utf8を一定文字数ごとに改行する。
その際、行頭に「、」や「。」がこないように改行をいれる。

バイト数チェックはjanssonライブラリのutf.hを使うべし。
https://github.com/akheron/jansson/blob/master/src/utf.h

aho.cpp

# include "utf.h"
//descriptionを17文字ずつ改行
//行数を返す
int TextHelper::descriptionR(std::string *description) {
    int lines = 1;
    int cnt = 0;
    const char *c = description->c_str();
    std::stringstream stream;
    int32_t codePoint = 0;
    char buf[4];
    int size;
    const char *next = utf8_iterate(c, &codePoint);
    bool pass = false;
    while (next[0] != '\0') {
        ASSERT(!utf8_encode(codePoint, buf, &size), "not false");
        c+= size;
        for(int i = 0; i<size; i++){
            stream << buf[i];
        }
        if (cnt++ > 16) {
            next = utf8_iterate(c, &codePoint);
            ASSERT(!utf8_encode(codePoint, buf, &size), "not false");
            if(codePoint == 0x3001 || codePoint == 0x3002){
                c+= size;
                for(int i = 0; i<size; i++){
                    stream << buf[i];
                }
            }
            cnt = 0;
            stream << '\n';
            lines++;
            if(next[0]== '\0')goto __skip;
        }
        next = utf8_iterate(c, &codePoint);
    }
    ASSERT(!utf8_encode(codePoint, buf, &size), "not false2");
    for(int i = 0; i<size; i++){
        stream << buf[i];
    }
__skip:
    *description = stream.str();
    return lines;
}