doc/todo/preview_changes.mdwn



When editing a page, it would help to have a "preview changes" or "show diff" button, which brings up a diff from the current page content to the proposed new page content. --[[JoshTriplett]]
Some discussion from the main [[/index/discussion]] page:

It would be nice to be able to have a button to show "Differences" (or "Show Diff") when
editing a page. Is that an option that can be enabled?

It's doable, it could even be done by a [[todo/plugin]], I think.
--[[Joey]]


I need help with this. Supposedly, such a plugin would provide a formbuilder_setup
hook which would add the button, and a cgi hook which would interecept
"Show Diff" clicks. This would show a diff between
titlepage(possibly_foolish_untaint($form->field("page")))
and the provided $form->field("editcontent").
But:

How could the case of concurrent editing be handled ?
Especially as (I think) only the RCS backend can know that
this has happened.
May I hijack the page_preview template variable to show
my diff output? (the patch below assumes this).
Using the formbuilder hook to add a button, and coerce editpage()
into showing the edit form again rather that saving the page needs
the following patch. (note that this is not the only template which has
its submit buttons hardcoded; is this supposed to work around something?)

I've got a preliminary implementation,
which depends on this patch
and the [[plugins/contrib/plaintext]] plugin.
There is still some tweaking needed, though.
--[[JeremieKoenig]]