UI: Change meter color to red when audio is clipping

Closes jp9000/obs-studio#738

UI/volume-control.cpp

@@ -3,6 +3,7 @@
 #include "obs-app.hpp"
 #include "mute-checkbox.hpp"
 #include "slider-absoluteset-style.hpp"
+#include <obs-audio-controls.h>
 #include <util/platform.h>
 #include <util/threading.h>
 #include <QHBoxLayout>
@@ -265,7 +266,10 @@ VolumeMeter::VolumeMeter(QWidget *parent)
 	magColor.setRgb(0x20, 0x7D, 0x17);
 	peakColor.setRgb(0x3E, 0xF1, 0x2B);
 	peakHoldColor.setRgb(0x00, 0x00, 0x00);
-	
+
+	clipColor1.setRgb(0x7F, 0x00, 0x00);
+	clipColor2.setRgb(0xFF, 0x00, 0x00);
+
 	updateTimerRef = updateTimer.toStrongRef();
 	if (!updateTimerRef) {
 		updateTimerRef = QSharedPointer<VolumeMeterTimer>::create();
@@ -329,15 +333,17 @@ void VolumeMeter::paintEvent(QPaintEvent *event)
 	int scaledPeak     = int((float)width * curPeak);
 	int scaledPeakHold = int((float)width * curPeakHold);
 
+	float db = obs_volmeter_get_cur_db(OBS_FADER_LOG, curPeakHold);
+
 	gradient.setStart(qreal(scaledMag), 0);
 	gradient.setFinalStop(qreal(scaledPeak), 0);
-	gradient.setColorAt(0, magColor);
-	gradient.setColorAt(1, peakColor);
+	gradient.setColorAt(0, db == 0.0f ? clipColor1 : magColor);
+	gradient.setColorAt(1, db == 0.0f ? clipColor2 : peakColor);
 
 	// RMS
 	painter.fillRect(0, 0, 
 			scaledMag, height,
-			magColor);
+			db == 0.0f ? clipColor1 : magColor);
 
 	// RMS - Peak gradient
 	painter.fillRect(scaledMag, 0,

UI/volume-control.hpp

@@ -31,6 +31,7 @@ private:
 	uint64_t lastUpdateTime = 0;
 
 	QColor bkColor, magColor, peakColor, peakHoldColor;
+	QColor clipColor1, clipColor2;
 
 public:
 	explicit VolumeMeter(QWidget *parent = 0);