On Linux I often use gedit and Geany, and love the interface of both. On Windows (8) however, non seem to support font fallback; that is, when I open a text file containing Chinese and Japanese characters, it displays boxes.
This is not an encoding problem, since changing the editor font to a specifically Chinese one fixes Chinese characters, but not Japanese ones, and I don't have any Chinese or Japanese font with fixed-width latin characters anyway...
How can I tell gedit or geany which fonts to use when the currently selected font misses some characters?