Well, first of all, I didn't realize there was a uc_attribute_add_to_cart theme. Still, I need to theme the entire add to cart form. I also didn't realize that the #theme attribute had to refer to a function defined in hook_theme().
So, in case anyone else does a similar search and comes across this post, here's what I did.
First, hook_theme():
<?php
function my_module_theme() {
return array(
'add_to_cart_form' => array(
'arguments' => array($form => NULL),
),
);
}
?>Then, hook_form_alter(), with a check to make sure the containing node type was of the type containing the attributes I need to style.
<?php
function my_module_form_alter(&$form, $form_state, $form_id) {
...
if($form['#parameters'][2]->type == 'my_type') {
$form['#theme'] = 'add_to_cart_form';
}
}
?>And, finally, my theme function, complete with form elements and product attributes.
<?php
function theme_add_to_cart_form($form) {
...
}
?>