refs #387, preparation for level meter

* not yet connected with audio

src/blackgui/components/audiovolumecomponent.ui

@@ -162,7 +162,7 @@
         <item>
          <widget class="QPushButton" name="pb_Volume100">
           <property name="sizePolicy">
-           <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
+           <sizepolicy hsizetype="Preferred" vsizetype="Maximum">
             <horstretch>0</horstretch>
             <verstretch>0</verstretch>
            </sizepolicy>
@@ -179,17 +179,14 @@
          </widget>
         </item>
         <item>
-         <spacer name="hs_AudioSoundButtons">
-          <property name="orientation">
-           <enum>Qt::Horizontal</enum>
+         <widget class="BlackGui::CLevelMeter" name="wip_LevelMeter" native="true">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="MinimumExpanding" vsizetype="Minimum">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
           </property>
-          <property name="sizeHint" stdset="0">
-           <size>
-            <width>40</width>
-            <height>20</height>
-           </size>
-          </property>
-         </spacer>
+         </widget>
         </item>
        </layout>
       </widget>
@@ -218,6 +215,14 @@
    </item>
   </layout>
  </widget>
+ <customwidgets>
+  <customwidget>
+   <class>BlackGui::CLevelMeter</class>
+   <extends>QWidget</extends>
+   <header>blackgui/levelmeter.h</header>
+   <container>1</container>
+  </customwidget>
+ </customwidgets>
  <resources>
   <include location="../../blackmisc/blackmisc.qrc"/>
  </resources>

src/blackgui/levelmeter.cpp

@@ -0,0 +1,111 @@
+/* Copyright (C) 2013
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ *
+ * Class based on qt example: Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)
+ */
+
+#include "levelmeter.h"
+
+#include <math.h>
+
+#include <QPainter>
+#include <QTimer>
+#include <QDebug>
+
+
+namespace BlackGui
+{
+    CLevelMeter::CLevelMeter(QWidget *parent)
+        :   QWidget(parent)
+        ,   m_peakDecayRate(PeakDecayRate)
+        ,   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, &QTimer::timeout, this, &CLevelMeter::ps_redrawTimerExpired);
+        m_redrawTimer->start(RedrawInterval);
+    }
+
+    CLevelMeter::~CLevelMeter()
+    { }
+
+    void CLevelMeter::reset()
+    {
+        m_rmsLevel = 0.0;
+        m_peakLevel = 0.0;
+        update();
+    }
+
+    void CLevelMeter::levelChanged(double rmsLevel, double peakLevel, int numSamples)
+    {
+        // Smooth the RMS signal
+        const double smooth = pow(double(0.9), static_cast<double>(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 CLevelMeter::ps_redrawTimerExpired()
+    {
+        // Decay the peak signal
+        const int elapsedMs = m_peakLevelChanged.elapsed();
+        const double 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 CLevelMeter::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);
+    }
+
+} // namespace

src/blackgui/levelmeter.h

@@ -0,0 +1,85 @@
+/* Copyright (C) 2013
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ *
+ * Class based on qt example: Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)
+ */
+
+//! \file
+
+#ifndef BLACKGUI_LEVELMETER_H
+#define BLACKGUI_LEVELMETER_H
+
+#include <QTime>
+#include <QWidget>
+
+namespace BlackGui
+{
+
+    /**
+     * 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 CLevelMeter : public QWidget
+    {
+        Q_OBJECT
+    public:
+        //! Constructor
+        CLevelMeter(QWidget *parent = 0);
+
+        //! Destructor
+        ~CLevelMeter();
+
+        //! \copydoc QWidget::paintEvent
+        void paintEvent(QPaintEvent *event) override;
+
+    public slots:
+
+        //! Clean up
+        void reset();
+
+        //! Values
+        void levelChanged(double rmsLevel, double peakLevel, int numSamples);
+
+    private slots:
+        void ps_redrawTimerExpired();
+
+    private:
+        const int RedrawInterval        = 100; // ms
+        const double PeakDecayRate      = 0.001;
+        const int PeakHoldLevelDuration = 2000; // ms
+
+        //! Height of RMS level bar, range 0.0 - 1.0.
+        double m_rmsLevel = 0.0;
+
+        //! Most recent peak level, range 0.0 - 1.0.
+        double m_peakLevel = 0.0;
+
+        //! 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.
+        double m_decayedPeakLevel = 0.0;
+
+        //! Time at which m_peakLevel was last changed.
+        QTime m_peakLevelChanged;
+
+        //! Rate at which peak level bar decays.  Expressed in level units / millisecond.
+        double m_peakDecayRate;
+
+        //! High watermark of peak level. Range 0.0 - 1.0.
+        double m_peakHoldLevel = 0.0;
+
+        //! Time at which m_peakHoldLevel was last changed.
+        QTime m_peakHoldLevelChanged;
+
+        QTimer *m_redrawTimer;
+        QColor m_rmsColor;
+        QColor m_peakColor;
+    };
+}
+
+#endif // guard