[gnome-flashback] How to get scaling factor from a shell script

[Ken Gilmer <kgilmer gmail com>]

It is common for users to expect all applications to respect the gnome-control-panel Display Scale Factor.  I would like to possibly set Xft.dpi based on this setting, however I cannot find a gsettings key that represents this value from the control panel.  I've recursively dumped all keys with 'scal' in them before and after changing scaling from 100% to 200% but no values change.  In source I find reference to the key 'scaling-factor' but again, do not see any gsettings changes after changing the value via Settings.  Any suggestions to how I can read this setting from a script?

TIA
ken