Right now if Gtk+ uses HiDPI scaling mutter goes crazy with e.g. window border rendering and event coordinates. Also, mutter kind of relies on GdkWindow and XWindows being "the same" size, etc. Not to mention that it needs to be able to handle other clients creating windows of an odd size (which is hard with gdk at scale 2).

So, I don't think it makes much sense to try to convert mutter to handle the Gdk automatic scale, instead we should just disable the gdk scaling and do the scaling ourselves.

Attaching a patch that just disables the scaling. This picks up the larger font dpi when in HiDPI, so its still pretty usable, but clearly we need to do more work later.