Modify arguments for parent theme's `wp_register_style` via child theme

Question

Working on a child theme for site with a good deal of separate stylesheets being registered/enqueued from the theme and plugins. I'd like to change some attributes of the <link> tags in the final output, while avoiding conflicts after a parent theme update by the site owner.

The goal is to not re-register/re-enqueue the same .css files already set by the parent theme and/or plugins, while effectively passing a new set of arguments to the wp_register_style function.

For example, currently this is what the parent theme & plugins are doing:

// parent theme or plugin's php
wp_register_style( 'a_stylesheet', $uri . 'css/a-stylesheet.css', array(), $version, 'screen' );

// html output
<link rel='stylesheet' id='a_stylesheet-css'  href='http://domain.com/wp-content/themes/theme/css/a-stylesheet.css' type='text/css' media='screen' />

The goal is for the child theme to in effect change the wp_register_style call, like so:

// child theme's php
some_function_to_reregister( 'already_registered_file', $inherit, $inherit, $inherit, 'handheld' )
// if the above doesn't exist, do nothing; else, re-register with the new argument(s).

// html output
<link rel='stylesheet' id='a_stylesheet-css'  href='http://domain.com/wp-content/themes/theme/css/a-stylesheet.css' type='text/css' media='handheld' />

This changes the <link media> attribute to handheld instead of screen, but preserves everything else being done by the parent theme/plugin, and skips registering the file if it hasn't been registered yet elsewhere (i.e. after an update).

Seems like this would be a much more efficient approach than de-registering/de-enqueuing css from the parent theme and plugins only to copy/paste it back in the child theme and have unexpected wreckage in future updates.

Answer 1

I don't think there's a built-in safe way to do this, but you could directly modify the $wp_styles global after things are registered but before they're output, or at least use it to fetch the parameters a style was originally registered with.

global $wp_styles;
if( isset( $wp_styles->registered['a_stylesheet'] ) ){
    $wp_styles->registered['a_stylesheet']->args = 'handheld';
}

Not ideal, but it may work for you.