I've been working on adding a new product type, because it may need to undergo customization, and because its original product type, "document_product" was subverted to other uses in my main store.
It's going to be for registering for events such as our national conference.
I have been studying "An Introduction to Product Types in Zen Cart v.1.2" which was included in the last 1.3 release. I've also peeked at the archived discussion http://www.zen-cart.com/forum/showthread.php?t=6888 but I confess I have not read all 8 pages of it yet. I also noticed the books model contrib, but didn't want to add complexities of additional features just yet.
My plan is to start by duplicating Document-Product and get that working before any customization, so I can get a better grasp of the ZC system.
So far I have successfully set up the Admin portion. I have edited database tables product_type and product_type_layout to create a new product type called "document_register".
Problem: the page does not display for customers.
I can create a category called Registration, limit it to type document_register, and create products in it. The products go into the zen_products table and that looks hunky dory. (I got a SQL output of product_layout, studied it, and made SQL insert statements for the rows for my new product type, using product_type_id value 6.)
I've been combing over the /includes/modules/pages files but can't find where I've gone wrong. I've basically mirrored all the original files for document_product. I also changed all the references to "document_product" to "document_register" in includes\modules\pages\document_register_info\main_template_vars.php and includes\modules\pages\document_register_info\main_template_vars_product_type.ph p.
You can see my sandbox at http://www.coreknowledge.org/register
Click the Register category on the left. You see that there is a product in there called "National Conference 2007" but nothing displays.
MANY MANY thanks to anyone who can point me in the right direction.