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>

     //#define PAINT_EVENT_TRACE
     #ifdef PAINT_EVENT_TRACE
     #   define WAVEFORM_PAINT_DEBUG qDebug()
     #else
     #   define WAVEFORM_PAINT_DEBUG nullDebug()
     #endif

     Waveform::Waveform(QWidget *parent)
         :   QWidget(parent)
         ,   m_bufferPosition(0)
         ,   m_bufferLength(0)
         ,   m_audioPosition(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_PAINT_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_PAINT_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_PAINT_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_PAINT_DEBUG << "Waveform::paintEvent" << "pos ->" << pos;
                         } else {
                             // Reached end of tile array
                             WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "reached end of tile array";
                             break;
                         }
                     } else {
                         // Passed last tile which is painted
                         WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "tile" << point.index << "not painted";
                         break;
                     }
                 } else {
                     // pos is past end of tile array
                     WAVEFORM_PAINT_DEBUG << "Waveform::paintEvent" << "pos" << pos << "past end of tile array";
                     break;
                 }
             }

             WAVEFORM_PAINT_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
                        << "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_bufferPosition = 0;
         m_buffer = QByteArray();
         m_audioPosition = 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::bufferChanged(qint64 position, qint64 length, const QByteArray &buffer)
     {
         WAVEFORM_DEBUG << "Waveform::bufferChanged"
                        << "audioPosition" << m_audioPosition
                        << "bufferPosition" << position
                        << "bufferLength" << length;
         m_bufferPosition = position;
         m_bufferLength = length;
         m_buffer = buffer;
         paintTiles();
     }

     void Waveform::audioPositionChanged(qint64 position)
     {
         WAVEFORM_DEBUG << "Waveform::audioPositionChanged"
                        << "audioPosition" << position
                        << "bufferPosition" << m_bufferPosition
                        << "bufferLength" << m_bufferLength;

         if (position >= m_bufferPosition) {
             if (position + m_windowLength > m_bufferPosition + m_bufferLength)
                 position = qMax(qint64(0), m_bufferPosition + m_bufferLength - m_windowLength);
             m_audioPosition = 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;
         }
     }

     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 tileStart = m_tileArrayStart + i * m_tileLength;
                 const qint64 tileEnd = tileStart + m_tileLength;
                 if (m_bufferPosition <= tileStart && m_bufferPosition + m_bufferLength >= tileEnd) {
                     paintTile(i);
                     updateRequired = true;
                 }
             }
         }

         if (updateRequired)
             update();

         return updateRequired;
     }

     void Waveform::paintTile(int index)
     {
         const qint64 tileStart = m_tileArrayStart + index * m_tileLength;

         WAVEFORM_DEBUG << "Waveform::paintTile"
                        << "index" << index
                        << "bufferPosition" << m_bufferPosition
                        << "bufferLength" << m_bufferLength
                        << "start" << tileStart
                        << "end" << tileStart + m_tileLength;

         Q_ASSERT(m_bufferPosition <= tileStart);
         Q_ASSERT(m_bufferPosition + m_bufferLength >= 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 - m_bufferPosition) / 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 int offset = reinterpret_cast<const char*>(ptr) - m_buffer.constData();
             Q_ASSERT(offset >= 0);
             Q_ASSERT(offset < m_bufferLength);

             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;
     }