From 5315bbd88a00f71c49cdc3151b00a525060441d3 Mon Sep 17 00:00:00 2001
From: Joe Taylor <joe@princeton.edu>
Date: Fri, 18 Dec 2020 15:14:17 -0500
Subject: [PATCH] Don't erase the red sync curve too soon.

---
 widgets/plotter.cpp | 5 ++++-
 widgets/plotter.h   | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/widgets/plotter.cpp b/widgets/plotter.cpp
index 948b6dfb0..737658de3 100644
--- a/widgets/plotter.cpp
+++ b/widgets/plotter.cpp
@@ -140,7 +140,10 @@ void CPlotter::draw(float swide[], bool bScroll, bool bRed)
 //move current data down one line (must do this before attaching a QPainter object)
   if(bScroll and !m_bReplot) m_WaterfallPixmap.scroll(0,1,0,0,m_w,m_h1);
   QPainter painter1(&m_WaterfallPixmap);
-  m_2DPixmap = m_OverlayPixmap.copy(0,0,m_w,m_h2);
+  if(m_bFirst or bRed or !m_bQ65_Sync) {
+    m_2DPixmap = m_OverlayPixmap.copy(0,0,m_w,m_h2);
+    m_bFirst=false;
+  }
   QPainter painter2D(&m_2DPixmap);
   if(!painter2D.isActive()) return;
   QFont Font("Arial");
diff --git a/widgets/plotter.h b/widgets/plotter.h
index 1aeacf811..ad35f4ff8 100644
--- a/widgets/plotter.h
+++ b/widgets/plotter.h
@@ -118,6 +118,7 @@ private:
   bool    m_bQ65_Sync;
   bool    m_bVHF;
   bool    m_bSingleDecode;
+  bool    m_bFirst=true;
 
   float   m_fSpan;