Hmm, gtk+ has a huge number of dependents.

Also, shouldn't gtk+ already have libxrandr in its inputs by virtue of gtk+
inheriting from gtk+-2, which does have it in its inputs?  Why doesn't it
work without the patch?

I suspect that other (xfce) packages actually should require libxrandr in THEIR
inputs, and it's missing there.

Of course adding it to propagated-inputs of gtk+ would "fix" (work around) the
problem, but that's usually not the correct place for it.