How to add custom css class to block wrapper

Question

I need to add custom css classes to several blocks (can be blocks from view, or facet api, etc). Is there a way to do it without creating a template for every block? It could be useful a theme function, or a hook, that should do something like:

 if ($var == 'block_name') {
   $class_custom = 'my-custom-class';
 }

Is it possible?

Answer 1

There's a template function for this: template_preprocess_block.

Use $variables['classes_array'] to add classes to the block.

Answer 2

You can also use the Block class project for the matter.

Block Class allows users to add classes to any block through the block's configuration interface. By adding a very short snippet of PHP to a theme's block.tpl.php file, classes can be added to the parent element of a block. Hooray for more powerful block theming!