Textured Surface Example

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 #include "surfacegraph.h"

 #include <QtWidgets/QApplication>
 #include <QtWidgets/QWidget>
 #include <QtWidgets/QHBoxLayout>
 #include <QtWidgets/QVBoxLayout>
 #include <QtWidgets/QGroupBox>
 #include <QtWidgets/QCheckBox>
 #include <QtWidgets/QLabel>
 #include <QtWidgets/QMessageBox>
 #include <QtGui/QScreen>
 #include <QtGui/QPainter>

 int main(int argc, char **argv)
 {
     QApplication app(argc, argv);
     Q3DSurface *graph = new Q3DSurface();
     QWidget *container = QWidget::createWindowContainer(graph);

     if (!graph->hasContext()) {
         QMessageBox msgBox;
         msgBox.setText("Couldn't initialize the OpenGL context.");
         msgBox.exec();
         return -1;
     }

     QSize screenSize = graph->screen()->size();
     container->setMinimumSize(QSize(screenSize.width() / 2, screenSize.height() / 1.6));
     container->setMaximumSize(screenSize);
     container->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
     container->setFocusPolicy(Qt::StrongFocus);

     QWidget *widget = new QWidget;
     QHBoxLayout *hLayout = new QHBoxLayout(widget);
     QVBoxLayout *vLayout = new QVBoxLayout();
     hLayout->addWidget(container, 1);
     hLayout->addLayout(vLayout);
     vLayout->setAlignment(Qt::AlignTop);

     widget->setWindowTitle(QStringLiteral("Textured surface example"));

     QCheckBox *enableTexture = new QCheckBox(widget);
     enableTexture->setText(QStringLiteral("Surface texture"));

     int height = 400;
     int width = 100;
     int border = 10;
     QLinearGradient gr(0, 0, 1, height - 2 * border);
     gr.setColorAt(1.0f, Qt::black);
     gr.setColorAt(0.8f, Qt::darkGreen);
     gr.setColorAt(0.6f, Qt::green);
     gr.setColorAt(0.4f, Qt::yellow);
     gr.setColorAt(0.2f, Qt::red);
     gr.setColorAt(0.0f, Qt::darkRed);

     QPixmap pm(width, height);
     pm.fill(Qt::transparent);
     QPainter pmp(&pm);
     pmp.setBrush(QBrush(gr));
     pmp.setPen(Qt::NoPen);
     pmp.drawRect(border, border, 35, height - 2 * border);
     pmp.setPen(Qt::black);
     int step = (height - 2 * border) / 5;
     for (int i = 0; i < 6; i++) {
         int yPos = i * step + border;
         pmp.drawLine(border, yPos, 55, yPos);
         pmp.drawText(60, yPos + 2, QString("%1 m").arg(550 - (i * 110)));
     }

     QLabel *label = new QLabel(widget);
     label->setPixmap(pm);

     QGroupBox *heightMapGroupBox = new QGroupBox(QStringLiteral("Highlight color map"));
     QVBoxLayout *colorMapVBox = new QVBoxLayout;
     colorMapVBox->addWidget(label);
     heightMapGroupBox->setLayout(colorMapVBox);

     vLayout->addWidget(enableTexture);
     vLayout->addWidget(heightMapGroupBox);

     widget->show();

     SurfaceGraph *modifier = new SurfaceGraph(graph);

     QObject::connect(enableTexture, &QCheckBox::stateChanged,
                      modifier, &SurfaceGraph::toggleSurfaceTexture);

     enableTexture->setChecked(true);

     return app.exec();
 }