Using the Qt signal-slot mechanism to connect a QGLViewer to your scene.
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 drawNeeded()
QGLViewer signal is connected to the Scene drawScene() slot.
#include <qobject.h>
class QGLViewer;
// The Scene class must derive from QObject in order to allow a
// signal slot mechanism.
class Scene : public QObject
{
Q_OBJECT
public :
Scene(const QGLViewer* const v);
public Q_SLOTS:
void draw();
};
#include <QGLViewer/qglviewer.h>
#include "callback.h"
#include <math.h>
Scene::Scene(const QGLViewer* const v)
{
// Connect the viewer signal to our draw slot.
connect(v, SIGNAL(drawNeeded()), this, SLOT(draw()));
}
// Draws a spiral
void Scene::draw()
{
const float nbSteps = 200.0;
glBegin(GL_QUAD_STRIP);
for (float i=0; i<nbSteps; ++i)
{
float ratio = i/nbSteps;
float angle = 21.0*ratio;
float c = cos(angle);
float s = sin(angle);
float r1 = 1.0 - 0.8*ratio;
float r2 = 0.8 - 0.8*ratio;
float alt = ratio - 0.5;
const float nor = .5;
const float up = sqrt(1.0-nor*nor);
glColor3f(1.0-ratio, 0.2f , ratio);
glNormal3f(nor*c, up, nor*s);
glVertex3f(r1*c, alt, r1*s);
glVertex3f(r2*c, alt+0.05, r2*s);
}
glEnd();
}
#include "callback.h"
#include <QGLViewer/qglviewer.h>
#include <qapplication.h>
#include <qmessagebox.h>
using namespace std;
void help()
{
QString text("<h2>C a l l b a c k</h2>");
text += "This example is conceptually the same as simpleViewer.<br>";
text += "The difference is that it uses the Qt signal/slot mechanism ";
text += "instead of deriving the QGLViewer class. ";
text += "The QGLViewer::drawNeeded() signal is connected to the Scene::draw() method. ";
text += "The two classes are otherwise completely independant.";
QMessageBox::information(NULL, "Callback exemple", text);
}
int main(int argc, char** argv)
{
QApplication application(argc,argv);
// Instantiate the viewer.
QGLViewer viewer;
// Restore the previous viewer state.
viewer.restoreStateFromFile();
// Create a scene, giving a pointer to the associated viewer.
Scene s(&viewer);
#if QT_VERSION < 0x040000
application.setMainWidget(&viewer);
#else
viewer.setWindowTitle("callback");
#endif
help();
viewer.show();
return application.exec();
}
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