https://wordpress.org/support/plugin/zvi-callback-widget/reviews/?filter=3
[ZVI CallBack widget] Reviews | WordPress.org
callback widgetzvireviewswordpress
https://adambrown.info/p/wp_hooks/hook/widget_display_callback?version=5.5&file=wp-includes/class-wp-widget.php
widget_display_callback hook - WordPress source view -- Adam Brown, BYU Political Science
Detailed information about every action hook and filter used in WordPress. Makes Plugin API easier to use. Lists appearance, file location, and deprecation...