Proposed Change to menu.inc and menu table to Allow Modules to Create Custom Menus

History: (see: http://drupal.org/node/14120 and the discussion that followed for the full history)

A while back Steven Dondley (aka nysus) proposed some changes to the book.module so that it would create individual blocks for individual books. It was agreed that the suggested functionality was desirable, but not the solution provided.

The preferred solution would have been to have the book.module use the menu system to create the individual blocks for the individual books.

I wrote some code to test the idea using the MENU_CUSTOM_MENU and MENU_CUSTOM_ITEM menu types as a proof of concept. It worked. However, I didn't think it would be desirable for the book.module to be creating menus of this type, because these menus are not (by any definition) custom. I had suggested that some new menu types be added to menu.inc - something along the lines of MENU_BOOK_MENU and MENU_BOOK_ITEM. This idea was not well received because it was felt that it would open the door to all module developers to ask for their own menu type. Still, it seemed that a more generic menu type that any module could use might be acceptable.

Proposal: (see patch for full details)

As an alternative I would now suggest that two new menu type flags be created, along with two new menu types.

define('MENU_MODIFIED_BY_MODULE', 0x0400);
define('MENU_CREATED_BY_MODULE', 0x0800);
/*
*....
*/
define('MENU_MODULE_MENU', MENU_IS_ROOT | MENU_VISIBLE_IN_TREE | MENU_CREATED_BY_MODULE);
define('MENU_MODULE_ITEM', MENU_VISIBLE_IN_TREE | MENU_VISIBLE_IN_BREADCRUMB | MENU_CREATED_BY_MODULE);

note there are also two other minor changes in the file to handle the inclusion of these menu types in the $_Menu array for display

In the case of the book.module, I wrote some code that would essentially replace the verbose block creation in the module by instead building menus (stored in the menu table) that maintained the book hierarchies using these new menu types. The result was the book.module automatically updated the menu system to display changes in the book hierarchy. And since the block module already has a mechanism for showing 'custom' menus as blocks, each book (and its associated menu) automatically had their own block created as well. (This is a separate patch and discussion, but I bring it up to show why the change might be desirable in the menu.inc file - and indeed necessary for me to submit the book.module patch).

The second proposal would be to add a 'module' field to the menu table. In the case of the book.module, prior to inserting the updated book hierarchy into the menu table, I delete the existing hierarchy. If separate modules are going to add/edit/delete their own menus in the menu table, it isn't enough to know that they are of type MENU_MODULE_MENU, but you would also need to know which module created them so that each module could only change its own menus and not ALL module menus. Essentially I am proposing the same thing that already exists in the block table.

The proposed changes would in no way affect how drupal works, it would just allow added flexibility for modules to create their own menus using the menu system.

I would appreciate any feedback and am happy to entertain questions regarding this proposal. I will submit an official feature request along with the patch if feedback is positive, (along with patches to the book module, database and update.inc).

Thanks
andre