woocommerce_variation_is_active filter-hook . WC 1.0

Controls whether this particular variation will appear greyed-out (inactive) or not (active). Used by extensions to make incompatible variations appear greyed-out, etc. Other possible uses: prevent out-of-stock variations from being selected.

Usage

add_filter( 'woocommerce_variation_is_active', 'filter_function_name_7549', 10, 2 );
function filter_function_name_7549( $true, $that ){
	// filter...

	return $true;
}

$true

-

$that

-

Where the hook is called

return apply_filters( 'woocommerce_variation_is_active', true, $this );

Where in WP core the hook is used WooCommerce