Qt 4.8: levelmeter.h Example File (demos/spectrum/app/levelmeter.h)

Qt Reference Documentation

- Qt 4.8
- ALL VERSIONS

- A
- A
- A
- Print

# levelmeter.h Example File

demos/spectrum/app/levelmeter.h

     /****************************************************************************
     **
     ** 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.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** 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 Digia Plc and its Subsidiary(-ies) 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:
         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