Hi,
I don't know Gnome but I use some applications, like the
mail-client/balsa.
It opens suitable applications for given mime types (in attachments).
The application invoked is read from
/usr/share/applications/mimeinfo.cache .
Unfortunately, that file is rebuild after each emerge of a related
package.
E.g., having reinstalled media-gfx/gimp it places gimp at the front of
the list of
packages suitable for viewing a postscript file.
Currently I am only able to modify
/usr/share/applications/mimeinfo.cache by changing
the order of coresponding applications.
Is there a more elegant (persistent) way?
Many thanks for a hint,
Helmut.