wheelwidget.cpp Example File | Qt WebKit Examples 5.4

- Qt 5.4
- Qt WebKit Examples
- Wheel Scroller Example
- wheelwidget.cpp Example File
- Qt 5.4.2 Reference Documentation

# wheelwidget.cpp Example File

webkitwidgets/scroller/wheel/wheelwidget.cpp

    /****************************************************************************
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    #include <QtWidgets>

    #include "wheelwidget.h"

    #define WHEEL_SCROLL_OFFSET 50000.0

    AbstractWheelWidget::AbstractWheelWidget(bool touch, QWidget *parent)
        : QWidget(parent)
        , m_currentItem(0)
        , m_itemOffset(0)
    {
    // ![0]
        QScroller::grabGesture(this, touch ? QScroller::TouchGesture : QScroller::LeftMouseButtonGesture);
    // ![0]
    }

    AbstractWheelWidget::~AbstractWheelWidget()
    { }

    int AbstractWheelWidget::currentIndex() const
    {
        return m_currentItem;
    }

    void AbstractWheelWidget::setCurrentIndex(int index)
    {
        if (index >= 0 && index < itemCount()) {
            m_currentItem = index;
            m_itemOffset = 0;
            update();
        }
    }

    bool AbstractWheelWidget::event(QEvent *e)
    {
        switch (e->type()) {
    // ![1]
        case QEvent::ScrollPrepare:
        {
            // We set the snap positions as late as possible so that we are sure
            // we get the correct itemHeight
            QScroller *scroller = QScroller::scroller(this);
            scroller->setSnapPositionsY( WHEEL_SCROLL_OFFSET, itemHeight() );

            QScrollPrepareEvent *se = static_cast<QScrollPrepareEvent *>(e);
            se->setViewportSize(QSizeF(size()));
            // we claim a huge scrolling area and a huge content position and
            // hope that the user doesn't notice that the scroll area is restricted
            se->setContentPosRange(QRectF(0.0, 0.0, 0.0, WHEEL_SCROLL_OFFSET * 2));
            se->setContentPos(QPointF(0.0, WHEEL_SCROLL_OFFSET + m_currentItem * itemHeight() + m_itemOffset));
            se->accept();
            return true;
        }
    // ![1]
    // ![2]
        case QEvent::Scroll:
        {
            QScrollEvent *se = static_cast<QScrollEvent *>(e);

            qreal y = se->contentPos().y();
            int iy = y - WHEEL_SCROLL_OFFSET;
            int ih = itemHeight();

    // ![2]
    // ![3]
            // -- calculate the current item position and offset and redraw the widget
            int ic = itemCount();
            if (ic>0) {
                m_currentItem = iy / ih % ic;
                m_itemOffset = iy % ih;

                // take care when scrolling backwards. Modulo returns negative numbers
                if (m_itemOffset < 0) {
                    m_itemOffset += ih;
                    m_currentItem--;
                }

                if (m_currentItem < 0)
                    m_currentItem += ic;
            }
            // -- repaint
            update();

            se->accept();
            return true;
    // ![3]
        }
        default:
            return QWidget::event(e);
        }
        return true;
    }

    void AbstractWheelWidget::paintEvent(QPaintEvent* event)
    {
        Q_UNUSED( event );

        // -- first calculate size and position.
        int w = width();
        int h = height();

        QPainter painter(this);
        QPalette palette = QApplication::palette();
        QPalette::ColorGroup colorGroup = isEnabled() ? QPalette::Active : QPalette::Disabled;

        // linear gradient brush
        QLinearGradient grad(0.5, 0, 0.5, 1.0);
        grad.setColorAt(0, palette.color(colorGroup, QPalette::ButtonText));
        grad.setColorAt(0.2, palette.color(colorGroup, QPalette::Button));
        grad.setColorAt(0.8, palette.color(colorGroup, QPalette::Button));
        grad.setColorAt(1.0, palette.color(colorGroup, QPalette::ButtonText));
        grad.setCoordinateMode( QGradient::ObjectBoundingMode );
        QBrush gBrush( grad );

        // paint a border and background
        painter.setPen(palette.color(colorGroup, QPalette::ButtonText));
        painter.setBrush(gBrush);
        // painter.setBrushOrigin( QPointF( 0.0, 0.0 ) );
        painter.drawRect( 0, 0, w-1, h-1 );

        // paint inner border
        painter.setPen(palette.color(colorGroup, QPalette::Button));
        painter.setBrush(Qt::NoBrush);
        painter.drawRect( 1, 1, w-3, h-3 );

        // paint the items
        painter.setClipRect( QRect( 3, 3, w-6, h-6 ) );
        painter.setPen(palette.color(colorGroup, QPalette::ButtonText));

        int iH = itemHeight();
        int iC = itemCount();
        if (iC > 0) {

            m_itemOffset = m_itemOffset % iH;

            for (int i=-h/2/iH; i<=h/2/iH+1; i++) {

                int itemNum = m_currentItem + i;
                while (itemNum < 0)
                    itemNum += iC;
                while (itemNum >= iC)
                    itemNum -= iC;

                paintItem(&painter, itemNum, QRect(6, h/2 +i*iH - m_itemOffset - iH/2, w-6, iH ));
            }
        }

        // draw a transparent bar over the center
        QColor highlight = palette.color(colorGroup, QPalette::Highlight);
        highlight.setAlpha(150);

        QLinearGradient grad2(0.5, 0, 0.5, 1.0);
        grad2.setColorAt(0, highlight);
        grad2.setColorAt(1.0, highlight.lighter());
        grad2.setCoordinateMode( QGradient::ObjectBoundingMode );
        QBrush gBrush2( grad2 );

        QLinearGradient grad3(0.5, 0, 0.5, 1.0);
        grad3.setColorAt(0, highlight);
        grad3.setColorAt(1.0, highlight.darker());
        grad3.setCoordinateMode( QGradient::ObjectBoundingMode );
        QBrush gBrush3( grad3 );

        painter.fillRect( QRect( 0, h/2 - iH/2, w, iH/2 ), gBrush2 );
        painter.fillRect( QRect( 0, h/2,        w, iH/2 ), gBrush3 );
    }

    /*!
        Rotates the wheel widget to a given index.
        You can also give an index greater than itemCount or less than zero in which
        case the wheel widget will scroll in the given direction and end up with
        (index % itemCount)
    */
    void AbstractWheelWidget::scrollTo(int index)
    {
        QScroller *scroller = QScroller::scroller(this);

        scroller->scrollTo(QPointF(0, WHEEL_SCROLL_OFFSET + index * itemHeight()), 5000);
    }

    /*!
        \class StringWheelWidget
        \brief The StringWheelWidget class is an implementation of the AbstractWheelWidget class that draws QStrings as items.
        \sa AbstractWheelWidget
    */

    StringWheelWidget::StringWheelWidget(bool touch)
        : AbstractWheelWidget(touch)
    { }

    QStringList StringWheelWidget::items() const
    {
        return m_items;
    }

    void StringWheelWidget::setItems( const QStringList &items )
    {
        m_items = items;
        if (m_currentItem >= items.count())
            m_currentItem = items.count()-1;
        update();
    }

    QSize StringWheelWidget::sizeHint() const
    {
        // determine font size
        QFontMetrics fm(font());

        return QSize( fm.width("m") * 10 + 6, fm.height() * 7 + 6 );
    }

    QSize StringWheelWidget::minimumSizeHint() const
    {
        QFontMetrics fm(font());

        return QSize( fm.width("m") * 5 + 6, fm.height() * 3 + 6 );
    }

    void StringWheelWidget::paintItem(QPainter* painter, int index, const QRect &rect)
    {
        painter->drawText(rect, Qt::AlignCenter, m_items.at(index));
    }

    int StringWheelWidget::itemHeight() const
    {
        QFontMetrics fm(font());
        return fm.height();
    }

    int StringWheelWidget::itemCount() const
    {
        return m_items.count();
    }