Allow the use of details+summary for extended image descriptions

[josteinaj]

Diagram Center, Best Practices for Authoring Extended Descriptions in EPUB: http://diagramcenter.org/best-practices-for-authoring-extended-descriptions.html

We would like to use the suggestion from Diagram Center for marking up extended image descriptions. From previous issues I understand that it's not been a priority in the guidelines revision work, and that each agency will have to sort this out in post-production.

@martinpub @AndersEkl @kalaspuffar would it be ok for you if we allow the markup suggested by Diagram Center in the validatior, even though it's not mentioned in the guidelines?

The change would be:

• allow the details element as the first following sibling of figure elements with class="image"
• allow (or possibly require) the summary element as the first child of the details element
• allow block level elements (we probably don't want headlines here) in the details element (I'll have to figure out which definition to use)
• allow aria-details on the img element to link to the details element

See "Code Example 1" in the link above.

See also:

• https://github.com/nlbdev/nordic-epub3-dtbook-migrator/issues/244
• https://github.com/nlbdev/epub3-guidelines-update/issues/34

[martinpub]

Hi @josteinaj!

Thanks for the update regarding your image descriptions format progress.

I would be in favour of allowing this, but I would also suggest we discuss the possibility of harmonising image descriptions markup in the Nordic Guidelines, as I think we definately have a joint interest here. They are already implictly part of the 2020-1 guidelines when it comes to text extraction.

I suggest we discuss it on the next validator meeting but also that we bring it up in the guidelines development group.

[martinpub]

Decision in validator group meeting on October 15: Allow the construction to be validated even though not documented in the guidelines. The guidelines group should consider this alternative in future updates.

[josteinaj]

Fixed in #504 (guidelines-revision branch).