Understanding types of layout handles

Question

I am going through this link to understand Layout handles. Here I have seen that the layout handles are in the form of [module_front_name]_[controller_name]_[action_name]. So, for example the layout handle for "Contact us" page is contacts_index_index, which calls the "indexAction" method available in "indexController" controller of "Contacts" module.

Later, I have seen other layout handles like:

• page_empty
• page_one_column
• page_two_columns_left
• page_two_columns_right
• page_three_columns

in "page.xml" layout file. (which are also in config.xml file of "page" module)

The above Layout handles are not in the form of [module_front_name]_[controller_name]_[action_name]. Then what are they?

My understanding is not clear on both the types of Layout handles. (Are there any other Layout handle types?)

Please explain

Answer 1

Layout handles are somehow independent from the actions.
You can declare any layout handle you want as long as it is a valid XML tag.
Each action loads by default the handle [module_front_name]_[controller_name]_[action_name] but you can load any layout handle either in the controller, see an example here: Mage_Catalog_CategoryController::viewAction()

$update->addHandle('catalog_category_layered_nochildren'); 

or you can load a handle inside an other handle using

<update handle="handle_here" />

See an example in the newsletter.xml layout file, inside the tag newsletter_manage_index.

Answer 2

In the next article the author digs deeper into layouts including creating your own layout handles.

http://magebase.com/magento-tutorials/digging-deeper-into-magentos-layout-xml-part-2/

Scroll about halfway down and there's a good explanation!