Source

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

public function show_screen_options() {
		global $wp_meta_boxes;

		if ( is_bool( $this->_show_screen_options ) ) {
			return $this->_show_screen_options;
		}

		$columns = get_column_headers( $this );

		$show_screen = ! empty( $wp_meta_boxes[ $this->id ] ) || $columns || $this->get_option( 'per_page' );

		$this->_screen_settings = '';

		if ( 'post' === $this->base ) {
			$expand                 = '<fieldset class="editor-expand hidden"><legend>' . __( 'Additional settings' ) . '</legend><label for="editor-expand-toggle">';
			$expand                .= '<input type="checkbox" id="editor-expand-toggle"' . checked( get_user_setting( 'editor_expand', 'on' ), 'on', false ) . ' />';
			$expand                .= __( 'Enable full-height editor and distraction-free functionality.' ) . '</label></fieldset>';
			$this->_screen_settings = $expand;
		}

		/**
		 * Filters the screen settings text displayed in the Screen Options tab.
		 *
		 * This filter is currently only used on the Widgets screen to enable
		 * accessibility mode.
		 *
		 * @since 3.0.0
		 *
		 * @param string    $screen_settings Screen settings.
		 * @param WP_Screen $this            WP_Screen object.
		 */
		$this->_screen_settings = apply_filters( 'screen_settings', $this->_screen_settings, $this );

		if ( $this->_screen_settings || $this->_options ) {
			$show_screen = true;
		}

		/**
		 * Filters whether to show the Screen Options tab.
		 *
		 * @since 3.2.0
		 *
		 * @param bool      $show_screen Whether to show Screen Options tab.
		 *                               Default true.
		 * @param WP_Screen $this        Current WP_Screen instance.
		 */
		$this->_show_screen_options = apply_filters( 'screen_options_show_screen', $show_screen, $this );
		return $this->_show_screen_options;
	}