The theme system was briefly introduced in the first chapter. In this chapter, we will start out with a more detailed overview of the theme system's architecture.
With each major release of Drupal, the theme system has enjoyed significant revision, and version 6 of Drupal is no exception. The new release of Drupal has introduced theme hook registration, theme .info files, and other features. We will make use of these new features in this chapter.
The goal of most theming systems—and Drupal's is no exception—is to separate the design elements from the processing logic. Doing so achieves two important (and related) goals:
A new look and feel can be created without the need to re-write any of the processing code. This makes the theme creator's life easier—one need not possess detailed knowledge of Drupal's internals to change the way the site looks.
Program logic is easier to maintain. When code isn't cluttered with layout elements (like HTML tags and CSS properties...