Qt Reference Documentation

# spectrograph.cpp Example File

demos/spectrum/app/spectrograph.cpp

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     #include "spectrograph.h"
     #include <QPainter>
     #include <QMouseEvent>
     #include <QDebug>
     #include <QTimerEvent>

     const int NullTimerId = -1;
     const int NullIndex = -1;
     const int BarSelectionInterval = 2000;

     Spectrograph::Spectrograph(QWidget *parent)
         :   QWidget(parent)
         ,   m_barSelected(NullIndex)
         ,   m_timerId(NullTimerId)
         ,   m_lowFreq(0.0)
         ,   m_highFreq(0.0)
     {
         setMinimumHeight(100);
     }

     Spectrograph::~Spectrograph()
     {

     }

     void Spectrograph::setParams(int numBars, qreal lowFreq, qreal highFreq)
     {
         Q_ASSERT(numBars > 0);
         Q_ASSERT(highFreq > lowFreq);
         m_bars.resize(numBars);
         m_lowFreq = lowFreq;
         m_highFreq = highFreq;
         updateBars();
     }

     void Spectrograph::timerEvent(QTimerEvent *event)
     {
         Q_ASSERT(event->timerId() == m_timerId);
         Q_UNUSED(event) // suppress warnings in release builds
         killTimer(m_timerId);
         m_timerId = NullTimerId;
         m_barSelected = NullIndex;
         update();
     }

     void Spectrograph::paintEvent(QPaintEvent *event)
     {
         Q_UNUSED(event)

         QPainter painter(this);
         painter.fillRect(rect(), Qt::black);

         const int numBars = m_bars.count();

         // Highlight region of selected bar
         if (m_barSelected != NullIndex && numBars) {
             QRect regionRect = rect();
             regionRect.setLeft(m_barSelected * rect().width() / numBars);
             regionRect.setWidth(rect().width() / numBars);
             QColor regionColor(202, 202, 64);
             painter.setBrush(Qt::DiagCrossPattern);
             painter.fillRect(regionRect, regionColor);
             painter.setBrush(Qt::NoBrush);
         }

         QColor barColor(51, 204, 102);
         QColor clipColor(255, 255, 0);

         // Draw the outline
         const QColor gridColor = barColor.darker();
         QPen gridPen(gridColor);
         painter.setPen(gridPen);
         painter.drawLine(rect().topLeft(), rect().topRight());
         painter.drawLine(rect().topRight(), rect().bottomRight());
         painter.drawLine(rect().bottomRight(), rect().bottomLeft());
         painter.drawLine(rect().bottomLeft(), rect().topLeft());

         QVector<qreal> dashes;
         dashes << 2 << 2;
         gridPen.setDashPattern(dashes);
         painter.setPen(gridPen);

         // Draw vertical lines between bars
         if (numBars) {
             const int numHorizontalSections = numBars;
             QLine line(rect().topLeft(), rect().bottomLeft());
             for (int i=1; i<numHorizontalSections; ++i) {
                 line.translate(rect().width()/numHorizontalSections, 0);
                 painter.drawLine(line);
             }
         }

         // Draw horizontal lines
         const int numVerticalSections = 10;
         QLine line(rect().topLeft(), rect().topRight());
         for (int i=1; i<numVerticalSections; ++i) {
             line.translate(0, rect().height()/numVerticalSections);
             painter.drawLine(line);
         }

         barColor = barColor.lighter();
         barColor.setAlphaF(0.75);
         clipColor.setAlphaF(0.75);

         // Draw the bars
         if (numBars) {
             // Calculate width of bars and gaps
             const int widgetWidth = rect().width();
             const int barPlusGapWidth = widgetWidth / numBars;
             const int barWidth = 0.8 * barPlusGapWidth;
             const int gapWidth = barPlusGapWidth - barWidth;
             const int paddingWidth = widgetWidth - numBars * (barWidth + gapWidth);
             const int leftPaddingWidth = (paddingWidth + gapWidth) / 2;
             const int barHeight = rect().height() - 2 * gapWidth;

             for (int i=0; i<numBars; ++i) {
                 const qreal value = m_bars[i].value;
                 Q_ASSERT(value >= 0.0 && value <= 1.0);
                 QRect bar = rect();
                 bar.setLeft(rect().left() + leftPaddingWidth + (i * (gapWidth + barWidth)));
                 bar.setWidth(barWidth);
                 bar.setTop(rect().top() + gapWidth + (1.0 - value) * barHeight);
                 bar.setBottom(rect().bottom() - gapWidth);

                 QColor color = barColor;
                 if (m_bars[i].clipped)
                     color = clipColor;

                 painter.fillRect(bar, color);
             }
         }
     }

     void Spectrograph::mousePressEvent(QMouseEvent *event)
     {
         const QPoint pos = event->pos();
         const int index = m_bars.count() * (pos.x() - rect().left()) / rect().width();
         selectBar(index);
     }

     void Spectrograph::reset()
     {
         m_spectrum.reset();
         spectrumChanged(m_spectrum);
     }

     void Spectrograph::spectrumChanged(const FrequencySpectrum &spectrum)
     {
         m_spectrum = spectrum;
         updateBars();
     }

     int Spectrograph::barIndex(qreal frequency) const
     {
         Q_ASSERT(frequency >= m_lowFreq && frequency < m_highFreq);
         const qreal bandWidth = (m_highFreq - m_lowFreq) / m_bars.count();
         const int index = (frequency - m_lowFreq) / bandWidth;
         if(index <0 || index >= m_bars.count())
             Q_ASSERT(false);
         return index;
     }

     QPair<qreal, qreal> Spectrograph::barRange(int index) const
     {
         Q_ASSERT(index >= 0 && index < m_bars.count());
         const qreal bandWidth = (m_highFreq - m_lowFreq) / m_bars.count();
         return QPair<qreal, qreal>(index * bandWidth, (index+1) * bandWidth);
     }

     void Spectrograph::updateBars()
     {
         m_bars.fill(Bar());
         FrequencySpectrum::const_iterator i = m_spectrum.begin();
         const FrequencySpectrum::const_iterator end = m_spectrum.end();
         for ( ; i != end; ++i) {
             const FrequencySpectrum::Element e = *i;
             if (e.frequency >= m_lowFreq && e.frequency < m_highFreq) {
                 Bar &bar = m_bars[barIndex(e.frequency)];
                 bar.value = qMax(bar.value, e.amplitude);
                 bar.clipped |= e.clipped;
             }
         }
         update();
     }

     void Spectrograph::selectBar(int index) {
         const QPair<qreal, qreal> frequencyRange = barRange(index);
         const QString message = QString("%1 - %2 Hz")
                                     .arg(frequencyRange.first)
                                     .arg(frequencyRange.second);
         emit infoMessage(message, BarSelectionInterval);

         if (NullTimerId != m_timerId)
             killTimer(m_timerId);
         m_timerId = startTimer(BarSelectionInterval);

         m_barSelected = index;
         update();
     }