main.cpp Example File

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 #include <QtCore>
 #include <QtWidgets>

 #include "flickable.h"

 // Returns a list of two-word color names
 static QStringList colorPairs(int max)
 {
     // capitalize the first letter
     QStringList colors = QColor::colorNames();
     colors.removeAll("transparent");
     int num = colors.count();
     for (int c = 0; c < num; ++c)
         colors[c] = colors[c][0].toUpper() + colors[c].mid(1);

     // combine two colors, e.g. "lime skyblue"
     QStringList combinedColors;
     for (int i = 0; i < num; ++i)
         for (int j = 0; j < num; ++j)
             combinedColors << QString("%1 %2").arg(colors[i]).arg(colors[j]);

     // randomize it
     colors.clear();
     while (combinedColors.count()) {
         int i = qrand() % combinedColors.count();
         colors << combinedColors[i];
         combinedColors.removeAt(i);
         if (colors.count() == max)
             break;
     }

     return colors;
 }

 class ColorList : public QWidget, public Flickable
 {
     Q_OBJECT

 public:
     ColorList(QWidget *parent = 0)
             : QWidget(parent) {
         m_offset = 0;
         m_height = QFontMetrics(font()).height() + 5;
         m_highlight = -1;
         m_selected = -1;

         QStringList colors = colorPairs(999);
         for (int i = 0; i < colors.count(); ++i) {
             QString c = colors[i];
             QString str;
             str.sprintf("%4d", i + 1);
             m_colorNames << (str + "   " + c);

             QStringList duet = c.split(' ');
             m_firstColor << duet[0];
             m_secondColor << duet[1];
         }

         setAttribute(Qt::WA_OpaquePaintEvent, true);
         setAttribute(Qt::WA_NoSystemBackground, true);

         setMouseTracking(true);
         Flickable::setAcceptMouseClick(this);
     }

 protected:
     // reimplement from Flickable
     virtual QPoint scrollOffset() const {
         return QPoint(0, m_offset);
     }

     // reimplement from Flickable
     virtual void setScrollOffset(const QPoint &offset) {
         int yy = offset.y();
         if (yy != m_offset) {
             m_offset = qBound(0, yy, m_height * m_colorNames.count() - height());
             update();
         }
     }

 protected:
     void paintEvent(QPaintEvent *event) {
         QPainter p(this);
         p.fillRect(event->rect(), Qt::white);
         int start = m_offset / m_height;
         int y = start * m_height - m_offset;
         if (m_offset <= 0) {
             start = 0;
             y = -m_offset;
         }
         int end = start + height() / m_height + 1;
         if (end > m_colorNames.count() - 1)
             end = m_colorNames.count() - 1;
         for (int i = start; i <= end; ++i, y += m_height) {

             p.setBrush(Qt::NoBrush);
             p.setPen(Qt::black);
             if (i == m_highlight) {
                 p.fillRect(0, y, width(), m_height, QColor(0, 64, 128));
                 p.setPen(Qt::white);
             }
             if (i == m_selected) {
                 p.fillRect(0, y, width(), m_height, QColor(0, 128, 240));
                 p.setPen(Qt::white);
             }

             p.drawText(m_height + 2, y, width(), m_height, Qt::AlignVCenter, m_colorNames[i]);

             p.setPen(Qt::NoPen);
             p.setBrush(m_firstColor[i]);
             p.drawRect(1, y + 1, m_height - 2, m_height - 2);
             p.setBrush(m_secondColor[i]);
             p.drawRect(5, y + 5, m_height - 11, m_height - 11);
         }
         p.end();
     }

     void keyReleaseEvent(QKeyEvent *event) {
         if (event->key() == Qt::Key_Down) {
             m_offset += 20;
             event->accept();
             update();
             return;
         }
         if (event->key() == Qt::Key_Up) {
             m_offset -= 20;
             event->accept();
             update();
             return;
         }
     }

     void mousePressEvent(QMouseEvent *event) {
         Flickable::handleMousePress(event);
         if (event->isAccepted())
             return;

         if (event->button() == Qt::LeftButton) {
             int y = event->pos().y() + m_offset;
             int i = y / m_height;
             if (i != m_highlight) {
                 m_highlight = i;
                 m_selected = -1;
                 update();
             }
             event->accept();
         }
     }

     void mouseMoveEvent(QMouseEvent *event) {
         Flickable::handleMouseMove(event);
     }

     void mouseReleaseEvent(QMouseEvent *event) {
         Flickable::handleMouseRelease(event);
         if (event->isAccepted())
             return;

         if (event->button() == Qt::LeftButton) {
             m_selected = m_highlight;
             event->accept();
             update();
         }
     }

 private:
     int m_offset;
     int m_height;
     int m_highlight;
     int m_selected;
     QStringList m_colorNames;
     QList<QColor> m_firstColor;
     QList<QColor> m_secondColor;
 };

 #include "main.moc"

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);

     ColorList list;
     list.setWindowTitle("Kinetic Scrolling");
     list.resize(320, 320);
     list.show();

     return app.exec();
 }