Get "create issue under Epic" context from CustomFieldType

[Jacopo Freddi]

I am trying to have my CustomField behave differently in the Create Issue view, depending on whether the issue is being created under a given parent or as an independent issue.

The behaviour I'm trying to achieve is similar to the Epic Link field, where if you're creating a Story under an Epic (with the plus sign in the Epic Issue View) the new issue's Epic Link field is already filled with the Epic and is read only. Ideally this behaviour would be available at all hierarchy levels (I'm using Portfolio for the higher links).

My CustomFieldType extends AbstractSingleFieldType. I couldn't find anything related to this context in the FIeldLayoutItem variable passed in the getVelocityParameters method, and there seems to be no information in the HTML of the CreateIssue dialog either. All I would need is a boolean telling me if I'm creating the issue under a given parent (and possibly which parent), either from JS / Velocity or from the Java API.

Any idea?