Question about special signs

[Martin Stromberger]

Hello,
first of all, thanks for developing this very useful and nice applicatin.
Now my question:
I'm using streamtuner version 0.12.3 on gentoo.
My default codepage is iso8859-15, locale shows following:
address@hidden
address@hidden
LC_NUMERIC="address@hidden"
LC_TIME="address@hidden"
LC_COLLATE="address@hidden"
LC_MONETARY="address@hidden"
LC_MESSAGES="address@hidden"
LC_PAPER="address@hidden"
LC_NAME="address@hidden"
LC_ADDRESS="address@hidden"
LC_TELEPHONE="address@hidden"
LC_MEASUREMENT="address@hidden"
LC_IDENTIFICATION="address@hidden"
LC_ALL=

The german translation works fine, except the special signs 'ä,ö,ü'. You 
can see it in screenshot one.
<one.png>.
In KDE, Gnome and all other applications translation to the special 
signs 'ä,ö,ü' works correct, for example
another application wich uses gtk <two.png>.

How can I configure streamtuner to show this signs correct ?
greetings

Martin Stromberger