cc @bfgeek

The MathML core spec now defines all the min-content / max-content values, however these two are equal and linebreaking is supposed to never happens.

I believe linebreaking could potentially happen in:

• Inline equations. However, I think defining CSS fragments will be a bit complicate.

• mrow-like element from display equations. We have an experiment like this in chromium. Currently that depends on the parent's width however, we could do something similar if width is specified on the element (Generate new PNGs for examples in the core spec #45).

• mtable (I guess that's already defined by CSS). Maybe we want to prevent it for now.

MathML 3 rules for linebreaking are quite complex, maybe we should have a simple version first and refine it later or get it improved by polyfills when the CSS Layout API is ready.

Just opening this so that it can be referenced from the spec.