[rt-users] clarification on callbacks

[Matt Zagrabelny]

Hey Alex,

On Tue, Oct 11, 2016 at 3:27 PM, Alex Hall <ahall at autodist.com> wrote:
> Hello list,
> I'm considering trying out a callback. Ken suggested it as a way to add a
> link to pages that will let users toggle between self-service and standard
> interfaces, and I'm very much hoping I can use it to customize the way
> history displays on ticket summary pages.
>
> From what I've read so far, it seems like a callback is analogous to a
> subclass. If I have a 'renderer' class that can make pretty text from raw
> HTML, I might then subclass it and override the function that parses text to
> make it work on XML. Yes, it's a very terrible example, but hopefully the
> idea is correct.
>
> Anyway, a callback in RT seems a lot like that. I want the ticket page to
> display how it already does, but I don't like the history part. Thus, I copy
> the file to the proper callback directory, then modify it. RT will, when it
> knows it has to use Display.html, look in callbacks first and use my
> version. Only if I don't provide one will it use the default one in
> share/html/Tickets.
>
> Do I have this right--copy the existing file to callbacks and modify it? Or
> do I make a blank file, override only the bits I want to in there, and not
> copy the whole thing? Am I thinking about callbacks all wrong?

You are thinking about Callbacks wrong. :)

They are hook points in the HTML (Mason) of RT.

Many (most?) RT extension will have some callbacks in them. Here is a
nice easy one to get your feet wet:

https://github.com/bestpractical/rt-extension-commentoncreate

Take a look at the source for this extension and note the
html/Callbacks directory. Then look in your RT share/html directory
for where those callbacks would appear.

In this particular instance, rt-extension-commentoncreate adds a
"comment" box just below the "create" content box on the
Ticket/Create.html page.

So you can see from the source of the extension, it will add something
to the AfterMessageBox callback in the Create.html Mason component.

I'll let you dig a little bit more with this extension or another one
to get more familiar with callbacks.

Also, read the documentation:

https://docs.bestpractical.com/rt/4.4.1/writing_extensions.html#Callbacks

-m