libQGLViewer callback example</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<link href="../qglviewer.css" rel="stylesheet" type="text/css" />
<link rel="shortcut icon" href="../images/qglviewer.ico" type="image/x-icon" />
<link rel="icon" href="../images/qglviewer.icon.png" type="image/png" />
</head>
<body>
<table class="banner">
<tr>
<td align="center"><a href="../index.html"><b>Home</b></a></td>
<td align="center"><a href="../refManual/hierarchy.html"><b>Documentation</b></a></td>
<td align="center"><a href="../download.html"><b>Download</b></a></td>
<td align="center" class="qindexHL"><a href="index.html"><b>Screenshots</b></a></td>
<td align="center"><a href="../developer.html"><b>Developer</b></a></td>
</tr>
</table>
<h1>The callback example</h1>
<center>
<img src="../images/callback.jpg" width="300" height="200" alt="callback"/>
</center>
<p>
Using the Qt signal-slot mechanism to connect a QGLViewer and your scene.
</p>
<p>
This very simple application uses the Qt signal-slot callback mechanism to link the QGLViewer and
your Scene. The two class hence remain totally independent. The <code>drawNeeded()</code>
QGLViewer signal is connected to the Scene <code>drawScene()</code> slot.
</p>
<h2>callback.h</h2>
<pre>
<span class="dir">#include <qobject.h>
</span>
<span class="key">class </span>QGLViewer;
<span class="com">// The Scene class must derive from QObject in order to allow a
</span><span class="com">// signal slot mechanism.
</span><span class="key">class </span>Scene : <span class="key">public </span>QObject
{
Q_OBJECT <span class="com">// must include this in order to use Qt signals/slots
</span>
<span class="key">public </span>:
Scene(<span class="typ">const </span>QGLViewer* <span class="typ">const </span>v);
<span class="key">public </span>slots:
<span class="typ">void </span>drawScene();
};</pre>
<h2>callback.cpp</h2>
<pre>
<span class="dir">#include <QGLViewer/qglviewer.h>
</span><span class="dir">#include </span><span class="dstr">"callback.h"</span><span class="dir">
</span><span class="dir">#include <math.h>
</span>
Scene::Scene(<span class="typ">const </span>QGLViewer* <span class="typ">const </span>v)
{
<span class="com">// Connect the viewer signal to our draw function slot
</span> connect(v, SIGNAL(drawNeeded()), <span class="key">this</span>, SLOT(drawScene()));
}
<span class="com">// Draws a spiral
</span><span class="typ">void </span>Scene::drawScene()
{
<span class="typ">const float </span>nbSteps = <span class="num">500.0</span>;
glBegin(GL_QUAD_STRIP);
<span class="key">for </span>(<span class="typ">float </span>i=<span class="num">0</span>; i<nbSteps; ++i)
{
<span class="typ">float </span>ratio = i/nbSteps;
<span class="typ">float </span>angle = <span class="num">21.0</span>*ratio;
<span class="typ">float </span>c = cos(angle);
<span class="typ">float </span>s = sin(angle);
<span class="typ">float </span>r1 = <span class="num">1.0 </span>- <span class="num">0.8</span>*ratio;
<span class="typ">float </span>r2 = <span class="num">0.8 </span>- <span class="num">0.8</span>*ratio;
<span class="typ">float </span>alt = ratio <span class="num">- 0.5</span>;
<span class="typ">const float </span>nor = .<span class="num">5</span>;
<span class="typ">const float </span>up = sqrt(<span class="num">1.0</span>-nor*nor);
glColor3f(<span class="num">1</span>-ratio, .<span class="num">2 </span>, ratio);
glNormal3f(nor*c, up, nor*s);
glVertex3f(r1*c, alt, r1*s);
glVertex3f(r2*c, alt+<span class="num">0.05</span>, r2*s);
}
glEnd();
}</pre>
<h2>main.cpp</h2>
<pre>
<span class="dir">#include <QGLViewer/qglviewer.h>
</span><span class="dir">#include <qapplication.h>
</span><span class="dir">#include <qmessagebox.h>
</span><span class="dir">#include </span><span class="dstr">"callback.h"</span><span class="dir">
</span>
<span class="key">using namespace </span>std;
<span class="typ">void </span>help()
{
QString text(<span class="str">"<h2>C a l l b a c k</h2>"</span>);
text += <span class="str">"This example is conceptually the same as simpleViewer."</span>;
text += <span class="str">"The difference is that it uses the Qt signal/slot mechanism "</span>;
text += <span class="str">"instead of deriving the QGLViewer class. "</span>;
text += <span class="str">"A Scene::draw() function is connected to the QGLViewer::drawNeeded() "</span>;
text += <span class="str">"signal. The two classes are otherwise completely independant."</span>;
QMessageBox::information(NULL, <span class="str">"Callback exemple"</span>, text);
}
<span class="typ">int </span>main(<span class="typ">int </span>argc, <span class="typ">char</span>** argv)
{
<span class="com">// Read command lines arguments.
</span> QApplication application(argc,argv);
<span class="com">// Instantiate the viewer.
</span> QGLViewer v;
<span class="com">// Make the viewer window visible on screen.
</span> v.show();
<span class="com">// Restore the previous viewer state.
</span> v.restoreFromFile();
<span class="com">// Create a scene, giving a pointer to the associated viewer.
</span> Scene s(&v);
<span class="com">// Set the viewer as the application main widget.
</span> application.setMainWidget(&v);
help();
<span class="com">// Run main loop.
</span> <span class="key">return </span>application.exec();
}</pre>
<p>
<a href="index.html">Go back</a> to the examples main page
</p>
<p>
<a href="http://validator.w3.org/check/referer"><img src="../images/xhtml.png" alt="Valid XHTML 1.0!" height="31" width="88" border="0"/></a>
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img src="../images/css.png" width="88" height="31" alt="Valid CSS!" border="0"/></a>
<i>Last modified on Thursday, February 5, 2004.</i>
</p>
</body>
</html>
