Windows © : Change the font/size used by GTK+

** for gtk3 ** (HomeBank >= v5.0)

go to C:\Program Files (x86)\HomeBank\etc\gtk-3.0
open settings.ini file with notepad or a text-editor
you have a commented line like this:
#gtk-font-name = Open Sans 14

just uncomment and set the font name you like
gtk-font-name = Segoe UI 12

to permanently change the font:
1) for all users
- create a C:\ProgramData\gtk-3.0 folder
- create file named settings.ini with just
gtk-font-name = Segoe UI 10

2) for only a single user
do the same but into C:\Users\<username>\AppData\Local\gtk-3.0\

note: the font for future transaction is a bit smaller at 80%

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** for gtk2** (HomeBank < v5.0)
To change the font face and size, just edit the file Program Files (x86)/HomeBank/etc/gtk-2.0/gtkrc
and change the "Segoe UI 10" by something suiting you like "Arial 12" or similar.

also have a look at:
http://amitp.blogspot.fr/2005/09/font-size-in-gtk-apps-under-windows.html