_itemsChanged(items) {
        /*
          items[n]
          {
            x: xi,
            y: yi,
            w: wi,
            h: hi
          }
        */

        let maxW = 1,
            maxH = 1;
        for ( let i = 0, e; e = items[i]; ++i ) {
          if (e.h > maxH) maxH = e.h;
          if (e.w > maxW) maxW = e.w;
        }
        if (maxW > this.columns) this.columns = maxW;

        let szmp = [];
        for ( let i = 1; i <= maxH; ++i ) {
          szmp.push([]);
          for ( let j = 0; j <= maxW; ++j ) {
            szmp[i-1].push([1,1]);
          }
        }

        /* Moongom Algorithm */
        for ( let i = 0,e; e = items[i]; ++i ) {
          items[i].index = i;

          let [px1,py1] = szmp[e.h-1][e.w-1];
          let px2 = px1 + e.w - 1;
          let py2 = py1 + e.h - 1;

          seeking:
          while (true) {

            while ( px2 <= this.columns ) {

              let hasCollision = false;
              for ( let j = i-1; j >= 0 && !hasCollision; --j) {

                let x1 = items[j].x,
                x2 = items[j].x + items[j].w - 1,
                y1 = items[j].y,
                y2 = items[j].y + items[j].h - 1;

                hasCollision = (px1 > x2 || px2 < x1 || py1 > y2 || py2 < y1) ? false : true;
              }
              if (!hasCollision) {
                szmp[e.h-1][e.w-1] = [px2+1,py1];
                e.x = px1;
                e.y = py1;
                e.szmpX = px2+1;
                e.szmpY = py1;

                break seeking;
              }

              ++px1;
              ++px2;
            }

            px1 = 1;
            ++py1;

            px2 = px1 + e.w -1;
            ++py2;
          }

        }
      }