WordPress at a glance
filter is not described

all_themes filter-hook . WP 3.1.0

Filters the full array of WP_Theme objects to list in the Multisite themes list table.

Usage

add_filter( 'all_themes', 'filter_function_name_7976' );
function filter_function_name_7976( $all ){
	// filter...

	return $all;
}
$all(array)
An array of WP_Theme objects to display in the list table.

Where the hook is called

WP_MS_Themes_List_Table::prepare_items()
wp-admin/includes/class-wp-ms-themes-list-table.php 100
'all' => apply_filters( 'all_themes', wp_get_themes() ),

Where the hook is used (in WP core)

Does not used.