- Qt 5.3
- Qt Multimedia
- Spectrum Example
- levelmeter.h Example File
- Qt 5.3.2 Reference Documentation

# levelmeter.h Example File

spectrum/app/levelmeter.h

    /****************************************************************************
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    ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
    ** Contact: http://www.qt-project.org/legal
    **
    ** This file is part of the examples of the Qt Toolkit.
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    ** $QT_BEGIN_LICENSE:BSD$
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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