Drupal 7 Module Development

Chapter 3
to simply implement a spook_preprocess_page() function, it would be run after
template_preprocess_page() and, thus, too late. So, instead we need to implement
the following code:
/**
* Implements hook_theme_registry_alter().
*/
function spook_theme_registry_alter(&$theme_registry) {
// Add our custom preprocess function to the beginning of
// the preprocess function list.
array_unshift($theme_registry['page']['preprocess functions'],
'spook_control_page_messages');
}
/**
* Implements a custom preprocess function; one that is not
* auto-discovered during the theme registry build.
*/
function spook_control_page_messages(&variables) {
// Override #show_messages before template_preprocess_page()
// accesses it.
$variables['page']['#show_messages'] = spook_get_control();
}
The order of preprocess functions described in the earlier section is created during
the theme's system registry build and is based on the naming conventions. However,
hook_theme_registry_alter() allows us to alter that ordering to suit our own
nefarious purposes.
What else?
For most modules you write, the contents of this chapter cover everything you
need to learn about the theme system. Actually, this chapter might have been TMI.
However, the theme system is chock full of yummy goodness not covered here,
including accessibility classes, hook_theme_enable, and hook_theme_disable to
name just a few. Drupal's online documentation includes a theme reference guide
which can be a very handy tool for understanding some of the more obscure topics.
It can be found at the following site:
http://drupal.org/theme-guide
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