Forums Technical Discussion Is it possible to add python callback to an HDA's parm without modifying the HDA Definition?

Is it possible to add python callback to an HDA's parm without modifying the HDA Definition?

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zdimaria
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I want to add a default python callback to all parm's on an hda that don't already have a callback set. Ideally I'd like to do this in OnCreated, but the only way I can see to add a callback is by modifying the parm templates in the asset definition. I'd rather not modify the asset definition.

If not, is there anything similar to Node's addEventCallback for parms?

I am open to even hacky ways of achieving this.


thanks!
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Andrew Graham
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I would also love to know how to do this!

I'd like to add a callback onto a standard rop geometry sop node to determine when a string parameter changes.
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Andrew Graham
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ahh its here

http://www.sidefx.com/docs/houdini/hom/hou/Node.html#addEventCallback [www.sidefx.com]

def name_changed(node, event_type, **kwargs):
    print("The geometry object is now named", node.name())

hou.node("/obj/geo1").addEventCallback((hou.nodeEventType.NameChanged, ), name_changed)
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Andrew Graham
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but what you want is hou.nodeEventType.ParmTupleChanged to find all altered parms.
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zdimaria
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Andrew Graham
hou.nodeEventType.ParmTupleChanged
This is perfect! I scanned through that page today and can't believe I missed it. Thank you!!
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Andrew Graham
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I just found though that callbacks added this way wont persist between houdini sessions, so if anyone has a recommended solution for that I'd love to know.

The only hack I can think of is adding callbacks on scene load, but that seems so diiiirty.
https://openfirehawk.com/ [openfirehawk.com]
Support Open Firehawk - An open source cloud rendering project for Houdini on Patreon.
This project's goal is to provide an open source framework for cloud computing for heavy FX based workflows and allows end users to pay the lowest possible price for cloud resources.
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