CustomFieldTypeDescriptor - get HTML input field

Several days ago I created a topic where I asked how to get the HTML Input Element of a Customfield Object

Unfortunetly nobody answered so I had to try it on my own. After a few days of “try and error” I found out how to get the input element for a specific customfield. The object which is needed is the CustomFieldTypeModuleDescriptor

https://docs.atlassian.com/jira/7.0.6/com/atlassian/jira/plugin/customfield/CustomFieldTypeModuleDescriptor.html

The “getEditHtml” function is the correct one but its not working everytime…it depends on the type of the field.
SingleSelect fields are working fine, but if I chose a datepicker field it wont work as expected because the datepicker aui resources arent acctually loaded. I fixed it by require the correct resource. But if I choose a UserSelect field it will be renderered with the message that I dont have the permission to browse users…but I actually have the permission.

Right now I have a few questions that need to be answered:

What is the difference between getEditHtml and getEditDefaultHtml?
What should be in the customFieldValuesHolder Map Parameter?
What should be in the displayParameter Map?
Why do I need to pass a issue object? Doesn’t make sence to me. And why can I pass a null value as issue parameter? What consequences does it have when I pass null?
Why do I need to pass a action object? I dont have any webwork actions, I used a ContextProvider for my view. And why can I pass null again? Consequences?! And when I acctually can pass null values why isnt it documented at the api?

Regards…