[development] implementing #format

[Gábor Hojtsy]

Hey,

In light of http://hojtsy.hu/blog/2008-feb-04/supporting-wysiwyg-editing-better-drupal-battle-plan
I'd like to implement direct input format support for Form API
constructs. I have been thinking and researching on the following
lately:

1. What form API element to support?

 - Drupal core only uses input formats with textareas
 - CCK also supports input formats with textfields

Any other field one would need to support? Do we need to support
textfields really?

2. How to add to the form structure?

 - Core does wrap the field in a wrapper FAPI element and then add the
textarea and the 'format' fieldset / radio group to that wrapper.
 - CCK adds the field and adds the format fieldset / radio group with
name: $field_name .'_format' (no specific wrapper).

Core things like teasers and the splitter require that wrapper so that
related fields are together. We should either enforce the wrapper
(which could complicate life for #tree forms), or do not care about a
wrapper existing or not, leave that off to the implementor.

3. How to make adding format selectors and acting on them easy?

 - The different (free to modify) methods of adding input format
support on fields makes it hard to act on it from form altering, etc.
 - Devise a unified approach to add format (selection) support => add
a #format (#input_format, something else?) key to FAPI
 - Expand textareas with #format to a textarea and a format selector
(or just help if there is only one format) with the help of #process

This should provide a one and only standard way to tie formats to
textareas, and form altering would have the important metadata
available at a predictable place. (I'd also like to add more metadata
about what type of field is actually presented for format selection,
so we would be able to limit input formats available for blocks,
nodes, comments, etc).

Anything obvious I am missing or total misdirection I am taking?
Better ideas or tips to get this done easier? Does someone see where
I'll stop and freeze without a way forward (because certain APIs will
not allow me to proceed without major refactoring)? :) If #format a
good idea for input format specification on forms, or should I use a
better name? (I would not like to get in conflict with #formatter and
friends).

Gabor