- Qt 5.5
- Qt Multimedia
- Spectrum Example
- levelmeter.h Example File
- Qt 5.5.1 Reference Documentation

# levelmeter.h Example File

spectrum/app/levelmeter.h

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
    **   * Neither the name of The Qt Company Ltd nor the names of its
    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
    **
    **
    ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    #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