Source

File: wp-admin/includes/class-wp-screen.php

public function render_meta_boxes_preferences() {
		global $wp_meta_boxes;

		if ( ! isset( $wp_meta_boxes[ $this->id ] ) ) {
			return;
		}
		?>
		<fieldset class="metabox-prefs">
		<legend><?php _e( 'Boxes' ); ?></legend>
		<?php
			meta_box_prefs( $this );

		if ( 'dashboard' === $this->id && has_action( 'welcome_panel' ) && current_user_can( 'edit_theme_options' ) ) {
			if ( isset( $_GET['welcome'] ) ) {
				$welcome_checked = empty( $_GET['welcome'] ) ? 0 : 1;
				update_user_meta( get_current_user_id(), 'show_welcome_panel', $welcome_checked );
			} else {
				$welcome_checked = (int) get_user_meta( get_current_user_id(), 'show_welcome_panel', true );
				if ( 2 === $welcome_checked && wp_get_current_user()->user_email !== get_option( 'admin_email' ) ) {
					$welcome_checked = false;
				}
			}
			echo '<label for="wp_welcome_panel-hide">';
			echo '<input type="checkbox" id="wp_welcome_panel-hide"' . checked( (bool) $welcome_checked, true, false ) . ' />';
			echo _x( 'Welcome', 'Welcome panel' ) . "</label>\n";
		}
		?>
		</fieldset>
		<?php
	}