WordPress at a glance
function is not described

WP_Customize_Widgets::print_preview_css() public WP 3.9.0

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

{} It's a method of the class: WP_Customize_Widgets{}

No Hooks.

Return

Null. Nothing.

Usage

$WP_Customize_Widgets = new WP_Customize_Widgets();
$WP_Customize_Widgets->print_preview_css();

Changelog

Since 3.9.0 Introduced.

Code of WP_Customize_Widgets::print_preview_css() WP 5.5.1

<?php
public function print_preview_css() {
	?>
	<style>
	.widget-customizer-highlighted-widget {
		outline: none;
		-webkit-box-shadow: 0 0 2px rgba(30, 140, 190, 0.8);
		box-shadow: 0 0 2px rgba(30, 140, 190, 0.8);
		position: relative;
		z-index: 1;
	}
	</style>
	<?php
}