Bug 521 - Lower half of Waveform (dB) vertical scale does not show dB level.

Added a DbMirrorValue for two sided dB scale on Waveform VRuler when in dB view mode.

src/TrackArtist.cpp

@@ -702,6 +702,7 @@ void TrackArtist::UpdateVRuler(const Track *t, wxRect & rect)
       min = tt->GetRangeLower() * 100.0;
       max = tt->GetRangeUpper() * 100.0;
 
+      vruler->SetDbMirrorValue( 0.0 );
       vruler->SetBounds(rect.x, rect.y, rect.x + rect.width, rect.y + rect.height-1);
       vruler->SetOrientation(wxVERTICAL);
       vruler->SetRange(max, min);
@@ -753,6 +754,7 @@ void TrackArtist::UpdateVRuler(const Track *t, wxRect & rect)
                wt->SetDisplayBounds(min, max);
             }
 
+            vruler->SetDbMirrorValue( 0.0 );
             vruler->SetBounds(rect.x, rect.y, rect.x + rect.width, rect.y + rect.height - 1);
             vruler->SetOrientation(wxVERTICAL);
             vruler->SetRange(max, min);
@@ -792,13 +794,17 @@ void TrackArtist::UpdateVRuler(const Track *t, wxRect & rect)
                      max = 0.0;
                   max *= sign;
                }
-               wt->SetDisplayBounds(min, max);
+               wt->SetDisplayBounds(min, max );
             }
             else if (dBRange != (lastdBRange = wt->GetLastdBRange())) {
                wt->SetLastdBRange();
                // Remap the max of the scale
                const float sign = (max >= 0 ? 1 : -1);
                float newMax = max;
+
+// This commented out code is problematic.
+// min and max may be correct, and this code cause them to change.
+#ifdef ONLY_LABEL_POSITIVE
                if (max != 0.) {
 
 // Ugh, duplicating from TrackPanel.cpp
@@ -815,16 +821,24 @@ void TrackArtist::UpdateVRuler(const Track *t, wxRect & rect)
                   if (min != 0.)
                      min = std::max(-extreme, newMax * min / max);
                }
-
+#endif
-               wt->SetDisplayBounds(min, newMax);
+               wt->SetDisplayBounds(min, newMax );
             }
 
+
+// Old code was if ONLY_LABEL_POSITIVE were defined.  
+// it uses the +1 to 0 range only.
+// the enabled code uses +1 to -1, and relies on set ticks labelling knowing about 
+// the dB scale.
+#ifdef ONLY_LABEL_POSITIVE
             if (max > 0) {
+#endif
                int top = 0;
                float topval = 0;
                int bot = rect.height;
                float botval = -dBRange;
 
+#ifdef ONLY_LABEL_POSITIVE
                if (min < 0) {
                   bot = top + (int)((max / (max - min))*(bot - top));
                   min = 0;
@@ -841,13 +855,19 @@ void TrackArtist::UpdateVRuler(const Track *t, wxRect & rect)
                if (min > 0) {
                   botval = -((1 - min) * dBRange);
                }
-
+#else
+               topval = -((1 - max) * dBRange);
+               botval = -((1 - min) * dBRange);
+               vruler->SetDbMirrorValue( dBRange );
+#endif
                vruler->SetBounds(rect.x, rect.y + top, rect.x + rect.width, rect.y + bot - 1);
                vruler->SetOrientation(wxVERTICAL);
                vruler->SetRange(topval, botval);
+#ifdef ONLY_LABEL_POSITIVE
             }
             else
                vruler->SetBounds(0.0, 0.0, 0.0, 0.0); // A.C.H I couldn't find a way to just disable it?
+#endif
             vruler->SetFormat(Ruler::RealLogFormat);
             vruler->SetLabelEdges(true);
             vruler->SetLog(false);
@@ -858,6 +878,7 @@ void TrackArtist::UpdateVRuler(const Track *t, wxRect & rect)
          const SpectrogramSettings &settings = wt->GetSpectrogramSettings();
          float minFreq, maxFreq;
          wt->GetSpectrumBounds(&minFreq, &maxFreq);
+         vruler->SetDbMirrorValue( 0.0 );
 
          switch (settings.scaleType) {
          default:

src/widgets/Ruler.cpp

@@ -139,6 +139,7 @@ Ruler::Ruler()
    mbTicksAtExtremes = false;
    mTickColour = wxColour( theTheme.Colour( clrTrackPanelText ));
    mPen.SetColour(mTickColour);
+   mDbMirrorValue = 0.0;
 
    // Note: the font size is now adjusted automatically whenever
    // Invalidate is called on a horizontal Ruler, unless the user
@@ -768,7 +769,7 @@ void Ruler::Tick(int pos, double d, bool major, bool minor)
    wxCoord strW, strH, strD, strL;
    int strPos, strLen, strLeft, strTop;
 
-   // FIXME: We don't draw a tick if of end of our label arrays
+   // FIXME: We don't draw a tick if off end of our label arrays
    // But we shouldn't have an array of labels.
    if( mNumMinorMinor >= mLength )
       return;
@@ -792,6 +793,9 @@ void Ruler::Tick(int pos, double d, bool major, bool minor)
    label->text = wxT("");
 
    mDC->SetFont(major? *mMajorFont: minor? *mMinorFont : *mMinorMinorFont);
+   // Bug 521.  dB view for waveforms needs a 2-sided scale.
+   if(( mDbMirrorValue > 1.0 ) && ( -d > mDbMirrorValue ))
+      d = -2*mDbMirrorValue - d;
    l = LabelString(d, major);
    mDC->GetTextExtent(l, &strW, &strH, &strD, &strL);
 

src/widgets/Ruler.h

@@ -81,6 +81,7 @@ class AUDACITY_DLL_API Ruler {
    // Specify the name of the units (like "dB") if you
    // want numbers like "1.6" formatted as "1.6 dB".
    void SetUnits(const wxString &units);
+   void SetDbMirrorValue( const double d ){ mDbMirrorValue = d ; };
 
    // Logarithmic
    void SetLog(bool log);
@@ -223,6 +224,7 @@ private:
    private:
    int          mOrientation;
    int          mSpacing;
+   double       mDbMirrorValue;
    bool         mHasSetSpacing;
    bool         mLabelEdges;
    RulerFormat  mFormat;