When previewing, ensures the proper previewing widgets are used.

Calls admin_print_footer_scripts and admin_print_scripts hooks to allow custom scripts from plugins.

Inserts default style for highlighted widget at early point so theme stylesheet can override.

Calls admin_print_scripts-widgets.php and admin_print_scripts hooks to allow custom scripts from plugins.

Calls admin_print_styles-widgets.php and admin_print_styles hooks to allow custom styles from plugins.

{@internal Missing Summary}

Ensures sidebar widget arrays only ever contain widget IDS.

Strips out widget IDs for widgets which are no longer registered.

Sanitizes a widget instance.

Converts a widget instance into JSON-representable format.