unicode for wxagg and gtkagg backends

Hello, Since I have problems with unicode conversion when

    > using wxagg and gtkagg backends I would like to ask which
    > files in matplotlib sources are responsible for this? To
    > understand the mechanism, if in the figure I get empty
    > squares instead of special characters where is the
    > problem: in the phase of processing a text by antigrain
    > or earlier?

All of the font rendering happens in src/ft2font.cpp, where the
freetype file is loaded, the glyphs set, and rendered to a pixel buffer.
agg just copies the bitmap into its own pixel buffer. So ft2font is
the place to look. Squares typically mean that the character you are
requesting is not in the font file you have loaded.