Extension:Popups

The Popups (known in Special:Version as Previews) extension displays page and reference previews when hovering over a link to an article or respectively to a reference. The former consists of summaries of an article's content, the latter shows the full content of the reference.

The extension is an initiative of the Design team, inspired by the popular Navigation popups gadget. Currently this feature is available on all Wikipedias by default for logged-out users. A description of how the extension functions and more information on its use on Wikimedia projects is available at Page Previews.

The Reference Previews feature was added eventually and aims to fulfill a wish from the German-speaking community's Technical Wishlist. A more detailed description and more information on its use is available at.

Dependencies
This extension has a hard dependency on and  when used with the default   gateway. There are also optional dependencies on (if you want to enable the Reference Previews as beta feature), and  and  (for instrumentation).

Installation

 * Install the dependencies.

Page previews API
Every project is different, and what displays in your previews is highly dependent on the content inside your wiki.

Popups extension has been optimized to work with Wikipedia-like content (e.g. wikitext).

If your wiki is using a different kind of content handler (for example as is the case for ) it will need to provide its own API.

The API can be written in any language, but the response of the API must match the spec defined here:

Defining new APIs is out of scope for the Popups extension.

Once defined, you can configure page previews to point to your API using configuration option.

Page previews content
The page preview popups show an image (if one is available) and a small text excerpt.

Image
The image comes from the which returns the single most appropriate thumbnail associated with an article. It ignores maintenance templates, stubs, flag icons etc.

Text
The page previews can be configured with any compatible API that is compatible with the Page content service summary endpoint using. For third parties we encourage using the Page Content Service to enjoy using Popups with your local wiki.

You can also use the extension. This extension has various caveats and we do not actively support use of this API.

Reference previews content


The content in the reference preview popups is taken directly from the reference section on the page itself. No external services are involved here. If the content exceeds the popup size scrollbars are shown so everything can be looked at.

Reference types
The reference types displayed are set by using specific CSS-classes on the tag that can be used to encapsulate the content of a reference, e.g.. Currently the following types are supported:, ,  ,  ,. Apart from that there is always a generic fallback if neither the cite tag was found nor an appropriate class was used. Please note, that it's not recommended to use the CSS-classes directly in wikitext, but rather by creating templates.

Renderers
This extensions currently has only one renderer, that is for ordinary pages.

New renderers for different kind of pages, or things like references can be easily added.

One needs to create a new object with the following methods:



You can see details of these methods in ext.popups.renderer.article.js or this patch that adds a renderer for references.

Known problems

 * Users of the extension should note that Page Previews requests previews in the content language of the page. If the preview contains a complete translatable block, then it will be translated. If, however, the preview contains an incomplete translateable block – because a sentence is cut off, say – then it isn't translated and will be displayed in the content language of the page. If you are observing this behavior, then you should consider marking up individual sentences in your lead section.  T167852 is for a technical audience but has more information on the underlying problem.
 * Longer math formulas cutting off in preview - long math or chemical formulas (formulas wider than the preview width) display as truncated in previews. We were not able to add a gradient in order to indicate that the formula is continued on the article itself.
 * Small files may be in the "Рage information" (action=info), but not in the "Popups". Some requirements are set here - for a portrait image: exact (min) height 250 px & max width 203 px; for a landscape image: exact (min) width 320 px &  max height 200 px . To display, images must be able to become a thumbnail that is larger or equal to these "exact" sizes. (If you are cropping a large image to make a leading picture for an article, be sure that the picture you are creating is not smaller than the specified sizes.)

Extensibility
In MediaWiki 1.40, extensions and skins can extend the page previews functionality with their own custom preview types. It does this by registering a PluginModules attribute in its extension.json or skin.json file that points to a ResourceLoaderModule that can register a preview type. The plugin module should export information about when the preview should be displayed (via selector), and how the preview data should be retrieved (via gateway library). This feature is still in its infancy, has a few bugs (example) and feedback/bug reports via Phabricator are encouraged.

Why can't I copy and paste text from a preview?
At time of writing, the cons of doing so outweigh the pros. Essentially it boils down to decreasing the touch area to read the article in full. Once Page Previews is deployed on English and German Wikipedia, feel free to reopen this task and reignite the discussion, but right now we have no plans.

How can I change the image that I see on preview?
See Extension:PageImages#Image choice.

How can I remove content from a page preview?
Any element marked with the class will be stripped from the summary.

Where do summaries come from?
These are provided by the summary REST API or the API in case your wiki is using the default  gateway.

Why are parenthetical stripped?
There's a good discussion going on in T91344 in Phabricator. If you have any views on this or see any problems relating to this, please let us know there.

Why don't I see Popups outside of content namespaces?
Popups appear on links to pages in content namespaces only. This is a limitation of Popups; TextExtracts are available from other namespaces. You may work around this by appending more namespaces into.

Links

 * Page Previews help page and central feedback page on MediaWiki.org
 * Reference Previews help page and central feedback page on MediaWiki.org
 * Reference Previews main project page on Meta
 * Related research: Wikimedia Performance Team/Authoring Popups: Best Practices