obs-studio/UI/volume-control.cpp

#include "volume-control.hpp"
#include "qt-wrappers.hpp"
#include "obs-app.hpp"
#include "mute-checkbox.hpp"
#include "slider-absoluteset-style.hpp"
#include <QFontDatabase>
#include <QHBoxLayout>
#include <QPushButton>
#include <QSlider>
#include <QLabel>
#include <QPainter>
#include <QStyleFactory>

using namespace std;

#define CLAMP(x, min, max) ((x) < (min) ? (min) : ((x) > (max) ? (max) : (x)))

QWeakPointer<VolumeMeterTimer> VolumeMeter::updateTimer;

void VolControl::OBSVolumeChanged(void *data, float db)
{
	Q_UNUSED(db);
	VolControl *volControl = static_cast<VolControl*>(data);

	QMetaObject::invokeMethod(volControl, "VolumeChanged");
}

void VolControl::OBSVolumeLevel(void *data,
		const float magnitude[MAX_AUDIO_CHANNELS],
		const float peak[MAX_AUDIO_CHANNELS],
		const float inputPeak[MAX_AUDIO_CHANNELS])
{
	VolControl *volControl = static_cast<VolControl*>(data);

	volControl->volMeter->setLevels(magnitude, peak, inputPeak);
}

void VolControl::OBSVolumeMuted(void *data, calldata_t *calldata)
{
	VolControl *volControl = static_cast<VolControl*>(data);
	bool muted = calldata_bool(calldata, "muted");

	QMetaObject::invokeMethod(volControl, "VolumeMuted",
			Q_ARG(bool, muted));
}

void VolControl::VolumeChanged()
{
	slider->blockSignals(true);
	slider->setValue((int) (obs_fader_get_deflection(obs_fader) * 100.0f));
	slider->blockSignals(false);

	updateText();
}

void VolControl::VolumeMuted(bool muted)
{
	if (mute->isChecked() != muted)
		mute->setChecked(muted);
}

void VolControl::SetMuted(bool checked)
{
	obs_source_set_muted(source, checked);
}

void VolControl::SliderChanged(int vol)
{
	obs_fader_set_deflection(obs_fader, float(vol) * 0.01f);
	updateText();
}

void VolControl::updateText()
{
	QString db = QString::number(obs_fader_get_db(obs_fader), 'f', 1)
			.append(" dB");
	volLabel->setText(db);

	bool muted = obs_source_muted(source);
	const char *accTextLookup = muted
		? "VolControl.SliderMuted"
		: "VolControl.SliderUnmuted";

	QString sourceName = obs_source_get_name(source);
	QString accText = QTStr(accTextLookup).arg(sourceName, db);

	slider->setAccessibleName(accText);
}

QString VolControl::GetName() const
{
	return nameLabel->text();
}

void VolControl::SetName(const QString &newName)
{
	nameLabel->setText(newName);
}

void VolControl::EmitConfigClicked()
{
	emit ConfigClicked();
}

void VolControl::SetMeterDecayRate(qreal q)
{
	volMeter->setPeakDecayRate(q);
}

void VolControl::setPeakMeterType(enum obs_peak_meter_type peakMeterType)
{
	volMeter->setPeakMeterType(peakMeterType);
}

VolControl::VolControl(OBSSource source_, bool showConfig, bool vertical)
		: source      (std::move(source_)),
		levelTotal    (0.0f),
		levelCount    (0.0f),
		obs_fader     (obs_fader_create(OBS_FADER_CUBIC)),
		obs_volmeter  (obs_volmeter_create(OBS_FADER_LOG)),
		vertical      (vertical)
{
	nameLabel = new QLabel();
	volLabel  = new QLabel();
	mute      = new MuteCheckBox();
	QString sourceName = obs_source_get_name(source);
	setObjectName(sourceName);

	if (showConfig) {
		config = new QPushButton(this);
		config->setProperty("themeID", "configIconSmall");
		config->setFlat(true);
		config->setSizePolicy(QSizePolicy::Maximum,
				QSizePolicy::Maximum);
		config->setMaximumSize(22, 22);
		config->setAutoDefault(false);

		config->setAccessibleName(QTStr("VolControl.Properties")
				.arg(sourceName));

		connect(config, &QAbstractButton::clicked,
				this, &VolControl::EmitConfigClicked);
	}

	QVBoxLayout *mainLayout = new QVBoxLayout;
	mainLayout->setContentsMargins(4, 4, 4, 4);
	mainLayout->setSpacing(2);

	if (vertical) {
		QHBoxLayout *nameLayout = new QHBoxLayout;
		QHBoxLayout *controlLayout = new QHBoxLayout;
		QHBoxLayout *volLayout = new QHBoxLayout;
		QHBoxLayout *meterLayout  = new QHBoxLayout;

		volMeter  = new VolumeMeter(nullptr, obs_volmeter, true);
		slider    = new QSlider(Qt::Vertical);

		nameLayout->setAlignment(Qt::AlignCenter);
		meterLayout->setAlignment(Qt::AlignCenter);
		controlLayout->setAlignment(Qt::AlignCenter);
		volLayout->setAlignment(Qt::AlignCenter);

		nameLayout->setContentsMargins(0, 0, 0, 0);
		nameLayout->setSpacing(0);
		nameLayout->addWidget(nameLabel);

		controlLayout->setContentsMargins(0, 0, 0, 0);
		controlLayout->setSpacing(0);

		if (showConfig)
			controlLayout->addWidget(config);

		controlLayout->addItem(new QSpacerItem(3, 0));
		// Add Headphone (audio monitoring) widget here
		controlLayout->addWidget(mute);

		meterLayout->setContentsMargins(0, 0, 0, 0);
		meterLayout->setSpacing(0);
		meterLayout->addWidget(volMeter);
		meterLayout->addWidget(slider);

		volLayout->setContentsMargins(0, 0, 0, 0);
		volLayout->setSpacing(0);
		volLayout->addWidget(volLabel);

		mainLayout->addItem(nameLayout);
		mainLayout->addItem(volLayout);
		mainLayout->addItem(meterLayout);
		mainLayout->addItem(controlLayout);

		setMaximumWidth(110);
	} else {
		QHBoxLayout *volLayout  = new QHBoxLayout;
		QHBoxLayout *textLayout = new QHBoxLayout;
		QHBoxLayout *botLayout  = new QHBoxLayout;

		volMeter  = new VolumeMeter(nullptr, obs_volmeter, false);
		slider    = new QSlider(Qt::Horizontal);

		textLayout->setContentsMargins(0, 0, 0, 0);
		textLayout->addWidget(nameLabel);
		textLayout->addWidget(volLabel);
		textLayout->setAlignment(nameLabel, Qt::AlignLeft);
		textLayout->setAlignment(volLabel,  Qt::AlignRight);

		volLayout->addWidget(slider);
		volLayout->addWidget(mute);
		volLayout->setSpacing(5);

		botLayout->setContentsMargins(0, 0, 0, 0);
		botLayout->setSpacing(0);
		botLayout->addLayout(volLayout);

		if (showConfig)
			botLayout->addWidget(config);

		mainLayout->addItem(textLayout);
		mainLayout->addWidget(volMeter);
		mainLayout->addItem(botLayout);
	}

	setLayout(mainLayout);

	QFont font = nameLabel->font();
	font.setPointSize(font.pointSize()-1);

	nameLabel->setText(sourceName);
	nameLabel->setFont(font);
	volLabel->setFont(font);
	slider->setMinimum(0);
	slider->setMaximum(100);

	bool muted = obs_source_muted(source);
	mute->setChecked(muted);
	mute->setAccessibleName(QTStr("VolControl.Mute").arg(sourceName));
	obs_fader_add_callback(obs_fader, OBSVolumeChanged, this);
	obs_volmeter_add_callback(obs_volmeter, OBSVolumeLevel, this);

	signal_handler_connect(obs_source_get_signal_handler(source),
			"mute", OBSVolumeMuted, this);

	QWidget::connect(slider, SIGNAL(valueChanged(int)),
			this, SLOT(SliderChanged(int)));
	QWidget::connect(mute, SIGNAL(clicked(bool)),
			this, SLOT(SetMuted(bool)));

	obs_fader_attach_source(obs_fader, source);
	obs_volmeter_attach_source(obs_volmeter, source);

	QString styleName = slider->style()->objectName();
	QStyle *style;
	style = QStyleFactory::create(styleName);
	if (!style) {
		style = new SliderAbsoluteSetStyle();
	} else {
		style = new SliderAbsoluteSetStyle(style);
	}

	style->setParent(slider);
	slider->setStyle(style);

	/* Call volume changed once to init the slider position and label */
	VolumeChanged();
}

VolControl::~VolControl()
{
	obs_fader_remove_callback(obs_fader, OBSVolumeChanged, this);
	obs_volmeter_remove_callback(obs_volmeter, OBSVolumeLevel, this);

	signal_handler_disconnect(obs_source_get_signal_handler(source),
			"mute", OBSVolumeMuted, this);

	obs_fader_destroy(obs_fader);
	obs_volmeter_destroy(obs_volmeter);
}

QColor VolumeMeter::getBackgroundNominalColor() const
{
	return backgroundNominalColor;
}

void VolumeMeter::setBackgroundNominalColor(QColor c)
{
	backgroundNominalColor = std::move(c);
}

QColor VolumeMeter::getBackgroundWarningColor() const
{
	return backgroundWarningColor;
}

void VolumeMeter::setBackgroundWarningColor(QColor c)
{
	backgroundWarningColor = std::move(c);
}

QColor VolumeMeter::getBackgroundErrorColor() const
{
	return backgroundErrorColor;
}

void VolumeMeter::setBackgroundErrorColor(QColor c)
{
	backgroundErrorColor = std::move(c);
}

QColor VolumeMeter::getForegroundNominalColor() const
{
	return foregroundNominalColor;
}

void VolumeMeter::setForegroundNominalColor(QColor c)
{
	foregroundNominalColor = std::move(c);
}

QColor VolumeMeter::getForegroundWarningColor() const
{
	return foregroundWarningColor;
}

void VolumeMeter::setForegroundWarningColor(QColor c)
{
	foregroundWarningColor = std::move(c);
}

QColor VolumeMeter::getForegroundErrorColor() const
{
	return foregroundErrorColor;
}

void VolumeMeter::setForegroundErrorColor(QColor c)
{
	foregroundErrorColor = std::move(c);
}

QColor VolumeMeter::getClipColor() const
{
	return clipColor;
}

void VolumeMeter::setClipColor(QColor c)
{
	clipColor = std::move(c);
}

QColor VolumeMeter::getMagnitudeColor() const
{
	return magnitudeColor;
}

void VolumeMeter::setMagnitudeColor(QColor c)
{
	magnitudeColor = std::move(c);
}

QColor VolumeMeter::getMajorTickColor() const
{
	return majorTickColor;
}

void VolumeMeter::setMajorTickColor(QColor c)
{
	majorTickColor = std::move(c);
}

QColor VolumeMeter::getMinorTickColor() const
{
	return minorTickColor;
}

void VolumeMeter::setMinorTickColor(QColor c)
{
	minorTickColor = std::move(c);
}

qreal VolumeMeter::getMinimumLevel() const
{
	return minimumLevel;
}

void VolumeMeter::setMinimumLevel(qreal v)
{
	minimumLevel = v;
}

qreal VolumeMeter::getWarningLevel() const
{
	return warningLevel;
}

void VolumeMeter::setWarningLevel(qreal v)
{
	warningLevel = v;
}

qreal VolumeMeter::getErrorLevel() const
{
	return errorLevel;
}

void VolumeMeter::setErrorLevel(qreal v)
{
	errorLevel = v;
}

qreal VolumeMeter::getClipLevel() const
{
	return clipLevel;
}

void VolumeMeter::setClipLevel(qreal v)
{
	clipLevel = v;
}

qreal VolumeMeter::getMinimumInputLevel() const
{
	return minimumInputLevel;
}

void VolumeMeter::setMinimumInputLevel(qreal v)
{
	minimumInputLevel = v;
}

qreal VolumeMeter::getPeakDecayRate() const
{
	return peakDecayRate;
}

void VolumeMeter::setPeakDecayRate(qreal v)
{
	peakDecayRate = v;
}

qreal VolumeMeter::getMagnitudeIntegrationTime() const
{
	return magnitudeIntegrationTime;
}

void VolumeMeter::setMagnitudeIntegrationTime(qreal v)
{
	magnitudeIntegrationTime = v;
}

qreal VolumeMeter::getPeakHoldDuration() const
{
	return peakHoldDuration;
}

void VolumeMeter::setPeakHoldDuration(qreal v)
{
	peakHoldDuration = v;
}

qreal VolumeMeter::getInputPeakHoldDuration() const
{
	return inputPeakHoldDuration;
}

void VolumeMeter::setInputPeakHoldDuration(qreal v)
{
	inputPeakHoldDuration = v;
}

void VolumeMeter::setPeakMeterType(enum obs_peak_meter_type peakMeterType)
{
	obs_volmeter_set_peak_meter_type(obs_volmeter, peakMeterType);
	switch (peakMeterType) {
	case TRUE_PEAK_METER:
		// For true-peak meters EBU has defined the Permitted Maximum,
		// taking into account the accuracy of the meter and further
		// processing required by lossy audio compression.
		//
		// The alignment level was not specified, but I've adjusted
		// it compared to a sample-peak meter. Incidently Youtube
		// uses this new Alignment Level as the maximum integrated
		// loudness of a video.
		//
		//  * Permitted Maximum Level (PML) = -2.0 dBTP
		//  * Alignment Level (AL) = -13 dBTP
		setErrorLevel(-2.0);
		setWarningLevel(-13.0);
		break;

	case SAMPLE_PEAK_METER:
	default:
		// For a sample Peak Meter EBU has the following level
		// definitions, taking into account inaccuracies of this meter:
		//
		//  * Permitted Maximum Level (PML) = -9.0 dBFS
		//  * Alignment Level (AL) = -20.0 dBFS
		setErrorLevel(-9.0);
		setWarningLevel(-20.0);
		break;
	}
}

VolumeMeter::VolumeMeter(QWidget *parent, obs_volmeter_t *obs_volmeter,
		bool vertical)
		: QWidget(parent), obs_volmeter(obs_volmeter),
		vertical(vertical)
{
	// Use a font that can be rendered small.
	tickFont = QFont("Arial");
	tickFont.setPixelSize(7);
	// Default meter color settings, they only show if
	// there is no stylesheet, do not remove.
	backgroundNominalColor.setRgb(0x26, 0x7f, 0x26);    // Dark green
	backgroundWarningColor.setRgb(0x7f, 0x7f, 0x26);    // Dark yellow
	backgroundErrorColor.setRgb(0x7f, 0x26, 0x26);      // Dark red
	foregroundNominalColor.setRgb(0x4c, 0xff, 0x4c);    // Bright green
	foregroundWarningColor.setRgb(0xff, 0xff, 0x4c);    // Bright yellow
	foregroundErrorColor.setRgb(0xff, 0x4c, 0x4c);      // Bright red
	clipColor.setRgb(0xff, 0xff, 0xff);                 // Bright white
	magnitudeColor.setRgb(0x00, 0x00, 0x00);            // Black
	majorTickColor.setRgb(0xff, 0xff, 0xff);            // Black
	minorTickColor.setRgb(0xcc, 0xcc, 0xcc);            // Black
	minimumLevel = -60.0;                               // -60 dB
	warningLevel = -20.0;                               // -20 dB
	errorLevel = -9.0;                                  //  -9 dB
	clipLevel = -0.5;                                   //  -0.5 dB
	minimumInputLevel = -50.0;                          // -50 dB
	peakDecayRate = 11.76;                              //  20 dB / 1.7 sec
	magnitudeIntegrationTime = 0.3;                     //  99% in 300 ms
	peakHoldDuration = 20.0;                            //  20 seconds
	inputPeakHoldDuration = 1.0;                        //  1 second

	channels = (int)audio_output_get_channels(obs_get_audio());

	handleChannelCofigurationChange();
	updateTimerRef = updateTimer.toStrongRef();
	if (!updateTimerRef) {
		updateTimerRef = QSharedPointer<VolumeMeterTimer>::create();
		updateTimerRef->start(34);
		updateTimer = updateTimerRef;
	}

	updateTimerRef->AddVolControl(this);
}

VolumeMeter::~VolumeMeter()
{
	updateTimerRef->RemoveVolControl(this);
	delete tickPaintCache;
}

void VolumeMeter::setLevels(const float magnitude[MAX_AUDIO_CHANNELS],
		const float peak[MAX_AUDIO_CHANNELS],
		const float inputPeak[MAX_AUDIO_CHANNELS])
{
	uint64_t ts = os_gettime_ns();
	QMutexLocker locker(&dataMutex);

	currentLastUpdateTime = ts;
	for (int channelNr = 0; channelNr < MAX_AUDIO_CHANNELS; channelNr++) {
		currentMagnitude[channelNr] = magnitude[channelNr];
		currentPeak[channelNr] = peak[channelNr];
		currentInputPeak[channelNr] = inputPeak[channelNr];
	}

	// In case there are more updates then redraws we must make sure
	// that the ballistics of peak and hold are recalculated.
	locker.unlock();
	calculateBallistics(ts);
}

inline void VolumeMeter::resetLevels()
{
	currentLastUpdateTime = 0;
	for (int channelNr = 0; channelNr < MAX_AUDIO_CHANNELS; channelNr++) {
		currentMagnitude[channelNr] = -M_INFINITE;
		currentPeak[channelNr] = -M_INFINITE;
		currentInputPeak[channelNr] = -M_INFINITE;

		displayMagnitude[channelNr] = -M_INFINITE;
		displayPeak[channelNr] = -M_INFINITE;
		displayPeakHold[channelNr] = -M_INFINITE;
		displayPeakHoldLastUpdateTime[channelNr] = 0;
		displayInputPeakHold[channelNr] = -M_INFINITE;
		displayInputPeakHoldLastUpdateTime[channelNr] = 0;
	}
}

inline void VolumeMeter::handleChannelCofigurationChange()
{
	QMutexLocker locker(&dataMutex);

	int currentNrAudioChannels = obs_volmeter_get_nr_channels(obs_volmeter);
	if (displayNrAudioChannels != currentNrAudioChannels) {
		displayNrAudioChannels = currentNrAudioChannels;

		// Make room for 3 pixels meter, with one pixel between each.
		// Then 9/13 pixels for ticks and numbers.
		if (vertical)
			setMinimumSize(displayNrAudioChannels * 4 + 14, 130);
		else
			setMinimumSize(130, displayNrAudioChannels * 4 + 8);

		resetLevels();
	}
}

inline bool VolumeMeter::detectIdle(uint64_t ts)
{
	double timeSinceLastUpdate = (ts - currentLastUpdateTime) * 0.000000001;
	if (timeSinceLastUpdate > 0.5) {
		resetLevels();
		return true;
	} else {
		return false;
	}
}

inline void VolumeMeter::calculateBallisticsForChannel(int channelNr,
		uint64_t ts, qreal timeSinceLastRedraw)
{
	if (currentPeak[channelNr] >= displayPeak[channelNr] ||
		isnan(displayPeak[channelNr])) {
		// Attack of peak is immediate.
		displayPeak[channelNr] = currentPeak[channelNr];
	} else {
		// Decay of peak is 40 dB / 1.7 seconds for Fast Profile
		// 20 dB / 1.7 seconds for Medium Profile (Type I PPM)
		// 24 dB / 2.8 seconds for Slow Profile (Type II PPM)
		float decay = float(peakDecayRate * timeSinceLastRedraw);
		displayPeak[channelNr] = CLAMP(displayPeak[channelNr] - decay,
			currentPeak[channelNr], 0);
	}

	if (currentPeak[channelNr] >= displayPeakHold[channelNr] ||
		!isfinite(displayPeakHold[channelNr])) {
		// Attack of peak-hold is immediate, but keep track
		// when it was last updated.
		displayPeakHold[channelNr] = currentPeak[channelNr];
		displayPeakHoldLastUpdateTime[channelNr] = ts;
	} else {
		// The peak and hold falls back to peak
		// after 20 seconds.
		qreal timeSinceLastPeak = (uint64_t)(ts -
			displayPeakHoldLastUpdateTime[channelNr]) * 0.000000001;
		if (timeSinceLastPeak > peakHoldDuration) {
			displayPeakHold[channelNr] = currentPeak[channelNr];
			displayPeakHoldLastUpdateTime[channelNr] = ts;
		}
	}

	if (currentInputPeak[channelNr] >= displayInputPeakHold[channelNr] ||
		!isfinite(displayInputPeakHold[channelNr])) {
		// Attack of peak-hold is immediate, but keep track
		// when it was last updated.
		displayInputPeakHold[channelNr] = currentInputPeak[channelNr];
		displayInputPeakHoldLastUpdateTime[channelNr] = ts;
	} else {
		// The peak and hold falls back to peak after 1 second.
		qreal timeSinceLastPeak = (uint64_t)(ts -
			displayInputPeakHoldLastUpdateTime[channelNr]) *
			0.000000001;
		if (timeSinceLastPeak > inputPeakHoldDuration) {
			displayInputPeakHold[channelNr] =
				currentInputPeak[channelNr];
			displayInputPeakHoldLastUpdateTime[channelNr] =
				ts;
		}
	}

	if (!isfinite(displayMagnitude[channelNr])) {
		// The statements in the else-leg do not work with
		// NaN and infinite displayMagnitude.
		displayMagnitude[channelNr] = currentMagnitude[channelNr];
	} else {
		// A VU meter will integrate to the new value to 99% in 300 ms.
		// The calculation here is very simplified and is more accurate
		// with higher frame-rate.
		float attack = float((currentMagnitude[channelNr] -
			displayMagnitude[channelNr]) *
				(timeSinceLastRedraw /
			magnitudeIntegrationTime) * 0.99);
		displayMagnitude[channelNr] = CLAMP(displayMagnitude[channelNr]
				+ attack, (float)minimumLevel, 0);
	}
}

inline void VolumeMeter::calculateBallistics(uint64_t ts,
		qreal timeSinceLastRedraw)
{
	QMutexLocker locker(&dataMutex);

	for (int channelNr = 0; channelNr < MAX_AUDIO_CHANNELS; channelNr++)
		calculateBallisticsForChannel(channelNr, ts,
				timeSinceLastRedraw);
}

void VolumeMeter::paintInputMeter(QPainter &painter, int x, int y, int width,
		int height, float peakHold)
{
	QMutexLocker locker(&dataMutex);
	QColor color;

	if (peakHold < minimumInputLevel)
		color = backgroundNominalColor;
	else if (peakHold < warningLevel)
		color = foregroundNominalColor;
	else if (peakHold < errorLevel)
		color = foregroundWarningColor;
	else if (peakHold <= clipLevel)
		color = foregroundErrorColor;
	else
		color = clipColor;

	painter.fillRect(x, y, width, height, color);
}

void VolumeMeter::paintHTicks(QPainter &painter, int x, int y, int width,
		int height)
{
	qreal scale = width / minimumLevel;

	painter.setFont(tickFont);
	painter.setPen(majorTickColor);

	// Draw major tick lines and numeric indicators.
	for (int i = 0; i >= minimumLevel; i-= 5) {
		int position = int(x + width - (i * scale) - 1);
		QString str = QString::number(i);

		if (i == 0 || i == -5)
			painter.drawText(position - 3, height, str);
		else
			painter.drawText(position - 5, height, str);
		painter.drawLine(position, y, position, y + 2);
	}

	// Draw minor tick lines.
	painter.setPen(minorTickColor);
	for (int i = 0; i >= minimumLevel; i--) {
		int position = int(x + width - (i * scale) - 1);
		if (i % 5 != 0)
			painter.drawLine(position, y, position, y + 1);
	}
}

void VolumeMeter::paintVTicks(QPainter &painter, int x, int y, int height)
{
	qreal scale = height / minimumLevel;

	painter.setFont(tickFont);
	painter.setPen(majorTickColor);

	// Draw major tick lines and numeric indicators.
	for (int i = 0; i >= minimumLevel; i-= 5) {
		int position = y + int((i * scale) - 1);
		QString str = QString::number(i);

		if (i == 0)
			painter.drawText(x + 5, position + 4, str);
		else if (i == -60)
			painter.drawText(x + 4, position, str);
		else
			painter.drawText(x + 4, position + 2, str);
		painter.drawLine(x, position, x + 2, position);
	}

	// Draw minor tick lines.
	painter.setPen(minorTickColor);
	for (int i = 0; i >= minimumLevel; i--) {
		int position = y + int((i * scale) - 1);
		if (i % 5 != 0)
			painter.drawLine(x, position, x + 1, position);
	}
}

#define CLIP_FLASH_DURATION_MS 1000

void VolumeMeter::ClipEnding()
{
	clipping = false;
}

void VolumeMeter::paintHMeter(QPainter &painter, int x, int y, int width,
		int height, float magnitude, float peak, float peakHold)
{
	qreal scale = width / minimumLevel;

	QMutexLocker locker(&dataMutex);
	int minimumPosition     = x + 0;
	int maximumPosition     = x + width;
	int magnitudePosition   = int(x + width - (magnitude * scale));
	int peakPosition        = int(x + width - (peak * scale));
	int peakHoldPosition    = int(x + width - (peakHold * scale));
	int warningPosition     = int(x + width - (warningLevel * scale));
	int errorPosition       = int(x + width - (errorLevel * scale));

	int nominalLength       = warningPosition - minimumPosition;
	int warningLength       = errorPosition - warningPosition;
	int errorLength         = maximumPosition - errorPosition;
	locker.unlock();

	if (clipping) {
		peakPosition = maximumPosition;
	}

	if (peakPosition < minimumPosition) {
		painter.fillRect(minimumPosition, y, nominalLength, height,
				backgroundNominalColor);
		painter.fillRect(warningPosition, y, warningLength, height,
				backgroundWarningColor);
		painter.fillRect(errorPosition, y, errorLength, height,
				backgroundErrorColor);
	} else if (peakPosition < warningPosition) {
		painter.fillRect(minimumPosition, y, peakPosition -
				minimumPosition, height,
				foregroundNominalColor);
		painter.fillRect(peakPosition, y, warningPosition -
				peakPosition, height, backgroundNominalColor);
		painter.fillRect(warningPosition, y, warningLength, height,
				backgroundWarningColor);
		painter.fillRect(errorPosition, y, errorLength, height,
				backgroundErrorColor);
	} else if (peakPosition < errorPosition) {
		painter.fillRect(minimumPosition, y, nominalLength, height,
				foregroundNominalColor);
		painter.fillRect(warningPosition, y,
				peakPosition - warningPosition, height,
				foregroundWarningColor);
		painter.fillRect(peakPosition, y, errorPosition -
				peakPosition, height, backgroundWarningColor);
		painter.fillRect(errorPosition, y, errorLength, height,
				backgroundErrorColor);
	} else if (peakPosition < maximumPosition) {
		painter.fillRect(minimumPosition, y, nominalLength, height,
				foregroundNominalColor);
		painter.fillRect(warningPosition, y, warningLength, height,
				foregroundWarningColor);
		painter.fillRect(errorPosition, y, peakPosition - errorPosition,
				height, foregroundErrorColor);
		painter.fillRect(peakPosition, y,
				maximumPosition - peakPosition, height,
				backgroundErrorColor);
	} else {
		if (!clipping) {
			QTimer::singleShot(CLIP_FLASH_DURATION_MS, this,
					SLOT(ClipEnding()));
			clipping = true;
		}

		int end = errorLength + warningLength + nominalLength;
		painter.fillRect(minimumPosition, y, end, height,
				QBrush(foregroundErrorColor));
	}

	if (peakHoldPosition - 3 < minimumPosition)
		;// Peak-hold below minimum, no drawing.
	else if (peakHoldPosition < warningPosition)
		painter.fillRect(peakHoldPosition - 3, y, 3, height,
				foregroundNominalColor);
	else if (peakHoldPosition < errorPosition)
		painter.fillRect(peakHoldPosition - 3, y, 3, height,
				foregroundWarningColor);
	else
		painter.fillRect(peakHoldPosition - 3, y, 3, height,
				foregroundErrorColor);

	if (magnitudePosition - 3 >= minimumPosition)
		painter.fillRect(magnitudePosition - 3, y, 3, height,
				magnitudeColor);
}

void VolumeMeter::paintVMeter(QPainter &painter, int x, int y, int width,
		int height, float magnitude, float peak, float peakHold)
{
	qreal scale = height / minimumLevel;

	QMutexLocker locker(&dataMutex);
	int minimumPosition     = y + 0;
	int maximumPosition     = y + height;
	int magnitudePosition   = int(y + height - (magnitude * scale));
	int peakPosition        = int(y + height - (peak * scale));
	int peakHoldPosition    = int(y + height - (peakHold * scale));
	int warningPosition     = int(y + height - (warningLevel * scale));
	int errorPosition       = int(y + height - (errorLevel * scale));

	int nominalLength       = warningPosition - minimumPosition;
	int warningLength       = errorPosition - warningPosition;
	int errorLength         = maximumPosition - errorPosition;
	locker.unlock();

	if (clipping) {
		peakPosition = maximumPosition;
	}

	if (peakPosition < minimumPosition) {
		painter.fillRect(x, minimumPosition, width, nominalLength,
				backgroundNominalColor);
		painter.fillRect(x, warningPosition, width, warningLength,
				backgroundWarningColor);
		painter.fillRect(x, errorPosition, width, errorLength,
				backgroundErrorColor);
	} else if (peakPosition < warningPosition) {
		painter.fillRect(x, minimumPosition, width, peakPosition -
				minimumPosition, foregroundNominalColor);
		painter.fillRect(x, peakPosition, width, warningPosition -
				peakPosition, backgroundNominalColor);
		painter.fillRect(x, warningPosition, width, warningLength,
				backgroundWarningColor);
		painter.fillRect(x, errorPosition, width, errorLength,
				backgroundErrorColor);
	} else if (peakPosition < errorPosition) {
		painter.fillRect(x,minimumPosition, width, nominalLength,
				foregroundNominalColor);
		painter.fillRect(x, warningPosition, width, peakPosition -
				warningPosition, foregroundWarningColor);
		painter.fillRect(x, peakPosition, width, errorPosition -
				peakPosition, backgroundWarningColor);
		painter.fillRect(x, errorPosition, width, errorLength,
				backgroundErrorColor);
	} else if (peakPosition < maximumPosition) {
		painter.fillRect(x, minimumPosition, width, nominalLength,
				foregroundNominalColor);
		painter.fillRect(x, warningPosition, width, warningLength,
				foregroundWarningColor);
		painter.fillRect(x, errorPosition, width, peakPosition -
				errorPosition, foregroundErrorColor);
		painter.fillRect(x, peakPosition, width, maximumPosition -
				peakPosition, backgroundErrorColor);
	} else {
		if (!clipping) {
			QTimer::singleShot(CLIP_FLASH_DURATION_MS, this,
					SLOT(ClipEnding()));
			clipping = true;
		}

		int end = errorLength + warningLength + nominalLength;
		painter.fillRect(x, minimumPosition, width, end,
				QBrush(foregroundErrorColor));
	}

	if (peakHoldPosition - 3 < minimumPosition)
		;// Peak-hold below minimum, no drawing.
	else if (peakHoldPosition < warningPosition)
		painter.fillRect(x, peakHoldPosition - 3, width, 3,
				foregroundNominalColor);
	else if (peakHoldPosition < errorPosition)
		painter.fillRect(x, peakHoldPosition - 3, width, 3,
				foregroundWarningColor);
	else
		painter.fillRect(x, peakHoldPosition - 3, width, 3,
				foregroundErrorColor);

	if (magnitudePosition - 3 >= minimumPosition)
		painter.fillRect(x, magnitudePosition - 3, width, 3,
				magnitudeColor);
}

void VolumeMeter::paintEvent(QPaintEvent *event)
{
	uint64_t ts = os_gettime_ns();
	qreal timeSinceLastRedraw = (ts - lastRedrawTime) * 0.000000001;

	const QRect rect = event->region().boundingRect();
	int width  = rect.width();
	int height = rect.height();

	handleChannelCofigurationChange();
	calculateBallistics(ts, timeSinceLastRedraw);
	bool idle = detectIdle(ts);

	// Draw the ticks in a off-screen buffer when the widget changes size.
	QSize tickPaintCacheSize;
	if (vertical)
		tickPaintCacheSize = QSize(14, height);
	else
		tickPaintCacheSize = QSize(width, 9);
	if (tickPaintCache == nullptr ||
		tickPaintCache->size() != tickPaintCacheSize) {
		delete tickPaintCache;
		tickPaintCache = new QPixmap(tickPaintCacheSize);

		QColor clearColor(0, 0, 0, 0);
		tickPaintCache->fill(clearColor);

		QPainter tickPainter(tickPaintCache);
		if (vertical) {
			tickPainter.translate(0, height);
			tickPainter.scale(1, -1);
			paintVTicks(tickPainter, 0, 11,
					tickPaintCacheSize.height() - 11);
		} else {
			paintHTicks(tickPainter, 6, 0,
					tickPaintCacheSize.width() - 6,
					tickPaintCacheSize.height());
		}
		tickPainter.end();
	}

	// Actual painting of the widget starts here.
	QPainter painter(this);
	if (vertical) {
		// Invert the Y axis to ease the math
		painter.translate(0, height);
		painter.scale(1, -1);
		painter.drawPixmap(displayNrAudioChannels * 4 - 1, 7,
				*tickPaintCache);
	} else {
		painter.drawPixmap(0, height - 9, *tickPaintCache);
	}

	for (int channelNr = 0; channelNr < displayNrAudioChannels;
		channelNr++) {

		int channelNrFixed = (displayNrAudioChannels == 1 &&
		                      channels > 2)
			? 2
			: channelNr;

		if (vertical)
			paintVMeter(painter, channelNr * 4, 8, 3, height - 10,
					displayMagnitude[channelNrFixed],
					displayPeak[channelNrFixed],
					displayPeakHold[channelNrFixed]);
		else
			paintHMeter(painter, 5, channelNr * 4, width - 5, 3,
					displayMagnitude[channelNrFixed],
					displayPeak[channelNrFixed],
					displayPeakHold[channelNrFixed]);

		if (idle)
			continue;

		// By not drawing the input meter boxes the user can
		// see that the audio stream has been stopped, without
		// having too much visual impact.
		if (vertical)
			paintInputMeter(painter, channelNr * 4, 3, 3, 3,
					displayInputPeakHold[channelNrFixed]);
		else
			paintInputMeter(painter, 0, channelNr * 4, 3, 3,
					displayInputPeakHold[channelNrFixed]);
	}

	lastRedrawTime = ts;
}

void VolumeMeterTimer::AddVolControl(VolumeMeter *meter)
{
	volumeMeters.push_back(meter);
}

void VolumeMeterTimer::RemoveVolControl(VolumeMeter *meter)
{
	volumeMeters.removeOne(meter);
}

void VolumeMeterTimer::timerEvent(QTimerEvent*)
{
	for (VolumeMeter *meter : volumeMeters)
		meter->update();
}