// requires element_attributes.js

   function gallery_active_index() {
      this.value = 0;
   }

   function gallery_image_substitute(gallery_id, gidxobject, new_gidx, num_images, image_array, dual) {
      var href = image_array[0];
      var js_href = image_array[1];
      var src = image_array[2];
      var title = image_array[3];
      var width = image_array[4];
      var height = image_array[5];
      
      var link_id = gallery_id+'-image-a';
      var cont_id = gallery_id+'-image';

      if (href.length > 0) {
         var imgcontainer_id = link_id;
      } else {
         var imgcontainer_id = cont_id;
      }
      var img_id = gallery_id+'-image-img';
      if (dual == undefined || dual == false) {
    	var prevlink_id = gallery_id+'-prevlink';
        var nextlink_id = gallery_id+'-nextlink';
        set_display(prevlink_id, new_gidx > 0 ? 'block' : 'none');
        set_display(nextlink_id, new_gidx < num_images-1 ? 'block' : 'none');
      }
      gidxobject.value = new_gidx;

      if (href.length > 0) {
         set_attribute(link_id, 'href', href);
         set_attribute(link_id, 'onclick', js_href);
      }
      
      remove_child(imgcontainer_id, img_id);
//      set_display(img_id, 'none');
//      set_display(img_id, 'block');
      append_child(imgcontainer_id, 'img', img_id);
      set_attribute(img_id, 'alt', title);
      set_attribute(img_id, 'title', title);
      set_attribute(img_id, 'width', width);
      set_attribute(img_id, 'height', height);
      set_attribute(img_id, 'src', src);
   }