data->metrics->GetWidthCallback(aChar, aFont, aData);
return data->metrics->GetWidthCallback(aString, aLen, aFont, aData);
StaticGetWidthCallback(FcChar32 aChar, nsFontXft *aFont, void *aData){    WidthData *data = (WidthData *)aData;    data->metrics->GetWidthCallback(aChar, aFont, aData);}