Source
File: wp-includes/class-wp-customize-widgets.php
public function output_widget_control_templates() {
?>
<div id="widgets-left"><!-- compatibility with JS which looks for widget templates here -->
<div id="available-widgets">
<div class="customize-section-title">
<button class="customize-section-back" tabindex="-1">
<span class="screen-reader-text"><?php _e( 'Back' ); ?></span>
</button>
<h3>
<span class="customize-action">
<?php
/* translators: ▸ is the unicode right-pointing triangle. %s: Section title in the Customizer. */
printf( __( 'Customizing ▸ %s' ), esc_html( $this->manager->get_panel( 'widgets' )->title ) );
?>
</span>
<?php _e( 'Add a Widget' ); ?>
</h3>
</div>
<div id="available-widgets-filter">
<label class="screen-reader-text" for="widgets-search"><?php _e( 'Search Widgets' ); ?></label>
<input type="text" id="widgets-search" placeholder="<?php esc_attr_e( 'Search widgets…' ); ?>" aria-describedby="widgets-search-desc" />
<div class="search-icon" aria-hidden="true"></div>
<button type="button" class="clear-results"><span class="screen-reader-text"><?php _e( 'Clear Results' ); ?></span></button>
<p class="screen-reader-text" id="widgets-search-desc"><?php _e( 'The search results will be updated as you type.' ); ?></p>
</div>
<div id="available-widgets-list">
<?php foreach ( $this->get_available_widgets() as $available_widget ) : ?>
<div id="widget-tpl-<?php echo esc_attr( $available_widget['id'] ); ?>" data-widget-id="<?php echo esc_attr( $available_widget['id'] ); ?>" class="widget-tpl <?php echo esc_attr( $available_widget['id'] ); ?>" tabindex="0">
<?php echo $available_widget['control_tpl']; ?>
</div>
<?php endforeach; ?>
<p class="no-widgets-found-message"><?php _e( 'No widgets found.' ); ?></p>
</div><!-- #available-widgets-list -->
</div><!-- #available-widgets -->
</div><!-- #widgets-left -->
<?php
}