Ctrl-mousewheel in vertical ruler of waveform dB view varies bottom of scale...

... provided the bottom is visible

src/prefs/WaveformSettings.cpp

@@ -126,10 +126,25 @@ void WaveformSettings::ConvertToActualDBRange()
    wxArrayString codes;
    GUIPrefs::GetRangeChoices(NULL, &codes);
    long value = 0;
-   codes[dBRange].ToLong(&value);
+   codes[std::max(0, std::min(int(codes.size()) - 1, dBRange))]
+      .ToLong(&value);
    dBRange = int(value);
 }
 
+void WaveformSettings::NextLowerDBRange()
+{
+   ConvertToEnumeratedDBRange();
+   ++dBRange;
+   ConvertToActualDBRange();
+}
+
+void WaveformSettings::NextHigherDBRange()
+{
+   ConvertToEnumeratedDBRange();
+   --dBRange;
+   ConvertToActualDBRange();
+}
+
 namespace
 {
    wxArrayString &scaleNamesArray()

src/prefs/WaveformSettings.h

@@ -47,6 +47,8 @@ public:
 
    void ConvertToEnumeratedDBRange();
    void ConvertToActualDBRange();
+   void NextLowerDBRange();
+   void NextHigherDBRange();
 
    enum ScaleType {
       stLinear,