what are 'unusual elements' ?

[bnjmnrsh]

I started to open an issue on https://github.com/mdn/browser-compat-data, but I thought perhaps some discussion here would be a better way to start.

Im currently researching behaviours around fieldset and legend, using grid and flex on the fieldset and display: contents on the nested legend.
My initial tests with Safari 16.5 +voiceover appear to announce fieldset and legend just the same as when the legend is unstyled. However, this wasn't the result I was expecting as the caniuse compatibility data for css.properties.display, specifically this page: CSS property: display: contents: Specific behaviour of unusual elements when display: contents is applied to them seems to indicate it shouldn't work.

The MDN reference page for display supports this and also makes an oblique reference to 'unusual elements' in the Browser Compatibility table. Where Safari is highlighted as not supporting display properties on both 'unusual elements' AND legend.

Now it's possible, even likely, I'm misinterpreting my own test results, as I'm, at best, a student of A11ty. However, between MDN and caniuse resources, I feel there should be some definition as to what elements are classed as 'unusual", specifically in the context of display: content

Questions:

• Shouldn't these resources point to the source of where the compatibility information is gathered from?
• ie what are these 'unusual elements', are fieldset and legend in that list?
• In writing this, I've just uncovered @aardrian 's article and feel that MDN and caniuse could be improved with some of his findings.

A significant amount of discussion and work has already been done to document issues around display: contents that is worth referencing:

CanIUse:
Fyrd/caniuse#6469
MDN Browser Compat Data:
https://github.com/mdn/browser-compat-data/issues?q=is%3Aissue+is%3Aopen+display+contents

Also:
https://adrianroselli.com/2022/07/use-legend-and-fieldset.html
https://adrianroselli.com/2022/07/its-mid-2022-and-browsers-mostly-safari-still-break-accessibility-via-display-properties.html
https://www.tpgi.com/fieldsets-legends-and-screen-readers-again/

Caniuse, receives its compatibility data from MDN: css.properties.display, which is where any issue related to this should ultimately be logged.

[pepelsbey]

Thank you for starting the discussion. I’m closing this now due to inactivity, but if you think that’s a mistake, feel free to reply. I’d also suggest filing an issue directly in the browser-compat-data repository, which handles all the content in the notes for each compat entry. You’re also welcome to join the MDN Discord if you’d prefer to chat with us more about it in sync.