fix chorus popSample read pointer drift; show welcome only on first open

Source/LcdPanel.cpp

@@ -185,7 +185,14 @@ LcdPanel::LcdPanel (RMX19AudioProcessor& p)
     presentImage = juce::Image (juce::Image::ARGB, gridW * presentScale, gridH * presentScale, false);
     backdrop = juce::Image (juce::Image::ARGB, gridW * subsample, gridH * subsample, false);
     buildBackdrop();
+    if (firstRunEver())
+    {
         splashUntil = juce::Time::getMillisecondCounter() + 1500;
+    }
+    else
+    {
+        screen = Screen::Home;
+    }
     lastMidi = proc.getLastMidiTime();
     startTimerHz (22);
 }
@@ -195,6 +202,25 @@ LcdPanel::~LcdPanel()
     stopTimer();
 }
 
+// The welcome splash plays only on the very first plugin open ever. A small
+// flag file under the user's Application Support dir records that it was shown,
+// so later instances start directly on the Home screen.
+static juce::File welcomeFlagFile()
+{
+    return juce::File::getSpecialLocation (juce::File::userApplicationDataDirectory)
+           .getChildFile ("RMX-19").getChildFile ("welcome.seen");
+}
+
+bool LcdPanel::firstRunEver()
+{
+    auto flag = welcomeFlagFile();
+    if (flag.exists())
+        return false;
+    flag.getParentDirectory().createDirectory();
+    flag.replaceWithText ("seen");
+    return true;
+}
+
 void LcdPanel::timerCallback()
 {
     bool needsRedraw = (screen == Screen::Splash);

Source/LcdPanel.h

@@ -18,6 +18,8 @@ public:
 
     void resetToHome();
 
+    static bool firstRunEver();
+
     static constexpr int gridW = 160;   // dot-matrix cell resolution
     static constexpr int gridH = 64;
     // internal supersampling: dots are rasterized as anti-aliased circles at 4x,

Source/PluginProcessor.cpp

@@ -81,10 +81,13 @@ public:
 
                 chorusL.pushSample (0, inL);
                 chorusR.pushSample (0, inR);
-                const float mL = 0.5f * (chorusL.popSample (0, chBase + chDepth * t1)
-                                         + chorusL.popSample (0, chBase + chDepth * t2));
-                const float mR = 0.5f * (chorusR.popSample (0, chBase + chDepth * t2)
-                                         + chorusR.popSample (0, chBase + chDepth * t3));
+                // multi-tap: only the first popSample advances the read pointer,
+                // otherwise one push + two pops drifts the taps through the whole
+                // buffer and late-stale echoes of old notes come back (octave up).
+                const float mL = 0.5f * (chorusL.popSample (0, chBase + chDepth * t1, true)
+                                         + chorusL.popSample (0, chBase + chDepth * t2, false));
+                const float mR = 0.5f * (chorusR.popSample (0, chBase + chDepth * t2, true)
+                                         + chorusR.popSample (0, chBase + chDepth * t3, false));
                 outL += mL * wet * 0.8f;
                 outR += mR * wet * 0.8f;
             }