widget form supplement

functions.php

	add_action( 'in_widget_form', 'in_widget_form', 20, 3 );
	add_filter( 'widget_update_callback', 'widget_update_callback', 20 , 4 );
	add_filter( 'widget_display_callback', 'widget_display_callback', 20, 3 );

	function in_widget_form( &$widget, &$return, $instance ){

		// $instance['nav_widget_is_sticky'] = 1;
			?>
			<p>
				<label>
					<?php if($instance['nav_widget_is_sticky'] === 1){ ?>
					<input type="checkbox" name="nav_widget_is_sticky" value="<?php echo $instance['nav_widget_is_sticky']; ?>" checked>
					<?php } else { ?>
					<input type="checkbox" name="nav_widget_is_sticky" value="1">
					<?php } ?>
					Sticky Widget
				</label>
			</p>
			<?php
		}

		function widget_update_callback( $instance, $new_instance, $old_instance, $widget ) {
			// print_r($instance);
			if(isset($new_instance['nav_widget_is_sticky'])){
				$instance['nav_widget_is_sticky'] = $new_instance['nav_widget_is_sticky'];
			} else {
				$instance['nav_widget_is_sticky'] = 0;
			}
			//$instance['nav_widget_is_sticky'] = isset( $new_instance['nav_widget_is_sticky'] ) ? $new_instance['nav_widget_is_sticky'] : '';

		return $instance;
	}

	function widget_display_callback( $instance, $widget, $args ){

		return $instance;
	}