Adding assets (css/js) for a custom module block (and withstanding a cache enabled install)

Question

I've created my own block which calls a hook_theme implementation which then prepares some data and then renders myblock.tpl.php

All of the above is working fine but my module does have some required assets, specifically some css & js files, currently I was doing drupal_add_css/js in my hook_block($delta = 'view') but I've discovered that both the hook_block and hook_theme do not get called when the Admin > Config > Performance - Enable Block Cache has been turned on.

Obviously when I clear the cache the first load of a page (with my block included) loads all assets properly, but anon-users etc do not see any of my assets.

How should I be including these assets in a way that would withstand caching and only add assets on a page which includes my block?

Thanks!

Answer 1

Modules can report how Drupal should cache the output of a module, through the use of a set of constants.

The constants should be used as in the following example of hook_block():

function mymodule_block($op = 'list', $delta = 0, $edit = array()) {
  if ($op == 'list') {
    $blocks[0] = array(
      'info' => t('Mymodule block #1 shows ...'), 
      'weight' => 0, 
      'status' => 1, 
      'region' => 'left',
    );
    // BLOCK_CACHE_PER_ROLE will be assumed for block 0.

    $blocks[1] = array(
      'info' => t('Mymodule block #2 describes ...'), 
      'cache' => BLOCK_CACHE_PER_ROLE | BLOCK_CACHE_PER_PAGE,
    );

    return $blocks;
  }
  // …
}

The constants that can be used are:

• BLOCK_NO_CACHE: The block should not be cached.
• BLOCK_CACHE_GLOBAL: The block is the same for every user, in every page it is shown.
• BLOCK_CACHE_PER_ROLE: The block could change basing on the roles the user who is watching the page has.
• BLOCK_CACHE_PER_USER: The block could change basing on the user who is watching the page.
• BLOCK_CACHE_PER_PAGE: The block could change basing on the page being viewed.

You could use some of the constants together; for example, if the block changes basing on the page, and the user who is watching the page, you can use BLOCK_CACHE_PER_PAGE|BLOCK_CACHE_PER_USER.

In Drupal 7, those constants have been renamed, and a new constant is added; this is the list of the constants used in Drupal 7:

• DRUPAL_NO_CACHE
• DRUPAL_CACHE_GLOBAL
• DRUPAL_CACHE_PER_ROLE
• DRUPAL_CACHE_PER_USER
• DRUPAL_CACHE_PER_PAGE
• DRUPAL_CACHE_CUSTOM

The last constant is used to report to Drupal 7 that the module uses its own cache. For Drupal it has the same effect of using DRUPAL_NO_CACHE.