Qt 5.11 | Qt Multimedia | Spectrum Example | waveform.h Example File

Qt 5.11.3 Reference Documentation

# waveform.h Example File

multimedia/spectrum/app/waveform.h

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      #ifndef WAVEFORM_H
      #define WAVEFORM_H

      #include <QAudioFormat>
      #include <QPixmap>
      #include <QScopedPointer>
      #include <QWidget>

      /**
       * Widget which displays a section of the audio waveform.
       *
       * The waveform is rendered on a set of QPixmaps which form a group of tiles
       * whose extent covers the widget.  As the audio position is updated, these
       * tiles are scrolled from left to right; when the left-most tile scrolls
       * outside the widget, it is moved to the right end of the tile array and
       * painted with the next section of the waveform.
       */
      class Waveform : public QWidget
      {
          Q_OBJECT

      public:
          explicit Waveform(QWidget *parent = 0);
          ~Waveform();

          // QWidget
          void paintEvent(QPaintEvent *event) override;
          void resizeEvent(QResizeEvent *event) override;

          void initialize(const QAudioFormat &format, qint64 audioBufferSize, qint64 windowDurationUs);
          void reset();

          void setAutoUpdatePosition(bool enabled);

      public slots:
          void bufferChanged(qint64 position, qint64 length, const QByteArray &buffer);
          void audioPositionChanged(qint64 position);

      private:
          static const int NullIndex = -1;

          void deletePixmaps();

          /*
           * (Re)create all pixmaps, repaint and update the display.
           * Triggers an update();
           */
          void createPixmaps(const QSize &newSize);

          /*
           * Update window position.
           * Triggers an update().
           */
          void setWindowPosition(qint64 position);

          /*
           * Base position of tile
           */
          qint64 tilePosition(int index) const;

          /*
           * Structure which identifies a point within a given
           * tile.
           */
          struct TilePoint
          {
              TilePoint(int idx = 0, qint64 pos = 0, qint64 pix = 0)
              :   index(idx), positionOffset(pos), pixelOffset(pix)
              { }

              // Index of tile
              int     index;

              // Number of bytes from start of tile
              qint64  positionOffset;

              // Number of pixels from left of corresponding pixmap
              int     pixelOffset;
          };

          /*
           * Convert position in m_buffer into a tile index and an offset in pixels
           * into the corresponding pixmap.
           *
           * \param position  Offset into m_buffer, in bytes

           * If position is outside the tile array, index is NullIndex and
           * offset is zero.
           */
          TilePoint tilePoint(qint64 position) const;

          /*
           * Convert offset in bytes into a tile into an offset in pixels
           * within that tile.
           */
          int tilePixelOffset(qint64 positionOffset) const;

          /*
           * Convert offset in bytes into the window into an offset in pixels
           * within the widget rect().
           */
          int windowPixelOffset(qint64 positionOffset) const;

          /*
           * Paint all tiles which can be painted.
           * \return true iff update() was called
           */
          bool paintTiles();

          /*
           * Paint the specified tile
           *
           * \pre Sufficient data is available to completely paint the tile, i.e.
           *      m_dataLength is greater than the upper bound of the tile.
           */
          void paintTile(int index);

          /*
           * Move the first n tiles to the end of the array, and mark them as not
           * painted.
           */
          void shuffleTiles(int n);

          /*
           * Reset tile array
           */
          void resetTiles(qint64 newStartPos);

      private:
          qint64                  m_bufferPosition;
          qint64                  m_bufferLength;
          QByteArray              m_buffer;

          qint64                  m_audioPosition;
          QAudioFormat            m_format;

          bool                    m_active;

          QSize                   m_pixmapSize;
          QVector<QPixmap*>       m_pixmaps;

          struct Tile {
              // Pointer into parent m_pixmaps array
              QPixmap*            pixmap;

              // Flag indicating whether this tile has been painted
              bool                painted;
          };

          QVector<Tile>           m_tiles;

          // Length of audio data in bytes depicted by each tile
          qint64                  m_tileLength;

          // Position in bytes of the first tile, relative to m_buffer
          qint64                  m_tileArrayStart;

          qint64                  m_windowPosition;
          qint64                  m_windowLength;
      };

      #endif // WAVEFORM_H