[Seaside] cancel button in canvas

[Lukas Renggli]

> Most PC users are pretty used to having the choice between accepting changes they did on a page and to throw away what they did. A cancel button is kind of a logical rollback to my changes on a dialog/page. This has nothing to do with a code smell but with user interfaces and workflows. You might be speaking of design smells and present another idea of what would be a good way to give your user a means of throwing away their last changes to business data combined with a secure feeling of not having done any harm to the system. A cancel button has done a good job in this for quite some years now, at least this is what my experience tells me...

I was not talking about design, only about implementation. I do agree
that forms should always have a cancel-button, but how the
cancel-button is implemented is another question ;-)

> Are you sure about this? My observation in old-style WAHtmlRenderer was that using a cancel-callback can easily avoid all this.

Well, I don't know your application. Just to clear with my statement
and to have something to discuss about, let me introduce the following
scenario:

1. the user fills a form and hits "save"
2. the form does not validate and is displayed again with the
(invalid) data and an error message
3. the users decides not to save the form and hits "cancel"

I don't understand how a cancel-callback could fit into this scenario?
Maybe you can clarify or give a better example?

- Without caching: at (1) the form gets submitted with the invalid
data into the model, there is nothing that the cancel-callback in (3)
can change about that.

- With caching: at (1) the form gets submitted into the cache, and in
(3) there is no need for a cancel-callback because only (2) does
commit the changes if valid.

Lukas

--
Lukas Renggli
http://www.lukas-renggli.ch