sweeping node graph changes for new rendering pipeline

The new rendering pipeline strives to simplify the nodes themselves as much
as possible and move much of the logic to an external rendering engine. This
change removes all of the responsibilities that no longer belong to the
nodes themselves and will soon be folded into the renderer.

app/common/timerange.cpp

@@ -21,6 +21,11 @@ const rational &TimeRange::out() const
   return out_;
 }
 
+const rational &TimeRange::length() const
+{
+  return length_;
+}
+
 void TimeRange::set_in(const rational &in)
 {
   in_ = in;
@@ -40,6 +45,36 @@ void TimeRange::set_range(const rational &in, const rational &out)
   normalize();
 }
 
+bool TimeRange::operator<(const TimeRange &r) const
+{
+  return length() < r.length();
+}
+
+bool TimeRange::operator<=(const TimeRange &r) const
+{
+  return length() <= r.length();
+}
+
+bool TimeRange::operator>(const TimeRange &r) const
+{
+  return length() > r.length();
+}
+
+bool TimeRange::operator>=(const TimeRange &r) const
+{
+  return length() >= r.length();
+}
+
+bool TimeRange::operator==(const TimeRange &r) const
+{
+  return length() == r.length();
+}
+
+bool TimeRange::operator!=(const TimeRange &r) const
+{
+  return length() != r.length();
+}
+
 void TimeRange::normalize()
 {
   // If `out` is earlier than `in`, swap them
@@ -48,4 +83,7 @@ void TimeRange::normalize()
     in_ = out_;
     out_ = temp;
   }
+
+  // Calculate length
+  length_ = out_ - in_;
 }