roro9stack/lib/ui/src/text_wrap.cpp

#include "text_wrap.h"

#include "utf8.h"

namespace roro {

namespace {

void wrapParagraph(const std::string& para, int maxWidth, const MeasureText& measure,
                   std::vector<std::string>& out) {
    std::string line;
    size_t pos = 0;
    while (pos < para.size()) {
        size_t space = para.find(' ', pos);
        std::string word = para.substr(pos, space == std::string::npos ? std::string::npos : space - pos);
        pos = space == std::string::npos ? para.size() : space + 1;

        std::string candidate = line.empty() ? word : line + " " + word;
        if (measure(candidate) <= maxWidth) {
            line = candidate;
            continue;
        }
        if (!line.empty()) {
            out.push_back(line);
            line.clear();
        }
        // The word alone may still be too wide: cut it character by character.
        while (measure(word) > maxWidth) {
            size_t cut = 0;
            while (true) {
                size_t nextCut = utf8::next(word, cut);
                if (measure(word.substr(0, nextCut)) > maxWidth) break;
                cut = nextCut;
            }
            if (cut == 0) cut = utf8::next(word, 0);  // a single character wider than the line
            out.push_back(word.substr(0, cut));
            word = word.substr(cut);
        }
        line = word;
    }
    out.push_back(line);
}

}  // namespace

std::vector<std::string> wrapText(const std::string& text, int maxWidth, const MeasureText& measure) {
    std::vector<std::string> lines;
    if (text.empty()) return lines;
    size_t start = 0;
    while (true) {
        size_t nl = text.find('\n', start);
        wrapParagraph(text.substr(start, nl == std::string::npos ? std::string::npos : nl - start), maxWidth,
                      measure, lines);
        if (nl == std::string::npos) break;
        start = nl + 1;
    }
    return lines;
}

}  // namespace roro