Define class NumberScale and enum NumberScaleType

src/Makefile.am

@@ -171,6 +171,7 @@ audacity_SOURCES = \
 	MixerBoard.h \
 	ModuleManager.cpp \
 	ModuleManager.h \
+        NumberScale.h \
 	PitchName.cpp \
 	PitchName.h \
 	PlatformCompatibility.cpp \

src/NumberScale.h

@@ -0,0 +1,164 @@
+/**********************************************************************
+
+Audacity: A Digital Audio Editor
+
+NumberScale.h
+
+Paul Licameli
+
+**********************************************************************/
+
+#ifndef __AUDACITY_NUMBER_SCALE__
+#define __AUDACITY_NUMBER_SCALE__
+
+#include <algorithm>
+#include <cmath>
+#include <wx/defs.h>
+#include <wx/debug.h>
+
+enum NumberScaleType {
+   nstLinear,
+   nstLogarithmic,
+
+   nstNumScaleTypes,
+};
+
+
+class NumberScale
+{
+public:
+   NumberScale(NumberScaleType type,
+      float value0, float value1, float unit)
+      : mType(type)
+   {
+      switch (mType) {
+      case nstLinear:
+      {
+         mValue0 = value0 / unit;
+         mValue1 = value1 / unit;
+         mUnit = 1.0;
+      }
+      break;
+      case nstLogarithmic:
+      {
+         mValue0 = logf(value0 / unit);
+         mValue1 = logf(value1 / unit);
+         mUnit = 1.0;
+      }
+      break;
+      default:
+         wxASSERT(false);
+      }
+   }
+
+   NumberScale Reversal() const
+   {
+      NumberScale result(*this);
+      std::swap(result.mValue0, result.mValue1);
+      return result;
+   }
+
+   bool operator == (const NumberScale& other) const
+   {
+      return mType == other.mType
+         && mValue0 == other.mValue0
+         && mValue1 == other.mValue1
+         && mUnit == other.mUnit;
+   }
+
+   bool operator != (const NumberScale &other) const
+   {
+      return !(*this == other);
+   }
+
+   // Random access
+   float PositionToValue(float pp) const
+   {
+      switch (mType) {
+      default:
+         wxASSERT(false);
+      case nstLinear:
+         return mValue0 + pp * (mValue1 - mValue0);
+      case nstLogarithmic:
+         return exp(mValue0 + pp * (mValue1 - mValue0));
+      }
+   }
+
+   // STL-idiom iteration
+
+   class Iterator
+   {
+   public:
+      Iterator(NumberScaleType type, float step, float value, float unit)
+         : mType(type), mStep(step), mValue(value), mUnit(unit)
+      {
+      }
+
+      float operator * () const
+      {
+         switch (mType) {
+         default:
+            wxASSERT(false);
+         case nstLinear:
+         case nstLogarithmic:
+            return mValue;
+         }
+      }
+
+      Iterator &operator ++()
+      {
+         switch (mType) {
+         case nstLinear:
+            mValue += mStep;
+            break;
+         case nstLogarithmic:
+            mValue *= mStep;
+            break;
+         default:
+            wxASSERT(false);
+         }
+         return *this;
+      }
+
+   private:
+      const NumberScaleType mType;
+      const float mStep;
+      float mValue;
+      float mUnit;
+   };
+
+   Iterator begin(float nPositions) const
+   {
+      switch (mType) {
+      default:
+         wxASSERT(false);
+      case nstLinear:
+         return Iterator
+            (mType, (mValue1 - mValue0) / nPositions, mValue0, mUnit);
+      case nstLogarithmic:
+         return Iterator
+            (mType, exp((mValue1 - mValue0) / nPositions), exp(mValue0), mUnit);
+      }
+   }
+
+   // Inverse
+   float ValueToPosition(float val) const
+   {
+      switch (mType) {
+      default:
+         wxASSERT(false);
+      case nstLinear:
+         return ((val - mValue0) / (mValue1 - mValue0));
+      case nstLogarithmic:
+         return ((log(val) - mValue0) / (mValue1 - mValue0));
+      }
+   }
+
+private:
+   const NumberScaleType mType;
+   float mValue0;
+   float mValue1;
+   float mUnit;
+};
+
+#endif

win/Projects/Audacity/Audacity.vcxproj

@@ -533,6 +533,7 @@
     <ClInclude Include="..\..\..\src\import\MultiFormatReader.h" />
     <ClInclude Include="..\..\..\src\import\SpecPowerMeter.h" />
     <ClInclude Include="..\..\..\src\ModuleManager.h" />
+    <ClInclude Include="..\..\..\src\NumberScale.h" />
     <ClInclude Include="..\..\..\src\prefs\SpectrogramSettings.h" />
     <ClInclude Include="..\..\..\src\RevisionIdent.h" />
     <ClInclude Include="..\..\..\src\SelectedRegion.h" />

win/Projects/Audacity/Audacity.vcxproj.filters

@@ -1685,6 +1685,9 @@
     <ClInclude Include="..\..\..\src\prefs\SpectrogramSettings.h">
       <Filter>src/prefs</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\..\src\NumberScale.h">
+      <Filter>src</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <Image Include="..\..\audacity.ico">