Hi

I don't find documentation about function / triggers to call when writting a payment plugin.
Is there some rules to follow?

I would like to create a single button (not a form as paypal plugin) which trigger an action on the server to process the call to he bank.
(In that case a binary to call with specific parameters)

Example :
First Screen : index.php?option=com_invoices&view=payment&id=40 (with fields & button to pay)
==> form.php

but when clicking :

Second screen:
it's should switch to a temporary screen ("processing")

My solution is to create a second layout named "processing.php" and put action_url with this layout in "form.php"

Is that correct ?
Any advices?