Select Language "Simplified Chinese" in the log in screen.

Run Nautilus, in the /tmp folder create and new folder.
(This new folder name is in chinese.)
Try to drag this folder to a GTK app that supports drag&drop.
In my case I used Eclipse (eclipse.org).

I could verify that the "data" of the drag_data_received callback is the string:
file:///tmp/%CE%B4%C3%FC%C3%FB%CE%C4%BC%FE%BC%D0
If a paste this string into mozilla (or nautilus) it will correctly open this
folder. Therefore I believe the URI is right.

The problem is: if I use g_filename_from_uri() to parse this URI it  returns a
error message:
The URI 'file:///tmp/%CE%B4%C3%FC%C3%FB%CE%C4%BC%FE%BC%D0' contains invalidly
escaped characters

Maybe the problem is that after unescaping the string glib expect to have a
valid UTF-8 string, I'm afraid that in this case the string might be encoded in
GB18030.

I believe this should work.

If after unescaping the URI the string resulting is already in the plaform
encoding it should bypass the "UTF-8"->"Platform encoding" conversion and return
the string.