Add halt_tree binding and use in demo

Author: kylc

Diff for: python_examples/ex06_async_nodes.py

@@ -33,10 +33,6 @@
 
 @ports(inputs=["start", "goal"], outputs=["command"])
 class MyAsyncNode(AsyncActionNode):
-    def __init__(self, name, config):
-        super().__init__(name, config)
-        self.halted = False
-
     def run(self):
         start = np.asarray(self.get_input("start"))
         goal = np.asarray(self.get_input("goal"))
@@ -46,7 +42,7 @@ def run(self):
         # caller until the next iteration of the tree, rather than block the
         # main thread.
         t0 = time.time()
-        while (t := time.time() - t0) < 1.0 and not self.halted:
+        while (t := time.time() - t0) < 1.0:
             command = (1.0 - t) * start + t * goal
             self.set_output("command", command)
             yield
@@ -55,8 +51,7 @@ def run(self):
         return NodeStatus.SUCCESS
 
     def on_halted(self):
-        # This will be picked up in the main iteration above.
-        self.halted = True
+        print("Trajectory halted!")
 
 
 @ports(inputs=["value"])
@@ -73,4 +68,8 @@ def tick(self):
 factory.register(Print)
 
 tree = factory.create_tree_from_text(xml_text)
-tree.tick_while_running()
+
+# Run for a bit, then halt early.
+for i in range(0, 10):
+    tree.tick_once()
+tree.halt_tree()

Diff for: src/python/bindings.cpp

@@ -169,7 +169,8 @@ PYBIND11_MODULE(btpy_cpp, m)
       .def("tick_once", &Tree::tickOnce)
       .def("tick_exactly_once", &Tree::tickExactlyOnce)
       .def("tick_while_running", &Tree::tickWhileRunning,
-           py::arg("sleep_time") = std::chrono::milliseconds(10));
+           py::arg("sleep_time") = std::chrono::milliseconds(10))
+      .def("halt_tree", &Tree::haltTree);
 
   py::enum_<NodeStatus>(m, "NodeStatus")
       .value("IDLE", NodeStatus::IDLE)