Gadgets that add portlet tabs to the page skin (such as T152013) can cause a 'flash' of moving web content due to the potentially large delay between loading the server-side-generated HTML and loading the gadget JS.

One possible fix for this would be to allow gadgets to register for custom tabs in a structured way, so the tab can be added via the server-side HTML.

Possible format:

• add [[MediaWiki:Gadget-foobar.json]] with:

{
 tabs: [
  {
   // options for https://www.mediawiki.org/wiki/ResourceLoader/Modules#addPortletLink
   "portletId": "p-awesome",
   "href": "/wiki/Special:Version",
   "text": "awesome-msg",
   "id": "t-awesome",
   "accessKey": "q",
   "nextNode": "#t-print"
  }
 ]
}

Possible issues:

• if tab should appear conditionally, how to specify?
• fallback behavior when no JS?