enforce generally imutable time values

src/lib/time/timevalue.hpp

@@ -169,7 +169,14 @@ namespace time {
   class Offset
     : public TimeValue
     {
-        
+    protected:
+      Offset&
+      operator= (Offset const& o) ///< derived classes allow mutation
+        {
+          TimeValue::operator= (o);
+          return *this;
+        }
+
     public:
       explicit 
       Offset (TimeValue const& distance)
@@ -246,6 +253,9 @@ namespace time {
   class Time
     : public TimeValue
     {
+      /// direct assignment prohibited
+      Time& operator= (Time const);
+      
     public:
       static const Time MAX ; 
       static const Time MIN ;
@@ -291,6 +301,9 @@ namespace time {
   class Duration
     : public Offset
     {
+      /// direct assignment prohibited
+      Duration& operator= (Duration const&);
+      
     public:
       Duration (Offset const& distance)
         : Offset(distance.abs())

src/proc/asset/meta/time-grid.hpp

@@ -59,6 +59,7 @@ namespace meta {
   
   using lib::Symbol;
   using lib::time::Time;
+  using lib::time::TimeVar;
   using lib::time::TimeValue;
   using lib::time::FrameRate;
   using lib::time::FSecs;
@@ -102,7 +103,7 @@ namespace meta {
       string id_;
       
       FrameRate fps_;
-      Time origin_;
+      TimeVar origin_;
       
       /** when building a compound or variable grid,
        *  the predecessor is the grid active \em before

tests/lib/time/time-formats-test.cpp

@@ -142,7 +142,7 @@ namespace test{
           CHECK (--smpte.mins == 38);
           CHECK ("  5:38:00:01" == string(smpte));
           
-          Time tx = smpte.getTime();
+          TimeVar tx = smpte.getTime();
           CHECK (tx == Time(0,0,38,5) + Time(FSecs(1,25)));
           
           // Extended SMPTE: extension of the axis beyond origin towards negative values
@@ -157,7 +157,7 @@ namespace test{
           tx = smpte.getTime();
           ++smpte.frames;                                 // now *increasing* the frame value
           CHECK ("- 0:22:00:00"== string(smpte));         // means decreasing the resulting time
-          CHECK (tx - Time(1000/25,0,0,0) == smpte.getTime());
+          CHECK (smpte.getTime() == tx - Time(1000/25,0,0,0));
           ++smpte;                                        // but the orientation of the increment on the *whole* TC values is unaltered
           CHECK ("- 0:21:59:24"== string(smpte));         // so this actually *advanced* time by one frame 
           CHECK (tx == smpte.getTime());
@@ -204,7 +204,7 @@ namespace test{
           CHECK (tx == smpte.getTime());                  // applying invertOrientation() doesn't change the value
           
           smpte.frames.setValueRaw(-1);
-          tx = tx - Time(FSecs(2,25));
+          tx -= Time(FSecs(2,25));
           CHECK (tx == smpte.getTime());
           CHECK ("  1:00:00:-1"== string(smpte));
           smpte.invertOrientation();                      // invoking on positive should create double negated representation