Paul L's new SelectedRegion class replacing use of t0 and t1. Also LabelTrack.h no longer in TrackPanel.h includes.

This change is believed to be a direct refactoring that does not change functionality.  It paves the way for more complex kinds of selection, such as selections involving frequency as well as time.  It also reduces risk of left and right edges being swapped in future code using SelectedRegion, as the default is to swap on assignment if needed.

src/SelectedRegion.h

@@ -0,0 +1,121 @@
+/**********************************************************************
+
+  Audacity: A Digital Audio Editor
+
+  SelectedRegion.h
+
+  Dominic Mazzoni
+
+**********************************************************************/
+
+#ifndef __AUDACITY_SELECTEDREGION__
+#define __AUDACITY_SELECTEDREGION__
+
+#include "Audacity.h"
+
+class AUDACITY_DLL_API SelectedRegion {
+
+   // Maintains the invariant:  t1() >= t0()
+
+public:
+   SelectedRegion()
+      : mT0(0.0)
+      , mT1(0.0)
+   {}
+
+   SelectedRegion(double t0, double t1)
+      : mT0(t0)
+      , mT1(t1)
+   { ensureOrdering(); }
+
+   explicit
+   SelectedRegion(const SelectedRegion &x)
+      : mT0(x.mT0)
+      , mT1(x.mT1)
+   {}
+
+   SelectedRegion& operator=(const SelectedRegion& x)
+   {
+      if (this != &x) {
+         mT0 = x.mT0;
+         mT1 = x.mT1;
+      }
+      return *this;
+   }
+
+   double t0() const { return mT0; }
+   double t1() const { return mT1; }
+   double duration() const { return mT1 - mT0; }
+   bool isPoint() const { return mT1 <= mT0; }
+
+   // PRL: to do: more integrity checks
+
+   // Returns true iff the bounds got swapped
+   bool setT0(double t, bool maySwap = true) {
+      mT0 = t;
+      if (maySwap)
+         return ensureOrdering();
+      else {
+         if (mT1 < mT0)
+            mT1 = mT0;
+         return false;
+      }
+   }
+
+   // Returns true iff the bounds got swapped
+   bool setT1(double t, bool maySwap = true) {
+      mT1 = t;
+      if (maySwap)
+         return ensureOrdering();
+      else {
+         if (mT1 < mT0)
+            mT0 = mT1;
+         return false;
+      }
+   }
+
+   // Returns true iff the bounds got swapped
+   bool setTimes(double t0, double t1) {
+      mT0 = t0;
+      mT1 = t1;
+      return ensureOrdering();
+   }
+
+   // Returns true iff the bounds got swapped
+   bool moveT0(double delta, bool maySwap = true) {
+      return setT0(mT0 + delta, maySwap);
+   }
+
+   // Returns true iff the bounds got swapped
+   bool moveT1(double delta, bool maySwap = true) {
+      return setT1(mT1 + delta, maySwap);
+   }
+
+   void move(double delta) {
+      mT0 += delta;
+      mT1 += delta;
+   }
+
+   void collapseToT0() { mT1 = mT0; }
+
+   void collapseToT1() { mT0 = mT1; }
+
+private:
+   bool ensureOrdering() 
+   {
+      if (mT1 < mT0) {
+         const double t = mT1;
+         mT1 = mT0;
+         mT0 = t;
+         return true;
+      }
+      else
+         return false;
+   }
+
+   double mT0;
+   double mT1;
+
+};
+
+#endif