In 5.x, Drupal modules saw the introduction of .info files to store meta data about the module (for example, the name, description, version, dependencies, etc.). Starting in 6.x, Drupal themes also have a .info file. See the complete guide to writing .info files for themes for more information.

Example themeName.info (partial list.):
name = Theme Name
description = One sentence description of theme.
core = 6.x
engine = phptemplate
Theme registry

All theme functions must now be registered. In Drupal 5, they were all discovered on the fly. New in 6.x, hook_theme() is used to register all themable output. PHPTemplate engine takes care of registering on behalf of the theme so in most situations you will not have to register manually.
There is one exception to this. Forms that do not have a default theme implementation will not be registered.
See the example in the theming handbooks for more details on theming forms.
Important note! Whenever you add a new theme function or template inside your theme the registry must be cleared!
Theming through template files

In 5.x, themable functions could be overridden with "themeEngine_hook()" or "themeName_hook()". All the markup could be placed inside the "template.php" file and returned with the data.

To go even further and allow the theme function to use separate template files (.tpl.php), _phptemplate_callback() could be used. Enabling the callback also allowed the hook to manipulate the variables with the following.

The following is no longer supported:
<?php
function _phptemplate_variables($hook, $variables) {
switch ($hook) {
case 'page':
// process variables for page hook.
break;
case 'node':
// process variables for node hook.
break;
}
return $variables;
}
?>

In 6.x, _phptemplate_callback() is no longer supported. It has been rolled in to the main theme() function. As long as the function is registered as a template, the template file will be used. _phptemplate_variables() has also been deprecated.

Registering as a normal function works just like overridding with "themeEngine_hook()" or "themeName_hook()" without the callback in 5.x.

PHPTemplate automatically registers the hook as a normal function or template. To register the function as a template, all you need to do is create a file named after the hook followed by ".tpl.php". For example, the hook "menu_tree" is themable so, create a template file inside your theme named "menu-tree.tpl.php". Note the underscore being changed into a hyphen. Clear the registry and it will take over.
More details on the overriding behavior is available.
You can take a look at the underlying changes between 5 and 6. –links to pdfs
Template management

Template files (.tpl.php) can now be managed more easily by organising them through sub-directories. PHPTemplate engine will find all files in the theme and register thier locations. There is no limit on its depth either.
New template files (.tpl.php)

In 5.x the following templates are implemented by phptemplate.engine (inside the theme engines folder):
page.tpl.php
node.tpl.php
comment.tpl.php
block.tpl.php
box.tpl.php

With the new changes under the hood, more default templates are provided and more will be available in future releases. The ones from PHPTemplate in 5.x were also moved. Read the comments inside these files to see where they are used and the available variables.

In order to override these templates, all you need to do is copy them into your theme folder and clear the theme registry.

See the complete list of new templates in the theming handbook.

The seldom used default core functions for the above templates are no longer present. For example, theme_page no longer exists. This affects all themable output converted into templates. Due to the nature of the change, they are no longer necessary. This change should not affect anyone. Do not confuse the removed functions with how they are called. theme('page') still works. It is the default implementation that has changed.

Alimentacion

Actually, I found the book very helpful.

Here's my review.

I hope there's more to come!

Cheers,

Marc Robinsone

I'm enjoying the book, but a bit disappointed about my timing. the current zen theme is totally different from the one described in the book and even though I installed the themeing api and selected "fixed" width, as someone suggested to me, the css files are very different and i'm having a hard time following chapter 6. I'm hoping there might be some suggestions - I am still learning quite a lot, but my thinking is quite concrete and I was trying to follow it exactly.

I'm not sure this is for me but please be candid.Can I install and design Drupral Themes from a Mac? I’m a newbe and can use all the help I can get. I’m now using a nice little slide show program called slideshowPro_director. It’s a server dependent product. So the reason I mentioned it I had to have my server set up a data base before I could install it. Is this the same with yours. So Can I incorporate this with Flash since slideshowPro is sort of a flash dependent product. What I mean is you have this small .xml file you create which was a first for me and ssp is a Flash Extension. As you cna tell I'm not a coder but willing to learn. Can I use this with Dreamweaver and Flash?

http://dreamweaverdrupalthemeextension.blogspot.com/2008/01/drupal-5-the...

did the pact pub inform you the final date of release?