How does observe_field work recursively

I use observe_field in a view page to monitor a field (field1). Whenever field1 changed, a action will render a partial (partial1). In partial1, I use observe_field to monitor a field (field2).

so the problem is: when a user changed the field1, its action will set some variables and render the partial1. In partial1, the field2 changed because of some variables changed in the action, but the observe_field doesn't invoke its action. If the user changed the field2 manually, the observe_field works fine. So I wander why the observe_field doesn't work if the field changed according to a render.

That's normal. observe_field observes user triggered events not things like javascript updating the page.

Fre