WP_Widget_Media_Gallery::form( array $instance )

	public function form( $instance ) {
		$instance = array_merge( wp_list_pluck( $this->get_instance_schema(), 'default' ), $instance );

		$title             = ! empty( $instance['title'] ) ? $instance['title'] : '';
		$ids               = ! empty( $instance['ids'] ) ? implode( ',', $instance['ids'] ) : '';
		$columns           = ! empty( $instance['columns'] ) ? $instance['columns'] : 3;
		$size              = ! empty( $instance['size'] ) ? $instance['size'] : 'thumbnail';
		$link_type         = ! empty( $instance['link_type'] ) ? $instance['link_type'] : 'post';
		$orderby_random    = ! empty( $instance['orderby_random'] ) ? $instance['orderby_random'] : false;
		$nonce             = wp_create_nonce( '_wpnonce' );
		?>

		<div class="media-widget-control selected">
			<fieldset>
				<label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php esc_html_e( 'Title:' ); ?></label>
				<input id="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" data-property="title" class="widefat" value="<?php echo esc_attr( $title ); ?>">
			</fieldset>

			<?php
			$files_exist = false;
			if ( $ids ) {
				foreach ( $instance['ids'] as $id ) {
					if ( file_exists( get_attached_file( $id ) ) ) {
						$files_exist = true;
						break;
					}
				}
			}

			if ( $ids && $files_exist ) {
				$gallery_html = '<ul class="gallery media-widget-gallery-preview">';
				foreach ( $instance['ids'] as $id ) {
					$attributes = '';
					$thumbnail = wp_get_attachment_image_src( $id, 'thumbnail', false );
					$alt = get_post_meta( $id, '_wp_attachment_image_alt', true );

					if ( $thumbnail && $thumbnail[0] ) {

						// Create an aria-label attribute if the image has no alt attribute.
						if ( $alt === '' ) {
							$aria_label = esc_attr(
								sprintf(
									/* translators: %s: The image file name. */
									__( 'The current image has no alternative text. The file name is: %s' ),
									basename( $thumbnail[0] )
								)
							);
							$attributes .= ' aria-label="' . $aria_label . '"';
						}

						$gallery_html .= '<li class="gallery-item">';
						$gallery_html .= '<div class="gallery-icon">';
						$gallery_html .= '<img alt="' . $alt . '" src="' . $thumbnail[0] . '" width="150" height="150"' . $attributes . '>';
						$gallery_html .= '</div>';
						$gallery_html .= '</li>';
					}
				}
				$gallery_html .= '</ul>';
				?>

				<div class="media-widget-preview media_gallery"><?php echo $gallery_html; ?></div>

				<fieldset class="media-widget-buttons">
					<button type="button" class="button edit-media selected" data-edit-nonce="<?php echo esc_attr( $nonce ); ?>" style="margin-top:0;"><?php esc_html_e( 'Edit Gallery' ); ?></button>
				</fieldset>

				<?php
			} else {
				?>

				<div class="media-widget-preview media_gallery">
					<div class="attachment-media-view">
						<button type="button" class="select-media button-add-media" data-edit-nonce="<?php echo esc_attr( $nonce ); ?>"><?php esc_html_e( 'Add Images' ); ?></button>
					</div>
				</div>

				<?php
			}
			?>

			<input id="<?php echo esc_attr( $this->get_field_id( 'ids' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'ids' ) ); ?>" type="hidden" data-property="ids" class="media-widget-instance-property" value="<?php echo esc_attr( $ids ); ?>">
			<input id="<?php echo esc_attr( $this->get_field_id( 'columns' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'columns' ) ); ?>" type="hidden" data-property="columns" class="media-widget-instance-property" value="<?php echo esc_attr( esc_attr( $columns ) ); ?>">
			<input id="<?php echo esc_attr( $this->get_field_id( 'size' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'size' ) ); ?>" type="hidden" data-property="size" class="media-widget-instance-property" value="<?php echo esc_attr( esc_attr( $size ) ); ?>">
			<input id="<?php echo esc_attr( $this->get_field_id( 'link_type' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'link_type' ) ); ?>" type="hidden" data-property="link_type" class="media-widget-instance-property" value="<?php echo esc_attr( $link_type ); ?>">
			<input id="<?php echo esc_attr( $this->get_field_id( 'orderby_random' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'orderby_random' ) ); ?>" type="hidden" data-property="orderby_random" class="media-widget-instance-property" value="<?php echo esc_attr( $orderby_random ); ?>">

		</div>
		<?php
	}