Add events

[DStrelak]

Is your feature request related to a problem? Please describe.
When I set e.g. input movie set, I would like to automatically preset some default values in the protocol, based on the e.g. size of the movie.

Describe the solution you'd like
I would like to be able to register specific callback for input change event

Describe alternatives you've considered
Similar functionality can be achieved by inheritance / overriding

[pconesa]

Thank you @DStrelak .

[delarosatrevin]

Please check the protocol base class...I think this is already implemented, although not used in many protocols. It is called trigger or something like that.

[pconesa]

Hi, @delarosatrevin. I wasn't aware of this. I've looked up for trigger in the code and nothing related pops up.

I've reviewed parms.py, and haven't seen any similar....please, please, please, enlighten us!

[delarosatrevin]

Input variables have a 'trace' where callback can be registered. The following example change the pointer class when another input changes:

https://github.com/scipion-em/scipion-em-emxlib/blob/devel/emxlib/protocols/protocol_export.py#L60