support setT() while interval is playing

direct/src/interval/Interval.py

@@ -62,8 +62,19 @@ class Interval(DirectObject):
         state = self.getState()
         if state == CInterval.SInitial:
             self.privInitialize(t)
+            if self.isPlaying():
+                self.setupResume()
         elif state == CInterval.SFinal:
             self.privReverseInitialize(t)
+            if self.isPlaying():
+                self.setupResume()
+        elif state == CInterval.SStarted:
+            # Support modifying t while the interval is playing.  We
+            # assume is_playing() will be true in this state.
+            assert(self.isPlaying())
+            self.privInterrupt()
+            self.privStep(t)
+            self.setupResume()
         else:
             self.privStep(t)
         self.privPostEvent()

direct/src/interval/cInterval.cxx

@@ -70,10 +70,25 @@ set_t(double t) {
   switch (get_state()) {
   case S_initial:
     priv_initialize(t);
+    if (is_playing()) {
+      setup_resume();
+    }
     break;
 
   case S_final:
     priv_reverse_initialize(t);
+    if (is_playing()) {
+      setup_resume();
+    }
+    break;
+
+  case S_started:
+    // Support modifying t while the interval is playing.  We assume
+    // is_playing() will be true in this state.
+    nassertv(is_playing());
+    priv_interrupt();
+    priv_step(t);
+    setup_resume();
     break;
 
   default: