qtmultimedia/examples/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);
    void resizeEvent(QResizeEvent *event);

    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