by 
I have limited experience in Gtk+, even though I studied it around four years ago. The newer version has brought some changes which sometimes seems confusing particularly when using Glade Interface Designer for building the UI.
Part of it is due to lack of good documentation and part of it is due to non-intuitive Glade Interface.
Anyhow, few days ago while I was working on my Ubuntu Indicator Weather project to add preference section, I came across using Gtk Adjustment switch for setting latitude and longitude. However, whatever I did to set upper (maximum) and lower (minimum) from Glade, I failed. Searching on the Internet did not solve the problem either.
Luckily, Glade files are pure XML (Unix philosophy, store everything in flat files), so it can be opened with text editors and apply the changes. To do so, just open the file and look for your Gtk Adjustment component and add the following lines between its object tag.
<property name="lower">-180</property>
<property name="upper">180</property>
