WordPress at a glance
filter is not described

use_default_gallery_style filter-hook . WP 3.1.0

Filters whether to print default gallery styles.

Usage

add_filter( 'use_default_gallery_style', 'filter_function_name_5715' );
function filter_function_name_5715( $print ){
	// filter...

	return $print;
}
$print(true/false)
Whether to print default gallery styles. Otherwise, defaults to true.
Default: false if the theme supports HTML5 galleries

Where the hook is called

gallery_shortcode()
wp-includes/media.php 1738
if ( apply_filters( 'use_default_gallery_style', ! $html5 ) ) {

Where the hook is used (in WP core)

Does not used.