srecord noeq G22_RegionToSSIs_v2(IImageRegion region) {
  RGB color;
  L<SSI> ssis;
  new L<GrowingSSI> growingSSIs;
  settable bool withDiagonals;
  
  class GrowingSSI {
    settable int y1;
    new ShortBuffer data;
    
    int y2() { ret y1+l(data)/2; }
    
    SSI finish() {
      ret new SSI(y1, y2()).data(data.toArray())
        .color(color);
    }
    
    bool isEmpty() { ret data.isEmpty(); }
    int lastx1() { ret data.get(l(data)-2); }
    int lastx2() { ret data.get(l(data)-1); }
    
    void add(int x1, int x2) {
      data.add(toShort_enforce(x1));
      data.add(toShort_enforce(x2));
    }
  }
  
  L<SSI> get() {
    if (region == null) null;
    
    color = region.color();
    ssis = new L;
    Rect r = region.bounds();
    int x1 = r.x1(), y1 = r.y1(), y2 = r.y2(), h = y2-y1, w = r.w;
    for (int y = y1; y < y2; y++) {
      reMutable y;
      L<IntRange> streaks = genericStreaks(w, x -> region.contains(x1+x, y));
      
      // advance iGrowingSSIs & iStreaks simultaneously
      int iStreak = 0, iSSI = 0;

      while (iStreak < l(streaks)) {
        var range = streaks.get(iStreak);
        
        var ssi = get(growingSSIs, iSSI);
        
        // insert new SSI left of current SSI (or to the right of everything)
        if (ssi == null || range.end < ssi.lastx1()) {
          var ssi = new GrowingSSI().y1(y);
          ssi.add(x1+range.start, x1+range.end);
          growingSSIs.insert(iSSI, ssi);
          ++iStreak;
          continue;
        }
        
        todo();
      }
    }
    
    for (ssi : cloneAndClear(growingSSIs))
      ssis.add(ssi.finish());
    
    ret ssis;
  }
}