FTR there was a working group to provide a Network Information API  to let JS handle this more easily. In trying to do that, they had a difficult time actually getting accurate information for the API to provide. So it was canned in order to further assess the cases specifically and other approaches. I highly doubt if there was trouble building a JS API for this type of thing that CSS alone can handle it in some way.
If something like this is to happen, it *needs* to happen in JS first. That way developers have control, from a working and proven implementation there we could find a syntax for CSS to work on top of. So for now, you're probably best off polyfilling some JS API and using that to experiment with to present as a solution. That way it can be more easily vetted and tested.  https://dvcs.w3.org/hg/dap/raw-file/tip/network-api/Overview.html On Fri, Dec 9, 2016 at 12:43 PM Michael A. Peters <mpet...@domblogger.net> wrote: > On 12/09/2016 09:03 AM, Boris Zbarsky wrote: > > On 12/9/16 5:57 AM, Michael A. Peters wrote: > >> max-height and max-width and orientation change, but device-width does > >> not change. > > > > Just as a point of fact, device-width can absolutely change. The > > simplest case is a two-monitor setup with the window getting dragged > > from one monitor to another, but similar things can happen when things > > are docked/undocked, monitors are plugged in or removed, etc. > > > > -Boris > > Ah yes, point taken. > > With a bandwidth query I would recommend it only change on a page reload > but it wouldn't have to be done that way. > > This wouldn't only be beneficial to fonts, a lot of images etc. are > defined in CSS too. >