I am presently working on a complete rewrite of the outdated Creative Commons module for Drupal 6 (it's currently available for Drupal 4.7 only).
The settings form's biggest difficulty is its use of dependent options: After choosing a license type (such as "Creative Commons" or "Sampling") further choices will become available. The 4.6 version (I hope not the 4.7 version too) used an onchange="form.submit()" to get multistep functionality.
We now have AHAH in the D6 Form API, which I've been able to use with beautiful results: Just select a license in the drop-down, see the throbber rotating for a few seconds, and a whole new options panel fades into view.
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Unfortunately, adding form options to an already built form is no trivial matter - you have to make sure to rebuild the form with these options so that the validator will not reject them as illegal input. I thought I'd solved it, but it still doesn't work.
Perhaps someone more versed in FormAPI could peek at my module code and point out what I'm doing wrong? The module is available over SVN here:
http://svn.ermarian.net/drupal/modules/creativecommons/trunk
(also accessible through the web).
Comments
Still not cleared up
I haven't found any documentation on modifying forms this way. The multistep documentation appears to be for 5.x and does not take into account such things as $form_state.
On ice
Whatever documentation there is for this, it's either too hard to find or not comprehensible, and nobody I've asked seems to know how to do this either. I don't have time to research it indefinitely, so my work on the module is more or less suspended until someone who wants Creative Commons for D6 badly enough to figure it out happens to stumble across this topic.