waveform.h Example File

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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

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