Behaviour Tree MVP

[stonier]

Goals

• Given the clunkiness with formatting, unicode, latching .... consolidate the ros2 comms into a single non-text snapshot message
• Decode the message with a client watcher that can usefully display all the things
• Decide how to best interleave a tick with rclpy and design api to encourage that
• Proof of life on a tutorial and a muppet

Messages

• create statistics msg → splintered-reality/py_trees_ros_interfaces#2

BehaviourTree

• winds of change visitor → #70
• ascii tree debug mode → #70
• publish snapshot on change → #70
• publish snapshot on start → #70
• publish snapshot on modifications → #70
• publish statistics (duration, period, averages, variances) → #70
• single tick api → #70
• investigate/review best way to interleave ticks with rclpy → #71
• periodic ticking continuously with node timers → #71
• periodic ticking for N ticks with node timers(?) → #71
• tree shutdown method → #71
• setup() that can pass it's node to children → splintered-reality/py_trees#182, #73
• fix exchange test → #74

Watcher

• deserialise snapshot message → #70
• draw ascii tree snapshot → #70
• draw ascii tree oneshot → #70
• add statistics to snapshot → #70
• add tip to snapshot → splintered-reality/py_trees#180
• render dot graph → #70

Behaviours

• Port subscriber to blackboard related behaviours → #73
• Subscriber behaviours under test → #76
• Port battery behaviours → #73
• Battery behaviour under test → #75

Proof of Life

• tutorial one - battery subscription with statistics → splintered-reality/py_trees_ros_tutorials#14, splintered-reality/py_trees_ros_tutorials#15
• muppet launcher demonstration - on a robot with battery subscriber (tutorial one with battery_state instead of battery/state)

Out of Scope

• logging