Added delay node and wait for enter keypress node

[indraneelpatil]

• This pull request is with reference to this issue 92

• Two new decorator nodes are proposed in this pull request called Delay Node and Wait for Enter Press node which I found personally very useful in my application

• The delay node allows the user to add a fixed millisecond delay before ticking the child

• The Wait for Enter Press Node as the name suggests stops execution of the child until enter key is pressed by the user

• I am very new to contributing code online and I welcome constructive criticism about this work.

I am also thankful to the owner of the library and all maintainers!

[facontidavide]

First, thanks a lot for contributing.

I think the WaitForKeyPressed should use ncurses, as https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/src/controls/manual_node.cpp

[facontidavide]

I see apractical problem with the DelayNode .

As you may now, Reactive nodes gives the illusion that the BT is multi-threaded, when actually it is single-threaded.

To achieve this, any code must block as little as possible. A "delay", therefore, must return RUNNING and stop execution, not freeze.

What if the DelayNode is a child of the ReactiveSequence and it has a sibling that preempt it?

[indraneelpatil]

@facontidavide Thanks for your kind words! I had no idea Manual Selector node existed, thanks for pointing it out. Its a much better solution than what I had pushed, so I removed Wait for Key Press node in the latest commit.

[indraneelpatil]

Regarding the delay node, I have added a TimerQueue timer to the node to keep a track of the delay and the node now has these three states ->

• If the timer has not yet triggered then the node will return RUNNING
• If the timer has triggered, then the node will tick the child and return the result of the child
• and if the delay node is preempted by its sibling (like in the example you specified) then the timer will be cancelled, child will not be ticked and the delay node will return FAILURE

Please let me know if this satisfies your requirement!

[indraneelpatil]

@facontidavide Hey, have you gotten any time to review this pull request?
Thanks in advance!

[gramss]

Looks solid to me. I cross checked it with https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/src/decorators/timeout_node.cpp

Just some small adjustments in style and clarity and it should be fine 👍

[indraneelpatil]

@gramss Thank you for your suggestions! I have pushed them in the latest commit.

[gramss]

Changes are looking good. Only already introduces methods are used like in other decorators. @facontidavide should be ready to be merged 🙂

[facontidavide]

thanks and sorry for the delay. overwhelmed with other things right now

[indraneelpatil]

No problem! I understand, we really appreciate all the work that you are doing to maintain Behaviour Trees library! I would also love to connect if you have any future feature additions in mind and if you think I can contribute further. Wishing you all the health during these tough times, Yours sincerely, Indraneel.

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