Thread:FishTank/@comment-3361105-20180507225752/@comment-4522253-20180509233916

Hey, Rab. Feel free to bug me; it's kinda my job. 😎

The first and most important thing here is the differences in the captions, labels, and descriptions of images and galleries. These are not always the same thing, which I'm sure you know, but I hope you'll bear with me for illustration.

Standard images have the image themselves (and a filename), plus potentially three pieces of textual information attached. Defines the alternative text (maps to the HTML attribute alt="..." of the generated element) of an image that will be rendered if either the referenced image cannot be downloaded and embedded, or if the support media must use the alternative description text (e.g. when using a Braille reader or with accessibility options set by the user in its browser). [...] If 'alt' is not specified and a caption is provided, the alternative text will be created automatically from the caption, stripped of formatting, except when [...] the caption is already readable by screen readers in that case. ― mw:Help:Images
 * The caption, in strictest sense, is meant to place an image in context or display a basic description ("Cover Art for The Flash v5 #46").
 * A link sends the click to a target page.
 * An alt-text, in contrast, is meant almost entirely for visually impaired readers (such as "The Flash runs through the Speed Force, cradling his aching head, with scenes from past timelines on either side"). At least, that's the intent of the tag, according to the WMF and W3C.

Image galleries and tabbers (which are identical inside PIs) add an additional complication because the caption becomes a tab label or handle to select the desired image. For portability and accessibility reasons (The same AJAX trigger should not change two types of content — so images only, not images + captions), there is no additional descriptive caption. The images in a gallery, per the caption rule above, have the alt-text of whatever the caption is. Unfortunately, FANDOM did not add in a facility to the feature to add additional descriptive alternative texts for images; presumably, this was to keep the syntax simple. However, I'm reasonably sure that we'd consider an alteration if a screen-reader-using FANDOM user requested an addition to the syntax as an accessibility issue.

Personally, if you're already on a given issue, I'm not sure it's any more descriptive to add "Textless Cover Art from PAGENAME", as it's still not describing the actual image, and the context is inherent and the relationship defined (on that article). I abbreviated them as "Cover" and "Textless" for simplicity and conciseness versus the full description. The best place to put the kind of description you're referring to, for SEO purposes as well as functional ones, is the File: page of the image. However, one way or another, whether it's in Lua or wikitext, there's not a way with the current PI or Gallery product to add a specific alt-text.