levelmeter.h Example File | Qt Multimedia 5.9

Qt 5.9 | Qt Multimedia | Spectrum Example | levelmeter.h Example File

Qt 5.9.2 Reference Documentation

# levelmeter.h Example File

multimedia/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) override;

      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