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# The interface example

Adding a graphical user interface around a `QGLViewer`.

Qt's `designer` has been used to create a very simple interface example, described by a `.ui` user interface description file.

Install the QGLViewer designer plugin so that the QGLViewer appears in the designer's widgets tabs. You can then connect signals and slots to and from the viewer. The viewer is fully functional and can be manipulated when you test your interface in `designer`.

The plugin code is in the `designerPlugin` directory. Start from there to create plugins for the classes you will derive from QGLViewer. Select your architecture in the download page for details on the plugin compilation and installation.

Here we use three slots and three signals (axis, grid and fps) to connect to and from the interface and the viewer.

## interface.h

    #include <QGLViewer/qglviewer.h>

    class Viewer : public QGLViewer
    {
    public :
    #if QT_VERSION < 0x040000
      Viewer(QWidget *parent, const char *name);
    #else
      Viewer(QWidget *parent);
    #endif

    protected :
      virtual void draw();
      virtual QString helpString() const;
    };

## interface.cpp

    #include "interface.h"
    #include <math.h>

    // Constructor must call the base class constructor.
    #if QT_VERSION < 0x040000
    Viewer::Viewer(QWidget *parent, const char *name)
      : QGLViewer(parent, name)
    #else
    Viewer::Viewer(QWidget *parent)
        : QGLViewer(parent)
    #endif
    {
      restoreStateFromFile();
      help();
    }

    void Viewer::draw()
    {
      // Draws a spiral
      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();
    }

    QString Viewer::helpString() const
    {
      QString text("<h2>I n t e r f a c e</h2>");
      text += "A GUI can be added to a QGLViewer widget using Qt's <i>Designer</i>. Signals and slots ";
      text += "can then be connected to and from the viewer.<br><br>";
      text += "You can install the QGLViewer designer plugin to make the QGLViewer appear as a ";
      text += "standard Qt widget in the Designer's widget tabs. See installation pages for details.";
      return text;
    }

## ui_viewerInterface.h

    /********************************************************************************
    ** Form generated from reading UI file 'viewerInterface.ui'
    **
    ** Created: Fri Sep 13 06:54:29 2013
    **      by: Qt User Interface Compiler version 5.0.0
    **
    ** WARNING! All changes made in this file will be lost when recompiling UI file!
    ********************************************************************************/

    #ifndef UI_VIEWERINTERFACE_H
    #define UI_VIEWERINTERFACE_H

    #include <QtCore/QVariant>
    #include <QtWidgets/QAction>
    #include <QtWidgets/QApplication>
    #include <QtWidgets/QButtonGroup>
    #include <QtWidgets/QCheckBox>
    #include <QtWidgets/QDialog>
    #include <QtWidgets/QHBoxLayout>
    #include <QtWidgets/QHeaderView>
    #include <QtWidgets/QPushButton>
    #include <QtWidgets/QSpacerItem>
    #include <QtWidgets/QVBoxLayout>
    #include "interface.h"

    QT_BEGIN_NAMESPACE

    class Ui_Dialog
    {
    public:
        QVBoxLayout *vboxLayout;
        Viewer *viewer;
        QHBoxLayout *hboxLayout;
        QCheckBox *FPSCheckBox;
        QCheckBox *GridCheckBox;
        QCheckBox *AxisCheckBox;
        QSpacerItem *spacerItem;
        QPushButton *cancelButton;

        void setupUi(QDialog *Dialog)
        {
            if (Dialog->objectName().isEmpty())
                Dialog->setObjectName(QStringLiteral("Dialog"));
            Dialog->resize(650, 468);
            vboxLayout = new QVBoxLayout(Dialog);
            vboxLayout->setObjectName(QStringLiteral("vboxLayout"));
            vboxLayout->setContentsMargins(8, 8, 8, 8);
            viewer = new Viewer(Dialog);
            viewer->setObjectName(QStringLiteral("viewer"));
            QSizePolicy sizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);
            sizePolicy.setHorizontalStretch(0);
            sizePolicy.setVerticalStretch(1);
            sizePolicy.setHeightForWidth(viewer->sizePolicy().hasHeightForWidth());
            viewer->setSizePolicy(sizePolicy);

            vboxLayout->addWidget(viewer);

            hboxLayout = new QHBoxLayout();
            hboxLayout->setObjectName(QStringLiteral("hboxLayout"));
            FPSCheckBox = new QCheckBox(Dialog);
            FPSCheckBox->setObjectName(QStringLiteral("FPSCheckBox"));

            hboxLayout->addWidget(FPSCheckBox);

            GridCheckBox = new QCheckBox(Dialog);
            GridCheckBox->setObjectName(QStringLiteral("GridCheckBox"));

            hboxLayout->addWidget(GridCheckBox);

            AxisCheckBox = new QCheckBox(Dialog);
            AxisCheckBox->setObjectName(QStringLiteral("AxisCheckBox"));

            hboxLayout->addWidget(AxisCheckBox);

            spacerItem = new QSpacerItem(141, 31, QSizePolicy::Expanding, QSizePolicy::Minimum);

            hboxLayout->addItem(spacerItem);

            cancelButton = new QPushButton(Dialog);
            cancelButton->setObjectName(QStringLiteral("cancelButton"));

            hboxLayout->addWidget(cancelButton);

            vboxLayout->addLayout(hboxLayout);

            retranslateUi(Dialog);
            QObject::connect(cancelButton, SIGNAL(clicked()), Dialog, SLOT(reject()));
            QObject::connect(FPSCheckBox, SIGNAL(clicked(bool)), viewer, SLOT(setFPSIsDisplayed(bool)));
            QObject::connect(AxisCheckBox, SIGNAL(clicked(bool)), viewer, SLOT(setAxisIsDrawn(bool)));
            QObject::connect(GridCheckBox, SIGNAL(clicked(bool)), viewer, SLOT(setGridIsDrawn(bool)));
            QObject::connect(viewer, SIGNAL(gridIsDrawnChanged(bool)), GridCheckBox, SLOT(setChecked(bool)));
            QObject::connect(viewer, SIGNAL(axisIsDrawnChanged(bool)), AxisCheckBox, SLOT(setChecked(bool)));
            QObject::connect(viewer, SIGNAL(FPSIsDisplayedChanged(bool)), FPSCheckBox, SLOT(setChecked(bool)));

            QMetaObject::connectSlotsByName(Dialog);
        } // setupUi

        void retranslateUi(QDialog *Dialog)
        {
            Dialog->setWindowTitle(QApplication::translate("Dialog", "Interface", 0));
            FPSCheckBox->setText(QApplication::translate("Dialog", "FPS", 0));
            GridCheckBox->setText(QApplication::translate("Dialog", "Grid", 0));
            AxisCheckBox->setText(QApplication::translate("Dialog", "Axis", 0));
            cancelButton->setText(QApplication::translate("Dialog", "Quit", 0));
        } // retranslateUi

    };

    namespace Ui {
        class Dialog: public Ui_Dialog {};
    } // namespace Ui

    QT_END_NAMESPACE

    #endif // UI_VIEWERINTERFACE_H

## main.cpp

    #include <qapplication.h>

    #if QT_VERSION >= 0x040000
    # include "ui_viewerInterface.h"
      class ViewerInterface : public QDialog, public Ui::Dialog
      {
      public:
        ViewerInterface() { setupUi(this); }
      };
    #else
    # include "interface.h"
    # include "viewerInterface.Qt3.h"
    #endif

    int main(int argc, char** argv)
    {
      QApplication application(argc,argv);

      ViewerInterface vi;

    #if QT_VERSION < 0x040000
      application.setMainWidget(&vi);
    #else
      vi.setWindowTitle("interface");
    #endif

      vi.show();

      return application.exec();
    }

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Last modified on Thursday, December 19, 2013.