Spectrum: allow zero decay so history (including max hold) is kept forever

sdrgui/gui/glspectrum.cpp

@@ -371,11 +371,11 @@ void GLSpectrum::updateHistogram(const std::vector<Real>& spectrum)
 {
 	quint8* b = m_histogram;
 	quint8* h = m_histogramHoldoff;
-	int sub = 1;
+	int sub = 0; // was 1;
 	int fftMulSize = 100 * m_fftSize;
 
-	if(m_decay > 0)
-		sub += m_decay;
+	//if(m_decay > 0)
+	sub += m_decay; // allow zero decay so history (including max hold) is kept forever
 
 	if (m_displayHistogram || m_displayMaxHold)
 	{
@@ -385,7 +385,7 @@ void GLSpectrum::updateHistogram(const std::vector<Real>& spectrum)
 		{
 			for (int i = 0; i < fftMulSize; i++)
 			{
-				if((*b>>4) > 0) // *b > 16
+				if (*b > 16) // was 20
 				{
 					*b = *b - sub;
 				}