TYPO3 Core

http://www.w3schools.com/tags/att_img_longdesc.asp
No browser support, no HTML5

http://www.w3.org/WAI/WCAG20/Techniques/ua-notes/html#H45
says it is supported in browsers.

Of course it's supported : http://www.w3.org/TR/html-longdesc/#intro

that's why I think it's a must have.

Furthermore, it should be implemented in FAL, with a link field and being overridable in tt_content.

You can add it for your own purposes, or even provide it as an extension for TYPO3

Steffen Ritter said:

You need an ext with a couple of files
ext_emconf ext_icon ex_tables.sql TCA/Override/sys_file_metadata TCA/Override/sys_file_reference locallang.xlf and some TypoScript

It's kinda obvious we have to redevelop features that were part of the core and had been removed for strange reasons.

By the way, if I implemented this by myself I'll do it in a way that fits my need, but I'm quite sure it won't fit generic needs and/or comply with community taste of quality.

Well, I'll have a look at what I can achieve, but should'nt it be easier that the teams in charge of either Fal, css_styled_content or accessibility take that into account ?

TYPO3 is providing some gouvernemental package... this should be implemented as a core feature in such distribution I think.

Further Information

@mattur on twitter pointed something out : https://twitter.com/mattur/status/483710007192846337

It seems to be no consensus on longdescurl.

W3C seems to say "you should use longdescurl to provide a link to access the description of an image : https://dvcs.w3.org/hg/html-proposals/raw-file/ac507017569f/longdesc1/longdesc.html
But discussions on the newslists are still trying to find a better approach for this concept.
See this post from apple : http://lists.w3.org/Archives/Public/public-html-a11y/2014Jun/0115.html

Well for now, this is what I think (personnal opinion).

- LongDescUrl might not be the best way to provide descriptions of an image.
- I agree that the best would be to have some self describing content, and or image could be described in the content of the page. Maybe with a simple link on the image.

But, as it was part of the core, I think we should try bring it back. Then wait to see if W3C and/or accessibility experts find a consensus on how to make picture accessible to visually impaired users.

Yes, this is a must have, if you search for "wai +longdesc" you will find the correct pages. I don't know why this feature was removed, but there is also no need to reimplement it. As you can see, WAI itself say it will be better to use figcaption for this, https://www.w3.org/WAI/tutorials/images/complex/.
So the best way for the future will be to make it possible to set a link inside the figcaption.