3ds Max 2021 - Python Callbacks with pymxs

[Anonymous]

Hello,

I have a question regarding callbacks and Python classes. In previous versions of Max, this was relatively simple to setup via MaxPlus. In the example below, I call 3 different functions that belong to a class depending on the callback that is triggered within Max.

self.selection_callback = MaxPlus.NotificationManager.Register(MaxPlus.NotificationCodes.SelectionsetChanged, self.test_function_A)
self.modifier_callback = MaxPlus.NotificationManager.Register(MaxPlus.NotificationCodes.PostModifierAdded, self.test_function_B)
self.node_change_callback = MaxPlus.NotificationManager.Register(MaxPlus.NotificationCodes.PostNodeUserPropChanged, self.test_function_C)

 Seeing as MaxPlus is no longer supported in 2021. What would the equivalent solution to this be using pymxs? 

I noticed an example at the following link:

http://help.autodesk.com/view/MAXDEV/2021/ENU/?guid=Max_Python_API_using_pymxs_pymxs_differences_pym... 

But cannot get this example to work with classes as it did with the MaxPlus method. 

[eric.brosseau]

Thank you for your question @Anonymous 

I would refer you to those reference pages. They will probably help you more:

• General help for handling callbacks with pymxs
  http://help.autodesk.com/view/MAXDEV/2021/ENU/?guid=Max_Python_API_using_pymxs_pymxs_registering_callbacks_html
• MaxPlus callback codes translated to pymxs (maxscript) event codes
  http://help.autodesk.com/view/MAXDEV/2021/ENU/?guid=Max_Python_API_notification_codes_html

I was able to create a small sample code to verify callback methods could be class methods. I am wondering where you are facing issues with your code. I may not fully understand your question.

from pymxs import runtime as mxs

class MyCallbackListener:
	def __init__(self):
		print("My Callback Listener Created")
		mxs.callbacks.addScript(mxs.Name('selectionSetChanged'), self.CallMeLaterAlligator, id=mxs.Name('MyListenerCallbacks'))
		
	def CallMeLaterAlligator(self):
		print("You fired a callback")
		notification = mxs.callbacks.notificationParam()
		print(" returning these params: ", notification)
	
myObject = MyCallbackListener()

[Huston94]

Is this solution backwards compatible with previous versions of 3ds Max (2019 specifically) or was this only added to pymxs in 2021 to account from the discontinuation of MaxPlus?

Thanks.

[Luna_Gu98]

I tried @eric.brosseau 's solution and the solution in 3ds Max 2020 Help | Registering Python Callbacks | Autodesk, they work with max 2022 but don't work with max 2020 😞  
@Anonymous thanks for your MaxPlus solution that helps me to find a walk-around in older versions!