levelmeter.h Example File

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  #ifndef LEVELMETER_H
  #define LEVELMETER_H

  #include <QTime>
  #include <QWidget>

  /**
   * Widget which displays a vertical audio level meter, indicating the
   * RMS and peak levels of the window of audio samples most recently analyzed
   * by the Engine.
   */
  class LevelMeter : public QWidget
  {
      Q_OBJECT

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

      void paintEvent(QPaintEvent *event);

  public slots:
      void reset();
      void levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples);

  private slots:
      void redrawTimerExpired();

  private:
      /**
       * Height of RMS level bar.
       * Range 0.0 - 1.0.
       */
      qreal m_rmsLevel;

      /**
       * Most recent peak level.
       * Range 0.0 - 1.0.
       */
      qreal m_peakLevel;

      /**
       * Height of peak level bar.
       * This is calculated by decaying m_peakLevel depending on the
       * elapsed time since m_peakLevelChanged, and the value of m_decayRate.
       */
      qreal m_decayedPeakLevel;

      /**
       * Time at which m_peakLevel was last changed.
       */
      QTime m_peakLevelChanged;

      /**
       * Rate at which peak level bar decays.
       * Expressed in level units / millisecond.
       */
      qreal m_peakDecayRate;

      /**
       * High watermark of peak level.
       * Range 0.0 - 1.0.
       */
      qreal m_peakHoldLevel;

      /**
       * Time at which m_peakHoldLevel was last changed.
       */
      QTime m_peakHoldLevelChanged;

      QTimer *m_redrawTimer;

      QColor m_rmsColor;
      QColor m_peakColor;

  };

  #endif // LEVELMETER_H