How to install RGtk2 on OS X 10.10.5? I am trying to install RGtk2. I have installed GTK+ and XQuartz with Homebrew:

$ brew cask install xquartz 
Warning: A Cask for xquartz is already installed. Add the "--force" option to force re-install.
$ brew install gtk
Warning: gtk+-2.24.28_2 already installed


But when I try installing it I get the error

Rgtk.c:7:10: fatal error: 'gdk/gdkx.h' file not found


Have I missed installing some necessary package?
Seems like a problem with RGtk2 which does not support Quartz GTK on OS X (and provided by Homebrew). I followed the advice posted here:

https://github.com/Homebrew/homebrew/issues/43290

Which suggests installing the binary version:

install.packages("RGtk2", dependencies = T, type = 'mac.binary.mavericks')