Qt Reference Documentation

waveform.cpp Example File

demos/spectrum/app/waveform.cpp
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 #include "waveform.h"
 #include "utils.h"
 #include <QPainter>
 #include <QResizeEvent>
 #include <QDebug>

 Waveform::Waveform(const QByteArray &buffer, QWidget *parent)
     :   QWidget(parent)
     ,   m_buffer(buffer)
     ,   m_dataLength(0)
     ,   m_position(0)
     ,   m_active(false)
     ,   m_tileLength(0)
     ,   m_tileArrayStart(0)
     ,   m_windowPosition(0)
     ,   m_windowLength(0)
 {
     setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     setMinimumHeight(50);
 }

 Waveform::~Waveform()
 {
     deletePixmaps();
 }

 void Waveform::paintEvent(QPaintEvent * /*event*/)
 {
     QPainter painter(this);

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

     if (m_active) {
         WAVEFORM_DEBUG << "Waveform::paintEvent"
                        << "windowPosition" << m_windowPosition
                        << "windowLength" << m_windowLength;
         qint64 pos = m_windowPosition;
         const qint64 windowEnd = m_windowPosition + m_windowLength;
         int destLeft = 0;
         int destRight = 0;
         while (pos < windowEnd) {
             const TilePoint point = tilePoint(pos);
             WAVEFORM_DEBUG << "Waveform::paintEvent" << "pos" << pos
                            << "tileIndex" << point.index
                            << "positionOffset" << point.positionOffset
                            << "pixelOffset" << point.pixelOffset;

             if (point.index != NullIndex) {
                 const Tile &tile = m_tiles[point.index];
                 if (tile.painted) {
                     const qint64 sectionLength = qMin((m_tileLength - point.positionOffset),
                                                      (windowEnd - pos));
                     Q_ASSERT(sectionLength > 0);

                     const int sourceRight = tilePixelOffset(point.positionOffset + sectionLength);
                     destRight = windowPixelOffset(pos - m_windowPosition + sectionLength);

                     QRect destRect = rect();
                     destRect.setLeft(destLeft);
                     destRect.setRight(destRight);

                     QRect sourceRect(QPoint(), m_pixmapSize);
                     sourceRect.setLeft(point.pixelOffset);
                     sourceRect.setRight(sourceRight);

                     WAVEFORM_DEBUG << "Waveform::paintEvent" << "tileIndex" << point.index
                                    << "source" << point.pixelOffset << sourceRight
                                    << "dest" << destLeft << destRight;

                     painter.drawPixmap(destRect, *tile.pixmap, sourceRect);

                     destLeft = destRight;

                     if (point.index < m_tiles.count()) {
                         pos = tilePosition(point.index + 1);
                         WAVEFORM_DEBUG << "Waveform::paintEvent" << "pos ->" << pos;
                     } else {
                         // Reached end of tile array
                         WAVEFORM_DEBUG << "Waveform::paintEvent" << "reached end of tile array";
                         break;
                     }
                 } else {
                     // Passed last tile which is painted
                     WAVEFORM_DEBUG << "Waveform::paintEvent" << "tile" << point.index << "not painted";
                     break;
                 }
             } else {
                 // pos is past end of tile array
                 WAVEFORM_DEBUG << "Waveform::paintEvent" << "pos" << pos << "past end of tile array";
                 break;
             }
         }

         WAVEFORM_DEBUG << "Waveform::paintEvent" << "final pos" << pos << "final x" << destRight;
     }
 }

 void Waveform::resizeEvent(QResizeEvent *event)
 {
     if (event->size() != event->oldSize())
         createPixmaps(event->size());
 }

 void Waveform::initialize(const QAudioFormat &format, qint64 audioBufferSize, qint64 windowDurationUs)
 {
     WAVEFORM_DEBUG << "Waveform::initialize"
                    << "audioBufferSize" << audioBufferSize
                    << "m_buffer.size()" << m_buffer.size()
                    << "windowDurationUs" << windowDurationUs;

     reset();

     m_format = format;

     // Calculate tile size
     m_tileLength = audioBufferSize;

     // Calculate window size
     m_windowLength = audioLength(m_format, windowDurationUs);

     // Calculate number of tiles required
     int nTiles;
     if (m_tileLength > m_windowLength) {
         nTiles = 2;
     } else {
         nTiles = m_windowLength / m_tileLength + 1;
         if (m_windowLength % m_tileLength)
             ++nTiles;
     }

     WAVEFORM_DEBUG << "Waveform::initialize"
                    << "tileLength" << m_tileLength
                    << "windowLength" << m_windowLength
                    << "nTiles" << nTiles;

     m_pixmaps.fill(0, nTiles);
     m_tiles.resize(nTiles);

     createPixmaps(rect().size());

     m_active = true;
 }

 void Waveform::reset()
 {
     WAVEFORM_DEBUG << "Waveform::reset";

     m_dataLength = 0;
     m_position = 0;
     m_format = QAudioFormat();
     m_active = false;
     deletePixmaps();
     m_tiles.clear();
     m_tileLength = 0;
     m_tileArrayStart = 0;
     m_windowPosition = 0;
     m_windowLength = 0;
 }

 void Waveform::dataLengthChanged(qint64 length)
 {
     WAVEFORM_DEBUG << "Waveform::dataLengthChanged" << length;
     const qint64 oldLength = m_dataLength;
     m_dataLength = length;

     if (m_active) {
         if (m_dataLength < oldLength)
             positionChanged(m_dataLength);
         else
             paintTiles();
     }
 }

 void Waveform::positionChanged(qint64 position)
 {
     WAVEFORM_DEBUG << "Waveform::positionChanged" << position;

     if (position + m_windowLength > m_dataLength)
         position = m_dataLength - m_windowLength;

     m_position = position;

     setWindowPosition(position);
 }

 void Waveform::deletePixmaps()
 {
     QPixmap *pixmap;
     foreach (pixmap, m_pixmaps)
         delete pixmap;
     m_pixmaps.clear();
 }

 void Waveform::createPixmaps(const QSize &widgetSize)
 {
     m_pixmapSize = widgetSize;
     m_pixmapSize.setWidth(qreal(widgetSize.width()) * m_tileLength / m_windowLength);

     WAVEFORM_DEBUG << "Waveform::createPixmaps"
                    << "widgetSize" << widgetSize
                    << "pixmapSize" << m_pixmapSize;

     Q_ASSERT(m_tiles.count() == m_pixmaps.count());

     // (Re)create pixmaps
     for (int i=0; i<m_pixmaps.size(); ++i) {
         delete m_pixmaps[i];
         m_pixmaps[i] = 0;
         m_pixmaps[i] = new QPixmap(m_pixmapSize);
     }

     // Update tile pixmap pointers, and mark for repainting
     for (int i=0; i<m_tiles.count(); ++i) {
         m_tiles[i].pixmap = m_pixmaps[i];
         m_tiles[i].painted = false;
     }

     paintTiles();
 }

 void Waveform::setWindowPosition(qint64 position)
 {
     WAVEFORM_DEBUG << "Waveform::setWindowPosition"
                    << "old" << m_windowPosition << "new" << position
                    << "tileArrayStart" << m_tileArrayStart;

     const qint64 oldPosition = m_windowPosition;
     m_windowPosition = position;

     if((m_windowPosition >= oldPosition) &&
         (m_windowPosition - m_tileArrayStart < (m_tiles.count() * m_tileLength))) {
         // Work out how many tiles need to be shuffled
         const qint64 offset = m_windowPosition - m_tileArrayStart;
         const int nTiles = offset / m_tileLength;
         shuffleTiles(nTiles);
     } else {
         resetTiles(m_windowPosition);
     }

     if(!paintTiles() && m_windowPosition != oldPosition)
         update();
 }

 qint64 Waveform::tilePosition(int index) const
 {
     return m_tileArrayStart + index * m_tileLength;
 }

 Waveform::TilePoint Waveform::tilePoint(qint64 position) const
 {
     TilePoint result;
     if (position >= m_tileArrayStart) {
         const qint64 tileArrayEnd = m_tileArrayStart + m_tiles.count() * m_tileLength;
         if (position < tileArrayEnd) {
             const qint64 offsetIntoTileArray = position - m_tileArrayStart;
             result.index = offsetIntoTileArray / m_tileLength;
             Q_ASSERT(result.index >= 0 && result.index <= m_tiles.count());
             result.positionOffset = offsetIntoTileArray % m_tileLength;
             result.pixelOffset = tilePixelOffset(result.positionOffset);
             Q_ASSERT(result.pixelOffset >= 0 && result.pixelOffset <= m_pixmapSize.width());
         }
     }

     return result;
 }

 int Waveform::tilePixelOffset(qint64 positionOffset) const
 {
     Q_ASSERT(positionOffset >= 0 && positionOffset <= m_tileLength);
     const int result = (qreal(positionOffset) / m_tileLength) * m_pixmapSize.width();
     return result;
 }

 int Waveform::windowPixelOffset(qint64 positionOffset) const
 {
     Q_ASSERT(positionOffset >= 0 && positionOffset <= m_windowLength);
     const int result = (qreal(positionOffset) / m_windowLength) * rect().width();
     return result;
 }

 bool Waveform::paintTiles()
 {
     WAVEFORM_DEBUG << "Waveform::paintTiles";
     bool updateRequired = false;

     for (int i=0; i<m_tiles.count(); ++i) {
         const Tile &tile = m_tiles[i];
         if (!tile.painted) {
             const qint64 tileEnd = m_tileArrayStart + (i + 1) * m_tileLength;
             if (m_dataLength >= tileEnd) {
                 paintTile(i);
                 updateRequired = true;
             }
         }
     }

     if (updateRequired)
         update();

     return updateRequired;
 }

 void Waveform::paintTile(int index)
 {
     WAVEFORM_DEBUG << "Waveform::paintTile" << "index" << index;

     const qint64 tileStart = m_tileArrayStart + index * m_tileLength;
     Q_ASSERT(m_dataLength >= tileStart + m_tileLength);

     Tile &tile = m_tiles[index];
     Q_ASSERT(!tile.painted);

     const qint16* base = reinterpret_cast<const qint16*>(m_buffer.constData());
     const qint16* buffer = base + (tileStart / 2);
     const int numSamples = m_tileLength / (2 * m_format.channels());

     QPainter painter(tile.pixmap);

     painter.fillRect(tile.pixmap->rect(), Qt::black);

     QPen pen(Qt::white);
     painter.setPen(pen);

     // Calculate initial PCM value
     qint16 previousPcmValue = 0;
     if (buffer > base)
         previousPcmValue = *(buffer - m_format.channels());

     // Calculate initial point
     const qreal previousRealValue = pcmToReal(previousPcmValue);
     const int originY = ((previousRealValue + 1.0) / 2) * m_pixmapSize.height();
     const QPoint origin(0, originY);

     QLine line(origin, origin);

     for (int i=0; i<numSamples; ++i) {
         const qint16* ptr = buffer + i * m_format.channels();
         const qint16 pcmValue = *ptr;
         const qreal realValue = pcmToReal(pcmValue);

         const int x = tilePixelOffset(i * 2 * m_format.channels());
         const int y = ((realValue + 1.0) / 2) * m_pixmapSize.height();

         line.setP2(QPoint(x, y));
         painter.drawLine(line);
         line.setP1(line.p2());
     }

     tile.painted = true;
 }

 void Waveform::shuffleTiles(int n)
 {
     WAVEFORM_DEBUG << "Waveform::shuffleTiles" << "n" << n;

     while (n--) {
         Tile tile = m_tiles.first();
         tile.painted = false;
         m_tiles.erase(m_tiles.begin());
         m_tiles += tile;
         m_tileArrayStart += m_tileLength;
     }

     WAVEFORM_DEBUG << "Waveform::shuffleTiles" << "tileArrayStart" << m_tileArrayStart;
 }

 void Waveform::resetTiles(qint64 newStartPos)
 {
     WAVEFORM_DEBUG << "Waveform::resetTiles" << "newStartPos" << newStartPos;

     QVector<Tile>::iterator i = m_tiles.begin();
     for ( ; i != m_tiles.end(); ++i)
         i->painted = false;

     m_tileArrayStart = newStartPos;
 }
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