Complimentary to "thumb" and "full", "fit" would either display the image as "full" if it fits horizontally within the page or scale it down to fit horizontally exactly.
Description
Description
Revisions and Commits
Revisions and Commits
Event Timeline
Comment Actions
You can use width=100%. This isn't quite what you're after, because it will also scale up small images.
I'll see if we can do this in CSS with max-width: 100%. If we can't, writing JS for this is probably Wontfix.
Comment Actions
max-width: 100% seems to work reasonably well. In effect, D9758 turns "size=full" into "size=fit". (I assume you don't have a use case for the current behavior (scroll all over the place) of "size=full"?)