/****************************************************************************

**

** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the examples of the Qt Toolkit.

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

#include "levelmeter.h"

#include <math.h>

#include <QPainter>

#include <QTimer>

#include <QDebug>

// Constants

const int RedrawInterval = 100; // ms

const qreal PeakDecayRate = 0.001;

const int PeakHoldLevelDuration = 2000; // ms

LevelMeter::LevelMeter(QWidget *parent)

    :   QWidget(parent)

    ,   m_rmsLevel(0.0)

    ,   m_peakLevel(0.0)

    ,   m_decayedPeakLevel(0.0)

    ,   m_peakDecayRate(PeakDecayRate)

    ,   m_peakHoldLevel(0.0)

    ,   m_redrawTimer(new QTimer(this))

    ,   m_rmsColor(Qt::red)

    ,   m_peakColor(255, 200, 200, 255)

{

    setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Preferred);

    setMinimumWidth(30);

    connect(m_redrawTimer, SIGNAL(timeout()), this, SLOT(redrawTimerExpired()));

    m_redrawTimer->start(RedrawInterval);

}

LevelMeter::~LevelMeter()

{

}

void LevelMeter::reset()

{

    m_rmsLevel = 0.0;

    m_peakLevel = 0.0;

    update();

}

void LevelMeter::levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples)

{

    // Smooth the RMS signal

    const qreal smooth = pow(qreal(0.9), static_cast<qreal>(numSamples) / 256); // TODO: remove this magic number

    m_rmsLevel = (m_rmsLevel * smooth) + (rmsLevel * (1.0 - smooth));

    if (peakLevel > m_decayedPeakLevel) {

        m_peakLevel = peakLevel;

        m_decayedPeakLevel = peakLevel;

        m_peakLevelChanged.start();

    }

    if (peakLevel > m_peakHoldLevel) {

        m_peakHoldLevel = peakLevel;

        m_peakHoldLevelChanged.start();

    }

    update();

}

void LevelMeter::redrawTimerExpired()

{

    // Decay the peak signal

    const int elapsedMs = m_peakLevelChanged.elapsed();

    const qreal decayAmount = m_peakDecayRate * elapsedMs;

    if (decayAmount < m_peakLevel)

        m_decayedPeakLevel = m_peakLevel - decayAmount;

    else

        m_decayedPeakLevel = 0.0;

    // Check whether to clear the peak hold level

    if (m_peakHoldLevelChanged.elapsed() > PeakHoldLevelDuration)

        m_peakHoldLevel = 0.0;

    update();

}

void LevelMeter::paintEvent(QPaintEvent *event)

{

    Q_UNUSED(event)

    QPainter painter(this);

    painter.fillRect(rect(), Qt::black);

    QRect bar = rect();

    bar.setTop(rect().top() + (1.0 - m_peakHoldLevel) * rect().height());

    bar.setBottom(bar.top() + 5);

    painter.fillRect(bar, m_rmsColor);

    bar.setBottom(rect().bottom());

    bar.setTop(rect().top() + (1.0 - m_decayedPeakLevel) * rect().height());

    painter.fillRect(bar, m_peakColor);

    bar.setTop(rect().top() + (1.0 - m_rmsLevel) * rect().height());

    painter.fillRect(bar, m_rmsColor);

}