I want to customise the functionality of the button Send An Email in the Activity History section of my Invoice object so all attached documents in the Notes and Attachments should be automatically added when EmailSending page is loaded.
I found out that the current version of Salesforce no longer allow to override
/_ui/core/email/author/EmailAuthor so I have to use a different method. My solution is that I'll create a button named Send An Email with Attachment(s).
The button is linked to a page which is prosssed by a controller class. The page should have all controls that EmailAuthor have. And the controller class should function like the controller class that possessing EmailAuthor.
My question is : How can I clone the whole EmailAuthor page and its controller class so I can customise them? It looks like Salesforce hides the code of those files.