Most of the time here in the begining of the gpredict for Gtk+ 2 development process will go with writing all sorts of small utility widgets, which can be re-used several places in the program.
One of these utilities is the locations tree widget, which can present the user with a list of pre-defined locations organised in a tree according to continent and country. Ham radio operators are probably not interested in this feature but users without knowledge of geographical coordinates may find it very usefull.
I have now finished the new locations tree widget including a conversion of the data file to use negative numbers for longitudes West of Greenwich. I let you take a sneak peak here:
As you can see on the images, it has the possibility to show the longitude either using sign or N, W, S and E suffixes. This has been very easy thanks to the possibility to use custom data formatting functions, which leave the actual data untouched, that is the coordinates will stay as plain floating point numbers in the GtkTreeStore. Very cool!