My WordPress site has a bunch of posts, all filed by a top-level category and a bunch of subcategories therein.
I have the main site nav rendering the category pages, which, when clicked, get all posts in that top-level category as an 'archive'.
The category highlights as you'd expect when you visit one of these category pages, however, when visiting a single post in this category, no highlighting for me. I'd expect that the top-level category to which this post belongs would be highlighted and it looks as if that is the intended behaviour.
So, my question is: What can I do to make the category the post belongs to highlight in the main nav when I'm viewing a single post?
The site gets quite a lot of traffic so I am keen to get a solution that scales well.