How do I include a javascript file in WordPress admin Widgets

Solution:

The correct hook is admin_print_scripts ¹ to enqueue styles and scripts.

Note that admin_footer and admin_head also accept the same screen targeting 'actionname-$hook':

add_action( 'admin_print_scripts-widgets.php', 'admin_enqueue_so_19228543' );

function admin_enqueue_so_19228543()
{
    wp_enqueue_script( 
            'my-script', 
            plugins_url( '/my-script.js', __FILE__ ), 
            array(), // dependencies
            false, // version
            true // on footer
    );
    wp_enqueue_style( 
        'my-style', plugins_url( '/my-style.css', __FILE__ ) 
    );

}

_{1 The Codex is saying otherwise, but I was pretty sure this was an official stance. I’m researching and will report back.}

update

I cannot find any reference to admin_print_scripts being the correct hook, although it works and I’ve seen used this way many times. For completeness, this is how admin_enqueue_scripts works:

add_action( 'admin_enqueue_scripts', 'admin_enqueue_so_19228543' );

function admin_enqueue_so_19228543( $hook )
{
    if( 'widgets.php' != $hook )
        return;

    wp_enqueue_script( 
            'my-script', 
            plugins_url( '/my-script.js', __FILE__ ), 
            array(), // dependencies
            false, // version
            true // on footer
    );
    wp_enqueue_style( 
        'my-style', plugins_url( '/my-style.css', __FILE__ ) 
    );

}